Sample records for exponential population growth

  1. Modelling population growth vialaguerre-type exponentials

    Microsoft Academic Search

    S. De Andreis; P. E. Ricci

    2005-01-01

    We use the Laguerre-type exponentials, i.e., eigenfunctions of the Laguerre-type derivatives, in order to construct new models for population growth. Relevant modifications of the classical exponential, logistic, and Volterra-Lotka models are investigated.

  2. Interpolation solution in generalized stochastic exponential population growth model

    Microsoft Academic Search

    M. Khodabin; K. Maleknejad; M. Rostami; M. Nouri

    In this paper, first we consider model of exponential population growth, then we assume that the growth rate at time t is not completely definite and it depends on some random environment effects. For this case the stochastic exponential population growth model is introduced. Also we assume that the growth rate at time t depends on many different random environment

  3. Impulsive exponential stabilization of discrete population growth models with time delays

    Microsoft Academic Search

    Yu Zhang; Jitao Sun

    2010-01-01

    The purpose of this paper is to investigate the impulsive exponential stabilization for the positive equilibrium points of a class of discrete population growth models with time delays. By using Lyapunov functionals, some new exponential stability criteria are given. It is shown that impulses can indeed make unstable equilibrium points exponentially stable, and when the impulses are employed to stabilize

  4. Exponential Population Growth and Doubling Times: Are They Dead or Merely Quiescent?

    Microsoft Academic Search

    John R. Bermingham

    2003-01-01

    Exponential Growth” and “Doubling Times”: Use of these popular population buzzwords of the last half of the twentieth century was fully justified by the growth rates of that period. However, those growth rates have now all but disappeared and so have the underlying reasons that those buzzwords made sense. Misuse of such expressions today costs credibility. Though the world's population

  5. The impact of accelerating faster than exponential population growth on genetic variation.

    PubMed

    Reppell, Mark; Boehnke, Michael; Zöllner, Sebastian

    2014-03-01

    Current human sequencing projects observe an abundance of extremely rare genetic variation, suggesting recent acceleration of population growth. To better understand the impact of such accelerating growth on the quantity and nature of genetic variation, we present a new class of models capable of incorporating faster than exponential growth in a coalescent framework. Our work shows that such accelerated growth affects only the population size in the recent past and thus large samples are required to detect the models' effects on patterns of variation. When we compare models with fixed initial growth rate, models with accelerating growth achieve very large current population sizes and large samples from these populations contain more variation than samples from populations with constant growth. This increase is driven almost entirely by an increase in singleton variation. Moreover, linkage disequilibrium decays faster in populations with accelerating growth. When we instead condition on current population size, models with accelerating growth result in less overall variation and slower linkage disequilibrium decay compared to models with exponential growth. We also find that pairwise linkage disequilibrium of very rare variants contains information about growth rates in the recent past. Finally, we demonstrate that models of accelerating growth may substantially change estimates of present-day effective population sizes and growth times. PMID:24381333

  6. Exponential growth in age-structured two-sex populations

    Microsoft Academic Search

    Maia Martcheva

    1999-01-01

    We consider a continuous age-structured two-sex population model which is given by a semilinear system of partial differential equations with nonlocal boundary conditions and is a simpler case of Fredrickson–Hoppensteadt model. The non-linearity is introduced by a source term, called from its physical meaning, the marriage function. The explicit form of the marriage function is not known; however, there is

  7. A Precalculus Project on Exponential Population Growth and Linear Food Production.

    ERIC Educational Resources Information Center

    McDonald, Michael A.; And Others

    1996-01-01

    Discusses a precalculus project in which students create a model United Nations to present and discuss the long-term prognosis for individual countries given data on population growth and food production. Students compare exponential and linear functions to determine whether starvation will occur and prepare oral and written presentations of their…

  8. Lecture 14: Population growth. Exponential growth described by R0, and r

    E-print Network

    Creel, Scott

    , as shown by reindeer on Pribilof Islands for 30 years after introduction. Exponential growth occurs when not often occur (for long) in nature. But colonizations like the reindeer example, or recovery

  9. Can the site-frequency spectrum distinguish exponential population growth from multiple-merger coalescents?

    PubMed

    Eldon, Bjarki; Birkner, Matthias; Blath, Jochen; Freund, Fabian

    2015-03-01

    The ability of the site-frequency spectrum (SFS) to reflect the particularities of gene genealogies exhibiting multiple mergers of ancestral lines as opposed to those obtained in the presence of population growth is our focus. An excess of singletons is a well-known characteristic of both population growth and multiple mergers. Other aspects of the SFS, in particular, the weight of the right tail, are, however, affected in specific ways by the two model classes. Using an approximate likelihood method and minimum-distance statistics, our estimates of statistical power indicate that exponential and algebraic growth can indeed be distinguished from multiple-merger coalescents, even for moderate sample sizes, if the number of segregating sites is high enough. A normalized version of the SFS (nSFS) is also used as a summary statistic in an approximate Bayesian computation (ABC) approach. The results give further positive evidence as to the general eligibility of the SFS to distinguish between the different histories. PMID:25575536

  10. An exponential growth model with decreasing r captures bottom-up effects on the population growth of Aphis glycines Matsumura (Hemiptera: Aphididae)

    Microsoft Academic Search

    A. C. Costamagna; W. van der Werf; F. J. J. A. Bianchi; D. A. Landis

    2007-01-01

    1 There is ample evidence that the life history and population dynamics of aphids are closely linked to plant phenology. Based on life table studies, it has been proposed that the growth of aphid populations could be modeled with an exponential growth model, with r decreasing linearly with time. This model has never been tested under field conditions. 2 The

  11. How well can the exponential-growth coalescent approximate constant-rate birth–death population dynamics?

    PubMed Central

    Stadler, Tanja; Vaughan, Timothy G.; Gavryushkin, Alex; Guindon, Stephane; Kühnert, Denise; Leventhal, Gabriel E.; Drummond, Alexei J.

    2015-01-01

    One of the central objectives in the field of phylodynamics is the quantification of population dynamic processes using genetic sequence data or in some cases phenotypic data. Phylodynamics has been successfully applied to many different processes, such as the spread of infectious diseases, within-host evolution of a pathogen, macroevolution and even language evolution. Phylodynamic analysis requires a probability distribution on phylogenetic trees spanned by the genetic data. Because such a probability distribution is not available for many common stochastic population dynamic processes, coalescent-based approximations assuming deterministic population size changes are widely employed. Key to many population dynamic models, in particular epidemiological models, is a period of exponential population growth during the initial phase. Here, we show that the coalescent does not well approximate stochastic exponential population growth, which is typically modelled by a birth–death process. We demonstrate that introducing demographic stochasticity into the population size function of the coalescent improves the approximation for values of R0 close to 1, but substantial differences remain for large R0. In addition, the computational advantage of using an approximation over exact models vanishes when introducing such demographic stochasticity. These results highlight that we need to increase efforts to develop phylodynamic tools that correctly account for the stochasticity of population dynamic models for inference. PMID:25876846

  12. Supercritical branching processes and the role of fluctuations under exponential population growth

    Microsoft Academic Search

    Susanna C. Manrubia; Mar??a Arribas; Ester Lázaro

    2003-01-01

    We study some exact properties of supercritical branching processes. A proper rescaling of the relevant variable allows us to determine the distribution of population sizes after a number of generations have elapsed. Both time-continuous and discrete processes are analysed and compared. The obtained results are of relevance for the growth of populations that are not resource limited (a typical situation

  13. A PRECALCULUS PROJECT ON EXPONENTIAL POPULATION GROWTH AND LINEAR FOOD PRODUCTION

    Microsoft Academic Search

    Michael A. McDonald; Emily Puckette; Charles Vuono

    1996-01-01

    We present a precalculus project based on a quote by Thomas Malthus—that population increases in a geometric ratio while sustenance increases only in an arithmetic ratio. A model United Nations is created to present and discuss the long term prognosis for individual countries given data on population growth and food production. Student groups, representing various nations, are asked to use

  14. HAS 222d-2009 Lecture 16 Exponential growth

    E-print Network

    HAS 222d-2009 Lecture 16 week 9 Exponential growth P.Rhines Digression on exponential growth and global population: exponential growth occurs when the growth is proportional to the population on the surface of a pond by reproducing at a constant rate...the effect is very slow growth, almost invisible

  15. Fitness Distributions in Exponentially Growing Asexual Populations

    Microsoft Academic Search

    Susanna C. Manrubia; Ester Lázaro; Juan Pérez-Mercader; Cristina Escarmís; Esteban Domingo

    2003-01-01

    We explore a mean-field model for the evolution of exponentially growing populations of mutating replicators. Motivated by recent in vitro experiments devised to analyze phenotypic properties of bacterial and viral populations subjected to serial population transfers, we allow our in silico individuals to undergo unrestricted growth before applying bottleneck events. Different dynamical regimes of our model can be mapped to

  16. Population Growth

    NSDL National Science Digital Library

    2009-01-01

    These activities explore population growth rates and its consequences with regard to the distribution of natural resources. Population growth is perhaps the most important environmental issue of our time. As population increases and as people seek to raise their standard of living, more stress is put on our earth’s finite resources.One aspect of the population issue is the sheer magnitude of the numbers involved. World population did not reach 1 billion until the year 1800. Since then it has grown exponentially to reach our current 6.7 billion.

  17. On Exponential Growth and Mathematical Purity: A Reply to Bartlett

    Microsoft Academic Search

    John R. Bermingham

    2003-01-01

    Though Bartlett has offered several constructive criticisms of the mathematical formulations that were included in my paper, Exponential Population Growth and Doubling Times, not one of them undermines either of the two basic points made in my paper—that exponential population growth is no longer being projected for any nation in the world and, this being so, writers and speakers addressing

  18. Lesson 29: Exponential Growth and Decay

    NSDL National Science Digital Library

    2011-01-01

    The lesson begins with a discussion about growth factors and percent increase, leading to the presentation of the compound interest formula. Following this focus on growth, exponential decay is introduced. The lesson concludes with a comparison between exponential and linear growth, highlighting the difference in the additive and multiplicative patterns in their growth patterns.

  19. 11CR 9/2/2007 1 1.1 Exponential growth and decay.

    E-print Network

    Taylor, Peter

    11CR 9/2/2007 1 1.1 Exponential growth and decay. Example 1. A year ago I bought a mint condition time t valuez z t #12;11CR 9/2/2007 4 Exponential growth and decay Some folks think that exponential. And that's exponential change. Examples? Biological populations grow this way when birth and death rates

  20. Analysis of the Stochastic Super-Exponential Growth Model

    NASA Astrophysics Data System (ADS)

    Avila, P.; Rekker, A.

    2011-11-01

    Empirical data suggests that the human population has grown super-exponentially for the past 2000 years. The super-exponential growth is the property of dynamical systems exhibiting endogenous nonlinear positive feedback. Based on the wide range of empirical evidence on global and local scale, we assume a strong correlation between the dynamics of population growth and the human technological innovations. A mathematical model have been devised to describe the dynamics of super-exponentially growing population with stochastic fluctuations. These fluctuations can be of environmental origin or can arise from the inherent fluctuations within the demographics. The noise has been assumed to act on the growth rate multiplicatively and is assumed to be Gaussian white noise à la Stratonovich. An analysis of the stochastic super-exponential growth model is presented. The exact analytical formulae for the conditional probability density of the population size and the first and second moments of population size are presented. We have also calculated the probability density of the population's lifetime, and the higher moments of the population size, as well as the population's prospective lifetime. Interpretations and various applications of the results are discussed.

  1. Population Growth in Planaria

    Microsoft Academic Search

    JOHN DAVISON

    Planaria reproduce by transverse fission. Isolated worms increase in number exponentially, while social animals at the same density are inhibited in terms of numerical increase, but over a 25 day period undergo a larger in- crease in mass. Isolated posterior fission products reproduce faster than isolated anterior fission products. Regulation of population growth is independent of density over a 16-fold

  2. The Ramsey model with logistic population growth

    Microsoft Academic Search

    Juan Gabriel Brida; Elvio Accinelli

    2007-01-01

    In standard economic growth theory it is assumed that labor force follows exponential growth, a not realistic assumption. As described in Maynard Smith (1974), the growth of natural populations is more accurately depicted by a logistic growth law. In this paper we analyze how the Ramsey growth model is affected by logistic growth of population, comparing it with the classic

  3. Black Hole Instabilities and Exponential Growth

    E-print Network

    Kartik Prabhu; Robert M. Wald

    2015-01-12

    Recently, a general analysis has been given of the stability with respect to axisymmetric perturbations of stationary-axisymmetric black holes and black branes in vacuum general relativity in arbitrary dimensions. It was shown that positivity of canonical energy on an appropriate space of perturbations is necessary and sufficient for stability. However, the notions of both "stability" and "instability" in this result are significantly weaker than one would like to obtain. In this paper, we prove that if a perturbation of the form $\\pounds_t \\delta g$---with $\\delta g$ a solution to the linearized Einstein equation---has negative canonical energy, then that perturbation must, in fact, grow exponentially in time. The key idea is to make use of the $t$- or ($t$-$\\phi$)-reflection isometry, $i$, of the background spacetime and decompose the initial data for perturbations into their odd and even parts under $i$. We then write the canonical energy as $\\mathscr E\\ = \\mathscr K + \\mathscr U$, where $\\mathscr K$ and $\\mathscr U$, respectively, denote the canonical energy of the odd part (kinetic energy) and even part (potential energy). One of the main results of this paper is the proof that $\\mathscr K$ is positive definite for any black hole background. We use $\\mathscr K$ to construct a Hilbert space $\\mathscr H$ on which time evolution is given in terms of a self-adjoint operator $\\tilde {\\mathcal A}$, whose spectrum includes negative values if and only if $\\mathscr U$ fails to be positive. Negative spectrum of $\\tilde{\\mathcal A}$ implies exponential growth of the perturbations in $\\mathscr H$ that have nontrivial projection into the negative spectral subspace. This includes all perturbations of the form $\\pounds_t \\delta g$ with negative canonical energy. A "Rayleigh-Ritz" type of variational principle is derived, which can be used to obtain lower bounds on the rate of exponential growth.

  4. Noise-driven unlimited population growth

    Microsoft Academic Search

    Baruch Meerson; Pavel V. Sasorov

    2008-01-01

    Demographic noise causes unlimited population growth in a broad class of models which, without noise, would predict a stable finite population. We study this effect on the example of a stochastic birth-death model which includes immigration, binary reproduction, and death. The unlimited population growth proceeds as an exponentially slow decay of a metastable probability distribution (MPD) of the population. We

  5. Generalized exponential function and discrete growth models

    NASA Astrophysics Data System (ADS)

    Souto Martinez, Alexandre; Silva González, Rodrigo; Lauri Espíndola, Aquino

    2009-07-01

    Here we show that a particular one-parameter generalization of the exponential function is suitable to unify most of the popular one-species discrete population dynamic models into a simple formula. A physical interpretation is given to this new introduced parameter in the context of the continuous Richards model, which remains valid for the discrete case. From the discretization of the continuous Richards’ model (generalization of the Gompertz and Verhulst models), one obtains a generalized logistic map and we briefly study its properties. Notice, however that the physical interpretation for the introduced parameter persists valid for the discrete case. Next, we generalize the (scramble competition) ?-Ricker discrete model and analytically calculate the fixed points as well as their stabilities. In contrast to previous generalizations, from the generalized ?-Ricker model one is able to retrieve either scramble or contest models.

  6. Modeling Population Growth and Extinction

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  7. Analyzing population growth curves

    Microsoft Academic Search

    L. L. Eberhardt; J. M. Breiwick; D. P. Demaster

    2008-01-01

    Assessing animal population growth curves is an essential feature of field studies in ecology and wildlife management. We used five models to assess population growth rates with a number of sets of population growth rate data. A 'generalized' logistic curve provides a better model than do four other popular models. Use of difference equations for fitting was checked by a

  8. Exponential growth rates of species of the yeast genus Kluyveromyces

    Microsoft Academic Search

    Socrates Bitzilekis; James A. Barnett

    1997-01-01

    Doubling times were measured during exponential growth of 19 strains belonging to 10 of the 17 species of the yeast genus Kluyveromyces. Growth was in shaken aerobic batch culture at 25°C, in a chemically defined medium with d-glucose as sole carbon source. Doubling times were strikingly uniform, being mainly between 2 and 3.5 h.

  9. Exponential order statistic models of software reliability growth

    NASA Technical Reports Server (NTRS)

    Miller, D. R.

    1985-01-01

    Failure times of a software reliabilty growth process are modeled as order statistics of independent, nonidentically distributed exponential random variables. The Jelinsky-Moranda, Goel-Okumoto, Littlewood, Musa-Okumoto Logarithmic, and Power Law models are all special cases of Exponential Order Statistic Models, but there are many additional examples also. Various characterizations, properties and examples of this class of models are developed and presented.

  10. World population growth—a general model

    Microsoft Academic Search

    A. S. Boughey

    1974-01-01

    National populations currently fall into two categories, those in or closely approaching a stationary “K” phase, those still in an “r” phase of exponential growth. Throughout human history the “K” phase, in which populations match their available resource bases, has generally predominated. The exploitive “r” phase has intermittently occurred, and has then normally featured some revolutionary improvement in extractive capacity,

  11. Exponential energy growth in adiabatically changing Hamiltonian systems

    NASA Astrophysics Data System (ADS)

    Pereira, Tiago; Turaev, Dmitry

    2015-01-01

    We show that the mixed phase space dynamics of a typical smooth Hamiltonian system universally leads to a sustained exponential growth of energy at a slow periodic variation of parameters. We build a model for this process in terms of geometric Brownian motion with a positive drift, and relate it to the steady entropy increase after each period of the parameters variation.

  12. Population growth with randomly distributed jumps

    Microsoft Academic Search

    Floyd B. Hanson; Henry C. Tuckwell

    1997-01-01

    .  ?The growth of populations with continuous deterministic and random jump components is treated. Three special models in which\\u000a random jumps occur at the time of events of a Poisson process and admit formal explicit solutions are considered: A)?Logistic\\u000a growth with random disasters having exponentially distributed amplitudes; B)?Logistic growth with random disasters causing\\u000a the removal of a uniformly distributed fraction of

  13. Critical Mutation Rate Has an Exponential Dependence on Population Size in Haploid and Diploid Populations

    E-print Network

    Channon, Alastair

    . This is in contrast to previous studies which identified that critical mutation rate was independent of populationCritical Mutation Rate Has an Exponential Dependence on Population Size in Haploid and Diploid Populations Elizabeth Aston1 *, Alastair Channon1 , Charles Day1 , Christopher G. Knight2 1 Research Institute

  14. The Hyperexponential Growth of the Human Population on a Macrohistorical Scale

    Microsoft Academic Search

    S. D. VARFOLOMEYEV; K. G. GUREVICH

    2001-01-01

    A qualitative comparison of human population dynamics with some other biological populations growth in free regime is given in this paper along with a quantitative description of human population growth in the last 2000 years. It is shown that human population growth law is very different from the growth laws of other populations: all biological populations grow according to exponential

  15. Reformulation of the Solow economic growth model whit the Richards population growth law

    Microsoft Academic Search

    Elvio Accinelli; Juan Gabriel Brida

    2005-01-01

    In standard economic growth theory it is usually assumed that labor force follows exponential growth. That is not a realistic assumption. In this paper we introduce a generalized logistic equation (Richards law) that describes more accurately population growth. Then we analyze the neoclassical Solow model with growth of population following the Richards law, and compares it with the classical model

  16. THE JOURNAL OF FINANCE VOL. LXIV, NO. 6 DECEMBER 2009 Exponential Growth Bias and Household Finance

    E-print Network

    Lotko, William

    /interest bias are potentially linked by a single cognitive micro-foundation: exponential growth bias, the tenTHE JOURNAL OF FINANCE · VOL. LXIV, NO. 6 · DECEMBER 2009 Exponential Growth Bias and Household Finance VICTOR STANGO and JONATHAN ZINMAN ABSTRACT Exponential growth bias is the pervasive tendency

  17. Population Growth and Periodic Instability of the International System

    Microsoft Academic Search

    Ingo Piepers

    2006-01-01

    From the perspective developed in this paper, it can be argued that exponential population growth resulted in the exponential decrease of the life-span of consecutive stable periods during the life-span of the European international system (1480-1945). However, it becomes evident as well that population growth as such is not a sufficient condition to generate a punctuated equilibrium dynamic in the

  18. Population Growth Curves

    NSDL National Science Digital Library

    2014-09-18

    Using Avida-ED freeware, students control a few factors in an environment populated with digital organisms, and then compare how changing these factors affects population growth. They experiment by altering the environment size (similar to what is called carrying capacity, the maximum population size that an environment can normally sustain), the initial organism gestation rate, and the availability of resources. How systems function often depends on many different factors. By altering these factors one at a time, and observing the results, students are able to clearly see the effect of each one.

  19. Connecting Population Growth and Biological Evolution

    NSDL National Science Digital Library

    This activity will allow students to develop a model of the mathematical nature of population growth. The investigation provides an excellent opportunity for consideration of the population growth of plant and animal species and the resultant stresses that contribute to natural selection. Students will discover that populations grow or decline through the combined effects of births and deaths and through emigration and immigration into specific areas, increase through linear or exponential growth, with effects on resource use and on environmental pollution, and reach limits to growth. They will realize that carrying capacity is limited and although living organisms have the capacity to produce populations of arbitrarily large size, environments and resources are finite and this fundamental tension has profound effects on the interactions between organisms. This site has a list of materials and all other information required to complete this activity.

  20. Exponential energy growth in adiabatically changing Hamiltonian Systems

    E-print Network

    Tiago Pereira; Dmitry Turaev

    2014-10-07

    Fermi acceleration is the process of energy transfer from massive objects in slow motion to light objects that move fast. The model for such process is a time-dependent Hamiltonian system. As the parameters of the system change with time, the energy is no longer conserved, which makes the acceleration possible. One of the main problems is how to generate a sustained and robust energy growth. We show that the non-ergodicity of any chaotic Hamiltonian system must universally lead to the exponential growth of energy at a slow periodic variation of parameters. We build a model for this process in terms of a Geometric Brownian Motion with a positive drift, and relate it to the entropy increase.

  1. Population growth in random media

    Microsoft Academic Search

    A. Greven; F. den Hollander

    1991-01-01

    In this second part of a two-part presentation, we continue with the model introduced in Part I. In this part, the initial configuration has one particle at each site to the left of 0 and no particle elsewhere. The expected number of particles observed at a site moving at speed t? has an exponential growth rate (speed-t growth rate) that

  2. Population Growth, Technology, and the Environment

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2008-09-30

    Overview: This Science Object is the second of four Science Objects in the Resources and Human Impact SciPack. It explores how technology can solve problems, but at the same time, can also create new strains on the environment. Improved technology used for harvesting food, coupled with the technology of improved sanitation, has accelerated the growth of the human population. A larger human population increases the impact on the environment and its resources, many of which are limited and non renewable. Due to the rapid growth of the human population and their use of technology in many parts of the world, humans have exceeded the carrying capacity of their environment, compromising human health. Learning Outcomes: Identify, compare, and contrast principles of population growth in humans and other organisms. Explain the limiting factors on the exponential growth of a population (for example: disease, competition for resources). Analyze how technology (antibiotics, harvesting food) has impacted human population growth in an ecosystem (for example: agriculture, aquaculture).

  3. U.S. Population Growth: What Does the Future Hold?

    NSDL National Science Digital Library

    James J. Rutledge

    College Algebra or Liberal Arts math students are presented with a ConcepTest, a Question of the Day and a write-pair-share activity involving U.S. population growth. The results are quite revealing and show that while students may have learned how to perform the necessary calculations, their conceptual understanding concerning exponential growth may remain faulty. Student knowledge (or lack thereof) of the size of our population and its annual growth rate may also be surprising.

  4. Determinants of human population growth.

    PubMed Central

    Lutz, Wolfgang; Qiang, Ren

    2002-01-01

    The 20th century has seen unprecedented growth of the human population on this planet. While at the beginning of the century the Earth had an estimated 1.6 billion inhabitants, this number grew to 6.1 billion by the end of the century, and further significant growth is a near certainty. This paper tries to summarize what factors lie behind this extraordinary expansion of the human population and what population growth we can expect for the future. It discusses the concept of demographic transition and the preconditions for a lasting secular fertility decline. Recent fertility declines in all parts of the world now make it likely that human population growth will come to an end over the course of this century, but in parts of the developing world significant population growth is still to be expected over the coming decades. The slowing of population growth through declining birth rates, together with still increasing life expectancy, will result in a strong ageing of population age structure. Finally, this paper presents a global level systematic analysis of the relationship between population density on the one hand, and growth and fertility rates on the other. This analysis indicates that in addition to the well-studied social and economic determinants, population density also presents a significant factor for the levels and trends of human birth rates. PMID:12396512

  5. Comparing several exponential populations with more than one control

    Microsoft Academic Search

    Parminder Singh; Asheber Abebe

    2009-01-01

    Suppose there are k\\u000a 1 (k\\u000a 1 ? 1) test treatments that we wish to compare with k\\u000a 2 (k\\u000a 2 ? 1) control treatments. Assume that the observations from the ith test treatment and the jth control treatment follow a two-parameter exponential distribution $${E\\\\left({\\\\xi_i ,\\\\theta}\\\\right)}$$ and $${E\\\\left({\\\\eta_j ,\\\\theta}\\\\right)}$$, where ? is a common scale parameter and $${{\\\\xi_i }}$$ and $${{\\\\eta_j}}$$ are

  6. Limited Population Growth

    NSDL National Science Digital Library

    Barker, William

    Created for the Connected Curriculum Project, this module models population as a function of time in a setting where there is a maximum population M that the environment will support. More specifically, to see that we can develop a graphical model from assumptions about the rate of change -- without any knowledge of an algebraic form for the model function. This is one within a much larger set of learning modules hosted by Duke University.

  7. Patterns in the effects of infectious diseases on population growth

    Microsoft Academic Search

    O. Diekmann; M. Kretzschmar

    1991-01-01

    An infectious disease may reduce or even stop the exponential growth of a population. We consider two very simple models for microparasitic and macroparasitic diseases, respectively, and study how the effect depends on a contact parameter K. The results are presented as bifurcation diagrams involving several threshold values of ?. The precise form of the bifurcation diagram depends critically on

  8. Weak extinction versus global exponential growth of total mass for superdiffusions

    E-print Network

    Song, Renming

    Weak extinction versus global exponential growth of total mass for superdiffusions J´anos Engl of local growth when it is positive, and implies local extinction otherwise. It is easy to show that 2 a sufficient and necessary condition for the superdiffusion X to exhibit weak extinction. We show

  9. The Outlook for Population Growth

    PubMed Central

    Lee, Ronald

    2011-01-01

    Projections of population size, growth rates and age distribution, although extending to distant horizons, shape policies today for the economy, environment, and government programs such as public pensions and health care. The projections can lead to costly policy adjustments which in turn can cause political and economic turmoil. The United Nations projects global population to grow from about 7 billion today to 9.3 billion in 2050 and 10.1 billion in 2100 while the Old Age Dependency Ratio doubles by 2050 and triples by 2100. How are such population projections made, and how certain can we be about the trends they foresee? PMID:21798936

  10. Evolution of linkage disequilibrium of the founders in exponentially growing populations

    Microsoft Academic Search

    Shuhei Mano

    2007-01-01

    Evolution of linkage disequilibrium of the founders in exponentially growing populations was studied using a time-inhomogeneous Itô process model. The model is an extension of the diffusion approximation of the Wright–Fisher model. As a measure of linkage disequilibrium, the squared standard linkage deviation, which is defined by a ratio of the moments, was considered. A system of ordinary differential equations

  11. Cellular Respiration and Population Growth

    NSDL National Science Digital Library

    2014-09-18

    Through two lessons and their associated activities, students explore cellular respiration and population growth in yeasts. Yeast cells are readily obtained and behave predictably, so they are very suitable for use in middle school classrooms. Students are presented with information that enables them to recognize that yeasts are unicellular organisms that are useful to humans.

  12. Line transect estimation of population size: the exponential case with grouped data

    USGS Publications Warehouse

    Anderson, D.R.; Burnham, K.P.; Crain, B.R.

    1979-01-01

    Gates, Marshall, and Olson (1968) investigated the line transect method of estimating grouse population densities in the case where sighting probabilities are exponential. This work is followed by a simulation study in Gates (1969). A general overview of line transect analysis is presented by Burnham and Anderson (1976). These articles all deal with the ungrouped data case. In the present article, an analysis of line transect data is formulated under the Gates framework of exponential sighting probabilities and in the context of grouped data.

  13. POPULATION GROWTH, ECONOMIC DEVELOPMENT, AND POPULATION CONTROL PROGRAMS

    Microsoft Academic Search

    KENT P. SCHWIRIAN

    In this paper the general pattern of world population growth and the variations by major world region are discussed. Comments on the relationship between population growth and economic development are included, but discussion of the implications of population growth for resource utilization is omitted, since the other papers in this symposium deal with this topic. Finally, the likelihood of short-run

  14. Rapid growth of seed black holes in the early universe by supra-exponential accretion.

    PubMed

    Alexander, Tal; Natarajan, Priyamvada

    2014-09-12

    Mass accretion by black holes (BHs) is typically capped at the Eddington rate, when radiation's push balances gravity's pull. However, even exponential growth at the Eddington-limited e-folding time t(E) ~ few × 0.01 billion years is too slow to grow stellar-mass BH seeds into the supermassive luminous quasars that are observed when the universe is 1 billion years old. We propose a dynamical mechanism that can trigger supra-exponential accretion in the early universe, when a BH seed is bound in a star cluster fed by the ubiquitous dense cold gas flows. The high gas opacity traps the accretion radiation, while the low-mass BH's random motions suppress the formation of a slowly draining accretion disk. Supra-exponential growth can thus explain the puzzling emergence of supermassive BHs that power luminous quasars so soon after the Big Bang. PMID:25103410

  15. The population genetic structure of clonal organisms generated by exponentially bounded and fat-tailed dispersal.

    PubMed

    Wingen, Luzie U; Brown, James K M; Shaw, Michael W

    2007-09-01

    Long-distance dispersal (LDD) plays an important role in many population processes like colonization, range expansion, and epidemics. LDD of small particles like fungal spores is often a result of turbulent wind dispersal and is best described by functions with power-law behavior in the tails ("fat tailed"). The influence of fat-tailed LDD on population genetic structure is reported in this article. In computer simulations, the population structure generated by power-law dispersal with exponents in the range of -2 to -1, in distinct contrast to that generated by exponential dispersal, has a fractal structure. As the power-law exponent becomes smaller, the distribution of individual genotypes becomes more self-similar at different scales. Common statistics like GST are not well suited to summarizing differences between the population genetic structures. Instead, fractal and self-similarity statistics demonstrated differences in structure arising from fat-tailed and exponential dispersal. When dispersal is fat tailed, a log-log plot of the Simpson index against distance between subpopulations has an approximately constant gradient over a large range of spatial scales. The fractal dimension D2 is linearly inversely related to the power-law exponent, with a slope of approximately -2. In a large simulation arena, fat-tailed LDD allows colonization of the entire space by all genotypes whereas exponentially bounded dispersal eventually confines all descendants of a single clonal lineage to a relatively small area. PMID:17660543

  16. The Western Africa Ebola Virus Disease Epidemic Exhibits Both Global Exponential and Local Polynomial Growth Rates

    PubMed Central

    Chowell, Gerardo; Viboud, Cécile; Hyman, James M; Simonsen, Lone

    2015-01-01

    Background: While many infectious disease epidemics are initially characterized by an exponential growth in time, we show that district-level Ebola virus disease (EVD) outbreaks in West Africa follow slower polynomial-based growth kinetics over several generations of the disease. Methods: We analyzed epidemic growth patterns at three different spatial scales (regional, national, and subnational) of the Ebola virus disease epidemic in Guinea, Sierra Leone and Liberia by compiling publicly available weekly time series of reported EVD case numbers from the patient database available from the World Health Organization website for the period 05-Jan to 17-Dec 2014. Results: We found significant differences in the growth patterns of EVD cases at the scale of the country, district, and other subnational administrative divisions. The national cumulative curves of EVD cases in Guinea, Sierra Leone, and Liberia show periods of approximate exponential growth. In contrast, local epidemics are asynchronous and exhibit slow growth patterns during 3 or more EVD generations, which can be better approximated by a polynomial than an exponential function. Conclusions: The slower than expected growth pattern of local EVD outbreaks could result from a variety of factors, including behavior changes, success of control interventions, or intrinsic features of the disease such as a high level of clustering. Quantifying the contribution of each of these factors could help refine estimates of final epidemic size and the relative impact of different mitigation efforts in current and future EVD outbreaks. PMID:25685633

  17. [Population growth and the environment].

    PubMed

    Hogan, D J

    1991-01-01

    The impact of population growth on the enviornment has been extensively researched; it consists of the depletion of resources (agricultural land absorbed by urban expansion, loss of soils, desertification, loss of biodiversity, less availability of minerals, dwindling of petroleum reserves) and the degradation of natural resources (air and water pollution). For politicians, journalists, and environmentalists, population growth is identified as the principal villain, which is a unidirectional and negative opinion. Demography is supposed to examine the negative and positive effects of the environment-population relationship; however, it is postulated that there has not been much produced in the last 2 centuries in this area. Examination of the research literature does not indicate any view that transcends the Malthusian vision, although a few empirical studies exist (Hogan, 1989). Durham (1979) identified the replacement of subsistence agriculture by export-oriented agriculture as the key factor in overpopulation in El Salvador and Honduras that led to migrations and international conflicts. Tudela (1987) related a similar process in the Mexican state of Tabasco, where a period of malnutrition was accompanied by the expansion of export agriculture and nutritional improvements emanated only from recapturing subsistence agriculture. Fearnside (1986) researched the dynamics of the occupation and destruction of Amazonia. However, Kahn and Simon went further and denied the existence of real environmental problems: population is the ultimate resource, and the more minds, the more good ideas and solutions for any problem. However, in all these cases of pure or modified Malthusianism the relation of population/resources is reduced to a unidimensional relationship; and fertility, mortality, migration, marriage, and age structure receive little attention. A prime candidate for the attention of population specialists should be migration and patterns of settlement and their relationships to the physical environment, aspects of the depletion and degradation of resources as well as socially useful alterations. PMID:12286258

  18. Abstract Despite the exponential growth in heart rate variability (HRV) research, the reproducibility

    E-print Network

    Abstract Despite the exponential growth in heart rate variability (HRV) research. The mean heart rate was more reproducible and could be more accu- rately estimated from very short segments be estimated accurately from short segments (Heart rate variability (HRV) Æ Interbeat

  19. Prion Disease: Exponential Growth Requires Membrane Binding Daniel L. Cox,*y

    E-print Network

    Yang, Sichun

    for infection in mammals and non-Mendelian inheritance in yeast/fungi requires the fission or autocatalysis A hallmark feature of prions, whether in mammals or yeast and fungi, is exponential growth associated membrane associated fission or autocatalysis with the membrane free fission of yeast and fungal prions

  20. Gene Genealogy and Properties of Test Statistics of Neutrality Under Population Growth

    Microsoft Academic Search

    Akinori Sano; Hidenori Tachida

    2005-01-01

    We consider the Wright-Fisher model with exponential population growth and investigate effects of pop- ulation growth on the shape of genealogy and the distributions of several test statistics of neutrality. In the limiting case as the population grows rapidly, the rapid-growth-limit genealogy is characterized. We obtained approximate expressions for expectations and variances of test statistics in the rapid-growth-limit genealogy and

  1. Mate location, population growth and species extinction

    Microsoft Academic Search

    Harrington Wells; Eric G. Strauss; Michael A. Rutter; Patrick H. Wells

    1998-01-01

    The effects of mate location efficiency on the dynamics of population growth and extinction were modeled with a view towards future species conservation efforts. Mate location is shown to be based on the Allee principle. Higher population densities produce greater mate location success rates. Low population densities generate population growth rates that are smaller than mortality rates, and, thus, produce

  2. Entire solutions with exponential growth for an elliptic system modelling phase separation

    NASA Astrophysics Data System (ADS)

    Soave, Nicola; Zilio, Alessandro

    2014-02-01

    We prove the existence of entire solutions with exponential growth for the semilinear elliptic system \\begin{equation*} \\left\\{\\begin{array}{@{}ll@{}} -\\Delta u = -u v^2 \\quad& in~{R}^N,\\\\ -\\Delta v= -u^2 v \\quad&in~{R}^N, \\\\ u,v>0, \\end{array}\\right. \\end{equation*} for every N ? 2. Our construction is based on an approximation procedure, whose convergence is ensured by suitable Almgren-type monotonicity formulae. The construction of the resulting solutions is extended to systems with k components, for every k > 2 in this case, the proof is much more involved and is achieved by approximation of solutions with exponential growth by means of solutions with algebraic growth of increasing degree, translating the limit \\begin{equation*}\\lim_{d \\to +\\infty} \\Im\\left[\\left(1+\\frac{z}{d}\\right)^{d}\\right] = \\rme^x \\sin y \\end{equation*} in the present setting.

  3. Improved exponential product cum dual to product type estimator of population mean

    NASA Astrophysics Data System (ADS)

    Singh, B. K.; Choudhury, Sanjib; Kumar, Abhishek

    2013-09-01

    In the present paper, an efficient exponential product cum dual to product type estimator has been proposed to estimate the population mean of the study variable by using simple random sampling scheme. The bias and mean squared error of the proposed estimator have been obtained up to the first order of approximation. A comparison has been made with existing similar estimators. The estimator has shown its efficiency over other estimators in terms of mean squared error (MSE). The numerical demonstrations have been made to show the gain in the estimator under study.

  4. Homage to Malthus, Ricardo, and Boserup: Toward a General Theory of Population, Economic Growth, Environmental

    E-print Network

    Richerson, Peter J.

    Homage to Malthus, Ricardo, and Boserup: Toward a General Theory of Population, Economic Growth when simple models are not enough to settle the issue, they are always the best place to start. Malthus. Malthus' discussion of the power of exponential growth, Ricardo's analysis of the link between economic

  5. Fatigue crack propagation model for plain concrete – An analogy with population growth

    Microsoft Academic Search

    Sonalisa Ray; J. M. Chandra Kishen

    2010-01-01

    In this work, an analytical model is proposed for fatigue crack propagation in plain concrete based on population growth exponential law and in conjunction with principles of dimensional analysis and self-similarity. This model takes into account parameters such as loading history, fracture toughness, crack length, loading ratio and structural size. The predicted results are compared with experimental crack growth data

  6. Population growth rates: issues and an application.

    PubMed Central

    Godfray, H Charles J; Rees, Mark

    2002-01-01

    Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering. PMID:12396521

  7. Future Population Growth Trends in California

    E-print Network

    Keller, Arturo A.

    - Migrate the Population Control Total Race/ethnic distribution Age and sex distribution #12;STEP 5Future Population Growth Trends in California Mary Heim Demographic Research Unit California Department of Finance #12;THE METHOD #12;Pn=P0+B-D+NM Pn=projected population Po=beginning population B

  8. Population and pavement: population growth and land development in Israel

    Microsoft Academic Search

    Daniel E. OrensteinSteven; Steven P. Hamburg

    2010-01-01

    This research examines land use change in Israel––an intriguing but understudied setting with regard to population–environment\\u000a dynamics. While Israel is fairly unique with regard to its combined high levels of economic prosperity and high population growth, this case study has relevance for developed countries and regions (like the south and southwest regions\\u000a of the USA) which must balance population growth

  9. An integrated model for predictive microbiology and simultaneous determination of lag phase duration and exponential growth rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new mechanistic growth model was developed to describe microbial growth under isothermal conditions. The development of the mathematical model was based on the fundamental phenomenon of microbial growth, which is normally a three-stage process that includes lag, exponential, and stationary phases...

  10. A Minimal Model of the E. Coli Bacterium in Exponential Phase Growth

    NASA Astrophysics Data System (ADS)

    Maitra, Arijit; Dill, Ken

    2013-03-01

    We study the fundamental process of exponential cell growth in the E. Coli bacterium under conditions of extracellular glucose limitations using a minimalistic reaction framework by accounting for energy metabolism and protein synthesis. The cell model has three nodes: ATP, the ribosomal and the non-ribosomal proteins. Their interdependencies and dynamics are wrapped in a system of ordinary differential equations. The formulations of their interactive fluxes capture the essence of cellular physiology under conditions of growth. We solve the model numerically for different glucose concentrations, and, where possible, explore the cell states analytically under steady state conditions. We verify the model predictions with available experimental data. The model lets us quantify the coupling between energy generation and biomass growth. An implication of this model is that it provides a layout to compute the fitness landscape in terms of the parameters of the cells, such as the protein translation rates, to make hypotheses about possible routes for cellular evolution under glucose limitation. We study the fundamental process of exponential cell growth in the E. Coli bacterium under conditions of extracellular glucose limitations using a minimalistic reaction framework by accounting for energy metabolism and protein synthesis. The cell model has three nodes: ATP, the ribosomal and the non-ribosomal proteins. Their interdependencies and dynamics are wrapped in a system of ordinary differential equations. The formulations of their interactive fluxes capture the essence of cellular physiology under conditions of growth. We solve the model numerically for different glucose concentrations, and, where possible, explore the cell states analytically under steady state conditions. We verify the model predictions with available experimental data. The model lets us quantify the coupling between energy generation and biomass growth. An implication of this model is that it provides a layout to compute the fitness landscape in terms of the parameters of the cells, such as the protein translation rates, to make hypotheses about possible routes for cellular evolution under glucose limitation. Laufer Center for Phys. and Quant. Biology.

  11. Nonlinear stochastic modeling of aphid population growth

    Microsoft Academic Search

    James H. Matis; Thomas R. Kiffe; Timothy I. Matis; Douglass E. Stevenson

    2005-01-01

    This paper develops a stochastic population size model for the black-margined pecan aphid. Prajneshu [Prajneshu, A nonlinear statistical model for aphid population growth. J. Indian Soc. Agric. Statist. 51 (1998), p. 73] proposes a novel nonlinear deterministic model for aphid abundance. The per capita death rate in his model is proportional to the cumulative population size, and the solution is

  12. The Growth of the Black Metropolitan Population.

    ERIC Educational Resources Information Center

    Taeuber, Conrad; Mosher, William T.

    The urbanization of the black population is a relatively recent phenomenon. Historically, migration has been the major source of the growth of the black population in the large cities of the North, yet the migration from nonmetropolitan to metropolitan areas has been going long enough to have established a substantial black population in the…

  13. THE NEOCLASSICAL MODEL OF SOLOW AND SWAN WITH LOGISTIC POPULATION GROWTH

    Microsoft Academic Search

    MASSIMILIANO FERRARA; LUCA GUERRINI

    This paper is an attempt at studying the neoclassical Solow-Swan model within a framework where the change over time of the labor-force is given by the logistic population model. In the canonical Solow-Swan model, the growth rate of population is constant, yielding an exponential behavior of population size over time, which is clearly unrealistic and unsustainable in the very long-run.

  14. Population Bulletin. World Population Projections: Alternative Paths to Zero Growth.

    ERIC Educational Resources Information Center

    Peck, Jennifer Marks

    1974-01-01

    This report is an adaptation of selected parts of a book on world population projections by Tomas Frejka. An explanation of the demographic terms that form a foundation for these projections is included, as well as discussions of the growth potentials for 24 nations throughout the world. Frejka's projections for a nongrowing population have been…

  15. Effects of body size and temperature on population growth.

    PubMed

    Savage, Van M; Gilloly, James F; Brown, James H; Charnov, Eric L

    2004-03-01

    For at least 200 years, since the time of Malthus, population growth has been recognized as providing a critical link between the performance of individual organisms and the ecology and evolution of species. We present a theory that shows how the intrinsic rate of exponential population growth, rmax, and the carrying capacity, K, depend on individual metabolic rate and resource supply rate. To do this, we construct equations for the metabolic rates of entire populations by summing over individuals, and then we combine these population-level equations with Malthusian growth. Thus, the theory makes explicit the relationship between rates of resource supply in the environment and rates of production of new biomass and individuals. These individual-level and population-level processes are inextricably linked because metabolism sets both the demand for environmental resources and the resource allocation to survival, growth, and reproduction. We use the theory to make explicit how and why rmax exhibits its characteristic dependence on body size and temperature. Data for aerobic eukaryotes, including algae, protists, insects, zooplankton, fishes, and mammals, support these predicted scalings for rmax. The metabolic flux of energy and materials also dictates that the carrying capacity or equilibrium density of populations should decrease with increasing body size and increasing temperature. Finally, we argue that body mass and body temperature, through their effects on metabolic rate, can explain most of the variation in fecundity and mortality rates. Data for marine fishes in the field support these predictions for instantaneous rates of mortality. This theory links the rates of metabolism and resource use of individuals to life-history attributes and population dynamics for a broad assortment of organisms, from unicellular organisms to mammals. PMID:15026978

  16. Estimates of in situ population growth rates of four tintinnine ciliate species near Kingston Harbour, Jamaica

    NASA Astrophysics Data System (ADS)

    Gilron, Guy L.; Lynn, Denis H.

    1989-07-01

    Population growth rates of four tintinnine species were estimated in situ by incubating predator-excluded, 201 seawater samples in plastic carboys. Initial ( t=0) and final ( t=24 h) abundances were enumerated from 20 ?m meshfiltered, Bouin's fixed subsamples. Assuming exponential growth, estimates of population growth rate averaged 0·80 day -1 or approximately one doubling per day. These estimates were lower than both those estimated for tintinnines from temperate regions and those predicted using a relationship that considers temperature and cell volume. Comparisons of temperate and tropical chlorophyll a concentrations suggest that food availability may limit growth rate in this tropical ecosystem.

  17. Population Growth Types in India, 1961-71

    ERIC Educational Resources Information Center

    Chakravarti, A. K.

    1976-01-01

    An effective means of cartographic representation of India's population growth and its spatial characteristics is the focus of this paper. A population growth index and population growth types are discussed. (Author/ND)

  18. Generalized Verhulst Laws for Population Growth

    Microsoft Academic Search

    Robert Zwanzig

    1973-01-01

    The growth or decay of population of a single species interacting with a large number of other species (or environment) according to the Volterra-Lotka model is investigated. When the environment is initially very close to its equilibrium level, the growth of a single species follows a generalized Verhulst law, containing hereditary effects. The derivation, modeled on statistical mechanical theories of

  19. Delay eect in models of population growth

    Microsoft Academic Search

    Dang Vu Giang; Yongwimon Lenbury; Thomas I. Seidman

    First, we systematize earlier results on the global stability of the model ? x + µx = f(x(· )) of population growth. Second, we investigate the eect of delay on the asymptotic behavior when the nonlinearity f is a unimodal function. Our results can be applied to several population models (7, 9-13) because the function f does not need to

  20. Population Growth and Earth's Human Carrying Capacity

    Microsoft Academic Search

    Joel E. Cohen

    1995-01-01

    Earth's capacity to support people is determined both by natural constraints and by human choices concerning economics, environment, culture (including values and politics), and demography. Human carrying capacity is therefore dynamic and uncertain. Human choice is not captured by ecological notions of carrying capacity that are appropriate for nonhuman populations. Simple mathematical models of the relation between human population growth

  1. A population growth model forced by random, episodic disturbances

    NASA Astrophysics Data System (ADS)

    Peckham, S. D.

    2011-12-01

    As a first step to quantify and better understand the nature of thresholds in ecosystems, a prototype population dynamics model has been developed and analyzed for the case where a population is subjected to random, episodic disturbances. This model assumes that disturbances occur at random times (following a Poisson event process) and have random magnitudes that determine the fraction of the population that survives the disturbance. Disturbances may be events such as fire, drought, disease or infestation. Between disturbances, the model assumes that population growth is deterministic and can be modeled by an exponential or logistic equation. The model is characterized by time, t, and four other parameters: the initial population size, N0, the per capita growth rate, r, the expected number of disturbance events per unit time, ? , and ? = E(X), where X is the random fraction (between 0 and 1) of the population that survives a given disturbance. What is nice about this simple, stochastic model is that it is mathematically tractable and clearly exhibits threshold behavior that can be computed explicitly in terms of the model parameters. In particular, the long-term behavior of the model is characterized by an easily-computed indicator that is a function of the model parameters. Whenever the model parameters are such that this indicator is less than zero, the expected value of the random population size declines over time and is unsustainable. But whenever it is greater than zero, the expected population size grows, despite the random disturbances. The case where the indicator is zero therefore represents a type of critical threshold for this problem that determines whether or not the population is likely to survive the disturbances. A number of analytic results will be presented along with numerical results from a large number of simulations.

  2. Development of a chemically defined minimal medium for the exponential growth of Leuconostoc mesenteroides ATCC8293.

    PubMed

    Kim, Yu Jin; Eom, Hyun-Ju; Seo, Eun-Young; Lee, Dong Yup; Kim, Jeong Hwan; Han, Nam Soo

    2012-11-01

    Leuconostoc mesenteroides is a heterofermentative Grampositive bacterium that plays key roles in fermentation of foods such as kimchi, sauerkraut, and milk, leading to the production of various organic acids and aromatic compounds. To study the microbiological and genomic characteristics of L. mesenteroides, we have developed a new chemically defined minimal medium by using the single omission technique. During the exponential cell growth, this species required glutamine, methionine, valine, and nicotinic acid as essential nutrients and 8 amino acids (arginine, cysteine, histidine, leucine, phenylalanine, proline, threonine, and tryptophan), 5 vitamins (ascorbic acid, folic acid, inosine, calcium panthothenate, and thiamine), and others (manganese, magnesium, adenine, uracil, and Tween 80) as supplemental nutrients. This medium is useful to study the metabolic characteristics of L. mesenteroides and to explain its role in food fermentation. PMID:23124343

  3. Simulating Population Growth and Regulation

    ERIC Educational Resources Information Center

    Moore, Paul J.; Holt, Elvis J.

    1973-01-01

    Describes a simple manual simulation exercise used in a college sophomore course in environmental biology. Demonstrates ways in which biotic potential and other physiological and behavioral characteristics of living organisms may interact with environmental factors to produce the kind of population behavior actually observed in the real world. (JR)

  4. Empower Women, Save the Planet? Science, Strategy, and Population-Environment Advocacy

    E-print Network

    Sasser, Jade

    2012-01-01

    how the “exponential growth” of population, food productionpopulation in imminent crisis, by codifying exponential growthexponential growth of humankind”. (Whitty 2010: 27) Scientific American published a special issue on population growth

  5. Five proposals re China's population growth control.

    PubMed

    Liu, Z; Wu, C; Lin, F

    1983-01-01

    China's population was 540 million in 1949. By the end of 1978 the population will reach 960 million, representing a 2% average annual growth rate. High population growth 1) is costly, 2) makes finding employment difficult, since there is little still land still to be reclaimed and agricultural productivity cannot be upgraded if backward farming techniques are used simply to employ more people, and 3) reduces the quality of material and cutural life. Nearly half of consumer funds accumulated in 1949-1977 was spent to provide basic needs for China's 600 million people. Housing has especially suffered: average per capita living space is only 2 square meters in some cities. With over 100 million primary school children and tens of millions in secondary schools, education funds must be allocated to the lower grades, to higher education's detriment. Each generation's age structure determines the next generation's reproduction scale and speed. This historical principle leads to the following: 1) population growth will continue to be vigorous given growth at a 2% rate, or if a percentage of rural (30%) and urban (10%) couples continue to have more than 2 children, or if every couple only has 2 children; 2) population stagnation requires continuous, persistent efforts, abolishing 2 or more children and encouraging one child per couple. Stagnation can be reached by 2008, with 1,200 million people. Political and ideological education combined with effective economic measures must solve the population problem. 5 strong measures must be taken: 1) economic policies and incentives should assist couples with one or no child, 2) every means should be used to communicate the population problem to the people, 3) population control should be part of the national economy program, 4) 3 births should be prohibited and one child per couple advocated, and 5) a permanent "population committee" should be established to insure ongoing population programs, policies, study, and evaluation. PMID:12313973

  6. Cell wall mannoproteins during the population growth phases in Saccharomyces cerevisiae

    Microsoft Academic Search

    E. Valentín; E. Herrero; H. Rico; F. Miragall; R. Sentandreu

    1987-01-01

    Mannoproteins from cell walls of Saccharomyces cerevisiae synthesized at successive stages of the population growth cycle have been solubilized with Zymolyase and subsequently analyzed. The major change along the population cycle concerned a large size mannoprotein material; the size of the newly-synthesized molecules varied from 120,000–500,000 (mean of about 200,000) at early exponential phase to 250,000–350,000 (mean of about 300,000)

  7. Philopatry and Population Growth of Red Kites, Milvus milvus, in Wales

    Microsoft Academic Search

    I. Newton; P. E. Davis; D. Moss

    1994-01-01

    Between 1946 and 1993, the number of territorial red kites, which form an isolated relict population in mid-Wales, has increased from 7 pairs to 113 pairs. Population growth has been approximately exponential at a mean rate of 5% per year. Breeding success was generally poor, but improved from an average of 0.53 young per pair in 1946-1960 to 0.71 young

  8. Modeling Microbial Growth

    NSDL National Science Digital Library

    Ethel D. Stanley (Beloit College; Biology)

    2006-05-20

    Is bacterial growth always exponential? Do bacteria with the fastest rate of growth always have the largest populations? Biota models offer extended opportunities to observe population growth over time. What are the factors that affect growth? Explore continuous, chaotic, and cyclic growth models. * examine the dynamics of growth for populations of virtual bacteria with differing growth rates and carrying capacities

  9. Modeling Population Dynamics Andre M. de Roos

    E-print Network

    Roos, André M. de

    -sexes population growth . . . . . . . . . . . . . . . . . . . . . . . . 17 2.6 Parameters and state variables.1 Describing a population and its environment . . . . . . . . . . . . . . . . . . 7 2.1.1 The population or p-state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.5.1 Exponential population growth . . . . . . . . . . . . . . . . . . . . . . . 15 2

  10. While exponential growth in data is not an unusual story these days, Alan Davis, from the National University of

    E-print Network

    Chaudhuri, Sanjay

    While exponential growth in data is not an unusual story these days, Alan Davis, from the National University of Singapore (NUS) is striving to keep ahead of the avalanche of data produced by instruments at the Centre for Bio Imaging Sciences (CBIS) and the Mechanical Biology Institute (MBI). Mr. Davis

  11. Keynes on population and economic growth.

    PubMed

    Toye, J

    1997-01-01

    This article discusses the evolution of Keynes's thinking on population based on an unpublished paper from 1914, "Is the Problem of Population a Pressing and Important One Now?" The paper is reported to have 39 pages, but in fact there are many missing page numbers. Keynes's "Essays in Biography" (1933) follows the basic structure and much of the verbal detail of the first 16 pages of "Population." Chapter 2 of the "Economic Consequences of the Peace" discusses the key ideas of "Population." The passages in "Population" and Chapter 2 were probably the sources of a fierce controversy in 1923-24 between Keynes and W.H. Beveridge over Keynes' neo-Malthusianism. "Population" was the basis for the three themes that were central to Keynes's writing on population. Keynes's framework shifted from a global perspective in "Population" to a progressively narrower focus in the 1930s on England and Wales. Keynes was stronger in his advocacy of birth control in "Population" compared to later writings. Keynes was concerned about the quality of population but disagreed on the methods of achieving this. Keynes argued that 75% of the world was not subject to Malthusian dynamics, and the other 25% had developed technology to relieve population pressure. "Population" sketches out the rudiments of the welfare implications of the great divide between North and South population growth rates. Keynes assumes that overpopulation in the South will be compensated for by the international market without consideration of income deficits. Keynes argues against pronatalism. The 1933 essay shows Keynes shift away from Malthus as population expert to Malthus as political economist. By 1937, Keynes had recanted and was very aware of the uncertainty of the economy. The author believes that it is unfortunate that this 1913-14 manuscript remains unknown and, if known, misunderstood. PMID:12293644

  12. Stochastic population growth in spatially heterogeneous environments

    E-print Network

    Evans, Steven N; Schreiber, Sebastian J; Sen, Arnab

    2011-01-01

    Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study the following model for population abundances in $n$ patches: the conditional law of $X_{t+dt}$ given $X_t=x$ is such that when $dt$ is small the conditional mean of $X_{t+dt}^i-X_t^i$ is approximately $[x^i\\mu_i+\\sum_j(x^j D_{ji}-x^i D_{ij})]dt$, where $X_t^i$ and $\\mu_i$ are the abundance and per capita growth rate in the $i$-th patch respectivly, and $D_{ij}$ is the dispersal rate from the $i$-th to the $j$-th patch, and the conditional covariance of $X_{t+dt}^i-X_t^i$ and $X_{t+dt}^j-X_t^j$ is approximately $x^i x^j \\sigma_{ij}dt$. We show for such a spatially extended population that if $S_t=(X_t^1+...+X_t^n)$ is the total population abundance, then $Y_t=X_t/S_t$, the vector of patch proportions, converges in law...

  13. Metabolic flux analysis during the exponential growth phase of Saccharomyces cerevisiae in wine fermentations.

    PubMed

    Quirós, Manuel; Martínez-Moreno, Rubén; Albiol, Joan; Morales, Pilar; Vázquez-Lima, Felícitas; Barreiro-Vázquez, Antonio; Ferrer, Pau; Gonzalez, Ramon

    2013-01-01

    As a consequence of the increase in global average temperature, grapes with the adequate phenolic and aromatic maturity tend to be overripe by the time of harvest, resulting in increased sugar concentrations and imbalanced C/N ratios in fermenting musts. This fact sets obvious additional hurdles in the challenge of obtaining wines with reduced alcohols levels, a new trend in consumer demands. It would therefore be interesting to understand Saccharomyces cerevisiae physiology during the fermentation of must with these altered characteristics. The present study aims to determine the distribution of metabolic fluxes during the yeast exponential growth phase, when both carbon and nitrogen sources are in excess, using continuous cultures. Two different sugar concentrations were studied under two different winemaking temperature conditions. Although consumption and production rates for key metabolites were severely affected by the different experimental conditions studied, the general distribution of fluxes in central carbon metabolism was basically conserved in all cases. It was also observed that temperature and sugar concentration exerted a higher effect on the pentose phosphate pathway and glycerol formation than on glycolysis and ethanol production. Additionally, nitrogen uptake, both quantitatively and qualitatively, was strongly influenced by environmental conditions. This work provides the most complete stoichiometric model used for Metabolic Flux Analysis of S. cerevisiae in wine fermentations employed so far, including the synthesis and release of relevant aroma compounds and could be used in the design of optimal nitrogen supplementation of wine fermentations. PMID:23967264

  14. Teaching the Verhulst Model: A Teaching Experiment in Covariational Reasoning and Exponential Growth

    ERIC Educational Resources Information Center

    Castillo-Garsow, Carlos

    2010-01-01

    Both Thompson and the duo of Confrey and Smith describe how students might be taught to build "ways of thinking" about exponential behavior by coordinating the covariation of two changing quantities, however, these authors build exponential behavior from different meanings of covariation. Confrey and Smith advocate beginning with discrete additive…

  15. Stochastic dynamics and logistic population growth

    NASA Astrophysics Data System (ADS)

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations.

  16. Was Malthus Right? Economic Growth and Population Dynamics

    Microsoft Academic Search

    Jesús Fernández-Villaverde

    2001-01-01

    This paper studies the relationship between population dynamics and economic growth. Prior to the Industrial Revolution increases in total output were roughly matched by increases in population. In contrast, during the last 150 years, incre- ments in per capita income have coexisted with slow population growth. Why are income and population growth no longer positively correlated? This paper presents a

  17. The time-profile of cell growth in fission yeast: model selection criteria favoring bilinear models over exponential ones

    PubMed Central

    Buchwald, Peter; Sveiczer, Akos

    2006-01-01

    Background There is considerable controversy concerning the exact growth profile of size parameters during the cell cycle. Linear, exponential and bilinear models are commonly considered, and the same model may not apply for all species. Selection of the most adequate model to describe a given data-set requires the use of quantitative model selection criteria, such as the partial (sequential) F-test, the Akaike information criterion and the Schwarz Bayesian information criterion, which are suitable for comparing differently parameterized models in terms of the quality and robustness of the fit but have not yet been used in cell growth-profile studies. Results Length increase data from representative individual fission yeast (Schizosaccharomyces pombe) cells measured on time-lapse films have been reanalyzed using these model selection criteria. To fit the data, an extended version of a recently introduced linearized biexponential (LinBiExp) model was developed, which makes possible a smooth, continuously differentiable transition between two linear segments and, hence, allows fully parametrized bilinear fittings. Despite relatively small differences, essentially all the quantitative selection criteria considered here indicated that the bilinear model was somewhat more adequate than the exponential model for fitting these fission yeast data. Conclusion A general quantitative framework was introduced to judge the adequacy of bilinear versus exponential models in the description of growth time-profiles. For single cell growth, because of the relatively limited data-range, the statistical evidence is not strong enough to favor one model clearly over the other and to settle the bilinear versus exponential dispute. Nevertheless, for the present individual cell growth data for fission yeast, the bilinear model seems more adequate according to all metrics, especially in the case of wee1? cells. PMID:16566825

  18. The Pessimistic and Optimistic View of Population Growth

    Microsoft Academic Search

    Yingyot Chiaravutthi

    2008-01-01

    Economists are divided over the impact of labor growth on economic growth. According to the pessimistic view, population growth could result in a negative impact on economic growth because an increase in labor could lower the economy's steady state and the labor productivity. On the other hand, the optimists would argue that a rapid population growth quickens the pace at

  19. [World population growth and the food supply].

    PubMed

    Huang, Y

    1982-07-29

    The general trend in the last several hundred years has been that the speed of growth in the food supply exceeds the speed of the population growth. For the time being, 2 major problems still exist. The 1st problem is that food production is still influenced by natural conditions. For example, abnormal weather conditions may cause regional food shortages. The 2nd problem is the imbalance of food consumption by the world population. This phenomenon exists between different social classes as well as between developed and developing countries. According to statistics released by the World Bank, 1 billion suffer from malnutrition today and most of them are in developing countries. In developed countries, about half of their increase in the food supply is for feed grains, and those countries follow the policy of reducing farm land for the purpose of maintaing stabl e grain prices. Up to the present time, grain prices have been unstable, and this has become a rather heavy economic burden for numerous developing countries. Many developing countries are trying to increase grain production by increasing their arable land and promoting their cultivating techniques. However, these countries are facing the problems of finding and adequate water supply, fertilizer, and pesticides. In addition, a rapid population growth in these countries has offset their endeavors in agriculture. In recent years, these counties have realized the necessity of birth control. The world population growth rate has decreased from 2% to about 1.7% in 1981. Birth control and an increase in the food supply will bring new hope to the world's problems of overpopulation and food supply. PMID:12265442

  20. On growth and dispersal of population.

    PubMed

    Puu, T

    1989-10-01

    In his unpublished Master's thesis of 1921, the young Hotelling invented an ingenious model of population growth and diffusion. The contribution remained widely unknown until Waldo Tobler and Alan Wilson edited it as an article in 1978. Not even then did it trigger any outburst of contributions. Meanwhile, in 1951, Skellam invented the same model for non-human populations. Unlike in economics, it was a great success in ecology. In a recent contribution, Skellam is named Father of Ecological Diffusion and more than 1000 articles on the subject are listed. There were many attempts at solving the equation, but none were quite successful. The Hotelling and Skellam models both assumed a given saturation population that nature could support. In 1985 the present author suggested that an explicit production function be introduced in the Hotelling model, as a man produces his own means of subsistence. Moreover, it was proposed that diffusion be related to spatial differences in per capita productivity, rather than to those in population density. The present contribution is a rejoinder. It is shown that the stationary solutions to the original Hotelling model are periodic and dip into negative populations, whereas this is avoided by the modified model suggested. It can thus be used to show how agglomerative structures may evolve. PMID:12282360

  1. World Population: Fundamentals of Growth. Student Chartbook. Third Edition.

    ERIC Educational Resources Information Center

    Kent, Mary Mederios

    This booklet is designed for K-12 students and educators to learn about world population growth factors. Data are shown through charts and graphs with brief explanations. The booklet contains: (1) "World Population Growth and Regional Distribution through History"; (2) "Population Growth through Natural Increase"; (3) "Effect of Migration on…

  2. The present value of population growth in the western world

    Microsoft Academic Search

    J. L. Simon

    1983-01-01

    In conventional steady-state growth theory with technical progress exogenous, faster population growth causes lower consumption. This conclusion has influenced national policies. With technical progress endogenous, however, higher population growth causes higher consumption. Steady-state equilibrium analysis is not appropriate for policy decisions, though. Rather, appropriate analysis compares two or more growth rates beginning from equal initial positions, with comparison of the

  3. Growth of Juniperus and Potentilla using Liquid Exponential and Controlled-release Fer til iz ers

    Microsoft Academic Search

    R. Kasten Dumroese

    Juniperus scopularum Sarg. (Rocky Mountain juniper) and Potentilla fruticosa L. 'Gold Drop? (gold drop po ten til la) plants grown in containers had sim i lar or bet ter morphology, higher nitrogen con cen tra tions and contents, and high er N-use ef ficien cy when grown with liquid fertilizer ap plied at an exponentially in creas ing rate as

  4. Living bacteria rheology: population growth, aggregation patterns, and collective behavior under different shear flows.

    PubMed

    Patrício, P; Almeida, P L; Portela, R; Sobral, R G; Grilo, I R; Cidade, T; Leal, C R

    2014-08-01

    The activity of growing living bacteria was investigated using real-time and in situ rheology-in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus-strain COL and its isogenic cell wall autolysis mutant, RUSAL9-were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage. PMID:25215771

  5. Lack of synchronization between iron uptake and cell growth leads to iron overload in Saccharomyces cerevisiae during post-exponential growth modes

    PubMed Central

    Park, Jinkyu; McCormick, Sean P.; Chakrabarti, Mrinmoy; Lindahl, Paul A.

    2014-01-01

    Fermenting cells growing exponentially on rich (YPAD) medium transitioned to a slow-growing state as glucose levels declined and their metabolism shifted to respiration. During exponential growth, Fe import and cell growth rates were matched, affording an approximately invariant cellular Fe concentration. During the transitionary period, the high-affinity Fe import rate declined slower than the cell growth rate declined, causing Fe to accumulate, initially as FeIII oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once in slow-growth mode, Fe import and cell growth rates were again matched, and the cellular Fe concentration was again approximately invariant. Fermenting cells grown on minimal medium (MM) grew more slowly during exponential phase and transitioned to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in stationary state. Fe initially accumulated as nanoparticles and high-spin FeII species, but vacuolar FeIII also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more ROS damage than younger cells, suggesting that Fe concentration alone does not accurately predict the extent of ROS damage. The mode and rate of growth at the time of harvesting dramatically affected cellular Fe content. A mathematical model of Fe metabolism in a growing cell was developed. The model included Fe import via a regulated high-affinity pathway and an unregulated low-affinity pathway. Fe import from the cytosol into vacuoles and mitochondria, and nanoparticle formation were also included. The model captured essential trafficking behavior, demonstrating that cells regulate Fe import in accordance with their overall growth rate and that they misregulate Fe import when nanoparticles accumulate. The lack of regulation of Fe in yeast is perhaps unique compared to the tight regulation of other cellular metabolites. This phenomenon likely derives from the unique chemistry associated with Fe nanoparticle formation. PMID:24344915

  6. Approximate models for the study of exponential changed quantities: Application on the plasma waves growth rate or damping

    SciTech Connect

    Xaplanteris, C. L., E-mail: cxaplanteris@yahoo.com [Plasma Physics Laboratory, IMS, NCSR “Demokritos”, Athens, Greece and Hellenic Army Academy, Vari Attica (Greece); Xaplanteris, L. C. [School of Physics, National and Kapodistrian University of Athens, Athens (Greece)] [School of Physics, National and Kapodistrian University of Athens, Athens (Greece); Leousis, D. P. [Technical High School of Athens, Athens (Greece)] [Technical High School of Athens, Athens (Greece)

    2014-03-15

    Many physical phenomena that concern the research these days are basically complicated because of being multi-parametric. Thus, their study and understanding meets with big if not unsolved obstacles. Such complicated and multi-parametric is the plasmatic state as well, where the plasma and the physical quantities that appear along with it have chaotic behavior. Many of those physical quantities change exponentially and at most times they are stabilized by presenting wavy behavior. Mostly in the transitive state rather than the steady state, the exponentially changing quantities (Growth, Damping etc) depend on each other in most cases. Thus, it is difficult to distinguish the cause from the result. The present paper attempts to help this difficult study and understanding by proposing mathematical exponential models that could relate with the study and understanding of the plasmatic wavy instability behavior. Such instabilities are already detected, understood and presented in previous publications of our laboratory. In other words, our new contribution is the study of the already known plasmatic quantities by using mathematical models (modeling and simulation). These methods are both useful and applicable in the chaotic theory. In addition, our ambition is to also conduct a list of models useful for the study of chaotic problems, such as those that appear into the plasma, starting with this paper's examples.

  7. Cosmic history of viable exponential gravity: Equation of state oscillations and growth index from inflation to dark energy era

    E-print Network

    Kazuharu Bamba; Antonio Lopez-Revelles; R. Myrzakulov; S. D. Odintsov; L. Sebastiani

    2012-11-13

    A generic feature of viable $F(R)$ gravity is investigated: It is demonstrated that during the matter dominated era the large frequency oscillations of the effective dark energy may influence the behavior of higher derivatives of the Hubble parameter with the risk to produce some singular unphysical solutions at high redshift. This behavior is explicitly analyzed for realistic $F(R)$ models, in particular, exponential gravity and a power form model. To stabilize such oscillations, we consider the additional modification of the models via a correction term which does not destroy the viability properties. A detailed analysis on the future evolution of the universe and the evolution history of the growth index of the matter density perturbations are performed. Furthermore, we explore two applications of exponential gravity to the inflationary scenario. We show how it is possible to obtain different numbers of $e$-folds during the early-time acceleration by making different choices of the model parameters in the presence of ultrarelativistic matter, which destabilizes inflation and eventually leads to the exit from the inflationary stage. We execute the numerical analysis of inflation in two viable exponential gravity models. It is proved that at the end of the inflation, the effective energy density and curvature of the universe decrease and thus a unified description between inflation and the $\\Lambda$CDM-like dark energy dominated era can be realized.

  8. Population Growth and Poverty in the Developing World.

    ERIC Educational Resources Information Center

    Birdsall, Nancy

    1980-01-01

    The link between rapid population growth and the absolute poverty which currently afflicts 780 million people in developing countries (excluding China and other centrally planned economies) is examined. As a result of rapid population growth, many countries suffer slow per capita income growth, a lack of progress in reducing income inequality, and…

  9. Rapid Population Growth-Cause or Result of Global Problems?

    ERIC Educational Resources Information Center

    Schwartz, Richard H.

    Explosive population growth is a symptom of the world's unjust and inequitable social, political, and economic conditions. The current rate of growth is staggering, particularly in the cities of the underdeveloped countries. While some progress has been made in slowing population growth, several factors still contribute to its momentum. One of…

  10. Economic Development and the Timing and Components of Population Growth

    Microsoft Academic Search

    David E. Bloom; Richard B. Freeman

    1987-01-01

    This paper examines the relationship between population growth and economic growth in developing countries from 1965 to 1985. Our results indicate that developing countries were able to shift their labor force from low-productivity agriculture to the higher-productivity industry and service sectors, and to increase productivity within those sectors, despite the rapid growth of their populations. We also find that at

  11. Closed form solutions to a generalization of the Solow growth model

    Microsoft Academic Search

    Erick José Limas Maldonado; Juan Gabriel Brida

    2005-01-01

    The Solow growth model assumes that labor force grows exponentially. This is not a realistic assumption because, exponential growth implies that population increases to infinity as time tends to infinity. In this paper we propose replacing the exponential population growth with a simple and more realistic equation - the Von Bertalanffy model. This model utilizes three hypotheses about human population

  12. Closed form solutions to a generalization of the Solow growth model

    Microsoft Academic Search

    Juan Gabriel; Bridaand Erick; José Limas Maldonadoy

    The Solow growth model assumes that labor force grows exponentially. This is not a realistic assumption because, exponential growth implies that population increases to in…nity as time tends to in…nity. In this paper we propose replacing the exponential population growth with a simple and more realistic equation - the Von Bertalany model. This model utilizes three hypotheses about human population

  13. INVESTIGATION Population Growth Inflates the Per-Individual

    E-print Network

    Keinan, Alon

    INVESTIGATION Population Growth Inflates the Per-Individual Number of Deleterious Mutations University, Ithaca, New York 14853 ABSTRACT This study addresses the question of how purifying selection operates during recent rapid population growth such as has been experienced by human populations

  14. Beijing moves to curb population growth.

    PubMed

    Pao, T K

    Education and incentives are being used to encourage a "one-child for one-family" campaign in Beijing. The goal is to reduce its population growth rate to 5%/1000 by 1985. Parents who have only child will receive a certificate entitling the only child to preferential treatment for nursery or kindergarten and medical care. 1-child families will receive an annual bonus of 60 yuan. Those who have more than 2 children will be taxed a minimum of 10% of salaries. Single, childless people will receive their full salaries as pensions on retirement. All urban families will receive the same housing space no matter what size the family. The same will be true for the size of small plots of land parcelled out for private use in the rural suburban area. Sterilization operations are available for those who wish them. Parents with 1 child who have such operations can have their tubes rejoined free of charge if their child is disabled or dies. The average growth rate for China projected for 1978-1000 is 1.2%. PMID:12309651

  15. Recent differential population growth in Sumatra: 1961–71

    Microsoft Academic Search

    William A Withington

    1980-01-01

    Sumatran population growth and influencesSumatra, Indonesia's large western Outer Island region, had general, urban and rural rates of population growth during 1961–71 as much as 50% or higher than those for the remainder of Indonesia. The rapid population growth in Sumatra, continuing into the later 1970s, has been associated with a variety of influences. Among these were: 1. New or

  16. Transition to independence by subadult beavers (Castor canadensis) in an unexploited, exponentially growing population

    USGS Publications Warehouse

    DeStefano, S.; Koenen, K.K.G.; Henner, C.M.; Strules, J.

    2006-01-01

    We conducted a 4-year study of beavers Castor canadensis to compare the movements, survival and habitat of adults established in existing colonies to juveniles dispersing to new sites in a region with high beaver densities along a suburban-rural gradient. Estimates of annual survival were high for adult and juvenile beavers. Of nine known mortalities, seven (78%) were juveniles. Mortalities occurred during spring-summer, and none during fall-winter. There was a trend toward higher-to-lower survival along the suburban-rural gradient, respectively. Human-induced mortality (e.g. trapping and shooting) was higher in rural areas, whereas nonhuman-induced mortality (e.g. disease, accidents) was higher in suburban areas. Fifteen (14 subadults and one adult) beavers moved from natal colonies to other areas. The average dispersal distance for subadults was 4.5 km (SE = 1.0) along streams or rivers, or 3.5 km (SE = 0.7) straight-line point-to-point. Most dispersal movements were made in spring (April-June). In two cases, individual subadults made return movements from their dispersal sites back to their natal colonies. Dispersal sites tended to be in smaller, shallower wetlands or streams and in areas with higher overstorey canopy closure compared with natal colonies. Woody vegetation usually preferred by beavers for food tended to be less common at dispersal sites than at natal colonies. In regions with high densities of beaver, dispersing juveniles are likely to attempt to colonize lower quality sites. High densities of beavers also lead to more human-beaver conflicts and, in Massachusetts, the pest control management options in place during the past decade have been ineffectual at controlling population levels. Alternately, in regions with no beavers or very low densities and where reintroductions are being attempted, the landscape matrix surrounding release sites should include suitable sites for dispersing young to establish colonies.

  17. RESEARCH ARTICLE Connecting phenological predictions with population growth

    E-print Network

    Powell, James

    RESEARCH ARTICLE Connecting phenological predictions with population growth rates for mountain pine It is expected that a significant impact of global warming will be disruption of phenology as environmental cues connecting phenology with population growth rates. In this paper we discuss connecting a distributional model

  18. Forecasting global biodiversity threats associated with human population growth

    Microsoft Academic Search

    Jeffrey K. McKee; Paul W. Sciulli; C. David Fooce; Thomas A. Waite

    2004-01-01

    The size and growth of the human population are often cited as key factors in threats to Earth’s biodiversity, yet the extent of their contribution to the endangerment and extinction of other species has remained unclear. Moreover, it could be valuable to know what additional threats may arise from continued human population growth. Here we quantify a model of the

  19. Pattern of variation in avian population growth rates.

    PubMed Central

    Saether, Bernt-Erik; Engen, Steinar

    2002-01-01

    A central question in population ecology is to understand why population growth rates differ over time. Here, we describe how the long-term growth of populations is not only influenced by parameters affecting the expected dynamics, for example form of density dependence and specific population growth rate, but is also affected by environmental and demographic stochasticity. Using long-term studies of fluctuations of bird populations, we show an interaction between the stochastic and the deterministic components of the population dynamics: high specific growth rates at small densities r(1) are typically positively correlated with the environmental variance sigma(e)(2). Furthermore, theta, a single parameter describing the form of the density regulation in the theta-logistic density-regulation model, is negatively correlated with r(1). These patterns are in turn correlated with interspecific differences in life-history characteristics. Higher specific growth rates, larger stochastic effects on the population dynamics and stronger density regulation at small densities are found in species with large clutch sizes or high adult mortality rates than in long-lived species. Unfortunately, large uncertainties in parameter estimates, as well as strong stochastic effects on the population dynamics, will often make even short-term population projections unreliable. We illustrate that the concept of population prediction interval can be useful in evaluating the consequences of these uncertainties in the population projections for the choice of management actions. PMID:12396511

  20. The systems dynamics of endogenous population growth in a renewable resource-based growth model

    Microsoft Academic Search

    Kerry Krutilla; Rafael Reuveny

    2006-01-01

    This paper evaluates the dynamic effects of adding an endogenous process for human population growth into a renewable resource-based economic growth model. Endogenizing human population growth in a static, constant technology form of the model gives rise to a dynamically complex system, with the possibility of multiple steady states of several types, and unusual comparative static responses to changes in

  1. The Cohort Approach to Population Growth: A Retrospective Decomposition of Growth Rates for Sweden

    Microsoft Academic Search

    Shiro Horiuchi

    1995-01-01

    Demographic changes affect population growth not only during the same period, but also in later years. A method for measuring those later effects is developed in this paper, by adopting a cohort perspective of population growth and decomposing the current growth rate into contributions of past demographic changes. Its application to 210 years of Swedish demographic history indicates that events

  2. Recovering population parameters from a single gene genealogy: an unbiased estimator of the growth rate.

    PubMed

    Maruvka, Yosef E; Shnerb, Nadav M; Bar-Yam, Yaneer; Wakeley, John

    2011-05-01

    We show that the number of lineages ancestral to a sample, as a function of time back into the past, which we call the number of lineages as a function of time (NLFT), is a nearly deterministic property of large-sample gene genealogies. We obtain analytic expressions for the NLFT for both constant-sized and exponentially growing populations. The low level of stochastic variation associated with the NLFT of a large sample suggests using the NLFT to make estimates of population parameters. Based on this, we develop a new computational method of inferring the size and growth rate of a population from a large sample of DNA sequences at a single locus. We apply our method first to a sample of 1,212 mitochondrial DNA (mtDNA) sequences from China, confirming a pattern of recent population growth previously identified using other techniques, but with much smaller confidence intervals for past population sizes due to the low variation of the NLFT. We further analyze a set of 63 mtDNA sequences from blue whales (BWs), concluding that the population grew in the past. This calls for reevaluation of previous studies that were based on the assumption that the BW population was fixed. PMID:21172828

  3. Lost in the ozone: Population growth and ozone in California

    Microsoft Academic Search

    James C. Cramer; Robin P. Cheney

    2000-01-01

    Demographers usually study population and environment in preindustrial settings where “environment” means food, forest, or\\u000a land. California, in contrast, is an advanced industrial state with rapid population growth and complex environmental stresses.\\u000a In this paper I examine the effects of population growth on carbon monoxide (CO) and ozone, the principal ingredient of smog.\\u000a Ozone and CO are monitored at numerous

  4. Propagation of Growth Uncertainty in a Physiologically Structured Population

    E-print Network

    we consider physiologically structured population models that have been widely studied and employedPropagation of Growth Uncertainty in a Physiologically Structured Population H.T. Banks and Shuhua in the literature to model the dynamics of a wide variety of populations. However in a number of cases these have

  5. Population growth and structure in a variable environment

    Microsoft Academic Search

    Uno Wennergren; Jan Landin

    1993-01-01

    When a population experiences temporal changes in the vital rates due to environmental or biotic variation, change is not only expected in the rate of population growth but also in the structure of the population. In this study we present a method for transforming observed patterns (notably how vital rates change with temperature) into functions that can be used in

  6. The influence of nonrandom mating on population growth.

    PubMed

    Schindler, Susanne; Neuhaus, Peter; Gaillard, Jean-Michel; Coulson, Tim

    2013-07-01

    When nonrandom mating alters offspring numbers or the distribution of offspring phenotypes, it has the potential to impact the population growth rate. Similarly, sex-specific demographic parameters that influence the availability of mating partners can leave a signature on the population growth rate. We develop a general framework to explore how mating patterns and sex differences influence the population growth rate. We do this by constructing a two-sex integral projection model to explore ways in which altering the mating behavior from random to nonrandom mating (assortative, disassortative, or selection for size) and altering demographic parameters in one or both sexes (growth, survival, and parental contribution to offspring phenotype) affect the population growth rate. We demonstrate our framework using data from a population of Columbian ground squirrels. Our results suggest that the population growth rate is substantially affected when nonrandom mating is linked to sex differences in demographic parameters or parental contributions to offspring phenotype, but interestingly, the effect of the mating pattern alone is rather small. Our results also suggest that the population growth rate of Columbian ground squirrels would increase with the degree of disassortative mating and with the degree of the mating advantage of large individuals. PMID:23778224

  7. Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat

    E-print Network

    Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat Daniel A. Koster.alon@weizmann.ac.il http://dx.doi.org/10.1016/j.jmb.2012.09.005 Edited by I. B. Holland Abstract The growth behavior conditions on surfaces where their growth is dependent on spatial position, especially in the case of motile

  8. Food Production, Population Growth, and Environmental Quality. Caltech Population Program Occasional Papers, Series 1, Number 7.

    ERIC Educational Resources Information Center

    Groth, Edward, III

    This paper, one in a series of occasional publications, discusses trends in food production and population growth, emphasizing how environmental quality will be affected. The series is intended to increase understanding of the interrelationships between population growth and socioeconomic and cultural patterns throughout the world, and to…

  9. Coagulation, Fragmentation and Growth Processes in a Size Structured Population.

    E-print Network

    Mottram, Nigel

    Coagulation, Fragmentation and Growth Processes in a Size Structured Population. Jacek Banasiak the effects of cell division and aggregration are incorporated by coupling the coagulation- fragmentation in the literature. Key words. semigroups of operators, semilinear Cauchy problem, coagulation, fragmentation, algal

  10. ORIGINAL PAPER Overestimates of maternity and population growth rates

    E-print Network

    Richner, Heinz

    and assessments of population viability. Keywords Maternity rate . Bias . Grizzly bear . Ursus arctos . Growth. Three methods that were described in the study of McLellan (1989) for grizzly bears (Ursus arctos

  11. LETTER Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa populations

    E-print Network

    Hui, Bowen

    by studying small disjunct populations of a colonising species using microsatellite- based parentage analysis to discriminate between long-distance dispersal and local parentage. We studied four populations of PinusLETTER Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa

  12. Optical measurement of cycle-dependent cell growth Mustafa Mira,b,1

    E-print Network

    Bashir, Rashid

    to mammalian cells. We found evidence of exponential growth in Escherichia coli, which agrees very well is mass- dependent and can be approximated by an exponential. quantitative phase imaging | population (exponential growth) (6­12). Each growth pattern carries its own biological significance. If the growth

  13. The New Population Debate: Two Views on Population Growth and Economic Development. Population Trends and Public Policy, Number 7.

    ERIC Educational Resources Information Center

    King, Timothy; Kelley, Allen C.

    Articles representing two views on the issue of rapid population growth and economic development are presented. Although the authors present different perspectives, they agree on many of the fundamentals. For example, both reject alarmism about impending "population explosions" and the use of population as a scapegoat for all Third World ills.…

  14. FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER

    E-print Network

    Rose, Michael R.

    FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER LAURENCE D. MUELLER cannot explain the large fitness depression of these lines. However, the homozygous lines show large. The average relative fitness of the homozygous lines, as determined from the growth rates at the lowest

  15. Parameter Estimates in Differential Equation Models for Population Growth

    ERIC Educational Resources Information Center

    Winkel, Brian J.

    2011-01-01

    We estimate the parameters present in several differential equation models of population growth, specifically logistic growth models and two-species competition models. We discuss student-evolved strategies and offer "Mathematica" code for a gradient search approach. We use historical (1930s) data from microbial studies of the Russian biologist,…

  16. Rural Immigrant Population Growth, 1950-2000: Waves or Ripples?

    Microsoft Academic Search

    Andrew Dust; Peter Orazem; Darin Wohlgemuth

    2008-01-01

    Using U.S. Census data from 1950 to 2000, this paper provides a framework to compare the responses of immigrant and native population growth to the economic incentives offered by rural counties in the Midwest and the South. We find that in marked contrast to traditional destinations for new immigrants such as urban areas or rural California, growth of the immigrant

  17. Differential expression profiles of Streptococcus mutans ftf, gtf and vicR genes in the presence of dietary carbohydrates at early and late exponential growth phases.

    PubMed

    Shemesh, Moshe; Tam, Avshalom; Feldman, Mark; Steinberg, Doron

    2006-09-01

    Dental caries is one of the most common infectious diseases that affects humans. Streptococcus mutans, the main pathogenic bacterium associated with dental caries, produces a number of extracellular sucrose-metabolizing enzymes, such as glucosyltransferases (GTFB, GTFC and GTFD) and fructosyltransferase (FTF). The cooperative action of these enzymes is essential for sucrose-dependent cellular adhesion and biofilm formation. A global response regulator (vicR) plays important roles in S. mutans ftf and gtf expression in response to a variety of stimuli. A real-time reverse-transcription polymerase chain-reaction was used to quantify the relative levels of ftf, gtfB, gtfC, gtfD and vicR transcription of S. mutans in the presence of various dietary carbohydrates: sucrose, D-glucose, D-fructose, D-glucitol (D-sorbitol), D-mannitol and xylitol. Ftf was highly expressed at late exponential phase in the presence of sorbitol and mannitol. GtfB was highly expressed in the presence of all the above carbohydrates except for xylitol at early exponential growth phase and glucose and fructose at late exponential growth phase. Similar to gtfB, the expression of gtfC was also induced with the presence of all the tested carbohydrates except for xylitol at early growth and glucose and fructose at late exponential phase. In addition, no effect of mannitol on gtfC expression at early exponential phase was observed. GtfD was less influenced compared to the gtfB and gtfC, demonstrating enhanced expression especially in the presence of sorbitol, glucose, mannitol and xylitol at early exponential phase and mannitol at late exponential phase. VicR expression was induced only at the presence of xylitol at late exponential phase, and a decrease in expression was recorded at early exponential phase. Our findings show that dietary carbohydrates have a major influence on the transcription of ftf, gtfB, gtfC and gtfD, but less on vicR. Sorbitol and mannitol, which are considered as noncariogenic sugar substitutes, may indirectly affect caries by promoting biofilm formation via enhanced expression of gtfs and ftf. These results suggest regulatory circuits for exopolysaccharide gene expression in S. mutans. PMID:16764842

  18. [Growth comparison among Psammosilene tunicoides populations in tissue culture].

    PubMed

    Yang, Yao-wen; Qian, Zi-gang; Wang, Xiao-jia; Wang, Shi-hui

    2006-02-01

    The comparison between the growth of eight populations from Psammosilene tunicoides at Yunnan Province was made by the tissue culture. The initial results showed out two populations from Yunshanping (Lijiang) and Xiaomoyu (Kunming) was dominant than orthers. It would be regard as one of fine germplasm resources for the culture of Psammosilence tunicoides. PMID:16617774

  19. Population Growth and Economic Development: New Empirical Evidence from Thailand

    Microsoft Academic Search

    Fumitaka Furuoka

    2009-01-01

    Population growth has a substantial impact on economic development. There are two schools of thought regarding this issue. Some researchers maintain that population has a negative impact on economic development while others are convinced that the effect is positive. This paper aims to provide additional evidence by employing the bounds test (Pesaran et al., 2001) to analyse a long-run relationship

  20. Interaction of Population Growth, Industrial Growth and Pollution Control

    Microsoft Academic Search

    Ernest W. Peterson

    1973-01-01

    A model is developed which predicts the level of pollution as a function of time given the rate of waste production and the persistence of the pollutant. In general, waste production is a function of the population density and the degree of industrialization of a society. With pollution control programs it is possible to reduce the per capita waste production

  1. Troublesome trends: population growth, distribution, migration.

    PubMed

    1994-09-01

    The upcoming International Conference on Population and Development and its draft plan of action call for international cooperation in protecting and assisting refugees and displaced persons and in assuring positive consequences in host and origin countries. The draft plan also aims to protect the elderly through enhancing self-reliance and continued work and independent living in their own communities. Social support systems for the elderly must also be strengthened. The document is also concerned with the movement of population to cities and across borders. Recommendations on migration encourage governments to evaluate the impact of economic and environmental policies on population distribution and migration, to promote development of medium-sized urban centers, to encourage rural economic development and placement of industries in rural areas, and to support access to land ownership or use and access to water resources in rural areas. Rural infrastructure and social services need to be improved. Grassroots organizations and cooperatives for establishing credit and marketing products are emphasized. Weak local area management is an obstacle to socioeconomic development, environmental protection, and population distribution. Waste, water, and land management strategies should be adopted. Prevention of the root causes of displacement is particularly important when environmental damage is the consequence or the cause. Women, children, and the elderly who are displaced need protection. Refugee numbers have swelled from 8.5 million in 1985 to 19 million in 1993. Sudden and mass refugee arrivals should be afforded temporary protection until a solution can be found. Conditions must be created for safe and dignified, voluntary repatriation. The social and economic integration of documented, longterm migrants must be assured. PMID:12289932

  2. population prediction 8/13/2007 1 y = 0.0723x -138.55

    E-print Network

    Taylor, Peter

    of growth for biological populations is exponential, simply be- cause the number of births and deaths ought of the class talked about exponential and logistic growth. He fitted a linear trend line to the z-t data. Checking for exponential growth I remind the students at the beginning that the standard or "default" mode

  3. Toxicity of polychlorinated biphenyls (PCBs) to Euglena gracilis: Cell population growth, carbon fixation, chlorophyll level, oxygen consumption, and protein and nucleic acid synthesis

    Microsoft Academic Search

    William G. Ewald; John E. French; Michael A. Champ

    1976-01-01

    Summary Populations ofEuglena gracilis in exponential growth under light were exposed to 2.5, 5.0, 7.5, and 10 ppm of Aroclor 1221. The ID50\\/48 of Aroclor 1221 was estimated to be 4.4 ppm, while Aroclor 1232 tested at 20, 35, 50, and 100 ppm resulted in an ID50\\/48 of 55 ppm. With Aroclor 1242, no inhibiton of growth was observed with

  4. Compound haplotypes at Xp11.23 and human population growth in Eurasia.

    PubMed

    Alonso, S; Armour, J A L

    2004-09-01

    To investigate patterns of diversity and the evolutionary history of Eurasians, we have sequenced a 2.8 kb region at Xp11.23 in a sample of African and Eurasian chromosomes. This region is in a long intron of CLCN5 and is immediately flanked by a highly variable minisatellite, DXS255, and a human-specific Ta0 LINE. Compared to Africans, Eurasians showed a marked reduction in sequence diversity. The main Euro-Asiatic haplotype seems to be the ancestral haplotype for the whole sample. Coalescent simulations, including recombination and exponential growth, indicate a median length of strong linkage disequilibrium, up to approximately 9 kb for this area. The Ka/Ks ratio between the coding sequence of human CLCN5 and its mouse orthologue is much less than 1. This implies that the region sequenced is unlikely to be under the strong influence of positive selective processes on CLCN5, mutations in which have been associated with disorders such as Dent's disease. In contrast, a scenario based on a population bottleneck and exponential growth seems a more likely explanation for the reduced diversity observed in Eurasians. Coalescent analysis and linked minisatellite diversity (which reaches a gene diversity value greater than 98% in Eurasians) suggest an estimated age of origin of the Euro-Asiatic diversity compatible with a recent out-of-Africa model for colonization of Eurasia by modern Homo sapiens. PMID:15469420

  5. A DNA-Binding Peroxiredoxin of Coxiella burnetii Is Involved in Countering Oxidative Stress during Exponential-Phase Growth?

    PubMed Central

    Hicks, Linda D.; Raghavan, Rahul; Battisti, James M.; Minnick, Michael F.

    2010-01-01

    Coxiella burnetii is a Gram-negative, obligate intracellular bacterial pathogen that resides within the harsh, acidic confines of a lysosome-like compartment of the host cell that is termed a parasitophorous vacuole. In this study, we characterized a thiol-specific peroxidase of C. burnetii that belongs to the atypical 2-cysteine subfamily of peroxiredoxins, commonly referred to as bacterioferritin comigratory proteins (BCPs). Coxiella BCP was initially identified as a potential DNA-binding protein by two-dimensional Southwestern (SW) blots of the pathogen's proteome, probed with biotinylated C. burnetii genomic DNA. Confirmation of the identity of the DNA-binding protein as BCP (CBU_0963) was established by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry (MALDI-TOF/TOF MS). Recombinant Coxiella BCP (rBCP) was generated, and its DNA binding was demonstrated by two independent methods, including SW blotting and electrophoretic mobility shift assays (EMSAs). rBCP also demonstrated peroxidase activity in vitro that required thioredoxin-thioredoxin reductase (Trx-TrxR). Both the DNA-binding and peroxidase activities of rBCP were lost upon heat denaturation (100°C, 10 min). Functional expression of Coxiella bcp was demonstrated by trans-complementation of an Escherichia coli bcp mutant, as evidenced by the strain's ability to grow in an oxidative-stress growth medium containing tert-butyl hydroperoxide to levels that were indistinguishable from, or significantly greater than, those observed with its wild-type parental strain and significantly greater than bcp mutant levels (P < 0.05). rBCP was also found to protect supercoiled plasmid DNA from oxidative damage (i.e., nicking) in vitro. Maximal expression of the bcp gene coincided with the pathogen's early (day 2 to 3) exponential-growth phase in an experiment involving synchronized infection of an epithelial (Vero) host cell line. Taken as a whole, the results show that Coxiella BCP binds DNA and likely serves to detoxify endogenous hydroperoxide byproducts of Coxiella's metabolism during intracellular replication. PMID:20173000

  6. Modeling Bacterial Population Growth from Stochastic Single-Cell Dynamics

    PubMed Central

    Molina, Ignacio; Theodoropoulos, Constantinos

    2014-01-01

    A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible. PMID:24928885

  7. Modeling bacterial population growth from stochastic single-cell dynamics.

    PubMed

    Alonso, Antonio A; Molina, Ignacio; Theodoropoulos, Constantinos

    2014-09-01

    A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible. PMID:24928885

  8. Impact of Demographic Distribution and Population Growth Rate on Haplotypic Diversity Linked to a Disease Gene and Their Consequences for the Estimation of Recombination Rate: Example of a French

    Microsoft Academic Search

    Frédéric Austerlitz; Evelyne Heyer

    A disease gene introduced into a rapidly growing population by a single individual remains in strong linkage disequilibrium with the surrounding molecular markers. Mapping strategies taking advantage of this phenomenon allow increased mapping resolution as compared to pedigree analysis. Demographic models underlying these strategies usually assume the population exponential growth approximated by Pois- son distribution of the number of children

  9. Population Growth Patterns of Four Species of Aphelenchoides on Fungi

    PubMed Central

    Perper, Timothy; Petriello, Richard

    1977-01-01

    Qualitative and quantitative differences in population growth patterns of Aphelenchoides rutgersi from Florida, A. sacchari from Jamaica, A. dactylocercus from Great Britain, and A. cibolensis from New Mexico were assessed on 28 species of fungi. The patterns of population growth of A. rutgersi and A. sacchari were statistically similar although not identical, and they differed considerably from those of A. dactylocercus and A. cibolensis. It is suggested that A. rutgersi and A. sacchari, from Florida and Jamaica respectively, may be more closely related to each other than to either A. dactylocercus or A. cibolensis. PMID:19305612

  10. Consequences of increased longevity for wealth, fertility, and population growth

    NASA Astrophysics Data System (ADS)

    Bogojevi?, A.; Balaž, A.; Karapandža, R.

    2008-01-01

    We present, solve and numerically simulate a simple model that describes the consequences of increased longevity for fertility rates, population growth and the distribution of wealth in developed societies. We look at the consequences of the repeated use of life extension techniques and show that they represent a novel commodity whose introduction will profoundly influence key aspects of the economy and society in general. In particular, we uncover two phases within our simplified model, labeled as ‘mortal’ and ‘immortal’. Within the life extension scenario it is possible to have sustainable economic growth in a population of stable size, as a result of dynamical equilibrium between the two phases.

  11. Land tenure, population, and long-run growth

    Microsoft Academic Search

    Dietrich Vollrath

    2012-01-01

    This paper brings together the development literature on land tenure with current research on population and long-run growth.\\u000a Landowners make a decision between fixed rent, fixed wage, and sharecropping contracts to hire tenants to operate their land.\\u000a The choice of tenure contract affects the share of output going to tenants, and within a simple unified growth model, this\\u000a affects the

  12. A stochastic computer model for simulating population growth

    Microsoft Academic Search

    Frank J. Sonleitner

    1977-01-01

    Summary  A model is described for investigating the interactions of age-specific birth and death rates, age distribution and density-governing\\u000a factors determining the growth form of single-species populations. It employs Monte Carlo techniques to simulate the births\\u000a and deaths of individuals while density-governing factors are represented by simple algebraic equations relating survival\\u000a and fecundity to population density. In all respects the model’s

  13. Correlation between PLD repair capacity and the survival curve of human fibroblasts in exponential growth phase: analysis in terms of several parameters

    SciTech Connect

    Fertil, B.; Deschavanne, P.J.; Debieu, D.; Malaise, E.P.

    1988-10-01

    Published data on the in vitro radiosensitivity of 46 nontransformed fibroblasts of different genetic origins studied in plateau phase with immediate or delayed plating were used to investigate to what extent potentially lethal damage repair capacity is related to intrinsic radiosensitivity (i.e., irradiated in exponential growth phase). While most of the survival curve analysis is conducted in terms of D0, Dq, and the mean inactivation dose D, some of the data are also discussed in terms of the linear-quadratic model parameter alpha. Using D it is shown that: (i) the radiosensitivity of human fibroblasts in exponential growth phase does not significantly differ from that of plateau-phase fibroblasts with immediate plating; (ii) the radiosensitivity of plateau-phase cells with delayed plating is correlated to the radiosensitivity of cells with immediate plating: the more radioresistant the cell strain in exponential growth phase, the higher its repair capacity; (iii) the repair capacity of the cell strains is related to their genetic origin. In conclusion, we suggest that the survival curve of growing cells depends on the repair capacity of the cells.

  14. The Population Growth Consequences of Variation in Individual Heterozygosity

    PubMed Central

    Di Fonzo, Martina M. I.; Pelletier, Fanie; Clutton-Brock, T.H.; Pemberton, Josephine M.; Coulson, Tim

    2011-01-01

    Heterozygosity has been associated with components of fitness in numerous studies across a wide range of taxa. Because heterozygosity is associated with individual performance it is also expected to be associated with population dynamics. However, investigations into the association between heterozygosity and population dynamics have been rare because of difficulties in linking evolutionary and ecological processes. The choice of heterozygosity measure is a further issue confounding such studies as it can be biased by individual differences in the frequencies of the alleles studied, the number of alleles at each locus as well as the total number of loci typed. In this study, we first examine the differences between the principal metrics used to calculate heterozygosity using long-term data from a marked population of Soay sheep (Ovis aries). Next, by means of statistical transformation of the homozygosity weighted by loci index, we determine how heterozygosity contributes to population growth in Soay sheep by modelling individual contributions to population growth (pt(i)) as a function of several covariates, including sex, weight and faecal egg count – a surrogate of parasitic nematode burden in the gut. We demonstrate that although heterozygosity is associated with some components of fitness, most notably adult male reproductive success, in general it is only weakly associated with population growth. PMID:21611172

  15. Optimal management strategies to control local population growth or population spread may not be the same.

    PubMed

    Shea, Katriona; Jongejans, Eelke; Skarpaas, Olav; Kelly, Dave; Sheppard, Andy W

    2010-06-01

    The objective of most pest management programs is to "control" the pest species. However, optimal control of local abundance and population growth may require different management strategies than optimal control of spatial spread. We use coupled demographic-dispersal models to address the relative importance of different management approaches to these two main control objectives for the invasive thistle Carduus nutans. The models are parameterized with data from thistle populations in the native (France) and invaded ranges (Australia and New Zealand). We assess a wide range of commonly used management strategies for their absolute and relative impacts on population growth and spread in both invaded-range scenarios. The projected population growth rate in New Zealand is more than twice that in Australia, while the spread rate is more than four times the Australian value. In general, spread and growth are both most strongly affected by the same life cycle transitions; however, in a few cases certain vital rates disproportionately affect either spread or growth. The transition that represents the contribution of large rosettes in one year to the number of large rosettes in the following year (the large rosette-large rosette transition) in Australia is dominated by reproduction (rather than survival) and hence is relatively more important to spread than to population growth. In New Zealand, the small rosette-small rosette transition is also predominantly dispersal-related. However, establishment of small plants from the seed bank contributes more to population growth than spread, as no dispersal is involved. The fine-resolution vital-rate-based modeling approach allows us to identify potentially novel optimal management strategies: approaches that reduce microsite availability show promise for reducing both population growth and spread, while strategies that affect dispersal parameters will affect spread. Additionally, the relative ranking of some biocontrol agents shifts depending on whether control of population growth or population spread is the desired outcome and therefore could alter which of the agents are preferred for release in a new area. The possibility of differences in ranked agent effectiveness has been predicted theoretically, but never before demonstrated using field data. PMID:20597297

  16. Water Quality and Quantity Concerns Population growth, increasing water demands,

    E-print Network

    systems, private water well screening, and soil nutrient management. Water conservation programs of AgriWater Quality and Quantity Concerns Population growth, increasing water demands, contamination issues and drought have placed the state's water supply under tremendous stress. Water demand in Texas

  17. An American Laboratory: Population Growth and Environmental Quality in California.

    ERIC Educational Resources Information Center

    McConnell, Robert

    1993-01-01

    Describes the cumulative impact of rapid population growth, industrial and military activity, agriculture, and motor vehicles on California's environmental and social fabric. Discusses these problems in California as a forecast for the nation and test to consensus-based U.S. representative government. (Author/ MCO)

  18. Population growth, distribution, and size in Latin America

    E-print Network

    Lopez-Carr, David

    LAST TIME · Population growth, distribution, and size in Latin America · Urbanization Problems and Environmental Change in Latin America · 519 million people in 2000 (UN, 2001) · 30 year doubling time, 1970 #12;© T. M. Whitmore Central America: Forest Cover Source: FAO, 2003 #12;© T. M. Whitmore South

  19. Keywords: Deforestation, development, fragmentation, land-use change, population growth.

    E-print Network

    Fried, Jeremy S.

    ; help to cleanse the air and water; supply timber, fuelwood, and other harvested products; serve, reduced long-term timber production possibilities and loss of open space). Socioeconomic drivers of land1 Keywords: Deforestation, development, fragmentation, land-use change, population growth. Forest

  20. The Educational Effects of Rapid Rural Population Growth.

    ERIC Educational Resources Information Center

    Ross, Peggy J.; Green, Bernal L.

    Rapid population growth in rural areas has confronted rural communities and particularly rural educational systems with a number of problems. Sudden, large increases in students crowd school facilities and strain budgets. The different values, attitudes, and orientations toward education of the newcomers act as a catalyst for changes and can cause…

  1. Computer Simulation of the Population Growth (Schizosaccharomyces Pombe) Experiment.

    ERIC Educational Resources Information Center

    Daley, Michael; Hillier, Douglas

    1981-01-01

    Describes a computer program (available from authors) developed to simulate "Growth of a Population (Yeast) Experiment." Students actively revise the counting techniques with realistically simulated haemocytometer or eye-piece grid and are reminded of the necessary dilution technique. Program can be modified to introduce such variables as…

  2. MODELING AGGREGATION AND GROWTH PROCESSES IN AN ALGAL POPULATION MODEL

    E-print Network

    MODELING AGGREGATION AND GROWTH PROCESSES IN AN ALGAL POPULATION MODEL: ANALYSIS AND COMPUTATIONS AZMY S. ACKLEH and BEN G. FITZPATRICK Department of Mathematics and Center for Research in Scientific simulation of an algal aggregation model. The numerical algorithm is then used to examine the basic model

  3. Matrix analysis of interregional population growth and distribution

    Microsoft Academic Search

    Andrei Rogers

    1967-01-01

    Among available operational methods for analyzing and forecasting population growth and change, one may broadly distinguish between those models which are concerned only with total births, deaths and migration from those which focus on the behavior of cohorts disaggregated by age and sex. The former class of models typically are referred to as components-of-change models; the latter have been defined

  4. Determinants of Population Growth in Rajasthan: An Analysis

    E-print Network

    Singh, V V; Sharma, Neetish; Smarandache, Florentin

    2010-01-01

    Rajasthan is the biggest State of India and is currently in the second phase of demographic transition and is moving towards the third phase of demographic transition with very slow pace. However, state's population will continue to grow for a time period. Rajasthan's performance in the social and economic sector has been poor in past. The poor performance is the outcome of poverty, illiteracy and poor development, which co-exist and reinforce each other. There are many demographic and socio-economic factors responsible for population growth. This paper attempts to identify the demographic and socio-economic variables, which are responsible for population growth in Rajasthan with the help of multivariate analysis.

  5. Effect of growth conditions on flow-induced inhibition of population growth of a red-tide dinoflagellate

    Microsoft Academic Search

    Andrew R. Juhl; Vivianna Velazquez; Michael I. Latz

    2000-01-01

    The population growth of some dinoflagellates is known to be reduced by exposure to fluid flow. The red-tide dinoflagellate Lingulodinium polyedrum was used to examine the effect of growth conditions on flow-induced inhibition of population growth. Three factors were tested: time of exposure relative to the light : dark (LD) cycle, illumination level, and culture growth phase (early vs. late

  6. Neighbors' problems, our problems: population growth in Central America.

    PubMed

    Fox, R W

    1990-06-01

    A largely ignored issue, Central America faces its most pressing problem in its soaring population growth, one that is wreaking havoc on its economic and social infrastructures. Rising by a factor of 7, Central America's population -- presently 28.9 million -- is expected to reach 7.7 million by the year 2000, and 62.8 million by 2025. Typical of most of the Third World, Central America's population explosion stems from the fact that while the latter half of the 20th century has seen reductions of mortality rates, brought on by improvements of general health conditions, birth rates have remained excessively high. Despite moderate declines in the birth rate, Central American women still average 3-6 children. These demographic factors pose catastrophic consequences for Central America's natural resources, urban development and labor force. And they also threaten to increase migration to the US. Economic pressures have put great demands on the region's rain forests, exploited both for its resources and cleared away to create farmland. Today, only 40% of the original forest remains, and almost 3% more is destroyed annually. The area's capital cities have seen their populations increase 3-6 fold between 1950 and 1980. This explosion places further demands on already overburdened urban infrastructures, and has led to a mushrooming of squatter settlements. It has also led to a massive increase in the urban labor force which cannot be accommodated by the region's economies, which are in disarray due to falling export commodity earnings, limited natural resources, and scant investment capital. The economic woes could further increase the flow of workers to the US (15-20% of El Salvador's total population has already filed to the US). Historically, the region had attempted to offset population growth through economic development, but such expectations were not met, especially with the economic decline that wiped out gains made during the 1960s and 70s. Only recently have the countries acknowledged the need to halt population growth. PMID:12178972

  7. Effect of molecular weight on the exponential growth and morphology of hyaluronan/chitosan multilayers: a surface plasmon resonance spectroscopy and atomic force microscopy investigation.

    PubMed

    Kujawa, Piotr; Moraille, Patricia; Sanchez, Jacqueline; Badia, Antonella; Winnik, Françoise M

    2005-06-29

    The layer-by-layer growth of multilayer assemblies of two polysaccharides, the polyanion hyaluronan (HA) and the polycation chitosan (CH), was investigated using atomic force microscopy (AFM) and surface plasmon resonance (SPR) spectroscopy, with primary emphasis on the effect of the polysaccharide molecular weights on the film thickness and surface morphology. The HA/CH multilayers exhibit an exponential increase of the optical film thickness with the number of deposited bilayers. We show that the multilayer thickness at a given stage depends on the size of both CH, the diffusing polyelectrolyte, and HA, the non-diffusing species. Assemblies (12 bilayers) of high molecular weight polysaccharides (HA, 360,000; CH, 160,000) were twice as thick (approximately 900 nm vs approximately 450 nm) as those obtained with low molecular weight polymers (HA, 30,000; CH, 31,000), as assessed by AFM scratch tests. The exponential growth rate is the same for the high and low molecular weight pairs; the larger film thicknesses observed by SPR and by AFM arising from an earlier onset of the steep exponential growth phase in the case of the high molecular weight pair. In all cases, isolated islets form during the deposition of the first CH layer onto the underlying HA. Upon further film growth, individual islets coalesce into larger vermiculate features. The transition from distinct islands to vermiculate structures depends on the molecular weights of the polysaccharides and the lower molecular weight construct presents larger worm-like surface domains than the high molecular weight pair. PMID:15969601

  8. Population growth capacities and regulatory factors in monospecific cultures of the cladocerans Moina micrura and Diaphanosoma excisum and the copepod Thermocyclops decipiens from Côte d’Ivoire (West Africa)

    Microsoft Academic Search

    Marc Pagano; Lucien Saint-Jean; Robert Arfi; Marc Bouvy; Helguilé Shep

    2000-01-01

    The cladocerans Moina micrura and Diaphanosoma excisum and the copepod Thermocyclops decipiens were studied in microcosms (0.8 m3) under semi-controlled experimental conditions at 25–29 °C for 32 days, by daily sampling after an initial monospecific inoculation. For each species, the time series began with an exponential population growth phase. M. micrura showed a higher daily population growth rate (mean = 1.19)

  9. 1.1exp change 9/5/2007 1 1. Exponential and Logarithm

    E-print Network

    Taylor, Peter

    1.1exp change 9/5/2007 1 1. Exponential and Logarithm 1.1 Exponential growth and decay. Two modes of growth­­additive and multiplicative. Suppose we have a quantity that's growing. Maybe it's the size of an organism or of a population. Or maybe the value of an objet d'art. Our quest will al- ways be to understand

  10. Ecology of Increasing Diseases: Population Growth and Environmental Degradation

    Microsoft Academic Search

    D. Pimentel; S. Cooperstein; H. Randell; D. Filiberto; S. Sorrentino; B. Kaye; C. Nicklin; J. Yagi; J. Brian; J. O’Hern; A. Habas; C. Weinstein

    2007-01-01

    The World Health Organization (WHO) and other organizations report that the prevalence of human diseases during the past decade\\u000a is rapidly increasing. Population growth and the pollution of water, air, and soil are contributing to the increasing number\\u000a of human diseases worldwide. Currently an estimated 40% of world deaths are due to environmental degradation. The ecology\\u000a of increasing diseases has

  11. U. S. population growth as an abstractly-perceived problem

    Microsoft Academic Search

    Larry D. Barnett

    1970-01-01

    Recent public opinion polls report that a majority of Americans consider the nation’s population growth rate to be a “serious”\\u000a problem. Little systematic evidence exists on whether they view the problem as a factor that the individual married couple\\u000a should consider in deciding on family size. A survey of 134 adult women living in a limited-income family housing project\\u000a in

  12. The problem of population and growth: A review of the literature from Malthus to contemporary models of endogenous population and endogenous growth

    Microsoft Academic Search

    Isaac Ehrlich; Francis Lui

    1997-01-01

    This paper deals with the evolution of the literature on the problem of population and growth from the classical period to the recent literature on endogenous growth and development. The ‘problem’ concerns two distinct issues: 1. how to explain the observed covariation of the levels and rates of growth of per capita income and population size over time and space,

  13. 847Parkyn et al.--Crayfish growth and population dynamics Growth and population dynamics of crayfish

    E-print Network

    Waikato, University of

    the differences in the timing of life cycles. Estimates of annual crayfish production (range = 0.8­3.4 g dry increased and longevity has decreased. Keywords crayfish; density; biomass; secondary production; growth in density and biomass in pasture streams, but com- munity composition has changed to favour pollution

  14. 2-DE based proteomic analysis of Saccharomyces cerevisiae wild and K+ transport-affected mutant (trk1,2) strains at the growth exponential and stationary phases.

    PubMed

    Curto, Miguel; Valledor, Luis; Navarrete, Clara; Gutiérrez, Dolores; Sychrova, Hana; Ramos, José; Jorrin, Jesús

    2010-11-10

    By using a 2-DE based workflow, the proteome of wild and potassium transport mutant trk1,2 under optimal growth potassium concentration (50mM) has been analyzed. At the exponential and stationary phases, both strains showed similar growth, morphology potassium content, and Vmax of rubidium transport, the only difference found being the Km values for this potassium analogue transport, higher for the mutant (20mM) than for the wild (3-6mM) cells. Proteins were buffer-extracted, precipitated, solubilized, quantified, and subjected to 2-DE analysis in the 5-8 pH range. More differences in protein content (37-64mgg(-1) cell dry weight) and number of resolved spots (178-307) were found between growth phases than between strains. In all, 164 spots showed no differences between samples and a total of 105 were considered to be differential after ANOVA test. 171 proteins, corresponding to 71 unique gene products have been identified, this set being dominated by cytosolic species and glycolitic enzymes. The ranking of the more abundant spots revealed no differences between samples and indicated fermentative metabolism, and active cell wall biosynthesis, redox homeostasis, biosynthesis of amino acids, coenzymes, nucleotides, and RNA, and protein turnover, apart from cell division and growth. PCA analysis allowed the separation of growth phases (PC1 and 2) and strains at the stationary phase (PC3 and 4), but not at the exponential one. These results are also supported by clustering analysis. As a general tendency, a number of spots newly appeared at the stationary phase in wild type, and to a lesser extent, in the mutant. These up-accumulated spots corresponded to glycolitic enzymes, indicating a more active glucose catabolism, accompanied by an accumulation of methylglyoxal detoxification, and redox-homeostasis enzymes. Also, more extensive proteolysis was observed at the stationary phase with this resulting in an accumulation of low Mr protein species. PMID:20638488

  15. Exponential Probabilities

    NSDL National Science Digital Library

    Anderson-Cook, C.

    The applet, created by Virginia Tech's Department of Statistics, allows you see how probabilities are determined from the exponential distribution. The user determines the mean of the distribution and the limits of probability. Three different probability expressions are available. Click "Calculate" to see the pdf and the cdf. The probability is highlighted in green on the pdf. This is a nice reference tool for anyone studying statistics.

  16. The Solow model in discrete time and decreasing population growth rate

    Microsoft Academic Search

    Juan Gabriel Brida

    2008-01-01

    This paper reformulates the neoclassical Solow-Swan model of economic growth in discrete time by introducing a generic population growth law that verifies the following properties: 1) population is strictly increasing and bounded 2) the rate of growth of population is decreasing to zero as time tends to infinity. We show that in the long run the capital per worker of

  17. RESEARCH ARTICLE Open Access Population growth of Mexican free-tailed bats

    E-print Network

    Russell, Amy L.

    RESEARCH ARTICLE Open Access Population growth of Mexican free-tailed bats (Tadarida brasiliensis population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed and time of onset of population growth in T. b. mexicana. Using an approximate Maximum Likelihood method

  18. Determinism, noise, and spurious estimations in a generalised model of population growth

    Microsoft Academic Search

    Harold P. de Vladar; Ido Pen

    2007-01-01

    We study a generalised model of population growth in which the state variable is population growth rate instead of population size. Stochastic parametric perturbations, modelling phenotypic variability, lead to a Langevin system with two sources of multiplicative noise. The stationary probability distributions have two characteristic power-law scales. Numerical simulations show that noise suppresses the explosion of the growth rate which

  19. Acetate Availability and Utilization Supports the Growth of Mutant Sub-Populations on Aging Bacterial Colonies

    PubMed Central

    Bergman, Jessica M.; Wrande, Marie; Hughes, Diarmaid

    2014-01-01

    When bacterial colonies age most cells enter a stationary phase, but sub-populations of mutant bacteria can continue to grow and accumulate. These sub-populations include bacteria with mutations in rpoB (RNA polymerase ?-subunit) or rpoS (RNA polymerase stress-response sigma factor). Here we have identified acetate as a nutrient present in the aging colonies that is utilized by these mutant subpopulations to support their continued growth. Proteome analysis of aging colonies showed that several proteins involved in acetate conversion and utilization were upregulated during aging. Acetate is known to be excreted during the exponential growth phase but can be imported later during the transition to stationary phase and converted to acetyl-CoA. Acetyl-CoA is used in multiple processes, including feeding into the TCA cycle, generating ATP via the glyoxylate shunt, as a source of acetyl groups for protein modification, and to support fatty acid biosynthesis. We showed that deletion of acs (encodes acetyl-CoA synthetase; converts acetate into acetyl-CoA) significantly reduced the accumulation of rpoB and rpoS mutant subpopulations on aging colonies. Measurement of radioactive acetate uptake showed that the rate of conversion decreased in aging wild-type colonies, was maintained at a constant level in the rpoB mutant, and significantly increased in the aging rpoS mutant. Finally, we showed that the growth of subpopulations on aging colonies was greatly enhanced if the aging colony itself was unable to utilize acetate, leaving more acetate available for mutant subpopulations to use. Accordingly, the data show that the accumulation of subpopulations of rpoB and rpoS mutants on aging colonies is supported by the availability in the aging colony of acetate, and by the ability of the subpopulation cells to convert the acetate to acetyl-CoA. PMID:25275605

  20. Interspecific synchrony of seabird population growth rate and breeding success

    PubMed Central

    Robinson, James P W; Dornelas, Maria; Ojanguren, Alfredo F

    2013-01-01

    Environmental variability can destabilize communities by causing correlated interspecific fluctuations that weaken the portfolio effect, yet evidence of such a mechanism is rare in natural systems. Here, we ask whether the population dynamics of similar sympatric species of a seabird breeding community are synchronized, and if these species have similar exceptional responses to environmental variation. We used a 24-year time series of the breeding success and population growth rate of a marine top predator species group to assess the degree of synchrony between species demography. We then developed a novel method to examine the species group – all species combined – response to environmental variability, in particular, whether multiple species experience similar, pronounced fluctuations in their demography. Multiple species were positively correlated in breeding success and growth rate. Evidence of “exceptional” years was found, where the species group experienced pronounced fluctuations in their demography. The synchronous response of the species group was negatively correlated with winter sea surface temperature of the preceding year for both growth rate and breeding success. We present evidence for synchronous, exceptional responses of a species group that are driven by environmental variation. Such species covariation destabilizes communities by reducing the portfolio effect, and such exceptional responses may increase the risk of a state change in this community. Our understanding of the future responses to environmental change requires an increased focus on the short-term fluctuations in demography that are driven by extreme environmental variability. PMID:23919147

  1. The Effect of Net Migration on the Population-Growth Relationship in Indonesia

    Microsoft Academic Search

    Koji Kotani

    2012-01-01

    This paper empirically examines the relationship between population growth and economic growth in Indonesia by considering lagged fertility and net migration as potential explanatory variables. In this way, we successfully differentiate the short-run and long-run effects of population growth on economic growth. In particular, our focus is on the effect of net migrants on the correlation between the two variables,

  2. Resource and environmental consequences of population and economic growth. [Monograph

    SciTech Connect

    Ridker, R.G.

    1980-01-01

    We need quantitative answers on how much the population growth and economic development strain natural resources and the earth's carrying capacity before effective policies can address specific problems. A series of global projections and in-depth studies of the US, India, Indonesia, Colombia, and the Philippines forecast growth in demand for resources and its environmental effects for several scenarios. The study concludes that the productive use of resources will outweigh availability for several decades, and that research, education, and policies can be transferred from those countries with the greatest capacity for efficient use to those with less productivity to soften regional imbalances. However, a longer time horizon than the traditional five-year planning span is necessary to allow for demographic variables. 10 references, 1 figure, 5 tables. (DCK)

  3. Deer Population

    NSDL National Science Digital Library

    Maryland Virtual High School

    The deer population activity allows students to experiment with the factors which influence population dynamics. In their exploration, they encounter both exponential and logistic growth curves. Students should be familiar with the concepts of birth and death rates, emigration and immigration, predation, limiting factors such as food supply and habitat size, and carrying capacity. The activity is self-paced with extensions provided for those who have extra time.

  4. Social policy and population growth in South-East Asia.

    PubMed

    You Poh Seng Rao, B; Shantakumar, G

    1974-01-01

    Social and population policies are considered for the 10 countries comprising Southeast Asia--Burma, Indonesia, the Khmer Republic, Laos, Malaysia, the Philippines, Singapore, Thailand, North Vietnam, and South Vietnam. All but Singapore have high fertility rates and Burma, Indonesia, the Khmer Republic, Laos and the two Vietnams have high mortality rates also. Government expenditures for education and social security systems is expanding throughout the region and it is hoped that their continued growth will contribute substantially to the effective implementation of population policies. Population policies in the 5 countries which have them are discussed. These are Indonesia, Malaysia, the Philippines, Singapore, and Thailand. It is noted, however, that declaration of policy is but the first step. Strategies and programs differ from one country to the next and depend very much on the stage of development, level of literacy, degree of urbanization, and other factors. Family planning activities generally are endogenous to urban social systems but exogenous to rural social systems. Thus, the rural elite has a large role to play in making population policies an integral part of rural life. The possibility is considered of developing workable incentive packages integrating health, education, and social security benefits with suitable emphasis on fertility reduction. PMID:12307191

  5. [The metropolitan area of Guadalajara. The population growth transition].

    PubMed

    Arroyo Alejandre, J

    1994-01-01

    The Guadalajara metropolitan area, containing approximately three million inhabitants in the municipios of Guadalajara, Zapopan, Tlaquepaque, Tonala, and El Salto, has high rates of population growth due to in-migration, natural increase, and annexation of localities. The average annual rate of growth declined from 6.8% in the 1950s to 2.6% in the 1980s. Despite the decline, which can be considered an indicator of transition, the increase in absolute numbers resulting from a 2.6% rate of growth amounts to 78,000 new inhabitants each year. A change has occurred in recent decades in the migratory patterns and urban spatial distribution of Western Mexico. In-migration to the Guadalajara metropolitan zone has slowed in both absolute and relative terms. Growth of smaller and intermediate sized cities is now more rapid than is that of the metropolitan zone. Surveys in Guadalajara indicate that the proportion of in-migrants from urban areas has increased substantially. Despite the slowing pace of growth, the Guadalajara metropolitan area faces serious problems of housing, land use, transport, and urban infrastructure and services in general. Because of rapid growth and the preponderance of young people among the migrants, the problems are likely to persist for some time. Population projections suggest that 66,000 new jobs will be needed during 1990-95 and 57,000 during 1995-2000, assuming no significant increases in the proportion of women who work. An average of 2500 hectares of land will be needed every five years, nearly equivalent to the total area of the city in 1940. The number of daily trips on urban transit is projected to increase from 6 million at present to 7 million in 2005. The daily load of solid waste is expected to increase from 4000 to 5000 tons in 2005. The economic structure of the city is also changing. Commerce and small and medium-sized manufacturing enterprises have lost their primacy and large national and transnational manufacturing and commercial enterprises have gained ascendancy. The urban development plans for the Guadalajara region were essentially created in the 1970s and do not adequately reflect economic and demographic changes. PMID:12158059

  6. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae)

    PubMed Central

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2014-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (?) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (?) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  7. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae).

    PubMed

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2013-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (?) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (?) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  8. Formulating variable carrying capacity by exploring a resource dynamics-based feedback mechanism underlying the population growth models

    Microsoft Academic Search

    Hsin-i Wu; Amit Chakraborty; Bai-Lian Li; Charles M. Kenerley

    2009-01-01

    Most of the population growth models comprise the concept of carrying capacity presume that a stable population would have a saturation level characteristic. This indicates that the population growth models have a common implicit feature of resource-limited growth, which contributes at a later stage of population growth by forming a numerical upper bound on the population size. However, a general

  9. The problem of population and growth: a review of the literature from Malthus to contemporary models of endogenous population and endogenous growth.

    PubMed

    Ehrlich, I; Lui, F

    1997-01-01

    This review traces the evolution of literature on population and economic growth through the main paradigms suggested to explain the observed covariation of per capita income and population levels (or their rates of growth) over time and space, and determine which public policies will improve the human condition. As the main paradigms evolved, key variables were progressively treated as endogenous (instead of exogenous) to the growth process. After the introduction, section 2 looks at the "classical model" of Malthusian population theory and its refinements. Section 3 identifies empirical data that bears on the secular and cross-sectional association between levels of rates of growth of population and per capita income. The inconsistency of these data with the classical model helps explain declining interest in this model over time and increased interest in a more systematic type of population and growth theory. The beginning of this new interest is traced in section 4 with a look at the "neo-classical growth model" and the reformulated theory of population, which was based on Becker's work on fertility behavior. The first line of inquiry branching from these theoretical works (section 5) treats population as an endogenous variable in static and dynamic settings. The second line of inquiry (section 6) analyzes population and growth within a unified model of growth and development. In section 7, recent studies of key policy issues (population control policies, mandatory social security schemes) are surveyed. The concluding section notes that contemporary research must face the challenge of providing additional insights into longevity as an aspect of economic growth and development and of developing a model of endogenous population and economic growth based on heterogeneous agents. PMID:12292267

  10. A Population Growth Trend Analysis for Neotricula aperta, the Snail Intermediate Host of Schistosoma mekongi, after Construction of the Pak-Mun Dam

    PubMed Central

    Attwood, Stephen W.; Upatham, E. Suchart

    2013-01-01

    Background The Pak-Mun dam is a controversial hydro-power project on the Mun River in Northeast Thailand. The dam is sited in a habitat of the freshwater snail Neotricula aperta, which is the intermediate host for the parasitic blood-fluke Schistosoma mekongi causing Mekong schistosomiasis in humans in Cambodia and Laos. Few data are available which can be used to assess the effects of water resource development on N. aperta. The aim of this study was to obtain data and to analyze the possible impact of the dam on N. aperta population growth. Methodology/Principal Findings Estimated population densities were recorded for an N. aperta population in the Mun River 27 km upstream of Pak-Mun, from 1990 to 2011. The Pak-Mul dam began to operate in 1994. Population growth was modeled using a linear mixed model expression of a modified Gompertz stochastic state-space exponential growth model. The N. aperta population was found to be quite stable, with the estimated growth parameter not significantly different from zero. Nevertheless, some marked changes in snail population density were observed which were coincident with changes in dam operation policy. Conclusions/Significance The study found that there has been no marked increase in N. aperta population growth following operation of the Pak-Mun dam. The analysis did indicate a large and statistically significant increase in population density immediately after the dam came into operation; however, this increase was not persistent. The study has provided the first vital baseline data on N. aperta population behavior near to the Pak-Mun dam and suggests that the operation policy of the dam may have an impact on snail population density. Nevertheless, additional studies are required for other N. aperta populations in the Mun River and for an extended time series, to confirm or refine the findings of this work. PMID:24244775

  11. Age Structure and Growth of Common Carp Populations in Malheur National Wildlife Refuge

    E-print Network

    Koford, Rolf R.

    Age Structure and Growth of Common Carp Populations in Malheur National Wildlife Refuge Principal"isnearingcompletionandtargetedforpublicationinNorthAmericanJournalofFisheriesManagement. Asecondmanuscriptentitled:"Ageandgrowthofcommoncarp(Cyprinuscarpio)inMalheurNationalWildlife Refuge be used to estimate age. Age and growth.--Age and growth varied for carp populations within the refuge

  12. Using a population growth model to simulate response of Plodia interpunctella Hübner to temperature and diet

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Response to temperature and diet are major factors in the potential population growth of Plodia interpunctella Hübner, a damaging pest of many stored products. A population growth model was used to simulate population development on an optimal wheat-based diet and a sub-optimal diet of raisins at 20...

  13. Aggregation and Population Growth: The Relational Logistic Regression and Markov Logic Cases

    E-print Network

    Poole, David

    to a different population size. For example, models from drug studies are acquired from very lim- ited probabilities represent a logistic regression model and show how the population growth of this well-studiedAggregation and Population Growth: The Relational Logistic Regression and Markov Logic Cases David

  14. Population Growth Makes Waves in the Distribution of Pairwise Genetic Differences '

    E-print Network

    Rogers, Alan R.

    Population Growth Makes Waves in the Distribution of Pairwise Genetic Differences ' Alan R. Rogers, Pennsylvania State University Episodes of population growth and decline leave characteristic signatures. The smaller the initial population, the steeper will be the leading face of the wave. The larger the increase

  15. Trophic interactions and population growth rates: describing patterns and identifying mechanisms

    Microsoft Academic Search

    Peter J. Hudson; Andy P. Dobson; Isabella M. Cattadori; David Newborn; Dan T. Haydon; Darren J. Shaw; Tim G. Benton; Bryan T. Grenfell

    2002-01-01

    While the concept of population growth rate has been of central importance in the development of the theory of population dynamics, few empirical studies consider the intrinsic growth rate in detail, let alone how it may vary within and between populations of the same species. In an attempt to link theory with data we take two approaches. First, we address

  16. Evolution of thermal physiology and growth rate between populations of the western fence lizard ( Sceloporus occidentalis )

    Microsoft Academic Search

    Barry Sinervo

    1990-01-01

    Hatchling Sceloporus occidentalis from northern populations (central Oregon) grow more slowly than hatchlings from southern populations (southern California) in nature. In this study, I determine whether this difference in growth rate results from differences in thermal environment and\\/or in thermoregulatory behavior. To determine the degree to which the thermal environment affects growth rate among populations, I reared hatchings from the

  17. Normal and slow growth states of microbial populations in essential resource-based chemostat

    E-print Network

    Wang, Yi

    Normal and slow growth states of microbial populations in essential resource-based chemostat Yi the population will be asymptotic to a steady state of persister cells, or a steady state of normal cells variations in growth characteristics and the inherent heterogeneity of bacterial populations

  18. Grassland ecology and population growth: striking a balance.

    PubMed

    Hou, D; Duan, C; Zhang, D

    2000-06-01

    Degradation of forest and grasslands in western China attributes to the soil erosion and desertification in the country. Researchers have established that the primary reason for the degradation of grasslands is overgrazing, which in turn is caused by a number of factors, including over-population and over-reliance on animal husbandry. In addition, the existing administrative system has also proved ineffective in ensuring sustainable development. On contrary, many local governments even encourage exploitative development of grassland; thus, localities opened up grassland for growing crops in an effort to increase income. According to estimates, degraded grassland accounts for more than one-third of utilizable acreage and another one-third suffers from a profusion of rats and pests. To redress the situation, central government should implement strategies in achieving sustainable development, such as providing banking and tax incentives for the development of the secondary and tertiary industries, and supporting education and training of youths from herding areas. Moreover, government should increase spending on infrastructural construction and ecological preservation. Finally, the family planning program needs to be enforced to control population growth and improve the quality of peoples¿ lives. PMID:12322589

  19. Population growth and a sustainable environment. The Machakos story.

    PubMed

    Mortimore, M; Tiffen, M

    1994-10-01

    The view is taken that population density in the Machakos District (boundaries prior to 1992) of Kenya influenced both environmental conservation and productivity through adaptation of new technologies. Changes in resource management in Machakos District are identified as a shift to cash crop production, experimentation with staple food options, faster tillage, use of fertilizers for enhancing soil fertility, and livestock and tree cultivation. These agricultural changes occurred due to subdivision of landholdings among sons, private appropriation of scarce grazing land, and land scarcity. Intensive practices such as intensive livestock feeding systems and the permanent manuring of fields increased the efficiency of nutrient cycling through plants, animals, and soils. The Akamba custom gave land rights to those who tilled the soil first. Formal land registration occurred after 1968 and favored owners and investors. Small farm investment was made possible through work off-farm and remittances. The value of output per square kilometer at constant prices increased during 1930-87. Cultivated land area also increased during this period, but mostly on poorer quality land. Agricultural changes were enhanced by social and institutional factors such as small family units and greater partnerships between husband and wife. Families pooled resources through collectives. Women played leadership roles. Competing interest groups and organizations have evolved and enabled people to articulate their needs and obtain access to resources at all levels. These institutions increased in strength over time and with increased density. The cost of service provision decreased with greater population numbers. Development of roads and schools facilitated formal education. Population density, market growth, and a generally supportive economic environment are viewed as the factors responsible for changes in Machakos District. Technological change is viewed as an endogenous process of adaptation to new technologies. Changes in Machakos District are viewed as driven by a combination of exogenous and endogenous practices and local initiative. PMID:12290153

  20. Metabolic Profiling and Flux Analysis of MEL-2 Human Embryonic Stem Cells during Exponential Growth at Physiological and Atmospheric Oxygen Concentrations

    PubMed Central

    Titmarsh, Drew; Krömer, Jens O.; Kao, Li-Pin; Nielsen, Lars; Wolvetang, Ernst; Cooper-White, Justin

    2014-01-01

    As human embryonic stem cells (hESCs) steadily progress towards regenerative medicine applications there is an increasing emphasis on the development of bioreactor platforms that enable expansion of these cells to clinically relevant numbers. Surprisingly little is known about the metabolic requirements of hESCs, precluding the rational design and optimisation of such platforms. In this study, we undertook an in-depth characterisation of MEL-2 hESC metabolic behaviour during the exponential growth phase, combining metabolic profiling and flux analysis tools at physiological (hypoxic) and atmospheric (normoxic) oxygen concentrations. To overcome variability in growth profiles and the problem of closing mass balances in a complex environment, we developed protocols to accurately measure uptake and production rates of metabolites, cell density, growth rate and biomass composition, and designed a metabolic flux analysis model for estimating internal rates. hESCs are commonly considered to be highly glycolytic with inactive or immature mitochondria, however, whilst the results of this study confirmed that glycolysis is indeed highly active, we show that at least in MEL-2 hESC, it is supported by the use of oxidative phosphorylation within the mitochondria utilising carbon sources, such as glutamine to maximise ATP production. Under both conditions, glycolysis was disconnected from the mitochondria with all of the glucose being converted to lactate. No difference in the growth rates of cells cultured under physiological or atmospheric oxygen concentrations was observed nor did this cause differences in fluxes through the majority of the internal metabolic pathways associated with biogenesis. These results suggest that hESCs display the conventional Warburg effect, with high aerobic activity despite high lactate production, challenging the idea of an anaerobic metabolism with low mitochondrial activity. The results of this study provide new insight that can be used in rational bioreactor design and in the development of novel culture media for hESC maintenance and expansion. PMID:25412279

  1. The social effect of population growth in the periurban region: The case of Adelaide

    Microsoft Academic Search

    Tania Ford; Y Heriot

    2001-01-01

    The forces driving periurban population growth and change vary, resulting in different scales of periurban development, and\\u000a local differences will undoubtedly modify the social effect of population growth in the periurban zone. The aim of this paper\\u000a is to assess the effect of recent population growth on the social structure of periurban communities. Drawing on results from\\u000a surveys of migration

  2. MECHANISMS OF FLUID SHEAR-INDUCED INHIBITION OF POPULATION GROWTH IN A RED-TIDE DINOFLAGELLATE

    EPA Science Inventory

    Net population growth of some dinoflagellates is inhibited by fluid shear at shear stresses comparable with those generated during oceanic turbulence. Decreased net growth may occur through lowered cell division, increased mortality, or both. The dominant mechanism under various ...

  3. Past, present and future: Immigration, high fertility fuel state's population growth

    E-print Network

    Clark, William A.V.

    2000-01-01

    States, that the California population will slow its growthpopulation growth in tradition- ally rural counties has increased pres- CALIFORNIA AGRICULTURE.JANUARY-FEBRUARY same time, the statepopulation growth is not American nations. new to California. The state

  4. Decomposing variation in population growth into contributions from environment and phenotypes in an age-structured population

    PubMed Central

    Pelletier, Fanie; Moyes, Kelly; Clutton-Brock, Tim H.; Coulson, Tim

    2012-01-01

    Evaluating the relative importance of ecological drivers responsible for natural population fluctuations in size is challenging. Longitudinal studies where most individuals are monitored from birth to death and where environmental conditions are known provide a valuable resource to characterize complex ecological interactions. We used a recently developed approach to decompose the observed fluctuation in population growth of the red deer population on the Isle of Rum into contributions from climate, density and their interaction and to quantify their relative importance. We also quantified the contribution of individual covariates, including phenotypic and life-history traits, to population growth. Fluctuations in composition in age and sex classes ((st)age structure) of the population contributed substantially to the population dynamics. Density, climate, birth weight and reproductive status contributed less and approximately equally to the population growth. Our results support the contention that fluctuations in the population's (st)age structure have important consequences for population dynamics and underline the importance of including information on population composition to understand the effect of human-driven changes on population performance of long-lived species. PMID:21715404

  5. On the Relationship Between Mobility, Population Growth, and Capital Spending in the United States

    Microsoft Academic Search

    Marco Bassetto; Leslie McGranahan

    2011-01-01

    In this paper, we investigate the relationship between public capital spending and population dynamics at the state level. Empirically, we document two robust facts. First, states with faster population growth do not spend more (per capita) to accommodate the needs of their growing population. Second, states whose population is more likely to leave do tend to spend more per capita

  6. Lesson 33: Applications of Exponential Functions

    NSDL National Science Digital Library

    2011-01-01

    The lesson begins with population application problems looking at doubling time, the constant time that it takes for an exponentially modeled population to double. Application problems concerning half life are then discussed.

  7. Population divergence in compensatory growth responses and their costs in sticklebacks

    PubMed Central

    Ab Ghani, Nurul Izza; Merilä, Juha

    2015-01-01

    Compensatory growth (CG) may be an adaptive mechanism that helps to restore an organisms’ growth trajectory and adult size from deviations caused by early life resource limitation. Yet, few studies have investigated the genetic basis of CG potential and existence of genetically based population differentiation in CG potential. We studied population differentiation, genetic basis, and costs of CG potential in nine-spined sticklebacks (Pungitius pungitius) differing in their normal growth patterns. As selection favors large body size in pond and small body size in marine populations, we expected CG to occur in the pond but not in the marine population. By manipulating feeding conditions (viz. high, low and recovery feeding treatments), we found clear evidence for CG in the pond but not in the marine population, as well as evidence for catch-up growth (i.e., size compensation without growth acceleration) in both populations. In the marine population, overcompensation occurred individuals from the recovery treatment grew eventually larger than those from the high feeding treatment. In both populations, the recovery feeding treatment reduced maturation probability. The recovery feeding treatment also reduced survival probability in the marine but not in the pond population. Analysis of interpopulation hybrids further suggested that both genetic and maternal effects contributed to the population differences in CG. Hence, apart from demonstrating intrinsic costs for recovery growth, both genetic and maternal effects were identified to be important modulators of CG responses. The results provide an evidence for adaptive differentiation in recovery growth potential. PMID:25628860

  8. Comparative Study of Population Growth and Agricultural Change: C - Case Study of India. Asian Population Studies Series No. 23.

    ERIC Educational Resources Information Center

    United Nations Economic and Social Commission for Asia and the Pacific, Bangkok (Thailand).

    This report, the third in a series of five reports of the Comparative Study of Population Growth and Agricultural Change, describes a study of the two states of India (Punjaband and Orissa) which attempted to clarify the relationship between population pressure and agricultural change through a time series analysis. This study: (1) outlines trends…

  9. Variation in juvenile growth rates among and within latitudinal populations of the medaka

    Microsoft Academic Search

    Kazunori Yamahira; Kenichi Takeshi

    2008-01-01

    In ectotherms, lower temperatures at high latitudes would theoretically reduce annual growth rates of individuals. If slower\\u000a growth and resulting smaller body size reduce fitness, individuals at high latitudes may evolve compensatory growth. This\\u000a study compares individual growth rates among and within 12 latitudinal populations of the medaka (Oryzias latipes). Growth rates during juvenile stage were measured in a common,

  10. GIS-Based Spatial Allocation Analysis of Population Growth in Regional Water Resource Planning

    Microsoft Academic Search

    F. Benjamin Zhan

    2002-01-01

    Adequate water resource management has become increasingly important in Central Texas because of the rapid population growth and the limited water resources in the region. The Lower Colorado River Authority (LCRA) is involved in water resource management in the region. One task in water resource planning at LCRA is to spatially allocate estimated countywide population growth for a given period

  11. On the relationship between mobility, population growth, and capital spending in the United States

    Microsoft Academic Search

    Marco Bassetto; Leslie McGranahan

    2009-01-01

    In this paper, we assess the empirical relationship between population growth, mobility, and state-level capital spending in the United States. To evaluate the magnitude of the coefficients, we introduce an explicit, quantitative political-economy model of government spending determination, where mobility and population growth generate departures from Ricardian equivalence. Our estimates find strong responses in the level of capital provision per

  12. Population Growth and Environmental Impact: Ideology and Academic Discourse in Israel

    Microsoft Academic Search

    Daniel E. Orenstein

    2004-01-01

    This article addresses the discourse of Israeli academics, policy makers, and environmental activists regarding the environmental implications of population growth in Israel. While there are compelling reasons that population growth should be a prominent topic for local environmental research and discussion, it is rarely considered in environmental campaigns or in the academic literature. I attribute this to the embeddedness of

  13. The effects of regional characteristics on population growth in Korean cities, counties and wards

    Microsoft Academic Search

    Bun Song Lee; Sun Eae Chun; Suk Young Kim

    2007-01-01

    This study identifies the regional characteristics influencing population growth in Korean cities during 1980–2000. Our results indicate that regions followed the fortunes of industries to which regions had been initially exposed. The initial employment share of manufacturing industries positively affects population growth, even though the strength of impact decreases in recent periods, which is consistent with Glaeser et al. [Glaeser,

  14. Evolution of thermal physiology and growth rate between populations of the western fence lizard (Sceloporus occidentalis).

    PubMed

    Sinervo, B

    1990-06-01

    Hatchling Sceloporus occidentalis from northern populations (central Oregon) grow more slowly than hatchlings from southern populations (southern California) in nature. In this study, I determine whether this difference in growth rate results from differences in thermal environment and/or in thermoregulatory behavior. To determine the degree to which the thermal environment affects growth rate among populations, I reared hatchings from the northern and southern populations in a cycling thermal regime in one of three experimental treatments differing in access to radiant heat (6, 9, or 12 h radiant heat; remainder of 24 h at 15°C). I also measured the body temperature that each individual voluntarily selected over the course of the daily activity cycle. Growth rate varied positively with duration of access to radiant heat. Within the three treatments, individual growth rate was positively correlated with body temperature. Moreover, the difference in growth rate between the northern and southern populations was due in part to differences in behavior - individuals from northern populations selected lower body temperatures. I found that significant variation in body temperature was associated with family membership, suggesting that thermal physiology has a genetic basis. Moreover, growth rate was correlated with body temperature among families in each population suggesting a genetic correlation underlies the phenotypic correlations. Thus, genetically based variation in thermal physiology contributes to differences in growth rate among individuals within a population as well as to differences among populations. PMID:22160116

  15. Differential Dependence of Levansucrase and ?-Amylase Secretion on SecA (Div) during the Exponential Phase of Growth of Bacillus subtilis

    PubMed Central

    Leloup, Laurence; Driessen, Arnold J. M.; Freudl, Roland; Chambert, Régis; Petit-Glatron, Marie-Françoise

    1999-01-01

    SecA, the translocation ATPase of the preprotein translocase, accounts for 0.25% of the total protein in a degU32(Hy) Bacillus subtilis strain in logarithmic phase. The SecA level remained constant irrespective of the demand for exoprotein production but dropped about 12-fold during the late stationary phase. Modulation of the level of functional SecA during the exponential phase of growth affected differently the secretion of levansucrase and ?-amylase overexpressed under the control of the sacB leader region. The level of SecA was reduced in the presence of sodium azide and in the div341 thermosensitive mutant at nonpermissive temperatures. Overproduction of SecA was obtained with a multicopy plasmid bearing secA. The gradual decrease of the SecA level reduced the yield of secreted levansucrase with a concomitant accumulation of unprocessed precursor in the cells, while an increase in the SecA level resulted in an elevation of the production of exocellular levansucrase. In contrast, ?-amylase secretion was almost unaffected by high concentrations of sodium azide or by very low levels of SecA. Secretion defects were apparent only under conditions of strong SecA deprivation of the cell. These data demonstrate that the ?-amylase and levansucrase precursors markedly differ in their dependency on SecA for secretion. It is suggested that these precursors differ in their binding affinities for SecA. PMID:10074074

  16. Transitional dynamics in the Solow-Swan growth model with AK technology and logistic population change

    Microsoft Academic Search

    Alberto BUCCI; Luca GUERRINI

    2008-01-01

    This paper offers an alternative way, based on the logistic population growth hypothesis, to yield transitional dynamics in the standard AK model with exogenous savings rate. Within this framework, we show that the dynamics of the capital stock per person and its growth rate can be non-monotonic over time. Moreover, even in the presence of negative growth, the capital stock

  17. Population growth and steady state welfare in an overlapping generations model

    Microsoft Academic Search

    Partha Sen

    2006-01-01

    In one-sector growth models, an increase in the population growth rate raises the economy's growth rate but lowers steady-state welfare (or consumption per capita). I show that in a two-sector overlapping generations model it can raise the steady-state welfare.

  18. Eco-evolutionary dynamics: fluctuations in population growth rate reduce effective population size in chinook salmon.

    PubMed

    Waples, Robin S; Jensen, David W; McClure, Michelle

    2010-03-01

    We empirically assess the relationship between population growth rate (lambda, a parameter central to ecology) and effective population size (N(e), a key parameter in evolutionary biology). Recent theoretical and numerical studies indicate that in semelparous species with variable age at maturity (such as Pacific salmon, many monocarpic plants, and various other species), differences in mean reproductive success among individuals reproducing in different years leads to variation in lambda, and this in turn can reduce N(e). However, this phenomenon has received little empirical evaluation. We examined time series of abundance data for 56 populations of chinook salmon (Onchorhynchus tshawytscha) from the northwestern United States and compared N(e) (calculated from demographic data) with the total number of spawners each generation (NT). Important results include: (1) The mean multigenerational ratio N(e)/N(T) was 0.64 (median = 0.67), indicating that annual variation in lambda reduces effective population size in chinook salmon by an average of approximately 35%. These reductions are independent of, and in addition to, factors that reduce N(e) within individual cohorts (uneven sex ratio and greater-than-random variance in reproductive success). (2) The coefficient of variation of lambda was the most important factor associated with reductions in N(e), explaining up to two-thirds of the variance in N(e)/N(T). (3) Within individual generations, N(e) was lower when there was a negative correlation between annual N(i) and lambda, i.e., when relatively few breeders produced relatively high numbers of offspring. Our results thus highlight an important and little-studied eco-evolutionary trade-off: density-dependent compensation has generally favorable ecological consequences (promoting stability and long-term viability) but incurs an evolutionary cost (reducing N(e) because a few individuals make a disproportionate genetic contribution). (4) For chinook salmon, N(eH) (an estimator based on the harmonic mean number of breeders per year) is generally a good proxy for true N(e) and requires much less data to calculate. PMID:20426347

  19. Habitat heterogeneity affects population growth in goshawk Accipiter gentilis

    Microsoft Academic Search

    Oliver Kruger; Jan Lindstrom

    2001-01-01

    Summary 1. The concept of site-dependent population regulation combines the ideas of Ideal Free Distribution-type of habitat settlement and density dependence in a vital rate mediated by habitat heterogeneity. The latter is also known as habitat heterogeneity hypothesis. Site-dependent population regulation hypothesis predicts that increasing population density should lead to inhabitation of increasingly poor territories and decreasing per capita population

  20. Testing Biopolitics against World Population growth in the 20th century Paul-Andr ROSENTAL

    E-print Network

    Paris-Sud XI, Université de

    of a field of biopolitical action cannot necessarily be reduced to population control if modes of political Connelly's work Fatal #12;2 Misconception: The Struggle to Control World Population (Belknap, Harvard1 Testing Biopolitics against World Population growth in the 20th century Paul-André ROSENTAL

  1. How Do Non-Reproductive Groups Affect Population Growth? Fabio Augusto Milner

    E-print Network

    Milner, Fabio Augusto

    groups is large enough, the population will decline and, eventually, extinguish itself. In contrastHow Do Non-Reproductive Groups Affect Population Growth? Fabio Augusto Milner Abstract We describe several models of population dynamics, both unstructured and gender-structured, that include groups

  2. Aerosol optical thickness trends and population growth in the Indian subcontinent

    Microsoft Academic Search

    Pavel Kishcha; Boris Starobinets; Olga Kalashnikova; Pinhas Alpert

    2011-01-01

    The Indian subcontinent occupies 2.4% of the world land mass and is home to ?17% of the world population. It is characterized by a wide range of population density (P), significant population growth and high levels of air pollution. The quantification of the effect of urbanization on aerosol optical thickness (AOT) trends was carried out by analysing 8-year (March 2000

  3. Effects of climate change on plant population growth rate and community composition change.

    PubMed

    Chang, Xiao-Yu; Chen, Bao-Ming; Liu, Gang; Zhou, Ting; Jia, Xiao-Rong; Peng, Shao-Lin

    2015-01-01

    The impacts of climate change on forest community composition are still not well known. Although directional trends in climate change and community composition change were reported in recent years, further quantitative analyses are urgently needed. Previous studies focused on measuring population growth rates in a single time period, neglecting the development of the populations. Here we aimed to compose a method for calculating the community composition change, and to testify the impacts of climate change on community composition change within a relatively short period (several decades) based on long-term monitoring data from two plots-Dinghushan Biosphere Reserve, China (DBR) and Barro Colorado Island, Panama (BCI)-that are located in tropical and subtropical regions. We proposed a relatively more concise index, Sln?, which refers to an overall population growth rate based on the dominant species in a community. The results indicated that the population growth rate of a majority of populations has decreased over the past few decades. This decrease was mainly caused by population development. The increasing temperature had a positive effect on population growth rates and community change rates. Our results promote understanding and explaining variations in population growth rates and community composition rates, and are helpful to predict population dynamics and population responses to climate change. PMID:26039073

  4. Effects of Climate Change on Plant Population Growth Rate and Community Composition Change

    PubMed Central

    Chang, Xiao-Yu; Chen, Bao-Ming; Liu, Gang; Zhou, Ting; Jia, Xiao-Rong; Peng, Shao-Lin

    2015-01-01

    The impacts of climate change on forest community composition are still not well known. Although directional trends in climate change and community composition change were reported in recent years, further quantitative analyses are urgently needed. Previous studies focused on measuring population growth rates in a single time period, neglecting the development of the populations. Here we aimed to compose a method for calculating the community composition change, and to testify the impacts of climate change on community composition change within a relatively short period (several decades) based on long-term monitoring data from two plots—Dinghushan Biosphere Reserve, China (DBR) and Barro Colorado Island, Panama (BCI)—that are located in tropical and subtropical regions. We proposed a relatively more concise index, Sln?, which refers to an overall population growth rate based on the dominant species in a community. The results indicated that the population growth rate of a majority of populations has decreased over the past few decades. This decrease was mainly caused by population development. The increasing temperature had a positive effect on population growth rates and community change rates. Our results promote understanding and explaining variations in population growth rates and community composition rates, and are helpful to predict population dynamics and population responses to climate change. PMID:26039073

  5. Stochastic stable population growth in integral projection models: theory and application

    Microsoft Academic Search

    Stephen P. Ellner; Mark Rees

    2007-01-01

    Stochastic matrix projection models are widely used to model age- or stage-structured populations with vital rates that fluctuate\\u000a randomly over time. Practical applications of these models rest on qualitative properties such as the existence of a long\\u000a term population growth rate, asymptotic log-normality of total population size, and weak ergodicity of population structure.\\u000a We show here that these properties are

  6. How Do Non-Reproductive Groups Afiect Population Growth?

    Microsoft Academic Search

    Fabio Augusto Milner

    We describe several models of population dynamics, both unstructured and gender-structured, that include groups of individuals who do not reproduce. We analyze the efiect that the non- reproductive group may have on the dynamics of the whole population in terms of the vital rates and the proportion of non-reproductive individuals, and we provide speciflc examples for real populations. Long-term trends

  7. A Photometer for Measuring Population Growth in Yeast.

    ERIC Educational Resources Information Center

    Tatina, Robert; Hartley, Tamela; Thomas, Danita

    1999-01-01

    Describes the construction and use of an inexpensive, portable photometer designed specifically for estimating population sizes in yeast cultures. Suggests activities for use with the photometer. (WRM)

  8. SSE 2300/CE4990: System Dynamics Population Dynamics and Carrying Capacity

    E-print Network

    Mukherjee, Amlan

    be growth forever in a system that has finite resources. · Such a system will initially exhibit exponential feedback the system will show exponential decay. Causal Loop Diagram Underlying Theory System populationSSE 2300/CE4990: System Dynamics Population Dynamics and Carrying Capacity April 12, 2010

  9. Coupled dynamics of energy budget and population growth of tilapia in response to pulsed waterborne copper.

    PubMed

    Chen, Wei-Yu; Lin, Chia-Jung; Ju, Yun-Ru; Tsai, Jeng-Wei; Liao, Chung-Min

    2012-11-01

    The impact of environmentally pulsed metal exposure on population dynamics of aquatic organisms remains poorly understood and highly unpredictable. The purpose of our study was to link a dynamic energy budget model to a toxicokinetic/toxicodynamic (TK/TD). We used the model to investigate tilapia population dynamics in response to pulsed waterborne copper (Cu) assessed with available empirical data. We mechanistically linked the acute and chronic bioassays of pulsed waterborne Cu at the scale of individuals to tilapia populations to capture the interaction between environment and population growth and reproduction. A three-stage matrix population model of larva-juvenile-adult was used to project offspring production through two generations. The estimated median population growth rate (?) decreased from 1.0419 to 0.9991 under pulsed Cu activities ranging from 1.6 to 2.0 ?g L(-1). Our results revealed that the influence on ? was predominately due to changes in the adult survival and larval survival and growth functions. We found that pulsed timing has potential impacts on physiological responses and population abundance. Our study indicated that increasing time intervals between first and second pulses decreased mortality and growth inhibition of tilapia populations, indicating that during long pulsed intervals tilapia may have enough time to recover. Our study concluded that the bioenergetics-based matrix population methodology could be employed in a life-cycle toxicity assessment framework to explore the effect of stage-specific mode-of-actions in population response to pulsed contaminants. PMID:22851126

  10. Introduced Brassica nigra populations exhibit greater growth and herbivore resistance but less tolerance than native populations in the native range.

    PubMed

    Oduor, Ayub M O; Lankau, Richard A; Strauss, Sharon Y; Gómez, José M

    2011-07-01

    Rapid post-introduction evolution has been found in many invasive plant species, and includes changes in defence (resistance and tolerance) and competitive ability traits. Here, we explored the post-introduction evolution of a trade-off between resistance to and tolerance of herbivory, which has received little attention. In a common garden experiment in a native range, nine invasive and 16 native populations of Brassica nigra were compared for growth and defence traits. Invasive populations had higher resistance to, but lower tolerance of, herbivore damage than native populations. Invasive populations survived better and produced more seeds than native ones when released from herbivores; but fitness was equivalent between the regions under ambient herbivory. The invasive populations grew taller, and produced more biomass and lighter seeds than natives, irrespective of insecticide treatment. In addition to supporting the idea of post-introduction rapid evolution of plant traits, our results also contribute to an emerging pattern of both increasing resistance and growth in invasive populations, contrary to the predictions of earlier theories of resistance-growth trade-offs. PMID:21410474

  11. The Distribution of the Kolmogorov-Smirnov, Cramer-von Mises, and Anderson-Darling Test Statistics for Exponential Populations with Estimated Parameters

    Microsoft Academic Search

    Diane L. Evans; John H. Drew; Lawrence M. Leemis

    2008-01-01

    This article presents a derivation of the distribution of the Kolmogorov–Smirnov, Cramer–von Mises, and Anderson–Darling test statistics in the case of exponential sampling when the parameters are unknown and estimated from sample data for small sample sizes via maximum likelihood.

  12. Incoming Population: Where Will the People Live? Coping with Growth.

    ERIC Educational Resources Information Center

    Siegler, Theodore R.

    The guide describes an assessment procedure that can be used by sparsely populated communities located near a potential development to help predict where the incoming population will choose to live and shop. First, a numerical model, the "gravity model," is presented which utilizes community size and the distance from the community to the…

  13. PLANTINSECT INTERACTIONS Inducible Responses in Papaya: Impact on Population Growth Rates of

    E-print Network

    Rosenheim, Jay A.

    PLANTÐINSECT INTERACTIONS Inducible Responses in Papaya: Impact on Population Growth Rates in their shared host plant, papaya. Three key parasites attack papaya foliage in Hawaii: the carmine spider mite, Tetranychus cinnabarinus (Boisduval); the papaya rust mite, Calacarus flagelliseta Fletch- mann

  14. Linking the Population Growth Rate and the Age-at-Death Distribution

    PubMed Central

    Schindler, Susanne; Tuljapurkar, Shripad; Gaillard, Jean-Michel; Coulson, Tim

    2013-01-01

    The population growth rate is linked to the distribution of age at death. We demonstrate that this link arises because both the birth and death rates depend on the variance of age-at-death. This bears the prospect to separate the influences of the age patterns of fertility and mortality on population growth rate. Here, we show how the age pattern of death affects population growth. Using this insight we derive a new approximation of the population growth rate that uses the first and second moments of the age-at-death distribution. We apply our new approximation to 46 mammalian life tables (including humans) and show that it is on par with the most prominent other approximations. PMID:23103877

  15. POPULATION GROWTH AND DEMOCRACY: AN EXTREME VALUE ANALYZES IN ROMANIA'S CASE

    Microsoft Academic Search

    Mihai Ioan MUTASCU

    The paper analyzes empirically, in Romania's case, the relationships between population growth (dependent variable) and the dimensions of democracy (independent variables). The analysis is based on the construction of a linear \\

  16. POPULATION ECOLOGY Divergent compensatory growth responses within species

    E-print Network

    Hutchings, Jeffrey A.

    ; Atlantic salmon (Salmo salar) Nicieza and Metcalfe 1997; brown trout (Salmo trutta) Johnnson and Bohlin growth following food restriction between groups (control, treatment) of two Atlantic salmon (Salmo salar

  17. Ramet population ecology of Panicum virgatum in the field – Competitively random growth of ramets and foraging behavior of ramet populations

    Microsoft Academic Search

    Xinguo Yang; Tianlong Wu; Xu Cheng

    2008-01-01

    The authors investigated the heterogeneous size patterns and dynamic growth of the ramet population of Panicum virgatum, a clonal caespitose plant, limited to the space occupied by a ramet bunch and the time of the ramet yearly life cycle, to understand the ecology of clonal caespitose plants in the field, where the ramet bunch generally consisted of more than one

  18. Population growth of Yellowstone grizzly bears: uncertainty and future monitoring

    E-print Network

    Harris, Richard B.

    (Ursus arctos) in the Greater Yellowstone Ecosystem of the US Rocky Mountains have recently increased, uncertainty, Ursus arctos, Yellowstone Ursus 18(2):168­178 (2007) The grizzly bear (Ursus arctos) population

  19. Cairo's urban growth and strategic master plans in the light of Egypt's 1996 population census results

    Microsoft Academic Search

    Keith Sutton; Wael Fahmi

    2001-01-01

    Cairo's annual growth rate of 2.74%, 1976–86, concerned planners and politicians. The 1996 census revealed a slowing down to 1.6% and a total population of 10.17 million. This regression in Cairo's primacy might suggest some success for the 1970 and 1983 master plans in their aim to divert population growth away from the “green land” to the north and south

  20. Assessing plausible rates of population growth in humpback whales from life-history data

    Microsoft Academic Search

    Alexandre N. ZerbiniPhillip; Phillip J. Clapham; Paul R. Wade

    2010-01-01

    The rate of growth of any population is a quantity of interest in conservation and management and is constrained by biological\\u000a factors. In this study, recent data on life-history parameters influencing rates of population growth in humpback whales,\\u000a including survival, age at first parturition and calving rate are reviewed. Monte Carlo simulations are used to compute a\\u000a distribution of rates

  1. Cell growth and size homeostasis in silico.

    PubMed

    Hu, Yucheng; Zhu, Tianqi

    2014-03-01

    Cell growth in size is a complex process coordinated by intrinsic and environmental signals. In a research work performed by a different group, size distributions of an exponentially growing population of mammalian cells were used to infer cell-growth rate in size. The results suggested that cell growth was neither linear nor exponential, but subject to size-dependent regulation. To explain the observed growth pattern, we built a mathematical model in which growth rate was regulated by the relative amount of mRNA and ribosomes in a cell. Under the growth model and a stochastic division rule, we simulated the evolution of a population of cells. Both the sampled growth rate and size distribution from this in silico population agreed well with experimental data. To explore the model space, alternative growth models and division rules were studied. This work may serve as a starting point to understand the mechanisms behind cell growth and size regulation using predictive models. PMID:24606924

  2. Flower Power: Sunflowers as a Model for Logistic Growth

    ERIC Educational Resources Information Center

    Fernandez, Eileen; Geist, Kristi A.

    2011-01-01

    Logistic growth displays an interesting pattern: It starts fast, exhibiting the rapid growth characteristic of exponential models. As time passes, it slows in response to constraints such as limited resources or reallocation of energy. The growth continues to slow until it reaches a limit, called capacity. When the growth describes a population,…

  3. The singularity is not near: slowing growth of Wikipedia

    Microsoft Academic Search

    Bongwon Suh; Gregorio Convertino; Ed H. Chi; Peter Pirolli

    2009-01-01

    Prior research on Wikipedia has characterized the growth in content and editors as being fundamentally exponential in nature, extrapolating current trends into the future. We show that recent editing activity suggests that Wikipedia growth has slowed, and perhaps plateaued, indicating that it may have come against its limits to growth. We measure growth, population shifts, and patterns of editor and

  4. A non-phenomenological model of competition and cooperation to explain population growth behaviors.

    PubMed

    Ribeiro, Fabiano L

    2015-03-01

    This paper is an extension of a previous work which proposes a non-phenomenological model of population growth that is based on the interactions among the individuals of a population. In addition to what had already been studied—that the individuals interact competitively—in the present work it is also considered that the individuals interact cooperatively. As a consequence of this new consideration, a richer dynamics is observed. For instance, besides getting the population models already reached from the original version of the model (as the Malthus, Verhulst, Gompertz, Richards, Bertalanffy and power-law growth models), the new formulation also reaches the von Foerster growth model and also a regime of divergence of the population at a finite time. An agent-based model is also presented in order to give support to the analytical results. Moreover, this new approach of the model explains the Allee effect as an emergent behavior of the cooperative and competitive interactions among the individuals. The Allee effect is the characteristic of some populations of increasing the population growth rate in a small-sized population. Whereas the models presented in the literature explain the Allee effect with phenomenological ideas, the model presented here explains this effect by the interactions between the individuals. The model is tested with empirical data to justify its formulation. Another interesting macroscopic emergent behavior from the model proposed is the observation of a regime of population divergence at a finite time. It is interesting that this characteristic is observed in humanity's global population growth. It is shown that in a regime of cooperation, the model fits very well to the human population growth data from 1000 AD to nowadays. PMID:25724311

  5. Modeling tradeoffs in avian life history traits and consequences for population growth

    USGS Publications Warehouse

    Clark, M.E.; Martin, T.E.

    2007-01-01

    Variation in population dynamics is inherently related to life history characteristics of species, which vary markedly even within phylogenetic groups such as passerine birds. We computed the finite rate of population change (??) from a matrix projection model and from mark-recapture observations for 23 bird species breeding in northern Arizona. We used sensitivity analyses and a simulation model to separate contributions of different life history traits to population growth rate. In particular we focused on contrasting effects of components of reproduction (nest success, clutch size, number of clutches, and juvenile survival) versus adult survival on ??. We explored how changes in nest success or adult survival coupled to costs in other life history parameters affected ?? over a life history gradient provided by our 23 Arizona species, as well as a broader sample of 121 North American passerine species. We further examined these effects for more than 200 passeriform and piciform populations breeding across North America. Model simulations indicate nest success and juvenile survival exert the largest effects on population growth in species with moderate to high reproductive output, whereas adult survival contributed more to population growth in long-lived species. Our simulations suggest that monitoring breeding success in populations across a broad geographic area provides an important index for identifying neotropical migratory populations at risk of serious population declines and a potential method for identifying large-scale mechanisms regulating population dynamics. ?? 2007 Elsevier B.V. All rights reserved.

  6. Individual and Population Level Variation in Growth Parameters for Steelhead Trout Oncorhynchus mykiss in

    E-print Network

    to growth data for juvenile steelhead trout (Oncorhynchus19 mykiss) from California. We grew fish fromIndividual and Population Level Variation in Growth Parameters for Steelhead Trout Oncorhynchus mykiss in Central California Christopher A. Simon(1), William H. Satterthwaite(1,2), Michael P. Beakes (1

  7. Experimental Design and Estimation of Growth Rate Distributions in Size-Structured Shrimp Populations

    E-print Network

    Experimental Design and Estimation of Growth Rate Distributions in Size-Structured Shrimp-structured shrimp populations and discuss a computational methodology for the design of exper- iments to validate the model and estimate growth rate distributions in shrimp pop- ulations. Parameter estimation findings

  8. Impacts of Climate Change and Population Growth on Water Stress Becky Witte

    E-print Network

    Fay, Noah

    Impacts of Climate Change and Population Growth on Water Stress by Becky Witte Master's Student, Technology and Research Initiative Fund 2011/2012, Water Sustainability Graduate Student Fellowship Program to assess the effects of changed climate and growth using the Water Stress Index as an objective index

  9. Stochastic model for population migration and the growth of human settlements during the Neolithic transition

    E-print Network

    Fedotov, Sergei

    Stochastic model for population migration and the growth of human settlements during the Neolithic and growth of semisedentary foragers and sedentary farmers along a river valley during the Neolithic-delayed theory for the Neolithic transition 7 which involves a hyperbolic correction to the Fisher-KPP equation

  10. CAUSES OF MORTALITY IN CALIFORNIA SEA OTTERS DURING PERIODS OF POPULATION GROWTH AND DECLINE

    Microsoft Academic Search

    James A. Estes; Brian B. Hatfield; Katherine Ralls; Jack Ames

    2003-01-01

    Elevated mortality appears to be the main reason for both sluggish growth and periods of decline in the threatened California sea otter population. We asses- sed causes of mortality from salvage records of 3,105 beach-cast carcasses recov- ered from 1968 through 1999, contrasting two periods of growth with two periods of decline. Overall, an estimated 409640% of the deaths were

  11. Coordination of Gene Expression and Growth-Rate in Natural Populations of Budding Yeast

    E-print Network

    Barkai, Naama

    Coordination of Gene Expression and Growth-Rate in Natural Populations of Budding Yeast Zvi Tamari expression. In the budding yeast, ribosomal-related gene expression correlates with cell growth rate across of twenty-four wild type yeast strains originating from diverse habitats, grown on the pentose sugar

  12. Population growth dynamics of the rotifer Brachionus plicatilis cultured in non-limiting food condition

    Microsoft Academic Search

    M. Yúfera; N. Navarro

    1995-01-01

    Population growth parameters in batch culture of Brachionus plicatilis under a continuous supply of freeze-dried microalgae powder have been determined. Two B. plicatilis strains (L- and S-types) and four microalgae species (Nannochloropsis oculata, Nannochloropsis gaditana, Nannochloris oculata and Tetraselmis suecica) have been tested, establishing the dynamics of growth at different daily food rations. Cultures showed a short lag phase, an

  13. Effect of food waste compost on microbial population, soil enzyme activity and lettuce growth

    Microsoft Academic Search

    Jae-Jung Lee; Ro-Dong Park; Yong-Woong Kim; Jae-Han Shim; Dong-Hyun Chae; Yo-Sup Rim; Bo-Kyoon Sohn; Tae-Hwan Kim; Kil-Yong Kim

    2004-01-01

    The effect of food waste (FW) composted with MS® (Miraculous Soil Microorganisms) was compared with commercial compost (CC) and mineral fertilizer (MF) on bacterial and fungal populations, soil enzyme activities and growth of lettuce in a greenhouse. Populations of fungi and bacteria, soil biomass, and soil enzyme activities in the rhizosphere of FW treatments significantly increased compared to control (CON),

  14. Consistent patterns of maturity and density-dependent growth among populations of walleye

    E-print Network

    Venturelli, Paul

    of walleye (Sander vitreus) from Ontario and Quebec, Canada (mean annual GDD = 1200 to 2300 8CÁdays´ provenant de 416 populations de dore´s jaunes (Sander vitreus) de l'Ontario et du Que´bec, Canada (moyenneConsistent patterns of maturity and density- dependent growth among populations of walleye (Sander

  15. SUBLETHAL NARCOSIS AND POPULATION PERSISTENCE: A MODELING STUDY ON GROWTH EFFECTS

    EPA Science Inventory

    This study of a Daphnia population model suggests that sublethal effects of nonpolar narcotics on growth of individual organisms can result in ultimate extinction of the population at chronic chemical concentrations near the effect concentration that leads to a 50% reduction in i...

  16. Population Growth and Economic Development: Lessons from Selected Asian Countries. Policy Development Studies, Number 10.

    ERIC Educational Resources Information Center

    Mason, Andrew; And Others

    The major findings of a research project on the relationship between population growth and economic development are summarized in this monograph. The study compares recent demographic and economic trends in Japan, Korea, Thailand, and Indonesia to worldwide experience as described by an econometric model of population and development. The study…

  17. Growth and physiological responses to varied environments among populations of Pinus ponderosa

    Microsoft Academic Search

    Jianwei Zhang; Bert M. Cregg

    2005-01-01

    We investigated population responses in physiology, morphology, and growth of mature Pinus ponderosa trees to an environmental gradient across Nebraska, USA. Ten populations from western Nebraska and eastern Wyoming were grown in three 26-year-old provenance tests from the warmest and wettest site in the east (Plattsmouth) to the intermediate site in the middle (Halsey) to the coldest and driest site

  18. Recovering Population Parameters from a Single Gene Genealogy: An Unbiased Estimator of the Growth Rate

    E-print Network

    ,212 mitochondrial DNA (mtDNA) sequences from China, confirming a pattern of recent population growth previously-standing goal of population genetics, which is to quantify the forces that shape varia- tion within the genomes the number of lineages ancestral to a sample depends on these two quantities. In striking contrast

  19. Models and model selection uncertainty in estimating growth rates of endangered freshwater mussel populations

    Microsoft Academic Search

    Yan Jiao; Richard Neves; Jess Jones

    2008-01-01

    Appropriate inference of population status for endangered species is extremely important. Using a single model for estimating population growth rates is typically inadequate for assessing endangered species because inferences based on only one ''best'' model ignore model uncertainty. In this study, the endangered dromedary pearlymussel (Dromus dro- mas) in the Clinch and Powell rivers of eastern Tennessee, USA, was used

  20. Modeling stem cell population growth: incorporating parameters for quiescence, differentiation and apoptosis

    Microsoft Academic Search

    B. M. Deasy; R. J. JankowskiiP; T. R. Payne; J. S. Greenberger; J. Huard

    2002-01-01

    The use of stem cells in cell-mediated therapies or cell transplantation applications will require a controlled, scalable system for expansion of the cells and for control of cellular differentiation. Modeling stem cell population growth is one step towards developing such a system. Stem cell populations are heterogeneous and include cells which are non-mitotic. In particular, stem cells may be quiescent

  1. Population Growth and Sprawl on the Pine Ridge Indian Reservation, South Dakota

    Microsoft Academic Search

    R. L. Campbell

    2006-01-01

    The most important impact on global land cover is human use and development. With the recent population growth occurring on the reservations in South Dakota, especially Pine Ridge Indian Reservation, the towns and agricultural areas of the reservation are undergoing a change. Although urban sprawl certainly is not a consideration on the reservations, the population explosion currently underway has seen

  2. A simple saddlepoint approximation for the equilibrium distribution of the stochastic logistic model of population growth

    Microsoft Academic Search

    James H. Matis; Thomas R. Kiffe; Eric Renshaw; Janet Hassan

    2003-01-01

    The deterministic logistic model of population growth and its notion of an equilibrium ‘carrying capacity’ are widely used in the ecological sciences. Leading texts also present a stochastic formulation of the model and discuss the concept and calculation of an equilibrium population size distribution. This paper describes a new method of finding accurate approximating distributions. Recently, cumulant approximations for the

  3. The Future and Population: What Will a No-Growth Society Be Like? A Teaching Module.

    ERIC Educational Resources Information Center

    Population Reference Bureau, Inc., Washington, DC.

    This teaching module for high school students and adults examines the future of zero population growth in 26 countries by the year 2000. The module contains an essay for students to read, followed by exercises, activities, and discussion questions based on the essay. Objectives include understanding the components of population change, identifying…

  4. Contributions of vital rates to growth of a protected population of American black bears

    E-print Network

    Mitchell, Mike

    have evaluated such contributions of vital rates to l for American black bears (Ursus americanus). We are consistent with predictions from studies on polar bears (U. maritimus) and grizzly bears (U. arctos Carolina, population growth rate, population modeling, sensitivity, Southern Appalachians, Ursus americanus

  5. Life histories of female red squirrels and their contributions to population growth and lifetime fitness

    Microsoft Academic Search

    Andrew G. McADAM; Stan BOUTIN; Ainsley K. SYKES; Murray M. HUMPHRIES

    2007-01-01

    The potential importance of life history traits to population growth rates has been well explored theoretically but has rarely been documented in wild mammals. In this study we used 18 consecutive years of data from a population of North American red squirrels (Tamiasciurus hudsonicus) in the southwest Yukon, Canada, to examine variation in female life history traits and their consequences

  6. LARGE NONLETHAL EFFECTS OF AN INVASIVE INVERTEBRATE PREDATOR ON ZOOPLANKTON POPULATION GROWTH RATE

    Microsoft Academic Search

    Kevin L. Pangle; Scott D. Peacor; Ora E. Johannsson

    2007-01-01

    We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus ,o n zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both

  7. Dynamical Feedbacks between Population Growth and Sociopolitical Instability in Agrarian States

    Microsoft Academic Search

    Peter Turchin

    Most preindustrial states experienced recurrent waves of political collapse and internal warfare. One possible explanation of this pattern, the demographic-structural theory, suggests that population growth leads to state instability and breakdown, which in turn causes population decline. Mathematical models incorporating this mechanism predict sustained oscillations in demographic and political dynamics. Here I test these theoretical predictions with time-series data on

  8. A Dynamic Model of Cognitive Growth in a Population: Spatial Tasks and Conservation

    Microsoft Academic Search

    Shulamith Graus Eckstein

    1999-01-01

    A dynamic model of cognitive growth is developed that is applicable to cross-sectional studies of growth in a population, and that predicts the distribution of scores as a function of age. This model modifies the theory of P. van Geert (1991,Psychological Review,98, 3–53) for the cognitive growth of an individual under limited resources, by taking into account the effect of

  9. The between-population genetic architecture of growth, maturation, and plasticity in Atlantic salmon.

    PubMed

    Debes, Paul Vincent; Fraser, Dylan John; Yates, Matthew; Hutchings, Jeffrey A

    2014-04-01

    The between-population genetic architecture for growth and maturation has not been examined in detail for many animal species despite its central importance in understanding hybrid fitness. We studied the genetic architecture of population divergence in: (i) maturation probabilities at the same age; (ii) size at age and growth, while accounting for maturity status and sex; and (iii) growth plasticity in response to environmental factors, using divergent wild and domesticated Atlantic salmon (Salmo salar). Our work examined two populations and their multigenerational hybrids in a common experimental arrangement in which salinity and quantity of suspended sediments were manipulated to mimic naturally occurring environmental variation. Average specific growth rates across environments differed among crosses, maturity groups, and cross-by-maturity groups, but a growth-rate reduction in the presence of suspended sediments was equal for all groups. Our results revealed both additive and nonadditive outbreeding effects for size at age and for growth rates that differed with life stage, as well as the presence of different sex- and size-specific maturation probabilities between populations. The major implication of our work is that estimates of the genetic architecture of growth and maturation can be biased if one does not simultaneously account for temporal changes in growth and for different maturation probabilities between populations. Namely, these correlated traits interact differently within each population and between sexes and among generations, due to nonadditive effects and a level of independence in the genetic control for traits. Our results emphasize the challenges to investigating and predicting phenotypic changes resulting from between-population outbreeding. PMID:24473933

  10. The Between-Population Genetic Architecture of Growth, Maturation, and Plasticity in Atlantic Salmon

    PubMed Central

    Debes, Paul Vincent; Fraser, Dylan John; Yates, Matthew; Hutchings, Jeffrey A.

    2014-01-01

    The between-population genetic architecture for growth and maturation has not been examined in detail for many animal species despite its central importance in understanding hybrid fitness. We studied the genetic architecture of population divergence in: (i) maturation probabilities at the same age; (ii) size at age and growth, while accounting for maturity status and sex; and (iii) growth plasticity in response to environmental factors, using divergent wild and domesticated Atlantic salmon (Salmo salar). Our work examined two populations and their multigenerational hybrids in a common experimental arrangement in which salinity and quantity of suspended sediments were manipulated to mimic naturally occurring environmental variation. Average specific growth rates across environments differed among crosses, maturity groups, and cross-by-maturity groups, but a growth-rate reduction in the presence of suspended sediments was equal for all groups. Our results revealed both additive and nonadditive outbreeding effects for size at age and for growth rates that differed with life stage, as well as the presence of different sex- and size-specific maturation probabilities between populations. The major implication of our work is that estimates of the genetic architecture of growth and maturation can be biased if one does not simultaneously account for temporal changes in growth and for different maturation probabilities between populations. Namely, these correlated traits interact differently within each population and between sexes and among generations, due to nonadditive effects and a level of independence in the genetic control for traits. Our results emphasize the challenges to investigating and predicting phenotypic changes resulting from between-population outbreeding. PMID:24473933

  11. The almost-sure population growth rate in branching Brownian motion with a quadratic breeding potential

    E-print Network

    Berestycki, J; Harris, J W; Harris, S C

    2009-01-01

    In this note we consider a branching Brownian motion (BBM) on $\\mathbb{R}$ in which a particle at spatial position $y$ splits into two at rate $\\beta y^2$, where $\\beta>0$ is a constant. This is a critical breeding rate for BBM in the sense that the expected population size blows up in finite time while the population size remains finite, almost surely, for all time. We find an asymptotic for the almost sure rate of growth of the population.

  12. Effects of sampling error and temporal correlations in population growth on process variance estimators

    Microsoft Academic Search

    David F. Staples; Mark L. Taper; Brian Dennis; Robert J. Boik

    2009-01-01

    Estimates of a population’s growth rate and process variance from time-series data are often used to calculate risk metrics\\u000a such as the probability of quasi-extinction, but temporal correlations in the data from sampling error, intrinsic population\\u000a factors, or environmental conditions can bias process variance estimators and detrimentally affect risk predictions. It has\\u000a been claimed (McNamara and Harding, Ecol Lett 7:16–20,

  13. A summary of the procedures applied to determine the amount of critical habitat needed for the recovery of the Atlantic salmon Gulf of Maine Distinct Population

    E-print Network

    is a stochastic exponential growth model of population size which is equivalent to a stochastic Leslie;Introduction Statistical methods can be utilized to quantitatively estimate population growth, decline or extinction probabilities for a species. The size of a population and its corresponding growth rate are both

  14. On the structure-bounded growth processes in plant populations.

    PubMed

    Kilian, H G; Kazda, M; Király, F; Kaufmann, D; Kemkemer, R; Bartkowiak, D

    2010-07-01

    If growing cells in plants are considered to be composed of increments (ICs) an extended version of the law of mass action can be formulated. It evidences that growth of plants runs optimal if the reaction-entropy term (entropy times the absolute temperature) matches the contact energy of ICs. Since these energies are small, thermal molecular movements facilitate via relaxation the removal of structure disturbances. Stem diameter distributions exhibit extra fluctuations likely to be caused by permanent constraints. Since the signal-response system enables in principle perfect optimization only within finite-sized cell ensembles, plants comprising relatively large cell numbers form a network of size-limited subsystems. The maximal number of these constituents depends both on genetic and environmental factors. Accounting for logistical structure-dynamics interrelations, equations can be formulated to describe the bimodal growth curves of very different plants. The reproduction of the S-bended growth curves verifies that the relaxation modes with a broad structure-controlled distribution freeze successively until finally growth is fully blocked thus bringing about "continuous solidification". PMID:20574848

  15. County wide employment and population growth: an analysis of the 1980s.

    PubMed

    Clark, D E; Murphy, C A

    1996-05-01

    "Regional scientists remain interested in studying interregional differences in the growth rates of population and employment. Following the earlier work of Carlino and Mills, this paper examines growth trends at the county level in the U.S. during the period 1981-1989. Five major sectors of employment are examined. A partial adjustment model is developed that captures intercounty differences in amenities, business and fiscal conditions, demography, employment structure, and relative location. Some evidence is given that population and employment growth was simultaneous, although feedback effects apparently were not strong." PMID:12291905

  16. The growth in the US uninsured population: trends in Hispanic subgroups, 1977 to 1992.

    PubMed Central

    Berk, M L; Albers, L A; Schur, C L

    1996-01-01

    This paper presents trends in the growth in the US uninsured population, using cross-sectional national estimates from 1977, 1987, 1989, and 1992 and focusing specifically on coverage problems experienced by Hispanic Americans. An examination of the composition of uninsured persons added between 1977 and 1992 shows that almost 40% of the difference is accounted for by persons of Hispanic origin, with those of Mexican origin alone constituting 27%. In addition, the annual average rate of growth in the uninsured Hispanic population between 1977 and 1992 was 9.7%, compared with only 2.3% for the uninsured non-Hispanic population. Images FIGURE 1 PMID:8604794

  17. Population Growth and Development of the Psocid Liposcelis brunnea (Psocoptera: Liposcelididae) at Constant Temperatures and Relative Humidities

    Microsoft Academic Search

    G. P. Opit; J. E. Throne

    2009-01-01

    We studied the effects of temperature and relative humidity on population growth and development of the psocid Liposcelis brunnea Motschulsky. L. brunnea did not survive at 43% RH, but populations increased from 22.5 to 32.5C and 55Ð75% RH. Interestingly, we found population growth was higher at 63% RH than at 75% RH, and the greatest population growth was recorded at

  18. Population Change in the Midwest: Nonmetro Population Growth Lags Metro Increase.

    ERIC Educational Resources Information Center

    Goudy, Willis

    2002-01-01

    Midwest population gains in the 1990s were eclipsed by other regions, and nonmetro areas fared worse than metro counties. Less populous and more isolated counties were more likely to lose residents and to lose youth. The Midwest gained Hispanic residents in the 1990s, but numerical increases were much larger in metro counties. Implications for…

  19. Adult survival and population growth rate in Colorado big brown bats (Eptesicus fuscus)

    USGS Publications Warehouse

    O'Shea, T.J.; Ellison, L.E.; Stanley, T.R.

    2011-01-01

    We studied adult survival and population growth at multiple maternity colonies of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado. We investigated hypotheses about survival using information-theoretic methods and mark-recapture analyses based on passive detection of adult females tagged with passive integrated transponders. We constructed a 3-stage life-history matrix model to estimate population growth rate (??) and assessed the relative importance of adult survival and other life-history parameters to population growth through elasticity and sensitivity analysis. Annual adult survival at 5 maternity colonies monitored from 2001 to 2005 was estimated at 0.79 (95% confidence interval [95% CI] = 0.77-0.82). Adult survival varied by year and roost, with low survival during an extreme drought year, a finding with negative implications for bat populations because of the likelihood of increasing drought in western North America due to global climate change. Adult survival during winter was higher than in summer, and mean life expectancies calculated from survival estimates were lower than maximum longevity records. We modeled adult survival with recruitment parameter estimates from the same population. The study population was growing (?? = 1.096; 95% CI = 1.057-1.135). Adult survival was the most important demographic parameter for population growth. Growth clearly had the highest elasticity to adult survival, followed by juvenile survival and adult fecundity (approximately equivalent in rank). Elasticity was lowest for fecundity of yearlings. The relative importances of the various life-history parameters for population growth rate are similar to those of large mammals. ?? 2011 American Society of Mammalogists.

  20. On the Distinction Between Lag and Delay in Population Growth

    Microsoft Academic Search

    Peter Vadasz; Alisa S. Vadasz

    2010-01-01

    The analysis and results presented in this paper provide conclusive evidence to distinguish between the delay effect and the\\u000a lag as two biologically distinct phenomena. It therefore dispels the incorrect notion that delay effects represented by delay\\u000a differential equations are the biological reason behind the lag phase in microorganism growth. The resulting consequence so\\u000a far is that the only other

  1. The environment and population growth: decade for action

    SciTech Connect

    Not Available

    1992-05-01

    The signs of environmental stress grow as the world's population increases: worn-out farmlands, eroded hillsides, polluted water, parched grasslands, smoke-laden air, depleted ozone, and treeless ranges. Each year about 17 million hectares of tropical forest vanish--an area the size of Tunisia or Uruguay. Fish catches are leveling off. Cities are clogged with refuse. Water and air, instead of sustaining life, cause disease.

  2. Modeling circadian clock-cell cycle interaction effects on cell population growth rates.

    PubMed

    El Cheikh, R; Bernard, S; El Khatib, N

    2014-12-21

    The circadian clock and the cell cycle are two tightly coupled oscillators. Recent analytical studies have shown counter-intuitive effects of circadian gating of the cell cycle on growth rates of proliferating cells which cannot be explained by a molecular model or a population model alone. In this work, we present a combined molecular-population model that studies how coupling the circadian clock to the cell cycle, through the protein WEE1, affects a proliferating cell population. We show that the cell cycle can entrain to the circadian clock with different rational period ratios and characterize multiple domains of entrainment. We show that coupling increases the growth rate for autonomous periods of the cell cycle around 24 h and above 48 h. We study the effect of mutation of circadian genes on the growth rate of cells and show that disruption of the circadian clock can lead to abnormal proliferation. Particularly, we show that Cry 1, Cry 2 mutations decrease the growth rate of cells, Per 2 mutation enhances it and Bmal 1 knockout increases it for autonomous periods of the cell cycle less than 21 h and decreases it elsewhere. Combining a molecular model to a population model offers new insight on the influence of the circadian clock on the growth of a cell population. This can help chronotherapy which takes benefits of physiological rhythms to improve anti-cancer efficacy and tolerance to drugs by administering treatments at a specific time of the day. PMID:25152215

  3. Genetic parameter estimation in seedstock Swine population for growth performances.

    PubMed

    Choi, Jae Gwan; Cho, Chung Il; Choi, Im Soo; Lee, Seung Soo; Choi, Tae Jeong; Cho, Kwang Hyun; Park, Byoung Ho; Choy, Yun Ho

    2013-04-01

    The objective of this study was to estimate genetic parameters that are to be used for across-herd genetic evaluations of seed stock pigs at GGP level. Performance data with pedigree information collected from swine breeder farms in Korea were provided by Korea Animal Improvement Association (AIAK). Performance data were composed of final body weights at test days and ultrasound measures of back fat thickness (BF), rib eye area (EMA) and retail cut percentage (RCP). Breeds of swine tested were Landrace, Yorkshire and Duroc. Days to 90 kg body weight (DAYS90) were estimated with linear function of age and ADG calculated from body weights at test days. Ultrasound measures were taken with A-mode ultrasound scanners by trained technicians. Number of performance records after censoring outliers and keeping records pigs only born from year 2000 were of 78,068 Duroc pigs, 101,821 Landrace pigs and 281,421 Yorkshire pigs. Models included contemporary groups defined by the same herd and the same seasons of births of the same year, which was regarded as fixed along with the effect of sex for all traits and body weight at test day as a linear covariate for ultrasound measures. REML estimation was processed with REMLF90 program. Heritability estimates were 0.40, 0.32, 0.21 0.39 for DAYS90, ADG, BF, EMA, RCP, respectively for Duroc population. Respective heritability estimates for Landrace population were 0.43, 0.41, 0.22, and 0.43 and for Yorkshire population were 0.36, 0.38, 0.22, and 0.42. Genetic correlation coefficients of DAYS90 with BF, EMA, or RCP were estimated to be 0.00 to 0.09, -0.15 to -0.25, 0.22 to 0.28, respectively for three breeds populations. Genetic correlation coefficients estimated between BF and EMA was -0.33 to -0.39. Genetic correlation coefficient estimated between BF and RCP was high and negative (-0.78 to -0.85) but the environmental correlation coefficients between these two traits was medium and negative (near -0.35), which describes a highly correlated genetic response to selection on one or the other of these traits. Genetic Trends of all three breeds tend to be towards bigger EMA or greater RCP and shorter DAYS90 especially from generations born after year 2000. PMID:25049811

  4. The growth of XXX females: population-based studies.

    PubMed

    Ratcliffe, S G; Pan, H; McKie, M

    1994-01-01

    Longitudinal measurements of height, sitting height and leg length are compared between 11 XXX girls identified by cytogenetic screening, and 16 chromosomally normal controls from the same population using a nonparametric method. While height velocity did not differ between the two groups either during the pubertal or the mid-childhood spurts, leg length velocity was significantly increased during the mid-childhood spurt, between 4 and 9 years of age. A further contribution to the increased leg length came from the slower decline in leg length velocity at the end of the pubertal spurt. The possible mechanisms involved in these changes are discussed. PMID:8147577

  5. Population growth of Euchlanis dilatata (Rotifera): combined effects of methyl parathion and food (Chlorella vulgaris).

    PubMed

    Sarma, S S; Nandini, S; Gama-Flores, J L; Fernandez-Araiza, M A

    2001-01-01

    In the present work, the combined impact of four concentrations (0, 0.0625, 0.125, and 0.25 mg/L) of methyl parathion and three densities (0.5 x 10(6), 1.0 x 10(6), and 2.0 x 10(6) cells/mL) of the green alga Chlorella vulgaris on the population growth of Euchlanis dilatata was studied. In general, regardless of the food level, an increase in the concentration of methyl parathion resulted in a significant reduction of the maximal population density and rate of population increase. The population growth rate in the controls ranged from 0.248 to 0.298; rates were lower in the presence of the pesticide. At any toxicant concentration, rotifers fed higher algal density showed significantly higher population growth compared with those at lower food levels. An interaction between toxicant and food level was evident on the population growth of E. dilatata. Results have been discussed in light of the protective role of algal density on the toxic effects of insecticides on rotifers and the differences in susceptibility to toxicants between planktonic and littoral rotifers. PMID:11281254

  6. Population growth of a gorgonian coral: equilibrium and non-equilibrium sensitivity to changes in life history variables

    Microsoft Academic Search

    Howard R. Lasker

    1991-01-01

    A size dependent model of population growth of the Caribbean gorgonian Plexaura A is developed based on observed rates of survival, growth and colony fragmentation at a site in the San Blas Islands, Panama. Sensitivity and elasticity analyses indicate that the fate of large colonies has the greatest effect on population growth. Variables which directly affect the generation of large

  7. Lab 1: Population growth Throughout the semester you will be using the program, Populus, written by Don

    E-print Network

    Nuismer, Scott L.

    Lab 1: Population growth Throughout the semester you will be using the program, Populus, written simple models of population growth. Future labs will depend significantly more on the use of the Populus the current population size of this frog at 1,237 individuals. State law requires that a captive breeding

  8. Potential population growth and harmful effects on humans from bed bug populations exposed to different feeding regimes.

    PubMed

    Pereira, R M; Taylor, A S; Lehnert, M P; Koehler, P G

    2013-06-01

    Effects of host availability and feeding period on bed bugs, Cimex lectularius (L.) (Hemiptera: Cimicidae), were measured. Population growth and the potential harmful effect of bed bug populations on human hosts were modelled. Bloodmeal sizes were affected by both feeding length and frequency, with >2-fold difference between insects fed daily or weekly. Blood consumption increased >2-fold between bed bugs fed occasionally and often, and 1.5-fold between occasional and daily feeding. Bed bugs fed more often than once a week, potentially every 2-4 days. Egg production was associated with nutrition, being strongly correlated with blood consumption in the previous week. Bed bug populations can grow under different feeding regimes and are hard to control with <80% mortality. Bed bugs can survive and grow even in locations with a limited blood supply, where bed bug persistence may be important for the continual spread of populations. Persistence in non-traditional locations and a potential association with human pathogens increase the health risks of bed bugs. Potential blood loss as a result of a bed bug can have serious consequences because uncontrolled populations can reach harmful levels in 3-8 months. The reproduction potential of bed bug populations suggests serious consequences to human health and the need for efficacious control measures. PMID:23046478

  9. Rapid Population Growth and Human Carrying Capacity: Two Perspectives. World Bank Staff Working Papers No. 690 and Population and Development Series No. 15.

    ERIC Educational Resources Information Center

    Mahar, Dennis J., Ed.; And Others

    Two perspectives on carrying capacity and population growth are examined. The first perspective, "Carrying Capacity and Rapid Population Growth: Definition, Cases, and Consequences" (Robert Muscat), explores the possible meanings of the idea of carrying capacity under developing country conditions, looks at historical and present-day cases of…

  10. Studies on the growth and encystment of Polytomella agilis

    Microsoft Academic Search

    Phillip Sheeler; Marvin Cantor; Joseph Moore

    1970-01-01

    Summary Changes in cell population density, cell protein and cell carbohydrate levels of the flagellatePolytomella agilis during growth in batch cultures on a complex medium at 25° C, 18° C and 9° C were examined. At 25° C, cell protein and carbohydrate levels fell markedly during exponential population growth. At 18° C, cell protein values remained fairly constant, while cell

  11. Modelling targets for anticancer drug control optimisation in physiologically structured cell population models

    E-print Network

    cell populations Solutions of linear models, such as McKendrick's, exhibit exponential growth. In Eq population models Frédérique Billy , Jean Clairambault , Olivier Fercoq , Tommaso Lorenzi , Alexander Lorz cell populations and occurrence of resistance to drugs in cancer cell populations. Depending

  12. A stochastic population model to evaluate Moapa dace (Moapa coriacea) population growth under alternative management scenarios

    USGS Publications Warehouse

    Perry, Russell W.; Jones, Edward; Scoppettone, G. Gary

    2015-01-01

    Increasing or decreasing the total carrying capacity of all stream segments resulted in changes in equilibrium population size that were directly proportional to the change in capacity. However, changes in carrying capacity to some stream segments but not others could result in disproportionate changes in equilibrium population sizes by altering density-dependent movement and survival in the stream network. These simulations show how our IBM can provide a useful management tool for understanding the effect of restoration actions or reintroductions on carrying capacity, and, in tur

  13. Natural growth of the population of Plovdiv, Bulgaria for the period 1895-1995.

    PubMed

    Dimitrov, I

    1998-01-01

    A study of the natural growth rate of the population using female cohorts by birth year has been carried out for the first time in our country. The study comprises 14 cohorts. The following characteristics are recorded: birth year, social group, educational level, number of live births, age of marriage, infant mortality rate, proto- and intergenetic intervals. Our report presents the key indicators of natural growth of population in the studied cohorts. A consistent trend of decreasing the number of livebirths is established. In the first studied cohort (1895-1899) the average number of offspring per woman is 3.94, reaching a level of 1.77 in the 1960-1964 cohort. The indicators for natural growth of population exhibit a similar trend. The summary fertility rate in the reference period decreases with more than 2 points--from 4.47 in 1895-1899 to 1.73 in 1960-1964. Likewise, the total reproduction rate goes down from 2.54 to 0.78 for the same period. Considerable changes have occurred in the indicators total period fertility rate and marriage fertility rate of women. For a period of 110 years the former has decreased 3.5 times, the latter--8 times. The drastic drop of the indicators of natural growth of the population is accounted for by an intricate complex of social, economic, psychological and biological factors. The marked aging of the population and the decrease of the percentage of women in active fertility age play a certain role in this process. The ascertained changes in the reproductive behavior and age structure of the female population are factors intensifying the unfavorable trends in the natural growth rate of the population in our country. PMID:9707807

  14. Age structure and spatial patterning of Trillium populations in old-growth forests

    Microsoft Academic Search

    Christopher R. Webster; Michael A. Jenkins

    2008-01-01

    We investigated the spatial cohort structure of Trillium populations in old-growth cove forests in Great Smoky Mountains National Park (TN, USA). We mapped the locations of all Trillium\\u000a erectum L., Trillium grandiflorum (Michaux) Salisbury, and Trillium vaseyi Harbison occurring within two 10 × 10 m sample plots at each of three old-growth sites—Anthony Creek, Cove Mountain, and\\u000a Kalanu Prong. The height and life

  15. Existence of Limit Cycles in the Solow Model with Delayed-Logistic Population Growth

    PubMed Central

    2014-01-01

    This paper is devoted to the existence and stability analysis of limit cycles in a delayed mathematical model for the economy growth. Specifically the Solow model is further improved by inserting the time delay into the logistic population growth rate. Moreover, by choosing the time delay as a bifurcation parameter, we prove that the system loses its stability and a Hopf bifurcation occurs when time delay passes through critical values. Finally, numerical simulations are carried out for supporting the analytical results. PMID:24592147

  16. The Temporal and Spatial Dynamics of Income and Population Growth in Ohio, 1950–1990

    Microsoft Academic Search

    C. Cindy Fan

    1994-01-01

    FAN C. C. (1994) The temporal and spatial dynamics of income and population growth in Ohio, 1950-1990, Reg. Studies28, 241–258. The regional dynamics literature has tended to pay more attention to regional variation of growth than to variation within states, although the latter defines the disaggregated realities that public officials and policy makers are most concerned with. This paper focuses

  17. Causes of mortality in California sea otters during periods of population growth and decline

    USGS Publications Warehouse

    Estes, J.A.; Hatfield, B.B.; Ralls, K.; Ames, J.

    2003-01-01

    Elevated mortality appears to be the main reason for both sluggish growth and periods of decline in the threatened California sea otter population. We assessed causes of mortality from salvage records of 3,105 beach-cast carcasses recovered from 1968 through 1999, contrasting two periods of growth with two periods of decline. Overall, an estimated 40%-60% of the deaths were not recovered and 70% of the recovered carcasses died from unknown causes. Nonetheless, several common patterns were evident in the salvage records during the periods of population decline. These included greater percentages of (1) prime age animals (3-10 yr), (2) carcasses killed by great white shark attacks, (3) carcasses recovered in spring and summer, and (4) carcasses for which the cause of death was unknown. Neither sex composition nor the proportion of carcasses dying of infectious disease varied consistently between periods of population increase and decline. The population decline from 1976 to 1984 was likely due to incidental mortality in a set-net fishery, and the decline from 1995 to 1999 may be related to a developing live-fish fishery. Long-term trends unrelated to periods of growth and decline included a decrease in per capita pup production and mass/length ratios of adult carcasses over the 31-yr study. The generally high proportion of deaths from infectious disease suggests that this factor has contributed to the chronically sluggish growth rate of the California sea otter population.

  18. Section 3.1. Population Ch. 3.1. Population Growth

    E-print Network

    Lopez-Carr, David

    , with Thomas Malthus's statement that, "The power of population is indefinitely greater than the power in the earth to produce subsistence for man," (Malthus, 1798). Malthus envisioned an impending human doomsday (Malthus 1798). He argued that arable land is finite and agricultural production grows geometrically while

  19. Growth analysis of a reestablished population versus a natural population of Bidens cernua L

    Microsoft Academic Search

    L. Gratani; M. F. Crescente; G. Fabrini; A. Bonito; L. Varone

    2009-01-01

    A reintroduction experiment of Bidens cernua L., a species included in the Red List of Italian Flora, was carried out at Lake Posta Fibreno (Lazio, central Italy). There were no significant differences in the length of the phenological phases between the reestablished population (Pr) and the natural one (Pn). The length of the phenological cycle, from seedling emergence to the

  20. Application of population growth models based on cumulative size to pecan aphids

    Microsoft Academic Search

    James H. Matis; Thomas R. Kiffe; Timothy I. Matis; Douglass E. Stevenson

    2006-01-01

    Models for aphid population growth based on cumulative (past) population size have been developed with both a deterministic\\u000a formulation and a stochastic formulation. This article applies these mechanistic models to analyze a large dataset on pecan\\u000a aphid. The models yield symmetric and right-skewed curves, which differ qualitatively from the observed data which tend to\\u000a be left-skewed. Nevertheless this model-based analysis

  1. Population Growth and Land Use Intensification in a Subsistence-based Indigenous Community in the Amazon

    Microsoft Academic Search

    Anders Henrik Sirén

    2007-01-01

    Shifting cultivation practiced by indigenous peoples living at low population densities in tropical forests has often been\\u000a described as sustainable and compatible with conservation. However, shifting cultivation at increasing population densities\\u000a has historically been, and still is, a main cause of deforestation worldwide. As many indigenous peoples in tropical forests\\u000a currently experience rapid demographic growth, this raises the question to

  2. Connecting phenological predictions with population growth rates for mountain pine beetle, an outbreak insect

    Microsoft Academic Search

    James A. Powell; Barbara J. Bentz

    2009-01-01

    It is expected that a significant impact of global warming will be disruption of phenology as environmental cues become disassociated\\u000a from their selective impacts. However there are few, if any, models directly connecting phenology with population growth rates.\\u000a In this paper we discuss connecting a distributional model describing mountain pine beetle phenology with a model of population\\u000a success measured using

  3. Dynamics of individual growth in a recovering population of lake trout (Salvelinus namaycush)

    USGS Publications Warehouse

    Fabrizio, Mary C.; Dorazio, Robert M.; Schram, Stephen T.

    2001-01-01

    In 1976, the Wisconsin Department of Natural Resources established a refuge for a nearly depleted population of lake trout (Salvelinus namaycush) at Gull Island Shoal, Lake Superior. The refuge was intended to reduce fishing mortality by protecting adult lake trout. We examined the growth dynamics of these lake trout during the period of recovery by comparing estimates of ndividual growth before and after the refuge was established. Our estimates are based on an annual mark-recapture survey conducted at the spawning area since 1969. We developed a model that allowed mean growth rates to differ among individuals of different sizes and that accommodated variation in growth rates of individuals of the same size. Likelihood ratio tests were used to determine if the mean growth increments of lake trout changed ater the refuge was established. Our results suggest that growth of mature lake trout (particularly wild fish) decreased significantly in the postrefuge period. This decreased growth may have been associated with a reduction in food availability. We also observed reductions in growth as wild fish grew older and larger, which suggests that the growth of these fish may be adequately approximated by a von Bertalanffy growth model if it becomes possible to obtain accurate ages.

  4. Population and economic growth: a cointegration analysis of lesser developed countries.

    PubMed

    Payne, J E; Ewing, B T

    1997-11-01

    The authors examine the temporal relationship between population growth and economic growth in Nepal, India, Ghana, Sri Lanka, Bolivia, Philippines, Guatemala, Syria, Peru, Thailand, Chile, Argentina, and Mexico, conducting Granger-causality tests in the context of error correction models when cointegration is present. Their goal is to provide additional time series econometric evidence on the short-run and long-run time series behavior of population growth and the growth of real per capita gross domestic product for a sample of low to middle income developing countries. Cointegration was found in only 3 of the 13 countries examined. Even though 10 countries in this study exhibited no properties of cointegration, researchers conducting time series studies of the relationship between population growth and economic growth using differenced data should nonetheless evaluate the possible long-term relationship. Capturing the short- and long-run behaviors of the respective time series may give the researcher a more robust test of Granger-causality. PMID:12348722

  5. EFFECT OF FLUID SHEAR AND IRRADIANCE ON POPULATION GROWTH AND CELLULAR TOXIN CONTENT OF THE DINOFLAGELLATE ALEXANDRIUM FUNDYENSE.

    EPA Science Inventory

    The potential for in situ turbulence to inhibit dinoflagellate population growth has been demonstrated by experimentally exposing dinoflagellate cultures to quantified shear flow. However, despite interest in understanding environmental factors that affect the growth of toxic din...

  6. Consequences of Rapid Population Growth: An Overview. World Bank Staff Working Papers No. 691 and Population and Development Series No. 16.

    ERIC Educational Resources Information Center

    McNicoll, Geoffrey

    A systematic discussion of the consequences of rapid population growth for economics and social systems examines growth resulting from mortality decline in the absence of comparable fertility decline. Growth resulting from net migration is also considered. The background and rationale for the study are supplied in a brief introduction. Part 2…

  7. An Exceptional Exponential Function

    ERIC Educational Resources Information Center

    Curgus, Branko

    2006-01-01

    We show that there is a link between a standard calculus problem of finding the best view of a painting and special tangent lines to the graphs of exponential functions. Surprisingly, the exponential function with the "best view" is not the one with the base "e." A similar link is established for families of functions obtained by composing…

  8. vol. 163, no. 3 the american naturalist march 2004 Effects of Body Size and Temperature on Population Growth

    E-print Network

    Brown, James H.

    on the Prin- ciple of Population, Thomas Malthus (1798) noted that all populations had the potential the time of Malthus, pop- ulation growth has been recognized as providing a critical link be- tween

  9. Comparison of native and introduced flathead catfish populations in Alabama and Georgia: Growth, mortality, and management

    USGS Publications Warehouse

    Sakaris, P.C.; Irwin, E.R.; Jolley, J.C.; Harrison, D.

    2006-01-01

    We compared growth of flathead catfish Pylodictis olivaris from two native populations in Alabama (Coosa and Tallapoosa rivers) and two introduced populations in Georgia (Ocmulgee and Satilla rivers). We also compared mortality rates and potential outcomes of various management regimes (minimum length limits [MLLs]) among the populations. Total length-log10(age) regression slopes for introduced fish were higher than those for native fish, and von Bertalanffy growth coefficients (K) were greater for introduced fish (Ocmulgee: 0.195; Satilla: 0.201) than for native individuals (Coosa: 0.057; Tallapoosa: 0.059). Therefore, introduced flathead catfish grew more rapidly than those in their native range. Mortality (instantaneous mortality rate, Z) was higher in the Satilla River population (Z = -0.602) than in the Ocmulgee River (Z = -0.227) and Coosa River (Z = -0.156) populations. However, fish in the Satilla River population had been introduced for only 10 years and presumably did not reach their theoretical maximum age, potentially biasing the mortality estimate for that population. Simulation of management regimes in Fishery Analyses and Simulation Tools software predicted that maximum biomass of flathead catfish in the Ocmulgee (1,668 kg) and Satilla (1,137 kg) rivers was substantially larger than that in the Coosa (873 kg) and Tallapoosa (768 kg) populations. However, increased exploitation rates in the Ocmulgee and Satilla River populations resulted in dramatic declines in overall biomass, especially at lower MLLs (254 and 356 mm, respectively). Therefore, in systems where introduced flathead catfish represent an important recreational fishery but have dramatically reduced the abundance of native fishes through predation, minimal protection is recommended. We contend that rapid growth of introduced flathead catfish has major implications for their management and the conservation of native fishes. ?? Copyright by the American Fisheries Society 2006.

  10. Growth rates of the population in a branching Brownian motion with an inhomogeneous breeding potential

    E-print Network

    Berestycki, Julien; Harris, John W; Harris, Simon C; Roberts, Matthew I

    2012-01-01

    We consider a branching particle system where each particle moves as an independent Brownian motion and breeds at a rate proportional to its distance from the origin raised to the power $p$, for $p\\in[0,2)$. The asymptotic behaviour of the right-most particle for this system is already known; in this article we give large deviations probabilities for particles following "difficult" paths, growth rates along "easy" paths, the total population growth rate, and we derive the optimal paths which particles must follow to achieve this growth rate.

  11. Traveling bands for the Keller-Segel model with population growth.

    PubMed

    Ai, Shangbing; Wang, Zhian

    2015-08-01

    This paper is concerned with the existence of the traveling bands to the Keller-Segel model with cell population growth in the form of a chemical uptake kinetics. We find that when the cell growth is considered, the profile of traveling bands, the minimum wave speed and the range of the chemical consumption rate for the existence of traveling wave solutions will change. Our results reveal that collective interaction of cell growth and chemical consumption rate plays an essential role in the generation of traveling bands. The research in the paper provides new insights into the mechanisms underlying the chemotactic pattern formation of wave bands. PMID:25974334

  12. Population Growth of Small Harmful Rats in Grassland Subjected to Noise

    NASA Astrophysics Data System (ADS)

    Liu, Xue-Mei; Li, Zhi-Bing; Xie, Hui-Zhang; Ai, Bao-Quan; Cheng, Xiao-Bo; Liu, Liang-Gang

    2007-07-01

    The population growth of small harmful rats in grassland subjected to environment fluctuation has been modelled in a logistic equation. Two correlated random variables responsible to the fluctuation of the genetic factor and the suppression factor are used. A two-peak structure of the steady probability distribution of rate population is observed in the large fluctuation regime of the genetic factor. With the increase of correlation constant ?, the steady probability distribution can change from two peaks to a single peak. The suppression factor ? and its fluctuation also affect the steady probability distribution and can push it toward a small population.

  13. Population versus Customized Fetal Growth Norms and Adverse Outcomes in an Intrapartum Cohort

    PubMed Central

    Costantine, Maged M.; Lai, Yinglei; Bloom, Steven L.; Spong, Catherine Y.; Varner, Michael W.; Rouse, Dwight J.; Ramin, Susan M.; Caritis, Steve N.; Peaceman, Alan M.; Sorokin, Yoram; Sciscione, Anthony; Mercer, Brian M.; Thorp, John M.; Malone, Fergal D.; Harper, Margaret; Iams, Jay D.

    2013-01-01

    Objective To compare population versus customized fetal growth norms in identifying neonates at risk for adverse outcomes (APO) associated with small for gestational age (SGA). Study Design Secondary analysis of an intrapartum fetal pulse oximetry trial in nulliparous women at term. Birthweight percentiles were calculated using ethnicity- & gender-specific population norms and customized norms (Gardosi). Results 508 (9.9%) and 584 (11.3%) neonates were SGA by population (SGApop) and customized (SGAcust) norms. SGApop infants were significantly associated with a composite adverse neonatal outcome, neonatal intensive care admission, low fetal oxygen saturation and reduced risk of cesarean delivery; while both SGApop and SGAcust were associated with a 5-minute Apgar score < 4. The ability of customized and population birthweight percentiles in predicting APO was poor (12 out of 14 APOs had AUC <0.6). Conclusion In this intrapartum cohort, neither customized nor normalized-population norms adequately identify neonates at risk of APO related to SGA. PMID:22893556

  14. Validity of Personal Growth Initiative Scale Scores with a Mexican American College Student Population

    ERIC Educational Resources Information Center

    Robitschek, Christine

    2003-01-01

    This study tested the validity of scores on the Personal Growth Initiative Scale (PGIS; C. Robitschek, 1998, 1999) with a Mexican American college student sample. Results indicated that the PGIS scores appear to be culturally relevant for this population, with scores on the PGIS having many similar relations with other variables that have been…

  15. Validity of Personal Growth Initiative Scale Scores With a Mexican American College Student Population

    Microsoft Academic Search

    Christine Robitschek

    2003-01-01

    This study tested the validity of scores on the Personal Growth Initiative Scale (PGIS; C. Robitschek, 1998, 1999) with a Mexican American college student sample. Results indicated that the PGIS scores appear to be culturally relevant for this population, with scores on the PGIS having many similar relations with other variables that have been found in prior research with mostly

  16. Teaching Population Growth Using Cultures of Vinegar Eels, "Turbatrix aceti" (Nematoda)

    ERIC Educational Resources Information Center

    Wallace, Robert L.

    2005-01-01

    A simple laboratory exercise is presented that follows the population growth of the common vinegar eel, "Turbatrix aceti" (Nematoda), in a microcosm using a simple culture medium. It lends itself to an exercise in a single semester course. (Contains 4 figures.)

  17. Population growth and development of the psocid Lepinotus reticulatus at constant temperatures and relative humidities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We investigated the effects of temperature and relative humidity on population growth and development of the psocid Lepinotus reticulatus Enderlein. Part of this study assessed the effects of marking psocids using methylene blue, chalk powder, and fluorescent powder to differentiate nymphal stages d...

  18. Root Growth and Yield of Differing Alfalfa Rooting Populations under Increasing Salinity and Zero Leaching

    E-print Network

    Smith, Steven E.

    Root Growth and Yield of Differing Alfalfa Rooting Populations under Increasing Salinity and Zero-rootedAccumulation of salinity in the root zone can be detrimental to crops such as alfalfa to exploit the lower average salinitysustained crop production. Irrigation, even with moderately saline water, pushes accumulated salts deeper

  19. Determinants of species rarity: population growth rates of species sharing the same habitat

    Microsoft Academic Search

    ZUZANA MUNZBERGOVA

    2005-01-01

    Determining differences between common and rare species is commonly used to identify factors responsible for rarity. Existing studies, however, suffer from two important drawbacks. First, studies compare species that are closely related phylogenetically but occupy different habitats. Second, these studies concentrate on single life history traits, with unknown relevance for population growth rates. Complete life cycles of one rare and

  20. Effects of Sample Size on Estimates of Population Growth Rates Calculated with Matrix Models

    E-print Network

    Bruna, Emilio M.

    Effects of Sample Size on Estimates of Population Growth Rates Calculated with Matrix Models Ian J the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of l due to increased. Finally, we conducted a review of the literature to determine the sample sizes typically used when

  1. Spatial Genetic Patterns in Four Old-Growth Populations of Coast Redwood1

    E-print Network

    Standiford, Richard B.

    , Rohnert Park, California. 2 Assistant Research Geneticist, Genetic Resources Conservation ProgramSpatial Genetic Patterns in Four Old-Growth Populations of Coast Redwood1 Deborah L. Rogers2 a pattern in the distribution of genetic diversity which is referred to as spatial genetic structure (Wright

  2. Contributions of vital rates to growth of a protected population of American black bears

    Microsoft Academic Search

    Michael S. Mitchell; Lara B. Pacifici; James B. Grand; Roger A. Powell

    2009-01-01

    Analyses of large, long-lived animals suggest that adult survival generally has the potential to contribute more than reproduction to population growth rate (l), but because survival varies little, high variability in reproduction can have a greater influence. This pattern has been documented for several species of large mammals, but few studies have evaluated such contributions of vital rates to l

  3. Fed up with parasites? A method for estimating asymptotic growth in fish populations

    Microsoft Academic Search

    D. Gibson; J. B. Jones

    1993-01-01

    The accumulation of parasites in a fish host is modelled as a function of the total amount of prey consumed. The accumulated parasite load is then expressed as a function of fish length so that the asymptotic growth, L8, of any population of commonly infected fish can be estimated. Estimates of L8 are obtained for orange roughy (Hoplostethus atlanticus), albacore

  4. EFFECTS OF CADMIUM ON THE POPULATION GROWTH OF A BENTHIC INVERTEBRATE AEOLOSOMA HEADLEYI (OLIGOCHAETA)

    EPA Science Inventory

    A chronic toxicity test using population growth of an aquatic oligochaete, Aeolosoma headleyi, was evaluated for usefulness in determining the hazard of chronic exposures to cadmium. Tests were conducted in artificial hard water (180 mg/L hardness) and dechlorinated tap water (60...

  5. On stochastic logistic population growth models with immigration and multiple births

    Microsoft Academic Search

    James H. Matis; Thomas R. Kiffe

    2004-01-01

    This paper develops a stochastic logistic population growth model with immigration and multiple births. The differential equations for the low-order cumulant functions (i.e., mean, variance, and skewness) of the single birth model are reviewed, and the corresponding equations for the multiple birth model are derived. Accurate approximate solutions for the cumulant functions are obtained using moment closure methods for two

  6. Population growth and savings rates: Some new cross-country estimates

    Microsoft Academic Search

    Christopher Cook

    2005-01-01

    It is widely recognised that population growth can have two conflicting effects on savings. It reduces savings as it leads to more dependent children, but if balanced it can also increase savings by increasing the number entering the working part of the life cycle and hence the number of potential savers. However, this positive effect has largely been ignored in

  7. Thermodynamics Constrains the Evolution of Insect Population Growth Rates: “Warmer Is Better”

    Microsoft Academic Search

    David Berrigan

    2006-01-01

    Diverse biochemical and physiological adaptations en- able different species of ectotherms to survive and reproduce in very different temperature regimes, but whether these adaptations fully compensate for the thermodynamically depressing effects of low tem- perature on rates of biological processes is debated. If such adap- tations are fully compensatory, then temperature-dependent pro- cesses (e.g., digestion rate, population growth rate) of

  8. Age-patterns of famine-related mortality increase: implications for long-term population growth

    Microsoft Academic Search

    Jane Menken; Cameron Campbell

    In this paper, we reaffirm Watkins and Menken's (1985) conclusion that there is 'little likelihood that famines will be a major determinant of population growth in the future, any more than ... in the past'. We find that age and sex-specific patterns of famine mortality change that have markedly different proportional change in group-specifi c mortality can nevertheless lead to

  9. How exponential are FREDs?

    NASA Astrophysics Data System (ADS)

    Schaefer, Bradley E.; Dyson, Samuel E.

    1996-08-01

    A common Gamma-Ray Burst-light curve shape is the ``FRED'' or ``fast-rise exponential-decay.'' But how exponential is the tail? Are they merely decaying with some smoothly decreasing decline rate, or is the functional form an exponential to within the uncertainties? If the shape really is an exponential, then it would be reasonable to assign some physically significant time scale to the burst. That is, there would have to be some specific mechanism that produces the characteristic decay profile. So if an exponential is found, then we will know that the decay light curve profile is governed by one mechanism (at least for simple FREDs) instead of by complex/multiple mechanisms. As such, a specific number amenable to theory can be derived for each FRED. We report on the fitting of exponentials (and two other shapes) to the tails of ten bright BATSE bursts. The BATSE trigger numbers are 105, 257, 451, 907, 1406, 1578, 1883, 1885, 1989, and 2193. Our technique was to perform a least square fit to the tail from some time after peak until the light curve approaches background. We find that most FREDs are not exponentials, although a few come close. But since the other candidate shapes come close just as often, we conclude that the FREDs are misnamed.

  10. Potential effects of environmental contamination on Yuma Myotis demography and population growth.

    PubMed

    Frick, Winifred F; Rainey, William E; Pierson, Elizabeth D

    2007-06-01

    Unplanned natural and anthropogenic disasters provide unique opportunities for investigating the influence of perturbations on population vital rates and species recovery times. We investigated the potential effects of a major pesticide spill by comparing annual survival rates using mark-recapture techniques on a riparian bat species, Yuma Myotis (Myotis yumanensis). Demography and population dynamics for most bat species remain poorly understood despite advances in mark-recapture estimation and modeling techniques. We compared survival and population growth rates of two roost populations exposed to a large chemical (metam sodium) spill in the upper Sacramento River in Northern California with two roost populations outside the contaminated area from 1992 to 1996. Hypotheses about long-term effects of the spill on female juvenile and adult survival were tested using an information-theoretic approach (AIC). Working hypotheses included effects of age, chemical spill, and time trend on survival. Female adult survival was higher than female juvenile survival across all sites, suggesting stage-specific mortality risks. Model-averaged estimates of female juvenile survival in the contaminated area (0.50-0.74) were lower than in control roosts (0.60-0.78) for each year in the study, suggesting that the spill may have reduced juvenile survival for several years. Female adult survival (0.73-0.89) did not appear to be strongly affected by the spill during the years of the study. There was an increase in survival for both stage-classes across all populations during the study period, which may have been caused by the end of an extended drought in California in the winter of 1993. The spill-affected population was in decline for the first year of the study as indicated by an estimated growth rate (lambda) < 1, but population growth rates increased during the four-year period. PMID:17555229

  11. Growth and Competitive Effects of Centaurea stoebe Populations in Response to Simulated Nitrogen Deposition

    PubMed Central

    He, Wei-Ming; Montesinos, Daniel; Thelen, Giles C.; Callaway, Ragan M.

    2012-01-01

    Increased resource availability can promote invasion by exotic plants, raising concerns over the potential effects of global increases in the deposition of nitrogen (N). It is poorly understood why increased N favors exotics over natives. Fast growth may be a general trait of good invaders and these species may have exceptional abilities to increase growth rates in response to N deposition. Additionally, invaders commonly displace locals, and thus may have inherently greater competitive abilities. The mean growth response of Centaurea stoebe to two N levels was significantly greater than that of North American (NA) species. Growth responses to N did not vary among C. stoebe populations or NA species. Without supplemental N, NA species were better competitors than C. stoebe, and C. stoebe populations varied in competitive effects. The competitive effects of C. stoebe populations increased with N whereas the competitive effects of NA species decreased, eliminating the overall competitive advantage demonstrated by NA species in soil without N added. These results suggest that simulated N deposition may enhance C. stoebe invasion through increasing its growth and relative competitive advantage, and also indicate the possibility of local adaptation in competitive effects across the introduced range of an invader. PMID:22563451

  12. Association with pathogenic bacteria affects life-history traits and population growth in Caenorhabditis elegans

    PubMed Central

    Diaz, S Anaid; Mooring, Eric Q; Rens, Elisabeth G; Restif, Olivier

    2015-01-01

    Determining the relationship between individual life-history traits and population dynamics is an essential step to understand and predict natural selection. Model organisms that can be conveniently studied experimentally at both levels are invaluable to test the rich body of theoretical literature in this area. The nematode Caenorhabditis elegans, despite being a well-established workhorse in genetics, has only recently received attention from ecologists and evolutionary biologists, especially with respect to its association with pathogenic bacteria. In order to start filling the gap between the two areas, we conducted a series of experiments aiming at measuring life-history traits as well as population growth of C. elegans in response to three different bacterial strains: Escherichia coli OP50, Salmonella enterica Typhimurium, and Pseudomonas aeruginosa PAO1. Whereas previous studies had established that the latter two reduced the survival of nematodes feeding on them compared to E. coli OP50, we report for the first time an enhancement in reproductive success and population growth for worms feeding on S. enterica Typhimurium. Furthermore, we used an age-specific population dynamic model, parameterized using individual life-history assays, to successfully predict the growth of populations over three generations. This study paves the way for more detailed and quantitative experimental investigation of the ecology and evolution of C. elegans and the bacteria it interacts with, which could improve our understanding of the fate of opportunistic pathogens in the environment. PMID:25937908

  13. Why sustainable population growth is a key to climate change and public health equity.

    PubMed

    Howat, Peter; Stoneham, Melissa

    2011-12-01

    Australia's population could reach 42 million by 2050. This rapid population growth, if unabated, will have significant social, public health and environmental implications. On the one hand, it is a major driver of climate change and environmental degradation; on the other it is likely to be a major contributor to growing social and health issues including a decline in quality of life for many residents. Disadvantaged and vulnerable groups will be most affected. The environmental, social and health-related issues include: pressure on the limited arable land in Australia; increased volumes of industrial and domestic waste; inadequate essential services; traffic congestion; lack of affordable housing; declining mental health; increased obesity problems; and inadequate aged care services. Many of these factors are related to the aggravation of climate change and health inequities. It is critical that the Australian Government develops a sustainable population plan with stabilisation of population growth as an option. The plan needs to ensure adequate hospitals and healthcare services, education facilities, road infrastructure, sustainable transport options, water quality and quantity, utilities and other amenities that are already severely overburdened in Australian cities. There is a need for a guarantee that affordable housing will be available and priority be given to training young people and Indigenous people for employment. This paper presents evidence to support the need for the stabilisation of population growth as one of the most significant measures to control climate change as well as to improve public health equity. PMID:22518917

  14. On stochastic logistic population growth models with immigration and multiple births.

    PubMed

    Matis, James H; Kiffe, Thomas R

    2004-02-01

    This paper develops a stochastic logistic population growth model with immigration and multiple births. The differential equations for the low-order cumulant functions (i.e., mean, variance, and skewness) of the single birth model are reviewed, and the corresponding equations for the multiple birth model are derived. Accurate approximate solutions for the cumulant functions are obtained using moment closure methods for two families of model parameterizations, one for badger and the other for fox population growth. For both model families, the equilibrium size distribution may be approximated well using the Normal approximation, and even more accurately using the saddlepoint approximation. It is shown that in comparison with the corresponding single birth model, the multiple birth mechanism increases the skewness and the variance of the equilibrium distribution, but slightly reduces its mean. Moreover, the type of density-dependent population control is shown to influence the sign of the skewness and the size of the variance. PMID:14642347

  15. Population and Scenarios: Worlds to win?

    Microsoft Academic Search

    Hilderink HBM

    2007-01-01

    Demographic developments have played an important role in the structure\\u000aand functioning of the Earth's system. The exponential population growth\\u000aof the last century has led to high pressures on the environmental\\u000asystem, with the issue of hunger as representative of harmful effects. \\u000aDespite the fact that the population growth is currently negative in some\\u000aof the world's regions, the

  16. Population and Scenarios: Worlds to Win?

    Microsoft Academic Search

    H. B. M. Hilderink

    2004-01-01

    Abstract Demographic,developments,have played an important role in the structure and functioning of the Earth’s system. The exponential population growth of the last century has led to high pressures on the environmental system, with the issue of hunger as representativ e of harmful effects. Despite the fact that the population growth is currently negative in some of the world’s regions, the

  17. Cell Growth and Size Homeostasis in Silico

    NASA Astrophysics Data System (ADS)

    Hu, Yucheng; Zhu, Tianqi

    2014-03-01

    Cell growth in size is a complex process coordinated by intrinsic and environmental signals. In a recent work [Tzur et al., Science, 2009, 325:167-171], size distributions in an exponentially growing population of mammalian cells were used to infer the growth rate in size. The results suggest that cell growth is neither linear nor exponential, but subject to size-dependent regulation. To explain their data, we build a model in which the cell growth rate is controlled by the relative amount of mRNA and ribosomes in a cell. Plus a stochastic division rule, the evolutionary process of a population of cells can be simulated and the statistics of the in-silico population agree well with the experimental data. To further explore the model space, alternative growth models and division rules are studied. This work may serve as a starting point for us to understand the rational behind cell growth and size regulation using predictive models.

  18. Impacts of invasive fish removal through angling on population characteristics and juvenile growth rate.

    PubMed

    Evangelista, Charlotte; Britton, Robert J; Cucherousset, Julien

    2015-06-01

    Exploitation can modify the characteristics of fish populations through the selective harvesting of individuals, with this potentially leading to rapid ecological and evolutionary changes. Despite the well-known effects of invasive fishes on aquatic ecosystems generally, the potential effects of their selective removal through angling, a strategy commonly used to manage invasive fish, are poorly understood. The aim of this field-based study was to use the North American pumpkinseed Lepomis gibbosus as the model species to investigate the consequences of selective removal on their population characteristics and juvenile growth rates across 10 populations in artificial lakes in southern France. We found that the maximal individual mass in populations decreased as removal pressure through angling increased, whereas we did not observed any changes in the maximal individual length in populations as removal pressure increased. Total population abundance did not decrease as removal pressure increased; instead, here was a U-shaped relationship between removal pressure and the abundance of medium-bodied individuals. In addition, population biomass had a U-shaped curve response to removal pressure, implying that invasive fish populations can modulate their characteristics to compensate for the negative effects of selective removals. In addition, individual lengths at age 2 and juvenile growth rates decreased as removal pressure through angling increased, suggesting a shift toward an earlier size at maturity and an overall slower growing phenotype. Therefore, these outputs challenge the efficiency of selective management methods, suggesting the use of more proactive strategies to control invasive populations, and the need to investigate the potential ecological and evolutionary repercussions of nonrandom removal. PMID:26078856

  19. Impacts of invasive fish removal through angling on population characteristics and juvenile growth rate

    PubMed Central

    Evangelista, Charlotte; Britton, Robert J; Cucherousset, Julien

    2015-01-01

    Exploitation can modify the characteristics of fish populations through the selective harvesting of individuals, with this potentially leading to rapid ecological and evolutionary changes. Despite the well-known effects of invasive fishes on aquatic ecosystems generally, the potential effects of their selective removal through angling, a strategy commonly used to manage invasive fish, are poorly understood. The aim of this field-based study was to use the North American pumpkinseed Lepomis gibbosus as the model species to investigate the consequences of selective removal on their population characteristics and juvenile growth rates across 10 populations in artificial lakes in southern France. We found that the maximal individual mass in populations decreased as removal pressure through angling increased, whereas we did not observed any changes in the maximal individual length in populations as removal pressure increased. Total population abundance did not decrease as removal pressure increased; instead, here was a U-shaped relationship between removal pressure and the abundance of medium-bodied individuals. In addition, population biomass had a U-shaped curve response to removal pressure, implying that invasive fish populations can modulate their characteristics to compensate for the negative effects of selective removals. In addition, individual lengths at age 2 and juvenile growth rates decreased as removal pressure through angling increased, suggesting a shift toward an earlier size at maturity and an overall slower growing phenotype. Therefore, these outputs challenge the efficiency of selective management methods, suggesting the use of more proactive strategies to control invasive populations, and the need to investigate the potential ecological and evolutionary repercussions of nonrandom removal.

  20. Rapid depletion of genotypes with fast growth and bold personality traits from harvested fish populations

    PubMed Central

    Biro, Peter A.; Post, John R.

    2008-01-01

    The possibility for fishery-induced evolution of life history traits is an important but unresolved issue for exploited fish populations. Because fisheries tend to select and remove the largest individuals, there is the evolutionary potential for lasting effects on fish production and productivity. Size selection represents an indirect mechanism of selection against rapid growth rate, because individual fish may be large because of rapid growth or because of slow growth but old age. The possibility for direct selection on growth rate, whereby fast-growing genotypes are more vulnerable to fishing irrespective of their size, is unexplored. In this scenario, faster-growing genotypes may be more vulnerable to fishing because of greater appetite and correspondingly greater feeding-related activity rates and boldness that could increase encounter with fishing gear and vulnerability to it. In a realistic whole-lake experiment, we show that fast-growing fish genotypes are harvested at three times the rate of the slow-growing genotypes within two replicate lake populations. Overall, 50% of fast-growing individuals were harvested compared with 30% of slow-growing individuals, independent of body size. Greater harvest of fast-growing genotypes was attributable to their greater behavioral vulnerability, being more active and bold. Given that growth is heritable in fishes, we speculate that evolution of slower growth rates attributable to behavioral vulnerability may be widespread in harvested fish populations. Our results indicate that commonly used minimum size-limits will not prevent overexploitation of fast-growing genotypes and individuals because of size-independent growth-rate selection by fishing. PMID:18299567

  1. Exponential Graphing Using Technology

    NSDL National Science Digital Library

    Cheryl Gaynr

    2012-07-27

    This lesson is teacher/student directed for discovering and translating exponential functions using a graphing app. The lesson focuses on the translations from a parent graph and how changing the coefficient, base and exponent values relate to the transformation.

  2. World Population: Trends, Mechanisms, Singularities 1 (References contain bolded blue live html links)

    E-print Network

    White, Douglas R.

    of population growth trends, endogenous and exogenous. We will consider these after we complete the discussion . In either the discrete or continuous case, equation (1) generates an exponential growth curve. Equation (2World Population: Trends, Mechanisms, Singularities 1 (References contain bolded blue live html

  3. Sex, population dynamics and resting egg production in rotifers

    Microsoft Academic Search

    Terry W. Snell

    1987-01-01

    The interaction between sexual reproduction and population growth in the rotifer Brachionus plicatilis was examined using exponential and logistic growth models. A computer simulation was used to explore the effects of the frequency\\u000a of sex and the proportion of a female's daughters reproducing sexually on population growth rate and resting egg production.\\u000a Within the parameters of the simulation, the proportion

  4. Effects of cyanobacterial toxicity and morphology on the population growth of freshwater zooplankton: Meta-analyses of laboratory experiments

    Microsoft Academic Search

    Alan E. Wilson; Orlando Sarnelle; Angeline R. Tillmanns

    2006-01-01

    We synthesized data from 66 published laboratory studies, representing 597 experimental comparisons, examining the effects of cyanobacterial toxicity and morphology on the population growth rate and survivorship of 17 genera (34 species) of freshwater, herbivorous zooplankton. Two meta-analyses were conducted with these data. The primary analysis compared herbivore population growth rates for grazers fed treatment diets containing cyanobacteria versus control

  5. Population growth of Asplanchna sieboldi fed two Brachionus spp. (Rotifera) raised on green alga and baker's yeast

    Microsoft Academic Search

    S. S. S. Sarma; P. S. Larios-Jurado; S. Nandini

    2002-01-01

    We conducted population growth experiments of A. sieboldi using Brachionus calyciflorus and Brachionus patulus as prey. The prey rotifers were mass cultured separately on Chlorella vulgaris, Saccharomyces cerevisiae or on their mixture. Data on population growth of A. sieboldi showed prey type and food density-related differences. At any given prey concentration, both B. calyciflorus and B. patulus raised on a

  6. Age, growth, and mortality of introduced flathead catfish in Atlantic rivers and a review of other populations

    USGS Publications Warehouse

    Kwak, T.J.; Pine, William E., III; Waters, D.S.

    2006-01-01

    Knowledge of individual growth and mortality rates of an introduced fish population is required to determine the success and degree of establishment as well as to predict the fish's impact on native fauna. The age and growth of flathead catfish Pylodictis olivaris have been studied extensively in the species' native and introduced ranges, and estimates have varied widely. We quantified individual growth rates and age structure of three introduced flathead catfish populations in North Carolina's Atlantic slope rivers using sagittal otoliths, determined trends in growth rates over time, compared these estimates among rivers in native and introduced ranges, and determined total mortality rates for each population. Growth was significantly faster in the Northeast Cape Fear River (NECFR) than in the Lumber and Neuse rivers. Fish in the NECFR grew to a total length of 700 mm by age 7, whereas fish in the Neuse and Lumber river populations reached this length by 8 and 10 years, respectively. The growth rates of fish in all three rivers were consistently higher than those of native riverine populations, similar to those of native reservoir populations, and slower than those of other introduced riverine populations. In general, recent cohorts (1998-2001 year-classes) in these three rivers exhibited slower growth among all ages than did cohorts previous to the 1998 year-class. The annual total mortality rate was similar among the three rivers, ranging from 0.16 to 0.20. These mortality estimates are considerably lower than those from the Missouri and Mississippi rivers, suggesting relatively low fishing mortality for these introduced populations. Overall, flathead catfish populations in reservoirs grow faster than those in rivers, the growth rates of introduced populations exceed those of native populations, and eastern United States populations grow faster than those in western states. Such trends constitute critical information for understanding and managing local populations.

  7. Population Growth of Soybean Aphid, Aphis glycines, Under Varying Levels of Predator Exclusion

    PubMed Central

    Meihls, Lisa N.; Clark, Thomas L.; Bailey, Wayne C.; Ellersieck, Mark R.

    2010-01-01

    Although soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has caused economic damage in several Midwestern states, growers in Missouri have experienced relatively minor damage. To evaluate whether existing predatory insect populations are capable of suppressing or preventing soybean aphid population growth or establishment in Missouri, a predator exclusion study was conducted to gauge the efficacy of predator populations. Three levels of predator exclusion were used; one that excluded all insects (small mesh), one that excluded insects larger than thrips (medium mesh), and one that excluded insects larger than Orius insidiosus (Say) (Hemiptera: Anthocoridae), a principal predator (large mesh). Along with manipulating predator exposure, timing of aphid arrival (infestation) was manipulated. Three infestation times were studied; vegetative (V5), beginning bloom (R1), and beginning pod set (R3). Timing of aphid and predator arrival in a soybean field may affect the soybean aphid's ability to establish and begin reproducing. Cages infested at V5 and with complete predator exclusion reached economic threshold within two weeks, while cages with predators reached economic threshold in four and a half weeks. Cages infested at R1 with complete predator exclusion reached economic threshold within five weeks; cages with predators reached economic threshold within six weeks. Cages infested at R3 never reached threshold (with or without predators). The predator population in Missouri seems robust, capable of depressing the growth of soybean aphid populations once established, and even preventing establishment when the aphid arrived late in the field. PMID:21073344

  8. Question 2.7: Logistic growth of a tumor. Zobl et al. [1] have studied the growth functions of tumors by inducing novel sarcomas in the kidneys of rats with Polyoma virus. These tumors

    E-print Network

    Utrecht, Universiteit

    exponentially and then approach a steady state volume. This growth function can therefore potentially linearly with the population size, i.e., (1 - N/K) gives a linear decline of the growth rate, which becomesQuestion 2.7: Logistic growth of a tumor. Zobl et al. [1] have studied the growth functions

  9. Comparison of Growth, Condition and Population Structure of White Crappie in Lake Carl Blackwell, 1984-1985 to 1998

    Microsoft Academic Search

    Wyatt J. Doyle; Dale W. Toetz; Mark E. Payton

    White crappie, Pomoxis annularis, is an important sport fish in Oklahoma, but some populations grow slowly or have undesirable population structure. The management of the species is not a settled issue and requires data bases for temporal and\\/or lake to lake comparisons. This paper reports decadal changes in growth, condition and population structure for white crappie in Lake Carl Blackwell,

  10. Socio-Economic Instability and the Scaling of Energy Use with Population Size

    PubMed Central

    DeLong, John P.; Burger, Oskar

    2015-01-01

    The size of the human population is relevant to the development of a sustainable world, yet the forces setting growth or declines in the human population are poorly understood. Generally, population growth rates depend on whether new individuals compete for the same energy (leading to Malthusian or density-dependent growth) or help to generate new energy (leading to exponential and super-exponential growth). It has been hypothesized that exponential and super-exponential growth in humans has resulted from carrying capacity, which is in part determined by energy availability, keeping pace with or exceeding the rate of population growth. We evaluated the relationship between energy use and population size for countries with long records of both and the world as a whole to assess whether energy yields are consistent with the idea of an increasing carrying capacity. We find that on average energy use has indeed kept pace with population size over long time periods. We also show, however, that the energy-population scaling exponent plummets during, and its temporal variability increases preceding, periods of social, political, technological, and environmental change. We suggest that efforts to increase the reliability of future energy yields may be essential for stabilizing both population growth and the global socio-economic system. PMID:26091499

  11. Comparative population growth of Ceriodaphnia dubia and Daphnia pulex (Cladocera) exposed to zinc toxicity.

    PubMed

    Sanchez-Ortiz, Jonathan Raul; Sarma, S S S; Nandini, S

    2010-01-01

    Population growth of two cladocerans (Ceriodaphnia dubia and Daphnia pulex) exposed to 4 different concentrations of ZnCl(2) (0.125, 0.25, 0.5 and 1.0 mg L(-1), plus controls) at one algal food (Scenedesmus acutus) density (0.5 X 10(6) cells mL(-1)) was quantified for 30 days. Population densities of C. dubia and D. pulex decreased with increasing concentration of Zn in the medium. At a concentration of 1 mg L(-1) of ZnCl(2), both C. dubia and D. pulex did not reproduce and died within a week. The peak population densities of C. dubia ranged from 0.2 to 6.0 ind. mL(-1), depending on the Zn level in the medium, whereas this range was lower for D. pulex (0.2 to 4.1 ind. mL(-1)). The peak population density was inversely related to the Zn concentration. The rate of population increase (r) varied from -0.12 to +0.14 and -0.02 to +0.23 per day for C. dubia and D. pulex, respectively, depending on the Zn level in the medium. Statistically, both the peak population density and the r were significantly affected by the heavy metal concentration in the medium. Multiple comparison tests showed that the rate of population increase (r) of D. pulex in the lowest ZnCl(2) level (0.125 mg L(-1)) was significantly higher than controls. However, under similar conditions, the r of C. dubia was significantly lower than controls. With a further increase in Zn level, the growth rates of both the cladoceran species were significantly reduced as compared to controls. The results are discussed in relation to published data on the toxicity of zinc to freshwater zooplankton. PMID:20390839

  12. The Role of Assortative Mating on Population Growth in Contemporary Developed Societies

    Microsoft Academic Search

    Mike Murphy

    Assortative mating is a widespread feature of human behaviour, which has a number of suggested benefits. The question of whether\\u000a it contributes to population growth in contemporary societies is considered using the micro simulation program SOCSIM. Ways\\u000a of parameterising heterogeneous fertility and nuptiality, and the relationship of such parameters to those of both fathers\\u000a and mothers are considered. The magnitude

  13. POPULATION GROWTH OF EUCHLANIS DILATATA (ROTIFERA): COMBINED EFFECTS OF METHYL PARATHION AND FOOD (CHLORELLA VULGARIS)

    Microsoft Academic Search

    S. S.S. Sarma; S. Nandini; José L. Gama-Flores; M. A. Fernandez-Araiza

    2001-01-01

    In the present work, the combined impact of four concentrations (0, 0.0625, 0.125, and 0.25 mg\\/L) of methyl parathion and three densities (0.5 × 10, 1.0 × 10, and 2.0 × 10 cells\\/mL) of the green alga Chlorella vulgaris on the population growth of Euchlanis dilatata was studied. In general, regardless of the food level, an increase in the concentration

  14. Effects of density and fire on the vital rates and population growth of a perennial goldenaster

    PubMed Central

    Gornish, Elise S.

    2013-01-01

    Intraspecific density effects are generally associated with other factors, like disturbance. Therefore, the ways in which density effects might interact with disturbance to modify the relationships between vital rates and population growth must be understood. I quantified the effects of density on the life-history stages of the perennial composite Pityopsis aspera over 3 years, the span of which included years in which fire did and did not occur. In an experimental study, I estimated the survival, growth and reproduction for shoots in plots established across a natural range of densities in Florida, USA. In a novel analysis, a regression-design life-table response experiment was used to determine which transitions were associated with density, how they contributed to differences in estimated population growth rates and how this relationship differed as a result of fire. The shape of the relationship between population growth rate (?) and density was modified by fire, primarily as a result of contributions from adult flowering stasis and survival, and first-year survival probabilities. Fire modified and even reversed the effect of extreme densities on adult flowering stasis and survival and of first-year survival, resulting in more positive contributions from these transitions to ? at the lowest and highest density values. These results demonstrate the first application of a regression-design life-table response experiment to elucidating the interactive effects of density and fire. They highlight the utility of this approach for both capturing the complex dynamics of populations and establishing a means of determining how vital rates might contribute to differences in demography across densities.

  15. National Culture, Economic Development, Population Growth and Environmental Performance: The Mediating Role of Education

    Microsoft Academic Search

    Yu-Shu Peng; Shing-Shiuan Lin

    2009-01-01

    Literature on ethical behavior has paid little attention to the mechanism between macro-\\u0009environmental variables and environmental\\u000a performance. This study aims at constructing a model to examine the?relationships which link cultural values, population growth,\\u000a economic development, and environmental performance by incorporating the mediating role of education. The multiple linear\\u000a regression model was employed to test the hypotheses on a 3-year-pooled

  16. Stationary solutions to a system of size-structured populations with nonlinear growth rate.

    PubMed

    Kato, Nobuyuki

    2012-01-01

    We study stationary solutions to a system of size-structured population models with nonlinear growth rate. Several characterizations of stationary solutions are provided. It is shown that the steady-state problem can be converted into different problems such as two types of eigenvalue problems and a fixed-point problem. In the two-species case, we give an existence result of nonzero stationary solutions by using the fixed-point problem. PMID:22873674

  17. A Distinct Macrophage Population Mediates Metastatic Breast Cancer Cell Extravasation, Establishment and Growth

    Microsoft Academic Search

    Binzhi Qian; Yan Deng; Jae Hong Im; Ruth J. Muschel; Yiyu Zou; Jiufeng Li; Richard A. Lang; Jeffrey W. Pollard; Stefan Bereswill

    2009-01-01

    BackgroundThe stromal microenvironment and particularly the macrophage component of primary tumors influence their malignant potential. However, at the metastatic site the role of these cells and their mechanism of actions for establishment and growth of metastases remain largely unknown.Methodology\\/Principal FindingsUsing animal models of breast cancer metastasis, we show that a population of host macrophages displaying a distinct phenotype is recruited

  18. Cell population growth in the rat parotid gland during postnatal development

    Microsoft Academic Search

    R Taga; A Sesso

    2001-01-01

    The growth kinetics of different cell populations in the rat parotid was studied. The evolution of the frequency and absolute number of each cell type was determined morphometrically by a particle-counting method and the evolution of the [3H]thymidine labeling indices of the same cell types was determined by autoradiography. The data obtained for the evolution of cell number in each

  19. Population growth and allergen accumulation of Dermatophagoides pteronyssinus cultured at 20 and 25°C

    Microsoft Academic Search

    Lakshmi Yella; Marjorie S. Morgan; Larry G. Arlian

    2011-01-01

    The house dust mites, Dermatophagoides pteronyssinus and D. farinae are cultured commercially and in research laboratories and material is harvested from these cultures to make extracts that\\u000a are used for diagnosis, immunotherapy and research. Temperature and other climatic conditions can influence population growth\\u000a rates, dynamics of allergen production, and the associated endotoxin, enzyme and protein levels of the mite material

  20. Periodic Matrix Population Models: Growth Rate, Basic Reproduction Number, and Entropy

    Microsoft Academic Search

    Nicolas Bacaër

    2009-01-01

    This article considers three different aspects of periodic matrix population models. First, a formula for the sensitivity\\u000a analysis of the growth rate ? is obtained that is simpler than the one obtained by Caswell and Trevisan. Secondly, the formula for the basic reproduction\\u000a number ?0 in a constant environment is generalized to the case of a periodic environment. Some inequalities

  1. Population growth of some genera of cladocerans (Cladocera) in relation to algal food ( Chlorella vulgaris ) levels

    Microsoft Academic Search

    S. Nandini; S. S. S. Sarma

    2003-01-01

    We studied the patterns of population growth of 7 cladoceran species (Alona rectangula, Ceriodaphnia dubia, Daphnia laevis, Diaphanosoma brachyurum, Moina macrocopa, Scapholeberis kingi and Simocephalus vetulus) using 6 algal densities, viz. 0.05×106, 0.1×106, 0.2×106, 0.4×106, 0.8×106 and 1.6×106 cells ml-1, of Chlorella vulgaris for 18 – 30 days. In terms of carbon content these algal concentrations corresponded to 0.29, 0.58,

  2. Study of the growth and development of chlorella populations in the culture as a whole

    Microsoft Academic Search

    R. ?etovský; I. Klástebská

    1959-01-01

    Summary  Two nutrient media were prepared, on which the growth and development of populations ofChlorella pyrenoidosa andChlorella vulgaris var.viridis were biologically the same. On medium both species of Chlorella proliferated chiefly by division of the cells into two autospores,\\u000a whereas on medium A different numbers of autospores were formed from maternal cells of different sizes.Chlorella protothecoides, which is maintained in the

  3. Effect of microstructure on population growth parameters of Escherichia coli in gelatin-dextran systems.

    PubMed

    Boons, Kathleen; Noriega, Estefanía; Van den Broeck, Rob; David, Charlotte C; Hofkens, Johan; Van Impe, Jan F

    2014-09-01

    Current literature acknowledges the effect of food structure on bacterial dynamics. Most studies introduce this "structure" factor using a single gelling agent, resulting in a homogeneous environment, whereas in practice most food products are heterogeneous. Therefore, this study focuses on heterogeneous protein-polysaccharide mixtures, based on gelatin and dextran. These mixtures show phase separation, leading to a range of heterogeneous microstructures by adjusting relative concentrations of both gelling agents. Based on confocal microscope observations, the growth of Escherichia coli in gelatin-dextran systems was observed to occur in the dextran phase. To find a relation between microscopic and population behavior, growth experiments were performed in binary and singular gelatin-dextran systems and culture broth at 23.5°C, with or without adding 2.9% (wt/vol) NaCl. The Baranyi and Roberts growth model was fitted to the experimental data and parameter estimates were statistically compared. For salted binary mixtures, a decrease in the population maximum cell density was observed with increasing gelatin concentration. In this series, for one type of microstructure, i.e., a gelatin matrix phase with a disperse dextran phase, the maximum cell density decreased with decreasing percentage of dextran phase. However, this relation no longer held when other types of microstructure were observed. Compared to singular systems, adding a second gelling agent in the presence of NaCl had an effect on population lag phases and maximum cell densities. For unsalted media, the growth parameters of singular and binary mixtures were comparable. Introducing this information into mathematical models leads to more reliable growth predictions and enhanced food safety. PMID:24951795

  4. Exponentially fitted symplectic integrator

    NASA Astrophysics Data System (ADS)

    Simos, T. E.; Vigo-Aguiar, Jesus

    2003-01-01

    In this paper a procedure for constructing efficient symplectic integrators for Hamiltonian problems is introduced. This procedure is based on the combination of the exponential fitting technique and symplecticness conditions. Based on this procedure, a simple modified Runge-Kutta-Nyström second-order algebraic exponentially fitted method is developed. We give explicitly the symplecticness conditions for the modified Runge-Kutta-Nyström method. We also give the exponential fitting and trigonometric fitting conditions. Numerical results indicate that the present method is much more efficient than the “classical” symplectic Runge-Kutta-Nyström second-order algebraic method introduced by M.P. Calvo and J.M. Sanz-Serna [J. Sci. Comput. (USA) 14, 1237 (1993)]. We note that the present procedure is appropriate for all near-unimodal systems.

  5. The relationship between population growth and real assessed market values: note.

    PubMed

    Gamble, H B; Downing, R H

    1985-07-01

    Various indices are commonly used to measure growth or decline in communities and regions, but this article suggests another measure which is fairly easy to obtain--the change over time in real assessed market values. Computer storage and analysis of real estate assessment and sales data make it possible to determine accurate true assessment ratios which can be used to calculate reasonable estimates of market values. This article shows the relationship between population growth from 1970 to 1980 and the changes in real assessed market values of various property classes for over 400 Pennsylvania townships. This can provide insight into the kind and nature of community change. The most noteworthy aspect of these data, not apparent in conventional growth measures, is the magnitude of increases of residential property values in all growth categories, but particularly in the high growth townships. This kind of data could be calculated by countries or by regions; this might be more informative and useful to planners and researchers in such form. Comparing local data to regional, community, or state landmark data can help identify strengths and weaknesses or the particular nature of a community's growth. PMID:12314193

  6. Matrix Models for Size-Structured Populations: Unrealistic Fast Growth or Simply Diffusion?

    PubMed Central

    Picard, Nicolas; Liang, Jingjing

    2014-01-01

    Matrix population models are widely used to study population dynamics but have been criticized because their outputs are sensitive to the dimension of the matrix (or, equivalently, to the class width). This sensitivity is concerning for the population growth rate () because this is an intrinsic characteristic of the population that should not depend on the model specification. It has been suggested that the sensitivity of to matrix dimension was linked to the existence of fast pathways (i.e. the fraction of individuals that systematically move up a class), whose proportion increases when class width increases. We showed that for matrix population models with growth transition only from class to class , was independent of the class width when the mortality and the recruitment rates were constant, irrespective of the growth rate. We also showed that if there were indeed fast pathways, there were also in about the same proportion slow pathways (i.e. the fraction of individuals that systematically remained in the same class), and that they jointly act as a diffusion process (where diffusion here is the movement in size of an individual whose size increments are random according to a normal distribution with mean zero). For 53 tree species from a tropical rain forest in the Central African Republic, the diffusion resulting from common matrix dimensions was much stronger than would be realistic. Yet, the sensitivity of to matrix dimension for a class width in the range 1–10 cm was small, much smaller than the sampling uncertainty on the value of . Moreover, could either increase or decrease when class width increased depending on the species. Overall, even if the class width should be kept small enough to limit diffusion, it had little impact on the estimate of for tree species. PMID:24905941

  7. Spatial analysis of cattle and shoat population in Ethiopia: growth trend, distribution and market access.

    PubMed

    Leta, Samson; Mesele, Frehiwot

    2014-01-01

    The livestock subsector has an enormous contribution to Ethiopia's national economy and livelihoods of many Ethiopians. The subsector contributes about 16.5% of the national Gross Domestic Product (GDP) and 35.6% of the agricultural GDP. It also contributes 15% of export earnings and 30% of agricultural employment. The livestock subsector currently support and sustain livelihoods for 80% of all rural population. The GDP of livestock related activities valued at 59 billion birr. Ethiopian livestock population trends, distribution and marketing vary considerably across space and time due to a variety of reasons. This study was aimed to assess cattle and shoat population growth trend, distribution and their access to market. Regression analysis was used to assess the cattle and shoat population growth trend and Geographic Information Systems (GIS) techniques were used to determine the spatial distribution of cattle and shoats, and their relative access to market. The data sets used are agricultural census (2001/02) and annual CSA agricultural sample survey (1995/96 to 2012/13). In the past eighteen years, the livestock population namely cattle, sheep and goat grew from 54.5 million to over 103.5 million with average annual increment of 3.4 million. The current average national cattle, sheep and goat population per km(2) are estimated to be 71, 33 and 29 respectively (excluding Addis Ababa, Afar and Somali regions). From the total livestock population the country owns about 46% cattle, 43% sheep and 40% goats are reared within 10 km radius from major livestock market centres and all-weather roads. On the other hand, three fourth of the country's land mass which comprises 15% of the cattle, 20% of the sheep and 21% of goat population is not accessible to market (greater than 30 km from major livestock market centres). It is found that the central highland regions account for the largest share of livestock population and also more accessible to market. Defining the spatial and temporal variations of livestock population is crucial in order to develop a sound and geographically targeted livestock development policy. PMID:25019048

  8. Vascular Endothelial Growth Factor-A Is Associated with Chronic Mountain Sickness in the Andean Population

    PubMed Central

    Espinoza, Jose R.; Alvarez, Giancarlo; León-Velarde, Fabiola; Ju Preciado, Hugo F.; Macarlupu, Jose-Luis; Rivera-Ch, Maria; Rodriguez, Jorge; Favier, Judith; Gimenez-Roqueplo, Anne-Paule

    2014-01-01

    Abstract Espinoza, Jose R., Giancarlo Alvarez, Fabiola León-Velarde, Hugo F. Ju Preciado, Jose-Luis Macarlupu, Maria Rivera-Ch, Jorge Rodriguez, Judith Favier, Anne-Paule Gimenez-Roqueplo, and Jean-Paul Richalet. Vascular endothelial growth factor-A is associated with chronic mountain sickness in Andean population. High Alt Med Biol. 15:146–154, 2014.—A study of chronic mountain sickness (CMS) with a candidate gene—vascular endothelial growth factor A (VEGFA)—was carried out in a Peruvian population living at high altitude in Cerro de Pasco (4380?m). The study was performed by genotyping of 11 tag SNPs encompassing 2.2?kb of region of VEGFA gene in patients with a diagnosis of CMS (n=131; 49.1±12.7 years old) and unrelated healthy controls (n=84; 47.2±13.4 years old). The VEGFA tag SNP rs3025033 was found associated with CMS (p<0.05), individuals with AG genotype have 2.5 more risk of CMS compared to those with GG genotype (p<0.02; OR, 2.54; 95% CI: 1.10–5.88). Pairwise Fst and Nei's distance indicate genetic differentiation between Cerro de Pasco population and HapMap3 population (Fst>0.36, p<0.01), suggesting selection is operating on the VEGF gene. Our results suggest that VEGFA is associated with CMS in long-term residents at high altitude in the Peruvian Andes. PMID:24971768

  9. Grid cells analysis of urban growth using remote sensing and population census data

    NASA Astrophysics Data System (ADS)

    Bagan, H.; Yamagata, Y.

    2012-12-01

    Urban growth and sprawl have drastically altered the ecosystems and ecosystem services. Urban areas are an increasingly important component of the global environment, yet they remain one of the most challenging areas for conducting research. Remote sensing based information is one of the most important resources to support urban planning and administration in megacities. It is possible to provide the up-to-date information regarding the extent, growth, and physical characteristics of urban land. Remote sensing provides spatially consistent image information that covers broad areas with both high spatial resolution and high temporal frequency. Therefore, remote sensing is an important tool for providing information on urban land-cover characteristics and their changes over time at various spatial and temporal scales. Urban land-use and land-cover changes are linked to socio-economic activities. Urbanization includes both the physical growth of a city and the movement of people to urban areas. As a consequence, it is essential to combine remote sensing derived parameters with socio-economic parameter to analyze the spatial-temporal changes and interaction of both factors. The aim of the research was to use1-km2 grid cells to investigate the spatial and temporal dynamics of urban growth in the world mega cities. The research was conducted in the 50 global cities using Landsat ETM/TM remote sensing imagery from 1985 - 2011, and time series population census data (1-km2 resolution gridded population census data of Japan and 2.5 arc-minute resolutions Gridded Population of the World). First, maximum likelihood classification (MLC) method were used to produce land cover maps by using Landsat images. Then intersect the land cover maps with 1-km2 grid cell maps to represents the proportion of each land cover category within each 1-km2 grid cell. Finally, we combined the proportional land cover maps with gridded population census data on 1-km2 resolution grid cells to investigate the spatial relationships between the changes of land-cover classes and changes of population density. A case study in Tokyo, Japan and Beijing, China were provided. The results showed that the urban area decreased in the metropolitan inner core as the city center experienced depopulation in Tokyo. Spatial correlation analysis showed a strong positive correlation between urban expansion and population density change and that urban expansion was strongly negatively correlated with cropland change both in Tokyo and Beijing. Time series of land-cover maps of the Tokyo in 1987, 2001, and 2011. Urban B. refers to the urban/built-up class. The black lines indicate the major railway and metro lines. Five broad land-cover categories;

  10. Associations of DNA polymorphisms in growth hormone and its transcriptional regulators with growth and carcass traits in two populations of Brangus bulls

    Microsoft Academic Search

    M. G. Thomas; R. M. Enns; K. L. Shirley; M. D. Garcia; A. J. Garrett

    Sequence polymorphisms in the growth hormone (GH) gene and its transcriptional regulators, Pit-1 and Prop-1, were evaluated for associations with growth and carcass traits in two populations of Brangus bulls Chihuahuan Desert Rangeland Research Center (CDRRC, N = 248 from 14 sires) and a cooperating breeding program (COOP, N = 186 from 34 sires). Polymorphisms were SNP mutations in intron

  11. Exponentially Enhanced Quantum Metrology

    SciTech Connect

    Roy, S. M. [Computer Science, University of York, York YO 10 5DD (United Kingdom); School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Braunstein, Samuel L. [Computer Science, University of York, York YO 10 5DD (United Kingdom)

    2008-06-06

    We show that when a suitable entanglement-generating unitary operator depending on a parameter is applied on N qubits in parallel, a precision of the order of 2{sup -N} in estimating the parameter may be achieved. This exponentially improves the precision achievable in classical and in quantum nonentangling strategies.

  12. [The decline in the population growth rate--a priority issue in international politics].

    PubMed

    Rhein, E

    1994-08-25

    The Third International UN Conference on Population and Development took place in Cairo in early September 1994 with the participation of 200 governments and 1000 nongovernmental organizations to discuss ways of stabilizing world population at the possible lowest level and how industrialized countries could contribute to this effort. As a consequence of the advances in reproductive medicine the use of contraceptives skyrocketed: in 1994 more than half of men and women were using contraception compared to only 5% in 1950. However, the demographic momentum would still increase world population for another 100 years, even if fertility would drop to 2.2 children per couple (compared to 4 children in 1990). Nevertheless, the present generation could be instrumental in deciding whether the world's population will remain around 8 billion or reach 12 billion between 2050 and 2150. Poor countries can no longer afford an annual growth rate of 2-4% while also trying to improve living standards; this would require an economic growth rate of 6-8%. For the control of population growth both a sustainable environmental policy in the North, with rapid transition to renewable energy and recycling, and a more effective population policy in the South are needed. Family planning (FP) is the precondition of stabilization. The global FP outlays are envisioned to double from the 1994 figure of $5 billion to over $10 billion in the year 2000, with donor contributions to increase from 20% to 40% of the total. The US contribution is to double from $500 million by 2000, while the European Commission decided to boost expenditures for FP from DM 30 million in 1994 to DM 600 million by 2000. Japan is also expending $3 billion during this period. Recent promising developments have emerged: national pronatalist policies have diminished sharply and the pronatalist influence of religions has also declined. Political commitment at the highest level is central to a successful population policy as demonstrated in Indonesia, Bangladesh, and Egypt, whereas its lack resulted in failures in Pakistan, Turkey, and Algeria. PMID:12290837

  13. Predators select against high growth rates and risk-taking behaviour in domestic trout populations.

    PubMed Central

    Biro, Peter A.; Abrahams, Mark V.; Post, John R.; Parkinson, Eric A.

    2004-01-01

    Domesticated (farm) salmonid fishes display an increased willingness to accept risk while foraging, and achieve high growth rates not observed in nature. Theory predicts that elevated growth rates in domestic salmonids will result in greater risk-taking to access abundant food, but low survival in the presence of predators. In replicated whole-lake experiments, we observed that domestic trout (selected for high growth rates) took greater risks while foraging and grew faster than a wild strain. However, survival consequences for greater growth rates depended upon the predation environment. Domestic trout experienced greater survival when risk was low, but lower survival when risk was high. This suggests that animals with high intrinsic growth rates are selected against in populations with abundant predators, explaining the absence of such phenotypes in nature. This is, to our knowledge, the first large-scale field experiment to directly test this theory and simultaneously quantify the initial invasibility of domestic salmonid strains that escape into the wild from aquaculture operations, and the ecological conditions affecting their survival. PMID:15539348

  14. Population growth rate and genetic variability of small and large populations of Red flour beetle (Tribolium castaneum) following multigenerational exposure to copper.

    PubMed

    Laskowski, Ryszard; Radwan, Jacek; Kuduk, Katarzyna; Mendrok, Magdalena; Kramarz, Paulina

    2015-07-01

    We reared large (1000 individuals) and small (20 individuals) populations of Tribolium castaneum on diet contaminated with copper in order to determine if the size of a population affects its ability to adapt to adverse environmental conditions. After 10 generations, we used microsatellite markers to estimate and subsequently compare the genetic variability of the copper-treated populations with that of the control populations, which were reared on uncontaminated medium. Additionally, we conducted a full cross-factorial experiment which evaluated the effects of 10 generations of "pre-exposure" to copper on a population's fitness in control and copper-contaminated environments. In order to distinguish results potentially arising from genetic adaptation from those due to non-genetic effects associated to parental exposure to copper, we subjected also F11 generation, originating from parents not exposed to copper, to the same cross-factorial experiment. The effects of long-term exposure to copper depended on population size: the growth rates of small populations that were pre-exposed to copper were inhibited compared to those of small populations reared in uncontaminated environments. Large Cu-exposed populations had a higher growth rate in the F10 generation compared to the control groups, while the growth rate of the F11 generation was unaffected by copper exposure history. The only factor that had a significant effect on genetic variability was population size, but this was to be expected given the large difference in the number of individuals between large and small populations. Neither copper contamination nor its interaction with population size affected the number of microsatellite alleles retained in the F10 generation. PMID:25920509

  15. Contributions of Covariance: Decomposing the components of stochastic population growth in Cypripedium calceolus

    PubMed Central

    Nicolè, Florence; Jacquemyn, Hans; Tuljapurkar, Shripad

    2013-01-01

    Although correlations between vital rates can have important effects on evolution and demography, few studies have investigated their effects on population dynamics. Here, we extend Life Table Response Experiments (LTREs) to variable environments, showing how to quantify contributions made by: (1) mean vital rates, (2) variability driven by environmental fluctuations, (3) correlations implying demographic tradeoffs and reflecting stage transition synchrony and (4) elasticities reflecting local selection pressures. Applying our methods to the Lady’s Slipper orchid Cypripedium calceolus, we found that mean rates accounted for 77.1% of all effects on the stochastic growth rate, variability accounted for 12.6%, elasticities 6.6% and correlations 3.7%. Stochastic effects accounted for 17.6%, 15.3% and 35.9% of the total in our three populations. Larger elasticities to transitions between dormancy states and stronger correlations between emergence and survival suggest that one population was under greater pressure to remain active while the other two showed survival payoffs for dormancy in poor years. Strong negative correlations between dormancy, emergence and stasis balanced opposing contributions, resulting in near-stationarity in two populations. These new methods provide an additional tool for researchers investigating stochastic population dynamics and should be useful for a broad range of applications in basic ecology and conservation biology. PMID:23448889

  16. Scaling laws governing stochastic growth and division of single bacterial cells

    E-print Network

    Scherer, Norbert F.

    conditions. single-cell dynamics | cell-to-cell variability | exponential growth | Hinshelwood cycle (1). Thus, observation of the population is insufficient to reveal the functional form of the growthScaling laws governing stochastic growth and division of single bacterial cells Srividya Iyer

  17. Local population extinction and vitality of an epiphytic lichen in fragmented old-growth forest.

    PubMed

    Ockinger, Erik; Nilsson, Sven G

    2010-07-01

    The population dynamics of organisms living in short-lived habitats will largely depend on the turnover of habitat patches. It has been suggested that epiphytes, whose host plants can be regarded as habitat patches, often form such patch-tracking populations. However, very little is known about the long-term fate of epiphyte individuals and populations. We estimated life span and assessed environmental factors influencing changes in vitality, fertility, abundance, and distribution of the epiphytic lichen species Lobaria pulmonaria on two spatial scales, individual trees and forest patches, over a period of approximately 10 years in 66 old-growth forest fragments. The lichen had gone extinct from 7 of the 66 sites (13.0%) where it was found 10 years earlier, even though the sites remained unchanged. The risk of local population extinction increased with decreasing population size. In contrast to the decrease in the number of occupied trees and sites, the mean area of the lichen per tree increased by 43.0%. The number of trees with fertile ramets of L. pulmonaria increased from 7 (approximately 1%) to 61 (approximately 10%) trees, and the number of forest fragments with fertile ramets increased from 4 to 23 fragments. The mean annual rate of L. pulmonaria extinction at the tree level was estimated to be 2.52%, translating into an expected lifetime of 39.7 years. This disappearance rate is higher than estimated mortality rates for potential host trees. The risk of extinction at the tree level was significantly positively related to tree circumference and differed between tree species. The probability of presence of fertile ramets increased significantly with local population size. Our results show a long expected lifetime of Lobaria pulmonaria ramets on individual trees and a recent increase in vitality, probably due to decreasing air pollution. The population is, however, declining slowly even though remaining stands are left uncut, which we interpret as an extinction debt. PMID:20715632

  18. Biodiversity of a Burkholderia cepacia population isolated from the maize rhizosphere at different plant growth stages.

    PubMed Central

    Di Cello, F; Bevivino, A; Chiarini, L; Fani, R; Paffetti, D; Tabacchioni, S; Dalmastri, C

    1997-01-01

    A Burkholderia cepacia population naturally occurring in the rhizosphere of Zea mays was investigated in order to assess the degree of root association and microbial biodiversity at five stages of plant growth. The bacterial strains isolated on semiselective PCAT medium were mostly assigned to the species B. cepacia by an analysis of the restriction patterns produced by amplified DNA coding for 16S rRNA (16S rDNA) (ARDRA) with the enzyme AluI. Partial 16S rDNA nucleotide sequences of some randomly chosen isolates confirmed the ARDRA results. Throughout the study, B. cepacia was strictly associated with maize roots, ranging from 0.6 to 3.6% of the total cultivable microflora. Biodiversity among 83 B. cepacia isolates was analyzed by the random amplified polymorphic DNA (RAPD) technique with two 10-mer primers. An analysis of RAPD patterns by the analysis of molecular variance method revealed a high level of intraspecific genetic diversity in this B. cepacia population. Moreover, the genetic diversity was related to divergences among maize root samplings, with microbial genetic variability markedly higher in the first stages of plant growth; in other words, the biodiversity of this rhizosphere bacterial population decreased over time. PMID:9361434

  19. Limits to Growth--A Role Playing Activity.

    ERIC Educational Resources Information Center

    Intercom, 1985

    1985-01-01

    In this lesson, junior high students consider two instances of exponential population growth--one at the local community level and one at the world level--as a way of illuminating some of the problems posed by growth and the limits that may curtail it. (RM)

  20. Effects of recombinant human fibroblast growth factor-2 on osteogenic cell populations during orthopic osteogenesis in vivo

    Microsoft Academic Search

    G Zellin; A Linde

    2000-01-01

    The osteogenic effects of fibroblast growth factor-2 (FGF-2) in vivo on different cell populations of the osteoblastic cell lineage have not been fully elucidated. In this study, the efficacy of recombinant human fibroblast growth factor-2 (rhFGF-2) to stimulate orthopic bone formation in transosseous rat mandibular defects, with different cell populations allowed access to the defects, was investigated with the aim

  1. Endogenous fertility, mortality and economic growth: Can a Malthusian framework account for the conflicting historical trends in population?

    Microsoft Academic Search

    Isaac Ehrlich; Jinyoung Kim

    2005-01-01

    The 19th century economist Thomas Robert Malthus hypothesized that the long-run supply of labor is completely elastic at a fixed wage-income level because population growth tends to outstrip real output growth. Dynamic equilibrium with constant income and population is achieved through equilibrating adjustments in “positive checks” (mortality, starvation) and “preventive checks” (marriage, fertility). Developing economies since the Industrial Revolution, and

  2. Long-run regional population disparities in Europe during modern economic growth: a case study of Spain

    Microsoft Academic Search

    María Isabel Ayuda; Fernando Collantes; Vicente Pinilla

    2010-01-01

    The objective of the present study is to analyze the disparities in long-run regional population growth in continental Europe.\\u000a To this end, we propose a convergence equation for regional population distribution for eight Western European countries in\\u000a the period 1850–2000. Our results show that divergence in economic growth at regional level has been a common pattern in Europe.\\u000a We choose

  3. Effects of salinity on growth and survival in five Artemia franciscana (Anostraca: Artemiidae) populations from Mexico Pacific Coast.

    PubMed

    Castro-Mejía, Jorge; Castro-Barrera, Talía; Hernández-Hernández, Luis Héctor; Arredondo-Figueroa, José Luis; Castro-Mejía, Germán; de Lara-Andrade, Ramón

    2011-03-01

    Salinity is an important factor influencing growth and survival of aquatic organisms such as Artemia, a valuable aquaculture species. This study evaluated the effects of salinity on A. franciscana populations from different water bodies in Mexico's Pacific Coast. With this purpose, five autochthonous bisexual Artemia populations were tested to assess their survival and growth values against salinities of 40, 60, 80, 100 and 120 g/l, under laboratory conditions (25 +/- 2 degrees C; pH 8-10; constant light and aeration). The organisms were fed with 100 mL of rice bran and 2L of Tetraselmis suecica (500 000 cel/ml). The culture experiments were made in 200L plastic tanks, and survival and growth final values were obtained after 21 culture days. Survival and growth curves were determined by a regression analysis (R2). The significant differences between salinities were determined by ANOVA test (p < 0.05). The best survival and growth rates were found at salinities of 100-120 g/l. When the Mexican Artemia populations were cultivated at 40 g/l of salinity, 100% mortality was observed in the juvenile stage. This study determined that survival and growth values of A. franciscana populations increased with salinity. The five A. franciscana populations presented significant differences in their survival rate under various salinity regimes. The studied populations experienced high mortality at salinities under 60 g/l and over 200 g/l, and especially during the metanauplius stage. The present study confirms that growth rates in Mexican A. franciscana populations from Pacific Coast habitats are not inversely proportional to salinity. These A. franciscana populations should be cultured at 100-120 g/l of salinity to obtain better survival and growth rates. This data is useful to improve culture systems in aquaculture biomass production systems. PMID:21513197

  4. Net interstate population growth rates and the Tiebout-Tullock hypothesis: New empirical evidence, 1990–2000

    Microsoft Academic Search

    Richard J. Cebula

    2002-01-01

    This study empirically investigates the Tiebout-Tullock hypothesis as it might have applied to the pattern of net interstate\\u000a population growth rates over the period 1990–2000. For the study period, it appears that the net state population growth rate\\u000a has been an increasing function of the ratio of the total state plus local government outlays on public education in a state

  5. Genetic analysis of bone quality traits and growth in a random mating broiler population.

    PubMed

    González-Cerón, F; Rekaya, R; Aggrey, S E

    2015-05-01

    We report the genetic relationship between growth and bone quality traits in a random mating broiler control population. Traits studied were growth rates from week 0 to 4 [body weight gain (BWG) 0 to 4], from week 0 to 6 (BWG 0 to 6), and residual feed intake (RFI) from week 5 to 6 (RFI 5 to 6). Bone quality traits were obtained at 6 weeks of age. These traits were shank weight (SW), shank length (SL), shank diameter (SDIAM), tibia weight (TW), tibia length (TL), and tibia diameter (TDIAM). Likewise, tibia was used to obtain the tibia density (TDEN), tibia breaking strength (TBS), tibia mineral density (TMD), tibia mineral content (TMC), and tibia ash content (TAC). At the phenotypic level, growth traits were positively correlated with most of the bone quality traits except with TDEN and TAC which tended to show unfavorable associations (-0.04 to -0.31). Heritability of bone quality traits ranged from 0.08 to 0.54. The additive genetic associations of growth traits with weight, length, and diameter of shank and tibia were positive (0.37 to 0.80). A similar pattern was observed with TMD and TMC (0.06 to 0.65). In contrast, growth traits showed unfavorable genetic associations with TDEN, TBS, and TAC (-0.03 to -0.18). It was concluded that bone quality traits have an additive genetic background and they can be improved by means of genetic tools. It appears that selection for growth is negatively correlated with some traits involved in the integrity, health, and maturity of leg bones. PMID:25784765

  6. Population growth kinetics of Tetrahymena pyriformis exposed to selected nonpolar narcotics.

    PubMed

    Bearden, A P; Gregory, B W; Schultz, T W

    1997-11-01

    This study describes effects of selected nonpolar narcotics of varying hydrophobicity (quantified by the 1-octanol-water partition coefficient, log Kow) and molecular structure on the population growth kinetics of the freshwater ciliate Tetrahymena pyriformis. The response of Tetrahymena exposed to different nonpolar narcotics varied from a change in generation time to a change in lag phase with similar generation time compared to control. Two narcotics with high (>3.00), intermediate (>0.00 and <3.00), and low log Kow (<0. 00) values were tested. Growth of Tetrahymena inhibited up to 85% by the high log Kow toxicants (2-decanone and butylbenzene) grew with similar rates as the control, but exhibited increased lag time, suggesting that the protozoan became acclimated to toxicant stress. Results from growth of Tetrahymena in the low log Kow toxicants (ethanol and acetone) indicate an increased generation time with increasing concentration. Cells inhibited by the intermediate log Kow chemicals, 1-pentanol and anisole, exhibited a response that was a combination of the previously mentioned two contrary responses. Cells inhibited <35% with 1-pentanol and <50% with anisole grew with similar generation times as control flasks, whereas in cells inhibited >35% or >50%, respectively, the doubling times were longer than control growth. PMID:9419258

  7. Climate change and population growth in Timor Leste: implications for food security.

    PubMed

    Molyneux, Nicholas; da Cruz, Gil Rangel; Williams, Robert L; Andersen, Rebecca; Turner, Neil C

    2012-12-01

    The climate in Timor Leste (East Timor) is predicted to become about 1.5 °C warmer and about 10 % wetter on average by 2050. By the same year, the population is expected to triple from 1 to 2.5-3 million. This article maps the predicted changes in temperature and rainfall and reviews the implications of climate change and population growth on agricultural systems. Improved cultivars of maize, rice, cassava, sweet potato and peanuts with high yield performance have been introduced, but these will need to be augmented in the future with better adapted cultivars and new crops, such as food and fodder legumes and new management practices. The requirements for fertilizers to boost yields and terracing and/or contour hedgerows to prevent soil erosion of steeply sloping terrain are discussed. Contour hedges can also be used for fodder for improved animal production to provide protein to reduce malnutrition. PMID:22569843

  8. Periodic Exponential Shear of Complex Fluids

    E-print Network

    Chirag Kalelkar; Gareth McKinley

    2012-05-31

    We define a class of flows with exponential kinematics termed Periodic Exponential Shear (PES) flow which involve periodic exponential stretching of fluid elements along with their rotation. We exhibit analytical and numerical results for PES flow by using the Oldroyd-B model for viscoelastic fluids. We calculate the growth in the shear and the normal stresses analytically as well as demonstrate that repeated application of the flow leads to stable oscillatory shear and normal stresses. We define a material function applicable to a periodic, unsteady shear flow and show numerically that this material function exhibits deformation-rate thickening behavior for viscoelastic fluids subject to PES flow. We demonstrate the feasibility of PES flow by presenting preliminary experimental results from a controlled-strain rate rheometer, using a Newtonian mineral oil.

  9. In the national interest: the PCSD puts population growth back on the agenda.

    PubMed

    Dixon, B

    1995-01-01

    In 1972, President Nixon launched the Rockefeller Commission on Population Growth and the American Future. The US population has grown by more than 50 million people since 1972. In 1995, a report by the President's Council on Sustainable Development (PCSD) states that failure on the part of the US to stabilize its population will jeopardize any effort to achieve sustainable development. As a follow-up to the Earth Summit, President Clinton established the PCSD in 1993 to identify ways to encourage sustainable development in the US. The Council has 25 members representing government, business, and public interest organizations and has 8 critical issues task forces, including Energy, Transportation, Sustainable Community, Education and Outreach, Natural Resources, Eco Efficiency and Sustainable Agriculture. Timothy Wirth, Under Secretary of State for Global Affairs, spearheaded efforts to create a task force on the twin issues of population and consumption. The Population and Consumption Task Force, which began its official discussions in the spring of 1994, aimed to solicit public comment on critical population-related issues. These meetings sought both general public and expert participation on subjects such as teen pregnancy, resource use, and economic indicators. Among these recommendations are improving access to family planning services for all Americans; focusing on special efforts to reduce teen pregnancy and childbearing; improving external factors such as poverty and a lack of economic opportunities for girls and women; and reducing immigration to the US. A combination of actions are needed, including a tax shift from labor and earnings to natural resource use; development of environmentally sound technologies; and public understanding of the importance of sustainable life style and consumption choices. Individual and community action is crucial since the current Congress is unlikely to adopt policies to promote sustainable development without significant public pressure. PMID:12320284

  10. Beaver-mediated methane emission: The effects of population growth in Eurasia and the Americas.

    PubMed

    Whitfield, Colin J; Baulch, Helen M; Chun, Kwok P; Westbrook, Cherie J

    2015-02-01

    Globally, greenhouse gas budgets are dominated by natural sources, and aquatic ecosystems are a prominent source of methane (CH4) to the atmosphere. Beaver (Castor canadensis and Castor fiber) populations have experienced human-driven change, and CH4 emissions associated with their habitat remain uncertain. This study reports the effect of near extinction and recovery of beavers globally on aquatic CH4 emissions and habitat. Resurgence of native beaver populations and their introduction in other regions accounts for emission of 0.18-0.80 Tg CH4 year(-1) (year 2000). This flux is approximately 200 times larger than emissions from the same systems (ponds and flowing waters that became ponds) circa 1900. Beaver population recovery was estimated to have led to the creation of 9500-42 000 km(2) of ponded water, and increased riparian interface length of >200 000 km. Continued range expansion and population growth in South America and Europe could further increase CH4 emissions. PMID:25515021

  11. Relation between Intrauterine Growth and Subsequent Intellectual Disability in a Ten-year Population Cohort of Children in Western Australia

    Microsoft Academic Search

    Helen Leonard; Natasha Nassar; Jenny Bourke; Eve Blair; Seonaid Mulroy; Nicholas de Klerk; Carol Bower

    The authors investigated the association between intrauterine growth and intellectual disability (ID). The appro- priateness of intrauterine growth was assessed using percentage of optimal birth weight, a measure that accounts for gestational age, maternal height, parity, and infant sex. Using population-based record linkage, singleton Caucasian and Aboriginal children born in Western Australia in 1983-1992 and alive in 2002 with ID

  12. VARIABLE POPULATION GROWTH OF VARROA DESTRUCTOR (MESOSTIGMATA: VARROIDAE) IN COLONIES OF HONEY BEES (HYMENOPTERA: APIDAE) DURING A 10-YEAR PERIOD

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The intrinsic growth rates for varroa mites (Varroa destructor) significantly varied among years during 1993--2002 in Baton Rouge, LA. Mite population growth was monitored in colonies of honey bees with queens obtained from different sources in the U.S. Queens were from sources that had not select...

  13. Growth and survivorship in a tidal-flat population of the bivalve Mercenaria mercenaria from Southampton water

    Microsoft Academic Search

    C. J. Hibbert

    1977-01-01

    A monthly sampling programme was conducted to investigate aspects of the biology of a population of Mercenaria mercenaria (L.) Smooth growth curves were constructed for each year class, and the factors affecting growth rate were considered. Seasonal cycles in flesh weight and calorific content appear to be related to gonal proliferation and subsequent spawning. Recruitment is sporadic and probably depends

  14. Population growth rate of a common understory herb decreases non-linearly across a gradient of deer herbivory

    E-print Network

    Population growth rate of a common understory herb decreases non-linearly across a gradient of deer-tailed deer (Odocoileus virginianus), and the resulting increase in herbivory of forest understory plants populations of white-tailed deer (henceforth deer) throughout eastern North America (McCabe and McCabe, 1997

  15. Population growth and agricultural land use in two agro?ecological zones of Ghana, 1960–2010

    Microsoft Academic Search

    Samuel Nii Ardey Codjoe

    2006-01-01

    Multiplicative and mediating variables are combined with a demographic variable, in non?linear multiple regression models to assess the effect of population growth on agricultural land use in two agro?ecological zones of Ghana. The paper uses data from a retrospective household survey (conducted among 1568 farmers in 504 households in 24 communities), population census reports of Ghana, for 1960, 1970, 1984

  16. Size bimodality in plant populations: an alternative hypothesis

    SciTech Connect

    Huston, M.

    1986-02-01

    Symmetric competition among seedlings in a spatially random population was simulated using the exponential growth function. In these simulations each plant was randomly assigned values for m/sub 0/ (initial seed mass), r (exponential growth rate), and germination time chosen from normal distributions. The growth rate reduction factor resulting from neighbors within each plant's zone of resource depletion was calculated as the inverse of the number of plants within the zone. This reduction factor was multiplied by the randomly assigned exponential growth rate to determine the actual exponential growth rate for each plant. Bimodality produced by this model is a consequence of the discontinuous distribution of exponential growth rates resulting from a Poisson distribution of the number of neighbors. This simple model based on symmetric competition in a spatially random population provides an alternative mechanism for the appearance of bimodality. The model may explain why increasing plant density in experiments with regularly spaced plants produces results that conflict with patterns found in experiments with a random spatial pattern. 10 references, 2 figures.

  17. Quaternions and Exponentials Michael Kazhdan

    E-print Network

    Kazhdan, Michael

    Quaternions and Exponentials Michael Kazhdan (600.357 / 600.457) HB A.6 FvDFH 21.1.3 #12;Recall We and (Skew) Symmetric Matrices · Quaternions · The Exponential Map #12;Cross Product Given two 3D vectors u and (Skew) Symmetric Matrices · Quaternions · The Exponential Map #12;Quaternions Quaternions are extensions

  18. Quaternions and Exponentials Michael Kazhdan

    E-print Network

    Kazhdan, Michael

    Quaternions and Exponentials Michael Kazhdan (600.357 / 600.457) HB A.6 FvDFH 21.1.3 #12;Recall We and (Skew) Symmetric Matrices · Quaternions · The Exponential Map #12;Cross Product Given 3D vectors = 1, 2: If = and = , then + = + . If = then = . If = - and = - , then + = - + . If = - then = - . #12;Overview · Cross Products and (Skew) Symmetric Matrices · Quaternions · The Exponential Map #12

  19. Growth, reproduction & population structure of the freshwater crab Sinopotamon yangtsekiense bott, 1967, from Zhejiang, China

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Lai, Wei; Du, Nan-Shan

    1994-03-01

    Monthly investigations were mae on the population of Chinese freshwater crab, Sinopotamon yangtsekiense Bott, 1967 from April, 1984 to March, 1985. The data on 4413 specimens show that the growth was affected mainly by temperature. During the April to November growth period, the crabs' major development occurred from June through October. One year was required for a fine white oocyte to develop into a mature egg. The reproduction period was June October. Females bearing eggs were taken from June August, and crabs with young were found from July October. The females reproduced once a year but could for more than one year. The number of eggs carried by a female varied greatly according to the size of the crab, ranging from 30 to 100 eggs. New-born crabs become mature after 1 2 years. The sex ratio was approximately 1?1 in the overall population. However, the larger crabs are predominantly male. The age distribution of S. yangtsekinese was estimated from size frequency histograms. There were more adult crabs (over 70%) from June to October and more immature crabs (over 50%) from November to May.

  20. Genetic diversity of different populations and improved growth in the F1 hybrids in the swimming crab (Portunus trituberculatus).

    PubMed

    Gao, B Q; Liu, P; Li, J; Wang, Q Y; Li, X P

    2014-01-01

    The swimming crab, Portunus trituberculatus, is widely distributed throughout the coastal waters of Asian-Pacific nations and is an important economic species in this region. The aquaculture of swimming crabs has been plagued by problems associated with low growth rates, poor flesh quality, and weak disease resistance. To overcome these problems, selective breeding programs have been suggested as a means of genetically improving these traits in stock populations. In this study, we evaluated the genetic differentiation of 3 different geographical populations (Zhoushan: S; Laizhou Bay: L; and Haizhou Bay: H) using 8 polymorphic microsatellite loci. Nine strains of first filial generation were obtained, with 3 geographically populations as parental stock. We assessed the growth and survival rates of the F1 generation to identify new strains or breeds showing improvements in these economically important traits. Our results indicated that pairwise FST among populations was significantly higher than 0 (P = 0.0000) for every population pair, ranging from 0.0810 to 0.1083 for 3 different geographical populations. We observed significant heterosis for the growth and viability (survival) traits, although some strains (crossbred combinations) showed evidence of hybrid weakness in some growth measurements. One particular strain ("SL") outperformed other combinations, displaying the greatest extent of heterosis over the growth and viability (survival) traits. These results indicate that hybridization may be used to increase the performance of P. trituberculatus in aquaculture. PMID:25511029

  1. Seawater chemistry, coccolithophore population growth, and the origin of Cretaceous chalk

    NASA Astrophysics Data System (ADS)

    Stanley, Steven M.; Ries, Justin B.; Hardie, Lawrence A.

    2005-07-01

    The magnesium/calcium ratio (Mg/Ca) and calcium (Ca) concentration of seawater have oscillated throughout geologic time; our experiments indicate that these variables have strongly influenced biomineralization and chalk production by coccolithophores. The high Mg/Ca ratio of modern seawater favors precipitation of high-Mg calcite and/or aragonite. In contrast, the low Mg/Ca ratio of imputed Cretaceous seawater favored precipitation of low-Mg calcite. We have discovered that some coccolithophore species today secrete skeletal elements of high-Mg calcite, rather than low-Mg calcite, as conventionally believed. These species incorporated less Mg when the ambient Mg/Ca ratio was lowered, secreting low-Mg calcite in imputed Cretaceous seawater. Calcification stimulates cocco lithophore population growth by contributing CO2 to photosynthesis. Three extant coc co lithophore species multiplied much faster as the composition of ambient seawater was shifted toward that estimated for Cretaceous seas. Two of these species secreted high-Mg calcite in ambient seawater having Mg/Ca > 1, and incorporation of Mg in a calcite crystal inhibits growth. Calcification of the third species, which secreted low-Mg calcite at all ambient Mg/Ca ratios, is hindered by the high Mg/Ca ratio and low absolute concentration of Ca of modern seawater. We conclude that the ionic composition of Cretaceous seawater enabled cocco lithophores to produce massive chalk deposits, and conversely, that the ionic composition of modern seawater inhibits population growth for most extant coccolitho phore species, which occupy nutrient-poor waters and fail to respond to fertilization by nitrate, phosphate, or iron.

  2. Population dynamics of Gluconacetobacter diazotrophicus in sugarcane cultivars and its effect on plant growth.

    PubMed

    Muñoz-Rojas, J; Caballero-Mellado, J

    2003-11-01

    Different experiments have estimated that the contribution of biological nitrogen fixation (BNF) is largely variable among sugarcane cultivars. Which bacteria are the most important in sugarcane-associated BNF is unknown. However, Gluconacetobacter diazotrophicus has been suggested as a strong candidate responsible for the BNF observed. In the present study, bacteria-free micropropagated plantlets of five sugarcane cultivars were inoculated with three G. diazotrophicus strains belonging to different genotypes. Bacterial colonization was monitored under different nitrogen fertilization levels and at different stages of plant growth. Analysis of the population dynamics of G. diazotrophicus strains in the different sugarcane varieties showed that the bacterial populations decreased drastically in relation to plant age, regardless of the nitrogen fertilization level, bacterial genotype or sugarcane cultivars. However, the persistence of the three strains was significantly longer in some cultivars (e.g., MEX 57-473) than in others (e.g., MY 55-14). In addition, some strains (e.g., PAl 5(T)) persisted for longer periods in higher numbers than other strains (e.g., PAl 3) inside plants of all the cultivars tested. Indeed, the study showed that the inoculation of G. diazotrophicus may be beneficial for sugarcane plant growth, but this response is dependent both on the G. diazotrophicus genotype and the sugarcane variety. The most positive response to inoculation was observed with the combination of strain PAl 5(T) and the variety MEX 57-473. Although the positive effect on sugarcane growth apparently occurred by mechanisms other than nitrogen fixation, the results show the importance of the sugarcane variety for the persistence of the plant-bacteria interaction, and it could explain the different rates of BNF estimated among sugarcane cultivars. PMID:14722690

  3. Cell Differentiation in a Bacillus thuringiensis Population during Planktonic Growth, Biofilm Formation, and Host Infection

    PubMed Central

    Verplaetse, Emilie; Slamti, Leyla; Gohar, Michel

    2015-01-01

    ABSTRACT Bacillus thuringiensis (Bt) is armed to complete a full cycle in its insect host. During infection, virulence factors are expressed under the control of the quorum sensor PlcR to kill the host. After the host’s death, the quorum sensor NprR controls a necrotrophic lifestyle, allowing the vegetative cells to use the insect cadaver as a bioincubator and to survive. Only a part of the Bt population sporulates in the insect cadaver, and the precise composition of the whole population and its evolution over time are unknown. Using fluorescent reporters to record gene expression at the single-cell level, we have determined the differentiation course of a Bt population and explored the lineage existing among virulent, necrotrophic, and sporulating cells. The dynamics of cell differentiation were monitored during growth in homogenized medium, biofilm formation, and colonization of insect larvae. We demonstrated that in the insect host and in planktonic culture in rich medium, the virulence, necrotrophism, and sporulation regulators are successively activated in the same cell. In contrast, in biofilms, activation of PlcR is dispensable for NprR activation and we observed a greater heterogeneity than under the other two growth conditions. We also showed that sporulating cells arise almost exclusively from necrotrophic cells. In biofilm and in the insect cadaver, we identified an as-yet-uncharacterized category of cells that do not express any of the reporters used. Overall, we showed that PlcR, NprR, and Spo0A act as interconnected integrators to allow finely tuned adaptation of the pathogen to its environment. PMID:25922389

  4. Histopathology of Growth Anomaly Affecting the Coral, Montipora capitata: Implications on Biological Functions and Population Viability

    PubMed Central

    Burns, John H. R.; Takabayashi, Misaki

    2011-01-01

    Growth anomalies (GAs) affect the coral, Montipora capitata, at Wai'?pae, southeast Hawai'i Island. Our histopathological analysis of this disease revealed that the GA tissue undergoes changes which compromise anatomical machinery for biological functions such as defense, feeding, digestion, and reproduction. GA tissue exhibited significant reductions in density of ova (66.1–93.7%), symbiotic dinoflagellates (38.8–67.5%), mesenterial filaments (11.2–29.0%), and nematocytes (28.8–46.0%). Hyperplasia of the basal body wall but no abnormal levels of necrosis and algal or fungal invasion was found in GA tissue. Skeletal density along the basal body wall was significantly reduced in GAs compared to healthy or unaffected sections. The reductions in density of the above histological features in GA tissue were collated with disease severity data to quantify the impact of this disease at the colony and population level. Resulting calculations showed this disease reduces the fecundity of M. capitata colonies at Wai'?pae by 0.7–49.6%, depending on GA severity, and the overall population fecundity by 2.41±0.29%. In sum, GA in this M. capitata population reduces the coral's critical biological functions and increases susceptibility to erosion, clearly defining itself as a disease and an ecological threat. PMID:22205976

  5. Histopathology of growth anomaly affecting the coral, Montipora capitata: implications on biological functions and population viability.

    PubMed

    Burns, John H R; Takabayashi, Misaki

    2011-01-01

    Growth anomalies (GAs) affect the coral, Montipora capitata, at Wai'?pae, southeast Hawai'i Island. Our histopathological analysis of this disease revealed that the GA tissue undergoes changes which compromise anatomical machinery for biological functions such as defense, feeding, digestion, and reproduction. GA tissue exhibited significant reductions in density of ova (66.1-93.7%), symbiotic dinoflagellates (38.8-67.5%), mesenterial filaments (11.2-29.0%), and nematocytes (28.8-46.0%). Hyperplasia of the basal body wall but no abnormal levels of necrosis and algal or fungal invasion was found in GA tissue. Skeletal density along the basal body wall was significantly reduced in GAs compared to healthy or unaffected sections. The reductions in density of the above histological features in GA tissue were collated with disease severity data to quantify the impact of this disease at the colony and population level. Resulting calculations showed this disease reduces the fecundity of M. capitata colonies at Wai'?pae by 0.7-49.6%, depending on GA severity, and the overall population fecundity by 2.41±0.29%. In sum, GA in this M. capitata population reduces the coral's critical biological functions and increases susceptibility to erosion, clearly defining itself as a disease and an ecological threat. PMID:22205976

  6. Growing pains: How risk perception and risk communication research can help to manage the challenges of global population growth.

    PubMed

    Dawson, Ian G J; Johnson, Johnnie E V

    2014-08-01

    In 2011, the global human population reached 7 billion and medium variant projections indicate that it will exceed 9 billion before 2045. Theoretical and empirical perspectives suggest that this growth could lead to an increase in the likelihood of adverse events (e.g., food shortages, climate change, etc.) and/or the severity of adverse events (e.g., famines, natural disasters, etc.). Several scholars have posited that the size to which the global population grows and the extent to which this growth increases the likelihood of adverse outcomes will largely be shaped by individuals' decisions (in households, organizations, governments, etc.). In light of the strong relationship between perceived risk and decision behaviors, it is surprising that there remains a dearth of empirical research that specifically examines the perceived risks of population growth and how these perceptions might influence related decisions. In an attempt to motivate this important strand of research, this article examines the major risks that may be exacerbated by global population growth and draws upon empirical work concerning the perception and communication of risk to identify potential directions for future research. The article also considers how individuals might perceive both the risks and benefits of population growth and be helped to better understand and address the related issues. The answers to these questions could help humanity better manage the emerging consequences of its continuing success in increasing infant survival and adult longevity. PMID:24593179

  7. Population growth of Brachionus macracanthus (Rotifera) in relation to cadmium toxicity: influence of algal (Chlorella vulgaris) density.

    PubMed

    Nandini, S; Chaparro-Herrera, Diego De Jesús; Cárdenas-Arriola, Sara Leticia; Sarma, S S S

    2007-08-01

    In the present work, we quantified the harmful effects of Cd(+ 2) to Brachionus macracanthus using both acute (median lethal) and chronic (population growth) toxicity tests. Chronic toxicity tests were conducted under 4 different concentrations (0.000625-0.005 mg L(- 1)) of cadmium chloride at 23 degrees C under 3 food (Chlorella vulgaris) levels (0.5 x 10(6), 1.0 x 10(6) and 2.0 x 10(6) cells mL(- 1)) using static renewal system for three weeks. The median lethal concentration bioassayed at 24 h (LC(50)) for B. macracanthus was 0.19 mg L(- 1) of CdCl(2). Cadmium adversely affected the population growth of B. macracanthus at all tested concentrations. Increase in algal food had a positive effect on the rotifer growth in controls; with increase in Cd levels, the population growth of B. macracanthus decreased even under the highest food level tested. The peak population abundance of B. macracanthus in controls at the highest food level of 2.0 x 10(6) cells mL(- 1) was 40 ind. mL(- 1). Depending on the heavy metal concentration and the algal level, the population growth rate (r) of B. macracanthus varied from 0.02 to 0.28 day(- 1). The relatively higher sensitivity of B. macracanthus to cadmium toxicity is discussed in relation to other species of the same genus. PMID:17680487

  8. From cellular properties to population asymptotics in the Population Balance Equation

    E-print Network

    Friedlander, Tamar

    2008-01-01

    Recent experiments have shown that cell populations at steady state growth often exhibit broad protein distributions with exponential tails. The sources of this variation in a dividing population and the degree of universality of steady state distributions is a topic of much theoretical interest. Here we address the problem by studying the Population Balance Equation, a general framework that describes growth (or production) and division in a population. We show that the tail of the steady state distribution is determined by a combination of the production and division functions, not by each of them separately, and is insensitive to other model details. Under general conditions this tail turns out to be exponential, as observed in experiments, with the correct dependence on system parameters. We discuss the conditions for this effect to be dominant over other sources of variation and the relation of the results to experiments.

  9. Predicting Individual Bacterium Cell Growth Behavior from Population Information We explore the kinetics of bacterial cells to predict the dependency of growth and division rates on cell length and

    E-print Network

    Watkins, Joseph C.

    ) - the steady-state length density function. - and a number k, the instantaneous growth rate of the populationPredicting Individual Bacterium Cell Growth Behavior from Population Information Abstract We explore the kinetics of bacterial cells to predict the dependency of growth and division rates on cell

  10. The 'Natural Laboratory', a tool for deciphering growth, lifetime and population dynamics in larger benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Hohenegger, Johann

    2015-04-01

    The shells of symbiont-bearing larger benthic Foraminifera (LBF) represent the response to physiological requirements in dependence of environmental conditions. All compartments of the shell such as chambers and chamberlets accommodate the growth of the cell protoplasm and are adaptations for housing photosymbiotic algae. Investigations on the biology of LBF were predominantly based on laboratory studies. The lifetime of LBF under natural conditions is still unclear. LBF, which can build >100 chambers during their lifetime, are thought to live at least one year under natural conditions. This is supported by studies on population dynamics of eulittoral foraminifera. In species characterized by a time-restricted single reproduction period the mean size of specimens increases from small to large during lifetime simultaneously reducing individual number. This becomes more complex when two or more reproduction times are present within a one-year cycle leading to a mixture of abundant small individuals with few large specimens during the year, while keeping mean size more or less constant. This mixture is typical for most sublittoral megalospheric (gamonts or schizonts) LBF. Nothing is known on the lifetime of agamonts, the diploid asexually reproducing generation. In all hyaline LBF it is thought to be significantly longer than 1 year based on the large size and considering the mean chamber building rate of the gamont/schizonts. Observations on LBF under natural conditions have not been performed yet in the deeper sublittoral. This reflects the difficulties due to intense hydrodynamics that hinder deploying technical equipment for studies in the natural environment. Therefore, studying growth, lifetime and reproduction of sublittoral LBF under natural conditions can be performed using the so-called 'natural laboratory' in comparison with laboratory investigations. The best sampling method in the upper sublittoral from 5 to 70 m depth is by SCUBA diving. Irregular sampling intervals caused by differing weather conditions may range from weeks to one month, whereby the latter represents the upper limit: larger intervals could render the data set worthless. The number of sampling points at the location must be more than 4, randomly distributed and approximately 5m apart to smooth the effects of patchy distributions, which are typical for most LBF. Only three simple measurements are necessary to determine chamber building rate and population dynamics under natural conditions. These are the number of individuals, number of chambers and the largest diameter of the individual. The determination of a standardized sample surface area, which is necessary for population dynamic investigations, depends on the sampling method. Reproduction and longevity can be estimated based on shell size using the date where the mean abundance of specimens with minimum size (expected after a one month's growth) characterizes the reproduction period. Then the difference to the date with the mean abundance of specimens characterized by large size indicating readiness for reproduction marks the life time. Calculation of the chamber-building rate based on chamber number is more complex and depends on the reproduction period and longevity. This can be fitted with theoretical growth functions (e.g. Michaelis Menten Function). According to the above mentioned methods, chamber building rates, longevity and population dynamics can be obtained for the shallow sublittoral symbiont-bearing LBF using the 'natural laboratory'.

  11. Estimating chronic wasting disease effects on mule deer recruitment and population growth.

    PubMed

    Dulberger, Jessie; Hobbs, N Thompson; Swanson, Heather M; Bishop, Chad J; Miller, Michael W

    2010-10-01

    Chronic wasting disease (CWD), a prion disease of mule deer (Odocoileus hemionus), accelerates mortality and in so doing has the potential to influence population dynamics. Although effects on mule deer survival are clear, how CWD affects recruitment is less certain. We studied how prion infection influenced the number of offspring raised to weaning per adult (?2 yr old) female mule deer and subsequently the estimated growth rate (?) of an infected deer herd. Infected and presumably uninfected radio-collared female deer were observed with their fawns in late summer (August-September) during three consecutive years (2006-2008) in the Table Mesa area of Boulder, Colorado, USA. We counted the number of fawns accompanying each female, then used a fully Bayesian model to estimate recruitment by infected and uninfected females and the effect of the disease on ?. On average, infected females weaned 0.95 fawns (95% credible interval=0.56-1.43) whereas uninfected females weaned 1.34 fawns (95% credible interval=1.09-1.61); the probability that uninfected females weaned more fawns than infected females was 0.93). We used estimates of prevalence to weight recruitment and survival parameters in the transition matrix of a three-age, single-sex matrix model and then used the matrix to calculate effects of CWD on ?. When effects of CWD on both survival and recruitment were included, the modeled ? was 0.97 (95% credible interval = 0.82-1.09). Effects of disease on ? were mediated almost entirely by elevated mortality of infected animals. We conclude that although CWD may affect mule deer recruitment, these effects seem to be sufficiently small that they can be omitted in estimating the influences of CWD on population growth rate. PMID:20966260

  12. Population.

    ERIC Educational Resources Information Center

    King, Pat; Landahl, John

    This pamphlet has been prepared in response to a new problem, a rapidly increasing population, and a new need, population education. It is designed to help teachers provide their students with some basic population concepts with stress placed on the elements of decision making. In the first section of the pamphlet, some of the basic concepts of…

  13. The Association Between Natural Amenities, Rural Population Growth, and Long-Term Residents’ Economic Well-Being*

    PubMed Central

    Hunter, Lori M.; Boardman, Jason D.; Saint Onge, Jarron M.

    2011-01-01

    Population growth in rural areas characterized by high levels of natural amenities has recently received substantial research attention. A noted concern with amenity-driven rural population growth is its potential to raise local costs-of-living while yielding only low-wage service sector employment for long-term residents. The work presented here empirically models long-term rural residents’ economic well-being, making use of longitudinal data from the Panel Study of Income Dynamics. In general, the results suggest that long-term rural families residing in high-growth amenity and recreation areas tend to have higher annual incomes than do their counterparts in non-growth amenity/recreation areas, regardless of the sex, race, or age of the family head. However, higher costs-of-living in these areas supplant any relative gains in income. As such, these analyses provide empirical evidence of patterns inferred by earlier anecdotal evidence and case studies. PMID:21874070

  14. Effect of Portulaca oleracea extracts on growth performance and microbial populations in ceca of broilers.

    PubMed

    Zhao, X H; He, X; Yang, X F; Zhong, X H

    2013-05-01

    The aim of this study was to investigate the effects of Portulaca oleracea extracts on growth performance and microbial populations in the ceca of broilers. A total of 120 one-day-old broilers were randomly divided into 3 groups. Portulaca oleracea extracts were added to diets at 0.2 and 0.4% (wt/wt; POL-0.2, POL-0.4), respectively. The control (CON) group was administered with no P. oleracea extract supplementation. Body weight gain and feed conversion ratio were recorded every 2 wk. On d 28 and 42, the cecal contents were collected and assayed for Escherichia coli, Lactobacillus, and Bifidobacterium populations. Additionally, the pH of the ileum and cecum was measured. The results showed that both on d 28 and 42 BW gain of P. oleracea extract supplementation groups was significantly higher, whereas the feed conversion ratio was lower (P < 0.05) compared with CON. On d 28 and 42, significantly (P < 0.05) fewer E. coli were recovered from ceca of broilers provided with the POL-0.2 diet than from broilers provided with the control diet. The quantities of Lactobacillus and Bifidobacterium of POL-0.2 were significantly (P < 0.05) higher than CON. Results showed P. oleracea extracts have no distinct influence on intestinal pH. These data suggest that P. oleracea extract supplementation significantly altered the cecal bacterial community without affecting the intestinal pH. PMID:23571345

  15. Phase Space Interpretation of Exponential Fermi Acceleration

    E-print Network

    Benno Liebchen; Robert Büchner; Christoph Petri; Fotis K. Diakonos; Florian Lenz; Peter Schmelcher

    2011-07-18

    Recently, the occurrence of exponential Fermi acceleration has been reported in a rectangular billiard with an oscillating bar inside [K. Shah, D. Turaev, and V. Rom-Kedar, Phys. Rev. E {\\bf 81}, 056205 (2010)]. In the present work, we analyze the underlying physical mechanism and show that the phenomenon can be understood as a sequence of highly correlated motions, consisting of alternating phases of free propagation and motion along the invariant spanning curves of the well-known one-dimensional Fermi-Ulam model. The key mechanism for the occurrence of exponential Fermi acceleration can be captured in a random walk model in velocity space with step width proportional to the velocity itself. The model reproduces the occurrence of exponential Fermi acceleration and provides a good ab initio prediction of the value of the growth rate including its full parameter-dependency. Our analysis clearly points out the requirements for exponential Fermi acceleration, thereby opening the perspective of finding other systems exhibiting this unusual behaviour.

  16. Insulin-like Growth Factors and Prostate Cancer: A Population-based Case-Control Study in China

    Microsoft Academic Search

    Anand P. Chokkalingam; Michael Pollak; Capri-mara Fillmore; Yu-tang Gao; Frank Z. Stanczyk; Jie Deng; Isabell A. Sesterhenn; F. Kash Mostofi; Thomas R. Fears; M. Patricia Madigan; Regina G. Ziegler; Joseph F. Fraumeni; Ann W. Hsing

    2001-01-01

    Abstract Insulin-like growth factors (IGFs) have potent mitogenic and antiapoptotic effects on prostate epithelial cells. Through modulation of IGF bioactivity and other mechanisms, IGF-binding proteins (IGFBPs) also have growth-regulatory effects on prostate cells. Recently, IGF-I and IGFBP-3 have been implicated in prostate cancer risk among,Western populations. To assess whether IGF-I, IGF-II, IGFBP-1, or IGFBP-3 are also associated with prostate cancer

  17. Long-term climate-related changes in somatic growth and population dynamics of Hokkaido chum salmon

    Microsoft Academic Search

    Hyunju Seo; Hideaki Kudo; Masahide Kaeriyama

    2011-01-01

    We used multiple regression and path analysis to examine the effects of regional and larger spatial scales of climatic\\/oceanic\\u000a conditions on the growth, survival, and population dynamics of Hokkaido chum salmon (Oncorhynchus keta). Variability in the growth of chum salmon at ages 1 to 4 was estimated from scale analysis and the back-calculation method\\u000a using scales of 4-year-old adults returning

  18. Population Growth in High-Amenity Rural Areas: Does it Bring Socioeconomic Benefits for Long-Term Residents? n

    Microsoft Academic Search

    Jarron M. Saint Onge; Lori M. Hunter; Jason D. Boardman

    2006-01-01

    Objective. A widely noted concern with amenity-driven rural population growth is its potential to yield only low-wage service-sector employment for long-term residents, while raising local costs of living. This research examines change in socioeconomic status during the 1990s for long-term residents of high-amenity, high-growth rural counties in the United States. Methods. Using longitudinal data from the Panel Study of Income

  19. Use of a large multiparent wheat mapping population in genomic dissection of coleoptile and seedling growth.

    PubMed

    Rebetzke, Greg J; Verbyla, Arunas P; Verbyla, Klara L; Morell, Matthew K; Cavanagh, Colin R

    2014-02-01

    Identification of alleles towards the selection for improved seedling vigour is a key objective of many wheat breeding programmes. A multiparent advanced generation intercross (MAGIC) population developed from four commercial spring wheat cultivars (cvv. Baxter, Chara, Westonia and Yitpi) and containing ca. 1000 F(2) -derived, F(6:7) RILs was assessed at two contrasting soil temperatures (12 and 20 °C) for shoot length and coleoptile characteristics length and thickness. Narrow-sense heritabilities were high for coleoptile and shoot length (h(2) = 0.68-0.70), indicating a strong genetic basis for the differences among progeny. Genotypic variation was large, and distributions of genotype means were approximately Gaussian with evidence for transgressive segregation for all traits. A number of significant QTL were identified for all early growth traits, and these were commonly repeatable across the different soil temperatures. The largest negative effects on coleoptile lengths were associated with Rht-B1b (-8.2%) and Rht-D1b (-10.9%) dwarfing genes varying in the population. Reduction in coleoptile length with either gene was particularly large at the warmer soil temperature. Other large QTL for coleoptile length were identified on chromosomes 1A, 2B, 4A, 5A and 6B, but these were relatively smaller than allelic effects at the Rht-B1 and Rht-D1 loci. A large coleoptile length effect allele (a = 5.3 mm at 12 °C) was identified on chromosome 1AS despite the relatively shorter coleoptile length of the donor Yitpi. Strong, positive genetic correlations for coleoptile and shoot lengths (r(g) = 0.85-0.90) support the co-location of QTL for these traits and suggest a common physiological basis for both. The multiparent population has enabled the identification of promising shoot and coleoptile QTL despite the potential for the confounding of large effect dwarfing gene alleles present in the commercial parents. The incidence of these alleles in commercial wheat breeding programmes should facilitate their ready implementation in selection of varieties with improved establishment and early growth. PMID:24151921

  20. Morphological Changes Induced by Insulin-Like Growth Factor-I Gene Therapy in Pituitary Cell Populations in Experimental Prolactinomas

    Microsoft Academic Search

    Gisela A. Camihort; Claudia B. Hereñú; Georgina C. Luna; Silvia S. Rodríguez; María I. Bracamonte; Rodolfo G. Goya; Gloria M. Cónsole

    2010-01-01

    In previous studies, we assessed the effects of intrapituitary injection of a recombinant adenoviral vector (RAd) harboring the cDNA for rat insulin-like growth factor type I (RAd-IGF-I) on the lactotrope and somatotrope populations in estrogen-induced prolactinomas. In the present study, we aimed to confirm these findings and further analyze the effect of transgenic RAd-IGF-I on the other pituitary cell populations

  1. Population Growth Rates of Reef Sharks with and without Fishing on the Great Barrier Reef: Robust Estimation with Multiple Models

    PubMed Central

    Hisano, Mizue; Connolly, Sean R.; Robbins, William D.

    2011-01-01

    Overfishing of sharks is a global concern, with increasing numbers of species threatened by overfishing. For many sharks, both catch rates and underwater visual surveys have been criticized as indices of abundance. In this context, estimation of population trends using individual demographic rates provides an important alternative means of assessing population status. However, such estimates involve uncertainties that must be appropriately characterized to credibly and effectively inform conservation efforts and management. Incorporating uncertainties into population assessment is especially important when key demographic rates are obtained via indirect methods, as is often the case for mortality rates of marine organisms subject to fishing. Here, focusing on two reef shark species on the Great Barrier Reef, Australia, we estimated natural and total mortality rates using several indirect methods, and determined the population growth rates resulting from each. We used bootstrapping to quantify the uncertainty associated with each estimate, and to evaluate the extent of agreement between estimates. Multiple models produced highly concordant natural and total mortality rates, and associated population growth rates, once the uncertainties associated with the individual estimates were taken into account. Consensus estimates of natural and total population growth across multiple models support the hypothesis that these species are declining rapidly due to fishing, in contrast to conclusions previously drawn from catch rate trends. Moreover, quantitative projections of abundance differences on fished versus unfished reefs, based on the population growth rate estimates, are comparable to those found in previous studies using underwater visual surveys. These findings appear to justify management actions to substantially reduce the fishing mortality of reef sharks. They also highlight the potential utility of rigorously characterizing uncertainty, and applying multiple assessment methods, to obtain robust estimates of population trends in species threatened by overfishing. PMID:21966402

  2. Population growth rates of reef sharks with and without fishing on the great barrier reef: robust estimation with multiple models.

    PubMed

    Hisano, Mizue; Connolly, Sean R; Robbins, William D

    2011-01-01

    Overfishing of sharks is a global concern, with increasing numbers of species threatened by overfishing. For many sharks, both catch rates and underwater visual surveys have been criticized as indices of abundance. In this context, estimation of population trends using individual demographic rates provides an important alternative means of assessing population status. However, such estimates involve uncertainties that must be appropriately characterized to credibly and effectively inform conservation efforts and management. Incorporating uncertainties into population assessment is especially important when key demographic rates are obtained via indirect methods, as is often the case for mortality rates of marine organisms subject to fishing. Here, focusing on two reef shark species on the Great Barrier Reef, Australia, we estimated natural and total mortality rates using several indirect methods, and determined the population growth rates resulting from each. We used bootstrapping to quantify the uncertainty associated with each estimate, and to evaluate the extent of agreement between estimates. Multiple models produced highly concordant natural and total mortality rates, and associated population growth rates, once the uncertainties associated with the individual estimates were taken into account. Consensus estimates of natural and total population growth across multiple models support the hypothesis that these species are declining rapidly due to fishing, in contrast to conclusions previously drawn from catch rate trends. Moreover, quantitative projections of abundance differences on fished versus unfished reefs, based on the population growth rate estimates, are comparable to those found in previous studies using underwater visual surveys. These findings appear to justify management actions to substantially reduce the fishing mortality of reef sharks. They also highlight the potential utility of rigorously characterizing uncertainty, and applying multiple assessment methods, to obtain robust estimates of population trends in species threatened by overfishing. PMID:21966402

  3. Implications of Unequal Rates of Population Growth for Trade Revisited : Lessons from Closed Form Solutions to an Overlapping Generations General Equilibrium Model under Autarky and Trade Scenarios

    Microsoft Academic Search

    Mohamed Mehdi Jelassi; Serdar Sayan

    2004-01-01

    We study closed form solutions that we obtained from a two-sector, two-factor overlap- ping generations model under autarky and free trade scenarios for ana la Heckscher-Ohlin exploration of the possible implications of population growth dierentials for the patterns of trade flows between economies that are identical except for population growth rates. Our analysis shows that dierences in population growth rates

  4. Evolution of invasive traits in nonindigenous species: increased survival and faster growth in invasive populations of rusty crayfish (Orconectes rusticus)

    PubMed Central

    Sargent, Lindsey W; Lodge, David M

    2014-01-01

    The importance of evolution in enhancing the invasiveness of species is not well understood, especially in animals. To evaluate evolution in crayfish invasions, we tested for differences in growth rate, survival, and response to predators between native and invaded range populations of rusty crayfish (Orconectes rusticus). We hypothesized that low conspecific densities during introductions into lakes would select for increased investment in growth and reproduction in invasive populations. We reared crayfish from both ranges in common garden experiments in lakes and mesocosms, the latter in which we also included treatments of predatory fish presence and food quality. In both lake and mesocosm experiments, O. rusticus from invasive populations had significantly faster growth rates and higher survival than individuals from the native range, especially in mesocosms where fish were present. There was no influence of within-range collection location on growth rate. Egg size was similar between ranges and did not affect crayfish growth. Our results, therefore, suggest that growth rate, which previous work has shown contributes to strong community-level impacts of this invasive species, has diverged since O. rusticus was introduced to the invaded range. This result highlights the need to consider evolutionary dynamics in invasive species mitigation strategies. PMID:25469173

  5. Evolution of invasive traits in nonindigenous species: increased survival and faster growth in invasive populations of rusty crayfish (Orconectes rusticus).

    PubMed

    Sargent, Lindsey W; Lodge, David M

    2014-09-01

    The importance of evolution in enhancing the invasiveness of species is not well understood, especially in animals. To evaluate evolution in crayfish invasions, we tested for differences in growth rate, survival, and response to predators between native and invaded range populations of rusty crayfish (Orconectes rusticus). We hypothesized that low conspecific densities during introductions into lakes would select for increased investment in growth and reproduction in invasive populations. We reared crayfish from both ranges in common garden experiments in lakes and mesocosms, the latter in which we also included treatments of predatory fish presence and food quality. In both lake and mesocosm experiments, O. rusticus from invasive populations had significantly faster growth rates and higher survival than individuals from the native range, especially in mesocosms where fish were present. There was no influence of within-range collection location on growth rate. Egg size was similar between ranges and did not affect crayfish growth. Our results, therefore, suggest that growth rate, which previous work has shown contributes to strong community-level impacts of this invasive species, has diverged since O. rusticus was introduced to the invaded range. This result highlights the need to consider evolutionary dynamics in invasive species mitigation strategies. PMID:25469173

  6. The Power of Exponentials, Big and Small - MIT Blossoms

    NSDL National Science Digital Library

    MIT BLOSSOMS

    2012-06-03

    Exponential growth is keenly applicable to a variety of different fields ranging from cell growth in biology, nuclear chain reactions in physics to computational complexity in computer science. In this video-based lesson, through various examples and activities, we have tried to compare exponential growth to polynomial growth and to develop an insight about how quickly the number can grow or decay in exponentials. A basic knowledge of scientific notation, plotting graphs and finding intersection of two functions is assumed. It would be better if the students have done pre-calculus, though this is not a requirement. The lesson is about 20 minutes, interspersed with simple activities that can require up to half an hour. The webpage for this video also includes tabs where additional resources and information can be found. These include a Teacher's Guide, a Powers of 2 table, links to other helpful lessons and resources, a transcript of the video, and even an option to download the video.

  7. On the Matrix Exponential Function

    ERIC Educational Resources Information Center

    Hou, Shui-Hung; Hou, Edwin; Pang, Wan-Kai

    2006-01-01

    A novel and simple formula for computing the matrix exponential function is presented. Specifically, it can be used to derive explicit formulas for the matrix exponential of a general matrix A satisfying p(A) = 0 for a polynomial p(s). It is ready for use in a classroom and suitable for both hand as well as symbolic computation.

  8. Euler's number II: Complex exponentials

    NSDL National Science Digital Library

    2013-06-21

    We express the exponential function of an imaginary variable in terms of sine and cosine. The "complex exponentials" that result trace out a circle in the complex plane. Pointing to one of the positions in the complex plane, we obtain the identity exp(i pi) = -1.

  9. Removing exponential backoff from TCP

    Microsoft Academic Search

    Amit Mondal; Aleksandar Kuzmanovic

    2008-01-01

    The well-accepted wisdom is that TCP's exponential backoff mechanism, introduced by Jacobson 20 years ago, is essen- tial for preserving the stability of the Internet. In this pa- per, we show that removing exponential backoff from TCP altogether can be done without inducing any stability side- effects. We introduce the implicit packet conservation prin- ciple and show that as long

  10. Population dynamics, growth and production of Sigara selecta (Fieber, 1848) (Hemiptera, Corixidae) in a Mediterranean hypersaline stream

    Microsoft Academic Search

    J. BARAHONA; A. MILLAN; J. VELASCO

    2005-01-01

    SUMMARY 1. This is the first study on the life cycle, growth and production of Sigara selecta ,a Palearctic corixid species typical of brackish and saline waters, at the warmest limit of its European distributional range. The study combines field and laboratory approaches. 2. The S. selecta population studied was multivoltine, producing four asynchronous cohorts from early spring to December

  11. Studies on the pebble crab, Eriphia smithi MacLeay 1838 (Xanthoidea Menippidae): patterns of relative growth and population structure

    Microsoft Academic Search

    M. Vannini; F. Gherardi

    1988-01-01

    Morphometry and population structure have been investigated in a large sample (about 800 specimens) of the tropical Xanthoidea Eriphia smithi MacLeay 1838 (Decapoda Brachyura), inhabiting a rocky cliff in Somalia. The analysis of relative growth in two sexual dimorphic characters (i.e., chelipeds and abdomen) showed that both sexes undergo the puberty molt at approximately 19 mm CL. However, functional maturity

  12. The impact of invasive grasses on the population growth of Anemone patens, a long-lived native forb.

    PubMed

    Williams, Jennifer L; Crone, Elizabeth E

    2006-12-01

    Negative impacts of invasive plants on natives have been well documented, but much less is known about whether invasive plants can cause population level declines. We used demographic models to investigate the effects of two invasive grasses on the demography and population growth of Anemone patens, a long-lived native perennial of North American grasslands. Demographic data of A. patens growing in patches characterized by Bromus inermis, Poa pratensis, or native grasses were used to parameterize integral projection models. Models based on both average conditions and those allowing for environmental stochasticity indicate that A. patens is slowly increasing in patches of native grass (lambda = 1.02) and declining in patches of invasive grasses, particularly those dominated by B. inermis (lambda = 0.93). Extinction probabilities indicate that A. patens should persist in native grass patches, but has a much higher probability of extinction in Bromus patches compared to Poa patches. While sensitivity analyses showed that survival had the biggest effect on population growth rates in all habitats, results of a Life Table Response Experiment (LTRE) revealed that slower individual growth rates in patches of invasive grasses contributed the most to the observed reduction in population growth. These results suggest that invasive grasses may cause slow declines in A. patens, despite short-term coexistence, and that controlling B. inermis only would not be sufficient to ensure A. patens persistence. PMID:17249243

  13. Mark-recapture estimates of recruitment, survivorship and population growth rates for the screwworm fly, Cochliomyia hominivorax

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pradel model mark, release, recapture estimates of survivorship, recruitment, and the rate of density-independent population growth, are presented for eight mark-recapture studies of the screwworm Cochliomyia hominivorax from Costa Rica, totaling 19,714 released and 4,504 recaptured flies. Corrobor...

  14. Life table demography and population growth of Brachionus variabilis Hempel, 1896 in relation to Chlorella vulgaris densities

    Microsoft Academic Search

    S. S. S. Sarma; S. Nandini

    2001-01-01

    We studied the life history variables and population growth characteristics of Brachionus variabilis, which was recorded for the first time from Mexico. The animals were fed Chlorella, using five concentrations (0.25, 0.5, 1, 2 and 4 × 106 cells ml-1) at 25 °C. Food density was observed to have significant effect on life expectancy, average lifespan, gross reproductive rate, net

  15. The role of population growth and land-use policy in deforestation: a case study in the western Venezuelan plains

    Microsoft Academic Search

    Ludwig Kammesheidt

    The western plains have shown the highest rates of population growth in Venezuela over the last 50 years. This was mainly due to the immigration of landless farmers coming from the Andean zone and neighbouring Colombia. The agrarian reform of 1960 assigned large areas of public forest in the study area to colonization programmes. In the 1950s and 1960s four

  16. Poll: Satisfied, Optimistic, but Deeply Concerned about Traffic, Affordable Housing, Public Education, Air Pollution, Population Growth, and Affordable Healthcare

    Microsoft Academic Search

    Amy Qiaoming Liu; Brenda M. Hofer

    Despite their confidence and contentment, people in the Sacramento region still have serious concerns about a wide range of issues, including traffic congestion, affordable housing, quality of public education, air pollution, and population growth and development. Two-thirds (66%) view traffic congestion as a big problem while almost half report that affordable housing (48%) and quality of public education (46%) are

  17. Long-term data reveal a population decline of the tropical lizard Anolis apletophallus, and a negative affect of el nino years on population growth rate.

    PubMed

    Stapley, Jessica; Garcia, Milton; Andrews, Robin M

    2015-01-01

    Climate change threatens biodiversity worldwide, however predicting how particular species will respond is difficult because climate varies spatially, complex factors regulate population abundance, and species vary in their susceptibility to climate change. Studies need to incorporate these factors with long-term data in order to link climate change to population abundance. We used 40 years of lizard abundance data and local climate data from Barro Colorado Island to ask how climate, total lizard abundance and cohort-specific abundance have changed over time, and how total and cohort-specific abundance relate to climate variables including those predicted to make the species vulnerable to climate change (i.e. temperatures exceeding preferred body temperature). We documented a decrease in lizard abundance over the last 40 years, and changes in the local climate. Population growth rate was related to the previous years' southern oscillation index; increasing following cooler-wetter, la niña years, decreasing following warmer-drier, el nino years. Within-year recruitment was negatively related to rainfall and minimum temperature. This study simultaneously identified climatic factors driving long-term population fluctuations and climate variables influencing short-term annual recruitment, both of which may be contributing to the population decline and influence the population's future persistence. PMID:25671423

  18. Exponential beams of electromagnetic radiation

    E-print Network

    Bialynicki-Birula, I; Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia

    2006-01-01

    We show that in addition to well known Bessel, Hermite-Gauss, and Laguerre-Gauss beams of electromagnetic radiation, one may also construct exponential beams. These beams are characterized by a fall-off in the transverse direction described by an exponential function of rho. Exponential beams, like Bessel beams, carry definite angular momentum and are periodic along the direction of propagation, but unlike Bessel beams they have a finite energy per unit beam length. The analysis of these beams is greatly simplified by an extensive use of the Riemann-Silberstein vector and the Whittaker representation of the solutions of the Maxwell equations in terms of just one complex function. The connection between the Bessel beams and the exponential beams is made explicit by constructing the exponential beams as wave packets of Bessel beams.

  19. EVOLUTION OF WHEAT STREAK MOSAIC VIRUS: Dynamics of Population Growth Within Plants May Explain Limited Variation

    Microsoft Academic Search

    Roy C. French; Drake C. Stenger

    2003-01-01

    Like many other plant RNA viruses, Wheat streak mosaic virus (WSMV) sequence diversity within and among infected plants is low given the large number of virions produced. This may be explained by considering aspects of plant virus life history. Intracellular replication of RNA viruses is predominately linear, not exponential, which means that the rate at which mutations accumulate also is

  20. The Exponential Phase of HIV/AIDS Epidemic in Japan

    E-print Network

    Inaba, Hisashi

    The Exponential Phase of HIV/AIDS Epidemic in Japan Hisashi INABA Institute of Population Problems 2-2, 1-Chome, Kasumigaseki, Chiyoda-ku Tokyo 100-45, Japan F--K"$K$*$1$k#H#I#V!?#A#I#D#S$N;X?t4X incidence in Japan has been growing exponentially. Using our calculation method, we conclude that the number

  1. The influence of density-dependent aggregation characteristics on the population biology of benthic broadcast-spawning gastropods : pink abalone (Haliotis corrugata), red abalone (Haliotis rufescens), and wavy turban snails (Megastraea undosa)

    E-print Network

    Button, Cynthia Aileen

    2008-01-01

    exponential curve: The effect of aggregation size on fecundity translates into a rapid decline in population growthexponential curve to the averaged ? values. The critical aggregation size for the population growthexponential curve. This effect of aggregation size on fecundity translates into a rapid decline in population growth

  2. The influence of density-dependent aggregation characteristics on the population biology of benthic broadcast-spawning gastropods: Pink abalone (Haliotis corrugata), red abalone (Haliotis rufescens), and wavy turban snails (Megastraea undosa)

    E-print Network

    Button, Cynthia A.

    2008-01-01

    exponential curve: The effect of aggregation size on fecundity translates into a rapid decline in population growthexponential curve to the averaged ? values. The critical aggregation size for the population growthexponential curve. This effect of aggregation size on fecundity translates into a rapid decline in population growth

  3. Comparisons of growth rates of popu-lations and species are important in

    E-print Network

    874 Comparisons of growth rates of popu- lations and species are important in fisheries science of the growth rates for the same species, say E, in which two sets of growth parameter esti- mates, ^ 1 and ^ 2, comparing absolute growth rates at age or length between species could be of practical interest. For example

  4. Cell Growth and Size Homeostasis in Silico

    PubMed Central

    Hu, Yucheng; Zhu, Tianqi

    2014-01-01

    Cell growth in size is a complex process coordinated by intrinsic and environmental signals. In a research work performed by a different group, size distributions of an exponentially growing population of mammalian cells were used to infer cell-growth rate in size. The results suggested that cell growth was neither linear nor exponential, but subject to size-dependent regulation. To explain the observed growth pattern, we built a mathematical model in which growth rate was regulated by the relative amount of mRNA and ribosomes in a cell. Under the growth model and a stochastic division rule, we simulated the evolution of a population of cells. Both the sampled growth rate and size distribution from this in silico population agreed well with experimental data. To explore the model space, alternative growth models and division rules were studied. This work may serve as a starting point to understand the mechanisms behind cell growth and size regulation using predictive models. PMID:24606924

  5. The Exponential Function, XI: The New Flat Earth Society.

    ERIC Educational Resources Information Center

    Bartlett, Albert A.

    1996-01-01

    Discusses issues related to perpetual population growth. Argues that if we believe that there are no limits to growth, we will have to abandon the concept of a spherical Earth which puts limits to growth. (JRH)

  6. Vascular endothelial growth factor gene polymorphisms in age-related macular degeneration in a Turkish population

    PubMed Central

    Bulgu, Yunus; Cetin, Gokhan Ozan; Caner, Vildan; Cetin, Ebru Nevin; Yaylali, Volkan; Yildirim, Cem

    2014-01-01

    AIM To assess the association between age-related macular degeneration (AMD) and three single nucleotide polymorphisms (SNPs) related to the vascular endothelial growth factor (VEGF) gene. METHODS The patients who were diagnosed with AMD were included in this prospective study. Three SNPs (rs1413711, rs2146323, and rs3025033) of the VEGF gene were genotyped by real-time polymerase chain reaction in the genomic DNA isolated from peripheral blood samples of the 82 patients and 80 controls. RESULTS The genotype frequencies of rs1413711 and rs2146323 were not significantly different between the study group and the control group (P=0.072 and P=0.058). However, there was a significant difference in the genotype frequencies of these SNPs between the wet type AMD and dry type AMD (P=0.005 and P=0.010, respectively). One of the SNPs (rs1413711) was also found to be associated with the severity of AMD (P=0.001) with significant genotype distribution between early, intermediate, and advanced stages of the disease. The ancestral alleles were protective for both SNPs while the polymorphic alleles increased the risk for dry AMD. CONCLUSION VEGF SNPs rs1413711 and rs2146323 polymorphisms are significantly associated with AMD subtypes in our population. PMID:25349791

  7. The importance of population growth and regulation in human life history evolution.

    PubMed

    Baldini, Ryan

    2015-01-01

    Explaining the evolution of human life history traits remains an important challenge for evolutionary anthropologists. Progress is hindered by a poor appreciation of how demographic factors affect the action of natural selection. I review life history theory showing that the quantity maximized by selection depends on whether and how population growth is regulated. I show that the common use of R, a strategy's expected lifetime number of offspring, as a fitness maximand is only appropriate under a strict set of conditions, which are apparently unappreciated by anthropologists. To concretely show how demography-free life history theory can lead to errors, I reanalyze an influential model of human life history evolution, which investigated the coevolution of a long lifespan and late age of maturity. I show that the model's conclusions do not hold under simple changes to the implicitly assumed mechanism of density dependence, even when stated assumptions remain unchanged. This analysis suggests that progress in human life history theory requires better understanding of the demography of our ancestors. PMID:25830310

  8. An evaluation of density-dependent and density-independent influences on population growth rates in Weddell seals

    USGS Publications Warehouse

    Rotella, J.J.; Link, W.A.; Nichols, J.D.; Hadley, G.L.; Garrott, R.A.; Proffitt, K.M.

    2009-01-01

    Much of the existing literature that evaluates the roles of density-dependent and density-independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state-space models to account for measurement errors, we evaluated a set of competing models for a 22-year time series of mark-resight estimates of abundance for a breeding population of female Weddell seals (Leptonychotes weddellii) studied in Erebus Bay, Antarctica. We tested for evidence of direct density dependence in growth rates and evaluated whether equilibrium population size was related to seasonal sea-ice extent and the Southern Oscillation Index (SOI). We found strong evidence of negative density dependence in annual growth rates for a population whose estimated size ranged from 438 to 623 females during the study. Based on Bayes factors, a density-dependence-only model was favored over models that also included en! vironmental covariates. According to the favored model, the population had a stationary distribution with a mean of 497 females (SD = 60.5), an expected growth rate of 1.10 (95% credible interval 1.08-1.15) when population size was 441 females, and a rate of 0.90 (95% credible interval 0.87-0.93) for a population of 553 females. A model including effects of SOI did receive some support and indicated a positive relationship between SOI and population size. However, effects of SOI were not large, and including the effect did not greatly reduce our estimate of process variation. We speculate that direct density dependence occurred because rates of adult survival, breeding, and temporary emigration were affected by limitations on per capita food resources and space for parturition and pup-rearing. To improve understanding of the relative roles of various demographic components and their associated vital rates to population growth rate, mark-recapture methods can be applied that incorporate both environmental covariates and the seal abundance estimates that were developed here. An improved understanding of why vital rates change with changing population abundance will only come as we develop a better understanding of the processes affecting marine food resources in the Southern Ocean.

  9. People and environment: what is the relationship between exploitation of natural resources and population growth in the South?

    PubMed

    Scherr, S J

    1997-01-01

    This article reviews the nature and scale of the problems between natural resource management (NRM), agricultural productivity, and population growth in developing countries. It suggests a framework for examining the dynamics of land quality change, and reviews the evidence on land management under population pressure in tropical hillside areas and suggests some lessons learned for policy development. The evidence suggests that the effect of population on land quality is unknown; it depends upon economic and institutional factors. Aggregate data obscures the dynamics of change. There are four distinct patterns of land use changes with different market, population, and agro-environmental conditions: irrigated lands, high potential rain-fed lands, long-settled marginal lands, and frontier marginal lands. Sustainable NRM and strategies of agricultural development vary with population and market growth in these four areas. Currently 50% of the poorest people live on marginal lands. When countries and regions are more dependent upon marginal lands for food production, the key environmental issues are devegetation, nutrient depletion, and erosion. The 1997 Templeton and Scheer review examined 150 studies that focused on land use, intensity, and quality under forest, crops, and pastures in hilly-mountainous areas. Studies suggest that many hill and mountain areas could sustain high production levels without excessive resource degradation, depending upon the impact of microeconomic incentives on choice of production systems. Local populations cannot cope with the challenge of sustainable intensification without supportive policy and institutions. PMID:12321782

  10. The interaction between the spatial distribution of resource patches and population density: consequences for intraspecific growth and morphology.

    PubMed

    Jacobson, Bailey; Grant, James W A; Peres-Neto, Pedro R

    2015-07-01

    How individuals within a population distribute themselves across resource patches of varying quality has been an important focus of ecological theory. The ideal free distribution predicts equal fitness amongst individuals in a 1 : 1 ratio with resources, whereas resource defence theory predicts different degrees of monopolization (fitness variance) as a function of temporal and spatial resource clumping and population density. One overlooked landscape characteristic is the spatial distribution of resource patches, altering the equitability of resource accessibility and thereby the effective number of competitors. While much work has investigated the influence of morphology on competitive ability for different resource types, less is known regarding the phenotypic characteristics conferring relative ability for a single resource type, particularly when exploitative competition predominates. Here we used young-of-the-year rainbow trout (Oncorhynchus mykiss) to test whether and how the spatial distribution of resource patches and population density interact to influence the level and variance of individual growth, as well as if functional morphology relates to competitive ability. Feeding trials were conducted within stream channels under three spatial distributions of nine resource patches (distributed, semi-clumped and clumped) at two density levels (9 and 27 individuals). Average trial growth was greater in high-density treatments with no effect of resource distribution. Within-trial growth variance had opposite patterns across resource distributions. Here, variance decreased at low-population, but increased at high-population densities as patches became increasingly clumped as the result of changes in the levels of interference vs. exploitative competition. Within-trial growth was related to both pre- and post-trial morphology where competitive individuals were those with traits associated with swimming capacity and efficiency: larger heads/bodies/caudal fins and less angled pectoral fins. The different degrees of within-population growth variance at the same density level found here, as a function of spatial resource distribution, provide an explanation for the inconsistencies in within-site growth variance and population regulation often noted with regard to density dependence in natural landscapes. PMID:25757660

  11. Population growth versus population spread of an ant-dispersed neotropical herb with a mixed reproductive strategy

    Microsoft Academic Search

    Josiane Le Corff; Carol C. Horvitz

    2005-01-01

    In plants that produce seeds with contrasting genetic background (selfed versus outcrossed), the question arises whether the ecological function of the two types of progeny differ. This paper addresses this issue for the ant-dispersed Calathea micans by introducing a novel application of the Neubert–Caswell model for analysis of wave speed for structured populations. Because dispersal as well as vital rates

  12. Future Coastal Population Growth and Exposure to Sea-Level Rise and Coastal Flooding - A Global Assessment

    PubMed Central

    Neumann, Barbara; Vafeidis, Athanasios T.; Zimmermann, Juliane; Nicholls, Robert J.

    2015-01-01

    Coastal zones are exposed to a range of coastal hazards including sea-level rise with its related effects. At the same time, they are more densely populated than the hinterland and exhibit higher rates of population growth and urbanisation. As this trend is expected to continue into the future, we investigate how coastal populations will be affected by such impacts at global and regional scales by the years 2030 and 2060. Starting from baseline population estimates for the year 2000, we assess future population change in the low-elevation coastal zone and trends in exposure to 100-year coastal floods based on four different sea-level and socio-economic scenarios. Our method accounts for differential growth of coastal areas against the land-locked hinterland and for trends of urbanisation and expansive urban growth, as currently observed, but does not explicitly consider possible displacement or out-migration due to factors such as sea-level rise. We combine spatially explicit estimates of the baseline population with demographic data in order to derive scenario-driven projections of coastal population development. Our scenarios show that the number of people living in the low-elevation coastal zone, as well as the number of people exposed to flooding from 1-in-100 year storm surge events, is highest in Asia. China, India, Bangladesh, Indonesia and Viet Nam are estimated to have the highest total coastal population exposure in the baseline year and this ranking is expected to remain largely unchanged in the future. However, Africa is expected to experience the highest rates of population growth and urbanisation in the coastal zone, particularly in Egypt and sub-Saharan countries in Western and Eastern Africa. The results highlight countries and regions with a high degree of exposure to coastal flooding and help identifying regions where policies and adaptive planning for building resilient coastal communities are not only desirable but essential. Furthermore, we identify needs for further research and scope for improvement in this kind of scenario-based exposure analysis. PMID:25760037

  13. Future coastal population growth and exposure to sea-level rise and coastal flooding--a global assessment.

    PubMed

    Neumann, Barbara; Vafeidis, Athanasios T; Zimmermann, Juliane; Nicholls, Robert J

    2015-01-01

    Coastal zones are exposed to a range of coastal hazards including sea-level rise with its related effects. At the same time, they are more densely populated than the hinterland and exhibit higher rates of population growth and urbanisation. As this trend is expected to continue into the future, we investigate how coastal populations will be affected by such impacts at global and regional scales by the years 2030 and 2060. Starting from baseline population estimates for the year 2000, we assess future population change in the low-elevation coastal zone and trends in exposure to 100-year coastal floods based on four different sea-level and socio-economic scenarios. Our method accounts for differential growth of coastal areas against the land-locked hinterland and for trends of urbanisation and expansive urban growth, as currently observed, but does not explicitly consider possible displacement or out-migration due to factors such as sea-level rise. We combine spatially explicit estimates of the baseline population with demographic data in order to derive scenario-driven projections of coastal population development. Our scenarios show that the number of people living in the low-elevation coastal zone, as well as the number of people exposed to flooding from 1-in-100 year storm surge events, is highest in Asia. China, India, Bangladesh, Indonesia and Viet Nam are estimated to have the highest total coastal population exposure in the baseline year and this ranking is expected to remain largely unchanged in the future. However, Africa is expected to experience the highest rates of population growth and urbanisation in the coastal zone, particularly in Egypt and sub-Saharan countries in Western and Eastern Africa. The results highlight countries and regions with a high degree of exposure to coastal flooding and help identifying regions where policies and adaptive planning for building resilient coastal communities are not only desirable but essential. Furthermore, we identify needs for further research and scope for improvement in this kind of scenario-based exposure analysis. PMID:25760037

  14. A white-box model of S-shaped and double S-shaped single-species population growth

    PubMed Central

    Kalmykov, Lev V.

    2015-01-01

    Complex systems may be mechanistically modelled by white-box modeling with using logical deterministic individual-based cellular automata. Mathematical models of complex systems are of three types: black-box (phenomenological), white-box (mechanistic, based on the first principles) and grey-box (mixtures of phenomenological and mechanistic models). Most basic ecological models are of black-box type, including Malthusian, Verhulst, Lotka–Volterra models. In black-box models, the individual-based (mechanistic) mechanisms of population dynamics remain hidden. Here we mechanistically model the S-shaped and double S-shaped population growth of vegetatively propagated rhizomatous lawn grasses. Using purely logical deterministic individual-based cellular automata we create a white-box model. From a general physical standpoint, the vegetative propagation of plants is an analogue of excitation propagation in excitable media. Using the Monte Carlo method, we investigate a role of different initial positioning of an individual in the habitat. We have investigated mechanisms of the single-species population growth limited by habitat size, intraspecific competition, regeneration time and fecundity of individuals in two types of boundary conditions and at two types of fecundity. Besides that, we have compared the S-shaped and J-shaped population growth. We consider this white-box modeling approach as a method of artificial intelligence which works as automatic hyper-logical inference from the first principles of the studied subject. This approach is perspective for direct mechanistic insights into nature of any complex systems. PMID:26038717

  15. A white-box model of S-shaped and double S-shaped single-species population growth.

    PubMed

    Kalmykov, Lev V; Kalmykov, Vyacheslav L

    2015-01-01

    Complex systems may be mechanistically modelled by white-box modeling with using logical deterministic individual-based cellular automata. Mathematical models of complex systems are of three types: black-box (phenomenological), white-box (mechanistic, based on the first principles) and grey-box (mixtures of phenomenological and mechanistic models). Most basic ecological models are of black-box type, including Malthusian, Verhulst, Lotka-Volterra models. In black-box models, the individual-based (mechanistic) mechanisms of population dynamics remain hidden. Here we mechanistically model the S-shaped and double S-shaped population growth of vegetatively propagated rhizomatous lawn grasses. Using purely logical deterministic individual-based cellular automata we create a white-box model. From a general physical standpoint, the vegetative propagation of plants is an analogue of excitation propagation in excitable media. Using the Monte Carlo method, we investigate a role of different initial positioning of an individual in the habitat. We have investigated mechanisms of the single-species population growth limited by habitat size, intraspecific competition, regeneration time and fecundity of individuals in two types of boundary conditions and at two types of fecundity. Besides that, we have compared the S-shaped and J-shaped population growth. We consider this white-box modeling approach as a method of artificial intelligence which works as automatic hyper-logical inference from the first principles of the studied subject. This approach is perspective for direct mechanistic insights into nature of any complex systems. PMID:26038717

  16. Water availability and population origin affect the expression of the tradeoff between reproduction and growth in Plantago coronopus.

    PubMed

    Hansen, C F; García, M B; Ehlers, B K

    2013-05-01

    Investment in reproduction and growth represent a classic tradeoff with implication for life history evolution. The local environment can play a major role in the magnitude and evolutionary consequences of such a tradeoff. Here, we examined the investment in reproductive and vegetative tissue in 40 maternal half-sib families from four different populations of the herb Plantago coronopus growing in either a dry or wet greenhouse environment. Plants originated from populations with an annual or a perennial life form, with annuals prevailing in drier habitats with greater seasonal variation in both temperature and precipitation. We found that water availability affected the expression of the tradeoff (both phenotypic and genetic) between reproduction and growth, being most accentuated under dry condition. However, populations responded very differently to water treatments. Plants from annual populations showed a similar response to drought condition with little variation among maternal families, suggesting a history of selection favouring genotypes with high allocation to reproduction when water availability is low. Plants from annual populations also expressed the highest level of plasticity. For the perennial populations, one showed a large variation among maternal families in resource allocation and expressed significant negative genetic correlations between reproductive and vegetative biomass under drought. The other perennial population showed less variation in response to treatment and had trait values similar to those of the annuals, although it was significantly less plastic. We stress the importance of considering intraspecific variation in response to environmental change such as drought, as conspecific plants exhibited very different abilities and strategies to respond to high versus low water availability even among geographically close populations. PMID:23621367

  17. Population Growth in High-Amenity Rural Areas: Does it Bring Socioeconomic Benefits for Long-Term Residents?

    PubMed Central

    Onge, Jarron M. Saint; Hunter, Lori M.; Boardman, Jason D.

    2011-01-01

    Objective A widely noted concern with amenity-driven rural population growth is its potential to yield only low-wage service-sector employment for long-term residents, while raising local costs of living. This research examines change in socioeconomic status during the 1990s for long-term residents of high-amenity, high-growth rural counties in the United States. Methods Using longitudinal data from the Panel Study of Income Dynamics, in combination with county-level information, we estimate growth-curve models to examine the extent to which the socioeconomic status of long-term residents is associated with amenity-related in-migration. Results We find that, on average, residents in high-growth, amenity-rich rural areas have higher income growth over time and higher levels of initial occupational prestige compared to those from other rural areas, but that socioeconomic gains are primarily for individuals with low baseline prestige. Conclusions The socioeconomic gains made by long-term residents of high-growth, amenity-rich rural areas associated with net in-migration may be limited to individuals with low initial prestige and growth may be due to low-skill service-sector jobs. PMID:21892234

  18. Exponential approximations in optimal design

    NASA Technical Reports Server (NTRS)

    Belegundu, A. D.; Rajan, S. D.; Rajgopal, J.

    1990-01-01

    One-point and two-point exponential functions have been developed and proved to be very effective approximations of structural response. The exponential has been compared to the linear, reciprocal and quadratic fit methods. Four test problems in structural analysis have been selected. The use of such approximations is attractive in structural optimization to reduce the numbers of exact analyses which involve computationally expensive finite element analysis.

  19. Population growth of Lepadella patella (O. F. Müller, 1786) at different algal (Chlorella vulgaris) densities and in association with Philodina roseola Ehrenberg, 1832

    Microsoft Academic Search

    S. Nandini; S. S. S. Sarma

    2001-01-01

    Population growth of Lepadella patella was studied using Chlorella as the sole food at five concentrations ranging from 0.25 × 106 to 4.0 × 106 cells ml-1 at 25 °C for 22 days. The population densities increased with increasing algal concentration up to 1.0 × 106 cells ml-1. The population growth of L. patella was lower at algal concentration of

  20. Effect of growth conditions and substratum composition on the persistence of coliforms in mixed-population biofilms.

    PubMed

    Camper, A K; Jones, W L; Hayes, J T

    1996-11-01

    Laboratory reactors operated under oligotrophic conditions were used to evaluate the importance of initial growth rate and substratum composition on the long-term persistence of coliforms in mixed-population biofilms. The inoculum growth rate had a dramatic effect on the ability of coliforms to remain on surfaces. The most slowly grown coliforms (mu = 0.05/h) survived at the highest cell concentration. Antibody staining revealed that Klebsiella pneumoniae existed primarily as discrete microcolonies on the surface. Both coliforms and heterotrophic plate count bacteria were supported in larger numbers on a reactive substratum, mild steel, than on polycarbonate. PMID:8899991

  1. Non-linearity and heterogeneity in modeling of population dynamics.

    PubMed

    Karev, Georgy P

    2014-12-01

    The study of population growth reveals that the behaviors that follow the power law appear in numerous biological, demographical, ecological, physical and other contexts. Parabolic models appear to be realistic approximations of real-life replicator systems, while hyperbolic models were successfully applied to problems of global demography and appear relevant in quasispecies and hypercycle modeling. Nevertheless, it is not always clear why non-exponential growth is observed empirically and what possible origins of the non-exponential models are. In this paper the power equation is considered within the frameworks of inhomogeneous population models; it is proven that any power equation describes the total population size of a frequency-dependent model with Gamma-distributed Malthusian parameter. Additionally, any super-exponential equation describes the dynamics of inhomogeneous Malthusian density-dependent population model. All statistical characteristics of the underlying inhomogeneous models are computed explicitly. The results of this analysis show that population heterogeneity can be a reasonable explanation for power law accurately describing total population growth. PMID:25262656

  2. Taylor's power law of fluctuation scaling and the growth-rate theorem.

    PubMed

    Cohen, Joel E

    2013-09-01

    Taylor's law (TL), a widely verified empirical relationship in ecology, states that the variance of population density is approximately a power-law function of mean density. The growth-rate theorem (GR) states that, in a subdivided population, the rate of change of the overall growth rate is proportional to the variance of the subpopulations' growth rates. We show that continuous-time exponential change implies GR at every time and, asymptotically for large time, TL with power-law exponent 2. We also show why diverse population-dynamic models predict TL in the limit of large time by identifying simple features these models share: If the mean population density and the variance of population density are (exactly or asymptotically) non-constant exponential functions of a parameter (e.g., time), then the variance of density is (exactly or asymptotically) a power-law function of mean density. PMID:23689021

  3. In a long-term experimental demography study, excluding ungulates reversed invader's explosive population growth rate and restored natives.

    PubMed

    Kalisz, Susan; Spigler, Rachel B; Horvitz, Carol C

    2014-03-25

    A major goal in ecology is to understand mechanisms that increase invasion success of exotic species. A recent hypothesis implicates altered species interactions resulting from ungulate herbivore overabundance as a key cause of exotic plant domination. To test this hypothesis, we maintained an experimental demography deer exclusion study for 6 y in a forest where the native ungulate Odocoileus virginianus (white-tailed deer) is overabundant and Alliaria petiolata (garlic mustard) is aggressively invading. Because population growth is multiplicative across time, we introduce metrics that correctly integrate experimental effects across treatment years, the cumulative population growth rate, ?c, and its geometric mean, ?per-year, the time-averaged annual population growth rate. We determined ?c and ?per-year of the invader and of a common native, Trillium erectum. Our results conclusively demonstrate that deer are required for the success of Alliaria; its projected population trajectory shifted from explosive growth in the presence of deer (?per-year = 1.33) to decline toward extinction where deer are excluded (?per-year = 0.88). In contrast, Trillium's ?per-year was suppressed in the presence of deer relative to deer exclusion (?per-year = 1.04 vs. 1.20, respectively). Retrospective sensitivity analyses revealed that the largest negative effect of deer exclusion on Alliaria came from rosette transitions, whereas the largest positive effect on Trillium came from reproductive transitions. Deer exclusion lowered Alliaria density while increasing Trillium density. Our results provide definitive experimental support that interactions with overabundant ungulates enhance demographic success of invaders and depress natives' success, with broad implications for biodiversity and ecosystem function worldwide. PMID:24616522

  4. Single dietary amino acids control resting egg production and affect population growth of a key freshwater herbivore

    Microsoft Academic Search

    Ulrike Koch; Dominik Martin-Creuzburg; Hans-Peter Grossart; Dietmar Straile

    The enormous success of the genus Daphnia in freshwater ecosystems is at least partially due to their cyclical parthenogenetic life cycle, in which asexual and sexual\\u000a reproduction alternate periodically. This temporal change between reproductive strategies allows for (1) rapid population\\u000a growth via subitaneously developing eggs when environmental conditions are appropriate and (2) the maintenance of genetic\\u000a diversity via sexual reproduction

  5. Changes in Population, Growth, and Physiological Indices of Longnose Dace ( Rhinichthys cataractae ) in the Red Deer River, Alberta, Canada

    Microsoft Academic Search

    Ken M. Jeffries; Leland J. Jackson; Lisa E. Peters; Kelly R. Munkittrick

    2008-01-01

    The Red Deer River, Alberta, Canada is a prairie river that is impacted by the point-source input of Red Deer’s municipal\\u000a wastewater effluent and non-point- source agricultural runoff. We used population, growth, and physiological performance end\\u000a points in longnose dace (Rhinichthys cataractae), an endemic and abundant minnow, to evaluate changes in fish health over a 220 km section of the

  6. Computer-assisted mapping of basic fibroblast growth factor immunoreactive nerve cell populations in the rat brain

    Microsoft Academic Search

    Kjell Fuxe; Barbro Tinner; Michele Zoli; Ralf F. Pettersson; Andrew Baird; Guiseppe Biagini; Gerson Chadi; Luigi F. Agnati

    1996-01-01

    We have performed a mapping of basic fibroblast growth factor (bFGF) immunoreactive (ir) glial and nerve cell populations in the male rat brain using a rabbit antibody raised against a synthetic peptide of bovine bFGF. Regional morphometric and microdensitometric analysis of the bFGF ir neuronal profiles in coronal brain sections was carried out by means of an automatic image analyser.

  7. Relationships between growth, population structure and sea surface temperature in the temperate solitary coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

    Microsoft Academic Search

    S. Goffredo; E. Caroselli; G. Mattioli; E. Pignotti; F. Zaccanti

    2008-01-01

    The demographic characteristics of the solitary zooxanthellate scleractinian Balanophyllia europaea, endemic to the Mediterranean, were determined in six populations, on a latitudinal gradient along the Italian coast, and\\u000a compared with the mean annual sea surface temperature (SST). Growth rate correlated negatively, and asymptotic length of the\\u000a individuals positively with SST. With increasing SST, the distributions of age frequencies moved away

  8. Annual shoot growth in different populations of Lonicera involucrata collected in North America and grown in Norway

    Microsoft Academic Search

    Johanna L. F. Erstad

    1991-01-01

    Seeds were collected from shrubs and brushwood of Lonicera involucrata (Rich.) Banks ex K. Spreng. in coastal Oregon (44–45° N) and interior British Columbia (54–55° N). The annual shoot growth of the resulting half-sib families and populations was studied in Ås, Norway (60° N). The move of these locally adapted types to a new environment revealed the great genetic variation

  9. In a long-term experimental demography study, excluding ungulates reversed invader's explosive population growth rate and restored natives

    PubMed Central

    Kalisz, Susan; Spigler, Rachel B.; Horvitz, Carol C.

    2014-01-01

    A major goal in ecology is to understand mechanisms that increase invasion success of exotic species. A recent hypothesis implicates altered species interactions resulting from ungulate herbivore overabundance as a key cause of exotic plant domination. To test this hypothesis, we maintained an experimental demography deer exclusion study for 6 y in a forest where the native ungulate Odocoileus virginianus (white-tailed deer) is overabundant and Alliaria petiolata (garlic mustard) is aggressively invading. Because population growth is multiplicative across time, we introduce metrics that correctly integrate experimental effects across treatment years, the cumulative population growth rate, ?c, and its geometric mean, ?per-year, the time-averaged annual population growth rate. We determined ?c and ?per-year of the invader and of a common native, Trillium erectum. Our results conclusively demonstrate that deer are required for the success of Alliaria; its projected population trajectory shifted from explosive growth in the presence of deer (?per-year = 1.33) to decline toward extinction where deer are excluded (?per-year = 0.88). In contrast, Trillium’s ?per-year was suppressed in the presence of deer relative to deer exclusion (?per-year = 1.04 vs. 1.20, respectively). Retrospective sensitivity analyses revealed that the largest negative effect of deer exclusion on Alliaria came from rosette transitions, whereas the largest positive effect on Trillium came from reproductive transitions. Deer exclusion lowered Alliaria density while increasing Trillium density. Our results provide definitive experimental support that interactions with overabundant ungulates enhance demographic success of invaders and depress natives’ success, with broad implications for biodiversity and ecosystem function worldwide. PMID:24616522

  10. Effect of increased private share of inpatient psychiatric resources on jail population growth: Evidence from the United States

    Microsoft Academic Search

    Jangho Yoon

    2011-01-01

    There is a strong connection between the mental health and criminal justice systems. This research empirically tested whether the privatization of the inpatient mental health system alters this relationship, contributing to jail population growth. Using state-level panel data on U.S. states and the District of Columbia for the years 1985–1998, this study analyzed the relationship between the size of jail

  11. Macrophage Ablation Reduces M2-Like Populations and Jeopardizes Tumor Growth in a MAFIA-Based Glioma Model12

    PubMed Central

    Gabrusiewicz, Konrad; Hossain, Mohammad B.; Cortes-Santiago, Nahir; Fan, Xuejun; Kaminska, Bozena; Marini, Frank C.; Fueyo, Juan; Gomez-Manzano, Candelaria

    2015-01-01

    Monocytes/macrophages are an influential component of the glioma microenvironment. However, understanding their diversity and plasticity constitute one of the most challenging areas of research due to the paucity of models to study these cells' inherent complexity. Herein, we analyzed the role of monocytes/macrophages in glioma growth by using a transgenic model that allows for conditional ablation of this cell population. We modeled glioma using intracranial GL261-bearing CSF-1R–GFP+ macrophage Fas-induced apoptosis (MAFIA) transgenic mice. Conditional macrophage ablation was achieved by exposure to the dimerizer AP20187. Double immunofluorescence was used to characterize M1- and M2-like monocytes/macrophages during tumor growth and after conditional ablation. During glioma growth, the monocyte/macrophage population consisted predominantly of M2 macrophages. Conditional temporal depletion of macrophages reduced the number of GFP+ cells, targeting mainly the repopulation of M2-polarized cells, and altered the appearance of M1-like monocytes/macrophages, which suggested a shift in the M1/M2 macrophage balance. Of interest, compared with control-treated mice, macrophage-depleted mice had a lower tumor mitotic index, microvascular density, and reduced tumor growth. These results demonstrated the possibility of studying in vivo the role and phenotype of macrophages in gliomas and suggested that transitory depletion of CSF-1R+ population influences the reconstitutive phenotypic pool of these cells, ultimately suppressing tumor growth. The MAFIA model provides a much needed advance in defining the role of macrophages in gliomas. PMID:25925380

  12. Predators with multiple ontogenetic niche shifts have limited potential for population growth and top-down control of their prey.

    PubMed

    van Leeuwen, Anieke; Huss, Magnus; Gårdmark, Anna; Casini, Michele; Vitale, Francesca; Hjelm, Joakim; Persson, Lennart; de Roos, André M

    2013-07-01

    Catastrophic collapses of top predators have revealed trophic cascades and community structuring by top-down control. When populations fail to recover after a collapse, this may indicate alternative stable states in the system. Overfishing has caused several of the most compelling cases of these dynamics, and in particular Atlantic cod stocks exemplify such lack of recovery. Often, competition between prey species and juvenile predators is hypothesized to explain the lack of recovery of predator populations. The predator is then considered to compete with its prey for one resource when small and to subsequently shift to piscivory. Yet predator life history is often more complex than that, including multiple ontogenetic diet shifts. Here we show that no alternative stable states occur when predators in an intermediate life stage feed on an additional resource (exclusive to the predator) before switching to piscivory, because predation and competition between prey and predator do not simultaneously structure community dynamics. We find top-down control by the predator only when there is no feedback from predator foraging on the additional resource. Otherwise, the predator population dynamics are governed by a bottleneck in individual growth occurring in the intermediate life stage. Therefore, additional resources for predators may be beneficial or detrimental for predator population growth and strongly influence the potential for top-down community control. PMID:23778226

  13. Field Assessment of the Influence of Temperature on Growth Rate in a Brown Trout Population

    Microsoft Academic Search

    Javier Lobón-Cerviá; Pedro A. Rincón

    1998-01-01

    Growth rates of age-0 brown trout Salmo trutta during the growing period (May–September) were estimated in nine consecutive year-classes in three sites of Arroyo Chabatchos (Esva River basin, northern Spain). Observed growth rates were highly correlated with average water temperature, which explained 48, 68 (90% excluding the severe drought of 1989), and 89% of the interannual variation in respective growth

  14. Investigations into the effects of environmental and physical variables on the growth of natural and transplanted populations of Ruppia maritima L. s.l. in the Galveston Bay System, Texas 

    E-print Network

    Schubert, William James

    2002-01-01

    The effects of sixteen environmental and physical variables on the growth of six natural populations and on the establishment and growth of transplanted populations of widgeon grass, Ruppia maritima L. s.l., were evaluated in the Galveston Bay...

  15. Development and utilization of a population growth history of Red Lake walleye, Stizostedion vitreum

    Microsoft Academic Search

    Michael J. Cyterski; George R. Spanglerz

    1996-01-01

    An environmental growth history of commercially harvested walleye, Stizostedion vitreum, in Red Lakes, Minnesota, was constructed for the years 1944–1992. This was accomplished using a linear model which was fitted to annular scale increment measurements. Increment size was separated into one component due to a combination of environmental factors, an environmental growth coefficient, and one due to the age of

  16. F-LE Exponential growth versus polynomial growth

    NSDL National Science Digital Library

    2012-05-01

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: The table below shows the values of $2^x$ and $2x^3 + 1$ for some whole number values of $x$: $x2^x2x^3+1$ 123 2417 3855 416129 532251 The numbers in t...

  17. F-LE Exponential growth versus linear growth II

    NSDL National Science Digital Library

    2012-05-01

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Using a scientific calculator, Alex makes the following table listing values of $(1.001)^x$ and $2x$ for a few inputs: $x(1.001)^x2x$ 11.0012 101.01004...

  18. F-LE Exponential growth versus linear growth I

    NSDL National Science Digital Library

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Mr. Wiggins gives his daughter Celia two choices of payment for raking leaves: Two dollars for each bag of leaves filled, She will be paid for the numb...

  19. Effects of chestnut tannins and coconut oil on growth performance, methane emission, ruminal fermentation, and microbial populations in sheep.

    PubMed

    Liu, H; Vaddella, V; Zhou, D

    2011-12-01

    This study was conducted to evaluate the effects of chestnut tannins (CT) and coconut oil (CO) on growth performance, methane (CH?) emission, ruminal fermentation, and microbial populations in sheep. A total of 48 Rideau Arcott sheep (average body weight 31.5±1.97 kg, 16 wk old) were randomly assigned into 6 treatment groups in a 3 × 2 factorial design, with CT and CO as the main effects (8 sheep per group). The treatments were control diet (CTR), 10 or 30 g of CT/kg of diet (CT10 and CT30), 25 g of CO/kg of concentrate (CO25), and 10 or 30 g of CT/kg of diet+25 g of CO/kg of concentrate (CT10CO25 and CT30CO25). After the feeding trial (60 d), all sheep were moved to respiratory chambers to measure CH? emission. After CH? emission measurements, all sheep were slaughtered to obtain rumen fluid samples. Results showed that the addition of CT, CO, and CT+CO had no significant effects on growth performance of sheep but reduced CH? emission. Addition of CT reduced the NH?-N concentration in rumen fluid in CT30. Addition of CO decreased the concentration of total volatile fatty acids in rumen fluid. No significant differences were observed in pH and molar proportion of volatile fatty acids among treatments. Addition of CT, CO, and CT+CO significantly decreased methanogen and protozoa populations. Moreover, CO decreased counts of Fibrobacter succinogenes. No significant differences were observed in populations of fungi, Ruminococcus flavefaciens, or Ruminococcus albus among treatments. In conclusion, supplementation of CT and CO seemed to be a feasible means of decreasing emissions of CH? from sheep by reduction of methanogen and protozoa populations with no negative effect on growth performance. PMID:22118094

  20. Identification of top-down forces regulating cotton aphid population growth in transgenic Bt cotton in central China.

    PubMed

    Han, Peng; Niu, Chang-ying; Desneux, Nicolas

    2014-01-01

    The cotton aphid Aphis gossypii Glover is the main aphid pest in cotton fields in the Yangtze River Valley Cotton-planting Zone (YRZ) in central China. Various natural enemies may attack the cotton aphid in Bt cotton fields but no studies have identified potential specific top-down forces that could help manage this pest in the YRZ in China. In order to identify possibilities for managing the cotton aphid, we monitored cotton aphid population dynamics and identified the effect of natural enemies on cotton aphid population growth using various exclusion cages in transgenic Cry1Ac (Bt)+CpTI (Cowpea trypsin inhibitor) cotton field in 2011. The aphid population growth in the open field (control) was significantly lower than those protected or restricted from exposure to natural enemies in the various exclusion cage types tested. The ladybird predator Propylaea japonica Thunberg represented 65% of Coccinellidae predators, and other predators consisted mainly of syrphids (2.1%) and spiders (1.5%). The aphid parasitoids Aphidiines represented 76.7% of the total count of the natural enemy guild (mainly Lysiphlebia japonica Ashmead and Binodoxys indicus Subba Rao & Sharma). Our results showed that P. japonica can effectively delay the establishment and subsequent population growth of aphids during the cotton growing season. Aphidiines could also reduce aphid density although their impact may be shadowed by the presence of coccinellids in the open field (likely both owing to resource competition and intraguild predation). The implications of these results are discussed in a framework of the compatibility of transgenic crops and top-down forces exerted by natural enemy guild. PMID:25170907

  1. Identification of Top-Down Forces Regulating Cotton Aphid Population Growth in Transgenic Bt Cotton in Central China

    PubMed Central

    Han, Peng; Niu, Chang-ying; Desneux, Nicolas

    2014-01-01

    The cotton aphid Aphis gossypii Glover is the main aphid pest in cotton fields in the Yangtze River Valley Cotton-planting Zone (YRZ) in central China. Various natural enemies may attack the cotton aphid in Bt cotton fields but no studies have identified potential specific top-down forces that could help manage this pest in the YRZ in China. In order to identify possibilities for managing the cotton aphid, we monitored cotton aphid population dynamics and identified the effect of natural enemies on cotton aphid population growth using various exclusion cages in transgenic Cry1Ac (Bt)+CpTI (Cowpea trypsin inhibitor) cotton field in 2011. The aphid population growth in the open field (control) was significantly lower than those protected or restricted from exposure to natural enemies in the various exclusion cage types tested. The ladybird predator Propylaea japonica Thunberg represented 65% of Coccinellidae predators, and other predators consisted mainly of syrphids (2.1%) and spiders (1.5%). The aphid parasitoids Aphidiines represented 76.7% of the total count of the natural enemy guild (mainly Lysiphlebia japonica Ashmead and Binodoxys indicus Subba Rao & Sharma). Our results showed that P. japonica can effectively delay the establishment and subsequent population growth of aphids during the cotton growing season. Aphidiines could also reduce aphid density although their impact may be shadowed by the presence of coccinellids in the open field (likely both owing to resource competition and intraguild predation). The implications of these results are discussed in a framework of the compatibility of transgenic crops and top-down forces exerted by natural enemy guild. PMID:25170907

  2. Anti-social cells: predicting the influence of E-cadherin loss on the growth of epithelial cell populations.

    PubMed

    Walker, D C; Georgopoulos, N T; Southgate, J

    2010-02-01

    The characteristics of biological tissues are determined by the interactions of large numbers of autonomous cells. These interactions can be mediated remotely by diffusive biochemical factors, or by direct cell-cell contact. E-cadherin is a protein expressed on the surface of normal epithelial cells that plays a key role in mediating intercellular adhesion via calcium-dependent homotypic interactions. E-cadherin is a metastasis-suppressor protein and its loss of function is associated with malignant progression. The purpose of this study was to apply an agent-based simulation paradigm in order to examine the emergent growth properties of mixed populations consisting of normal and E-cadherin defective cells in monolayer cell culture. Specifically, we have investigated the dynamics of normal cell:cell interactions in terms of intercellular adhesion and migration, and have used a simplified rule to represent the concepts of juxtacrine epidermal growth factor receptor (EGFR) activation and subsequent effect on cell proliferation. This cellular level control determines the overall population growth in a simulated experiment. Our approach provides a tool for modelling the development of defined biological abnormalities in epithelial and other biological tissues, raising novel predictions for future experimental testing. The results predict that even a relatively small number of abnormal ('anti-social') cells can modify the rate of the total population expansion, but the magnitude of this effect also depends on the extrinsic (culture) environment. In addition to directly influencing population dynamics, 'anti-social' cells can also disrupt the behaviour of the normal cells around them. PMID:19852973

  3. Past, Present and Future: Immigration, High Fertility Fuel State's Population Growth.

    ERIC Educational Resources Information Center

    Clark, William A. V.

    2000-01-01

    Presents demographic information on California's increasing population and ethnic diversity. Describes age pyramids and fertility rates by ethnic group, indicating that Asians and Hispanics will comprise over two-thirds of the state's population by 2030. Discusses implications for education, teenage pregnancy, political representation, prenatal…

  4. THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVIY OF POPULATION GROWTH RATE TO REPRODUCTION

    EPA Science Inventory

    In recent years there has been an increasing interest in using population models in environmental assessments. Matrix population models represent a valuable tool for extrapolating from life stage-specific stressor effects on survival and reproduction to effects on finite populati...

  5. Temporal stability in size distributions and growth rates of three Esox lucius L. populations.

    E-print Network

    Roos, André M. de

    trajectories for three stream living pike Esox lucius populations were studied for 7 years. All three to differences in prey:predator size ratios. The pike populations in the more open and larger streams grew, available online at http://www.blackwell-synergy.com 461 # 2006 The Authors Journal compilation # 2006

  6. Potential Effects of Environmental Contamination on Yuma Myotis Demography and Population Growth

    Microsoft Academic Search

    Winifred F. Frick; William E. Rainey; Elizabeth D. Pierson

    2007-01-01

    Unplanned natural and anthropogenic disasters provide unique opportunities for investigating the influence of perturbations on population vital rates and species recovery times. We investigated the potential effects of a major pesticide spill by comparing annual survival rates using mark-recapture techniques on a riparian bat species, Yuma Myotis (Myotis yumanensis). Demography and population dynamics for most bat species remain poorly understood

  7. MODELING POPULATION GROWTH OF THE OVENBIRD (SEIURUS AUROCAPILLA) IN THE SOUTHERN APPALACHIANS

    Microsoft Academic Search

    Andrei L. Podolsky; Theodore R. Simons; Jaime A. Collazo

    2007-01-01

    Studies of source-sink dynamics are oft en prompted by concerns about negative population trends. Estimates of population trajectories are usually based on assumptions about survival rates and empirical measures of fecundity. Most models ignore the infl uence of the rates of renesting and multiple brooding. We used the Ovenbird (Seiurus aurocapilla) as a model Neotropical migratory songbird species to investigate

  8. Rural Population Growth, 1950–1990: The Roles of Human Capital, Industry Structure, and Government Policy

    Microsoft Academic Search

    Tzu-Ling Huang; Peter F; Darin Wohlgemuth

    2002-01-01

    A human capital investment model of migration is applied to data on changes in county working- age populations. Counties having more highly educated populations grew more slowly. While human capital raises rural incomes, this effect is swamped by the higher returns to human capital in urban markets. This leads to \\

  9. Modeling tradeoffs in avian life history traits and consequences for population growth

    Microsoft Academic Search

    M. E. Clark; T. E. Martin

    2007-01-01

    Variation in population dynamics is inherently related to life history characteristics of species, which vary markedly even within phylogenetic groups such as passerine birds. We computed the finite rate of population change (?) from a matrix projection model and from mark-recapture observations for 23 bird species breeding in northern Arizona. We used sensitivity analyses and a simulation model to separate

  10. Regularity underlies erratic population abundances in marine ecosystems.

    PubMed

    Sun, Jie; Cornelius, Sean P; Janssen, John; Gray, Kimberly A; Motter, Adilson E

    2015-06-01

    The abundance of a species' population in an ecosystem is rarely stationary, often exhibiting large fluctuations over time. Using historical data on marine species, we show that the year-to-year fluctuations of population growth rate obey a well-defined double-exponential (Laplace) distribution. This striking regularity allows us to devise a stochastic model despite seemingly irregular variations in population abundances. The model identifies the effect of reduced growth at low population density as a key factor missed in current approaches of population variability analysis and without which extinction risks are severely underestimated. The model also allows us to separate the effect of demographic stochasticity and show that single-species growth rates are dominantly determined by stochasticity common to all species. This dominance-and the implications it has for interspecies correlations, including co-extinctions-emphasizes the need for ecosystem-level management approaches to reduce the extinction risk of the individual species themselves. PMID:25972438

  11. mlRho a program for estimating the population mutation and recombination rates from shotgun-

    E-print Network

    Lynch, Michael

    is to account for uneven coverage and the errors intro- duced by the widening spectrum of sequencing chemis- try nucleotide. In addition, they estimate the scaled exponential population growth rate. Both statistics-generation sequencing instruments can have error rates on the order of the sampled genetic diversity. Jiang et al. (2009

  12. Raindrop Momentum Triggers Growth of Leaf-Associated Populations of Pseudomonas syringae on Field-Grown Snap Bean Plants

    PubMed Central

    Hirano, S. S.; Baker, L. S.; Upper, C. D.

    1996-01-01

    Observational and microclimate modification experiments were conducted under field conditions to determine the role of the physical environment in effecting large increases in phyllosphere population sizes of Pseudomonas syringae pv. syringae, the causal agent of bacterial brown spot disease of snap bean (Phaseolus vulgaris L.). Comparisons of daily changes in population sizes of P. syringae on three plantings of snap bean cultivar Cascade and one of cultivar Eagle with weather conditions indicated a strong association of rainfalls with periods of 1 to 3 days in duration during which increases in bacterial population sizes were greater than 10-fold and up to 1,000-fold. The effects of rain on populations of P. syringae were explored further by modifying the microclimate of bean plants in the field with polyethylene shelters to shield plants from rain and fine-mesh inert screens to modify the momentum of raindrops. After each of three separate intense rains, the greater-than-10-fold increases in population sizes of P. syringae observed on plants exposed to the rains did not occur on plants in the shelters or under the screens. The screens decreased the velocity and, thus, the momentum of raindrops but not the volume or quality of rainwater that fell on plants under the screens. Thus, the absence of increases in population sizes of P. syringae on plants under the screens suggests that raindrop momentum plays a role in the growth-triggering effect of intense rains on populations of P. syringae on bean plants under field conditions. PMID:16535362

  13. Approximating Functions with Exponential Functions

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2005-01-01

    The possibility of approximating a function with a linear combination of exponential functions of the form e[superscript x], e[superscript 2x], ... is considered as a parallel development to the notion of Taylor polynomials which approximate a function with a linear combination of power function terms. The sinusoidal functions sin "x" and cos "x"…

  14. Non exponential decays of hadrons

    E-print Network

    Giuseppe Pagliara; Francesco Giacosa

    2011-08-13

    We analyze the survival probability of unstable particles in the context of quantum field theory. After introducing the spectral function of resonances, we show that deviations from the exponential decay law occur at short times after the creation of the unstable particle. For hadronic decays, these deviations are sizable and could lead to observable effects.

  15. Adaptation to metal-contaminated soils in populations of the moss, Ceratodon purpureus: Vegetative growth and reproductive expression

    SciTech Connect

    Jules, E.S.; Shaw, A.J. (Univ. of Michigan, Ann Arbor, MI (United States))

    1994-06-01

    Many observations suggest that morphological evolution occurs slowly in bryophytes, and this has been suggested to reflect low genetic diversity within species. Isozyme studies, however, stand in apparent contrast and have shown that bryophytes can contain high levels of genetic variability within and among populations. In light of this conflict, we tested the potential of the moss, Ceratodon purpureus, to undergo adaptive change (i.e., ecotypic differentiation) in response to soils that have been contaminated with high levels of metals for 90 years by measuring gametophytic growth and reproductive expression under experimental conditions. Variation in protonemal growth in sterile culture indicates that plants from one population growing on contaminated soil near a smelter are significantly more tolerant of zinc, cadmium, and lead than plants from uncontaminated sites. Results from a common garden experiment, in which plants were grown on soil from the smelter site, indicate that plants from near the smelter are significantly more tolerant of contaminated soils than plants from uncontaminated sites for vegetative growth. The same experiment suggests that plants from the smelter site are also more tolerant in terms of gametangial production (although we could not test this statistically). Our results demonstrate that C. purpureus has been able to undergo relatively rapid evolution in response to strong selective pressures. 29 refs., 4 figs., 5 tabs.

  16. Population Dynamics of a Salmonella Lytic Phage and Its Host: Implications of the Host Bacterial Growth Rate in Modelling

    PubMed Central

    Santos, Sílvio B.; Carvalho, Carla; Azeredo, Joana; Ferreira, Eugénio C.

    2014-01-01

    The prevalence and impact of bacteriophages in the ecology of bacterial communities coupled with their ability to control pathogens turn essential to understand and predict the dynamics between phage and bacteria populations. To achieve this knowledge it is essential to develop mathematical models able to explain and simulate the population dynamics of phage and bacteria. We have developed an unstructured mathematical model using delay-differential equations to predict the interactions between a broad-host-range Salmonella phage and its pathogenic host. The model takes into consideration the main biological parameters that rule phage-bacteria interactions likewise the adsorption rate, latent period, burst size, bacterial growth rate, and substrate uptake rate, among others. The experimental validation of the model was performed with data from phage-interaction studies in a 5 L bioreactor. The key and innovative aspect of the model was the introduction of variations in the latent period and adsorption rate values that are considered as constants in previous developed models. By modelling the latent period as a normal distribution of values and the adsorption rate as a function of the bacterial growth rate it was possible to accurately predict the behaviour of the phage-bacteria population. The model was shown to predict simulated data with a good agreement with the experimental observations and explains how a lytic phage and its host bacteria are able to coexist. PMID:25051248

  17. Morphological changes induced by insulin-like growth factor-I gene therapy in pituitary cell populations in experimental prolactinomas.

    PubMed

    Camihort, Gisela A; Hereñú, Claudia B; Luna, Georgina C; Rodríguez, Silvia S; Bracamonte, María I; Goya, Rodolfo G; Cónsole, Gloria M

    2010-01-01

    In previous studies, we assessed the effects of intrapituitary injection of a recombinant adenoviral vector (RAd) harboring the cDNA for rat insulin-like growth factor type I (RAd-IGF-I) on the lactotrope and somatotrope populations in estrogen-induced prolactinomas. In the present study, we aimed to confirm these findings and further analyze the effect of transgenic RAd-IGF-I on the other pituitary cell populations in female rats. All animals except the intact group (no estrogen and no stereotaxic injection) received subcutaneous estrogen for 30 days, and the groups which received RAd-IGF-I or RAd expressing green fluorescent protein (control) were additionally treated with the appropriate vectors on experimental day 0. The RAd-IGF-I group showed a significant decrease in serum growth hormone and prolactin levels and lactotrope and somatotrope cell size induced by estrogen treatment. Cell density was not affected by 7 days of IGF-I gene therapy. Estrogen had an inhibitory effect on thyrotrope cell density, whereas with RAd-IGF-I there was a nonsignificant trend towards restoration of cell density, without changes in cell size. RAd-IGF-I treatment decreased corticotrope cell size without changing cell density. Estrogen decreased gonadotrope cell size and density, which was reversed by RAd-IGF-I. We conclude that in estrogen-induced pituitary tumors, IGF-I gene therapy has inhibitory effects on the lactotrope, somatotrope and corticotrope populations, while reversing the effect of estrogen on gonadotropic cells. PMID:19923782

  18. Morphological Changes Induced by Insulin-Like Growth Factor-I Gene Therapy in Pituitary Cell Populations in Experimental Prolactinomas

    PubMed Central

    Camihort, Gisela A.; Hereñú, Claudia B.; Luna, Georgina C.; Rodríguez, Silvia S.; Bracamonte, María I.; Goya, Rodolfo G.; Cónsole, Gloria M.

    2010-01-01

    In previous studies, we assessed the effects of intrapituitary injection of a recombinant adenoviral vector (RAd) harboring the cDNA for rat insulin-like growth factor type I (RAd-IGF-I) on the lactotrope and somatotrope populations in estrogen-induced prolactinomas. In the present study, we aimed to confirm these findings and further analyze the effect of transgenic RAd-IGF-I on the other pituitary cell populations in female rats. All animals except the intact group (no estrogen and no stereotaxic injection) received subcutaneous estrogen for 30 days, and the groups which received RAd-IGF-I or RAd expressing green fluorescent protein (control) were additionally treated with the appropriate vectors on experimental day 0. The RAd-IGF-I group showed a significant decrease in serum growth hormone and prolactin levels and lactotrope and somatotrope cell size induced by estrogen treatment. Cell density was not affected by 7 days of IGF-I gene therapy. Estrogen had an inhibitory effect on thyrotrope cell density, whereas with RAd-IGF-I there was a nonsignificant trend towards restoration of cell density, without changes in cell size. RAd-IGF-I treatment decreased corticotrope cell size without changing cell density. Estrogen decreased gonadotrope cell size and density, which was reversed by RAd-IGF-I. We conclude that in estrogen-induced pituitary tumors, IGF-I gene therapy has inhibitory effects on the lactotrope, somatotrope and corticotrope populations, while reversing the effect of estrogen on gonadotropic cells. PMID:19923782

  19. Growth and differentiation potential of main- and side-population cells derived from murine skeletal muscle

    Microsoft Academic Search

    Tetsuro Tamaki; Akira Akatsuka; Yoshinori Okada; Yumi Matsuzaki; Hideyuki Okano; Minoru Kimura

    2003-01-01

    Skeletal muscle-derived CD34+\\/45? (Sk-34) cells were identified as a new candidate for stem cells. However, the relationship between Sk-34 cells and side-population (SP) cells is unknown. Here, we demonstrate that Sk-34 cells prepared from murine skeletal muscles consist wholly of main-population (MP) cells. The Sk-34 cells included only a few SP cells (1:1000, SP:MP). Colony-forming units of Sk-34 cells of

  20. Measurements of the effect of heat shocks on survival and growth of natural zooplankton populations

    Microsoft Academic Search

    M. Donze

    1979-01-01

    Summary  In our research on the biological effects of thermal pollution on fresh-water plankton, natural plankton populations are enclosed in floating tanks of 2 m3 capacity, depth 2 m. The tanks are filled with water that has or has not passed an industrial cooling circuit. In experiments lasting 14 days, plankton counts are made. From the population dynamics of individual species