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1

Modeling Exponential Population Growth  

ERIC Educational Resources Information Center

The concept of population growth patterns is a key component of understanding evolution by natural selection and population dynamics in ecosystems. The National Science Education Standards (NSES) include standards related to population growth in sections on biological evolution, interdependence of organisms, and science in personal and social…

McCormick, Bonnie

2009-01-01

2

Population Growth - Exponential and Logistic Models vs. Complex Reality  

NSDL National Science Digital Library

This analysis and discussion activity is designed to help students develop an intuitive understanding of the exponential and logistic models of population growth, including the biological processes that result in exponential or logistic population growth. Students learn about the simplifying assumptions built into the exponential and logistic models and explore how deviations from these assumptions can result in discrepancies between the predictions of these models and actual trends in population size for natural populations. This activity is designed to help high school students meet the Next Generation Science Standards and the Common Core State Standards.

Ingrid Waldron

3

Logistic Growth The logistic equation is a model of limited population growth. The exponential growth model  

E-print Network

9­28­1998 Logistic Growth The logistic equation is a model of limited population growth of organisms runs out of food, encounters predators, or fouls its own environment with waste. The logistic the carrying capacity. Example. A population of roaches grows logistically in Calvin Butterball's kitchen

Ikenaga, Bruce

4

Modeling the Pre-Industrial Roots of Modern Super-Exponential Population Growth  

PubMed Central

To Malthus, rapid human population growth—so evident in 18th Century Europe—was obviously unsustainable. In his Essay on the Principle of Population, Malthus cogently argued that environmental and socioeconomic constraints on population rise were inevitable. Yet, he penned his essay on the eve of the global census size reaching one billion, as nearly two centuries of super-exponential increase were taking off. Introducing a novel extension of J. E. Cohen's hallmark coupled difference equation model of human population dynamics and carrying capacity, this article examines just how elastic population growth limits may be in response to demographic change. The revised model involves a simple formalization of how consumption costs influence carrying capacity elasticity over time. Recognizing that complex social resource-extraction networks support ongoing consumption-based investment in family formation and intergenerational resource transfers, it is important to consider how consumption has impacted the human environment and demography—especially as global population has become very large. Sensitivity analysis of the consumption-cost model's fit to historical population estimates, modern census data, and 21st Century demographic projections supports a critical conclusion. The recent population explosion was systemically determined by long-term, distinctly pre-industrial cultural evolution. It is suggested that modern globalizing transitions in technology, susceptibility to infectious disease, information flows and accumulation, and economic complexity were endogenous products of much earlier biocultural evolution of family formation's embeddedness in larger, hierarchically self-organizing cultural systems, which could potentially support high population elasticity of carrying capacity. Modern super-exponential population growth cannot be considered separately from long-term change in the multi-scalar political economy that connects family formation and intergenerational resource transfers to wider institutions and social networks. PMID:25141019

Stutz, Aaron Jonas

2014-01-01

5

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

PubMed

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

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

2015-03-01

6

A Simulation To Model Exponential Growth.  

ERIC Educational Resources Information Center

Describes a simulation using dice-tossing students in a population cluster to model the growth of cancer cells. This growth is recorded in a scatterplot and compared to an exponential function graph. (KHR)

Appelbaum, Elizabeth Berman

2000-01-01

7

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

PubMed

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

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

2015-05-01

8

Population Growth  

NSDL National Science Digital Library

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.

2009-01-01

9

Population Explosion Using an Exponential Function  

NSDL National Science Digital Library

This intermediate algebra lesson has students use data from the U.S. Census Bureau's website to explore population growth and exponential functions. The learning object demonstrates how these mathematical functions can be used in a real world situation. Student materials, which include a continuous change model worksheet and a constant rate growth model worksheet, can be found here (the fourth row, second column of the table).

2011-01-05

10

Lesson 29: Exponential Growth and Decay  

NSDL National Science Digital Library

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.

2011-01-01

11

Population: Growth  

NSDL National Science Digital Library

This lesson discusses population growth, both in the United States and in the world. Topics include factors that influence population growth, such as government policy, religion, education or economic levels, energy use per capita, and whether a country is agrarian or industrial. The lesson includes an activity in which students research an online resource on population growth and answer questions as they navigate through its presentation.

Matt Laposata

12

Population Growth  

NSDL National Science Digital Library

This series of activities explores the mathematical and environmental aspects of population growth. Using archived census and demographic data as well as up-to-the-minute population estimates from the U.S. Census Bureau, students learn how to model population growth and study the implications of a changing population. The project provides instructions, activities, back-up information, data links, reference materials, on-line help, and an instructor guide. Although intended for high school students, activities 1 through 5 and 9 avoid higher mathematics and offer students work on statistical and historical aspects of population growth appropriate for the middle school level. This on-line project is part of the Center for Improved Engineering and Science Education (CIESE) program, which has developed internet activities for the elementary, middle, and high school level student.

2007-12-12

13

A Simple Mechanical Experiment on Exponential Growth  

NASA Astrophysics Data System (ADS)

With a rod, cord, pulleys, and slotted masses, students can observe and graph exponential growth in the cord tension over a factor of increase as large as several hundred. This experiment is adaptable for use either in algebra-based or calculus-based physics courses, fitting naturally with the study of sliding friction. Significant parts of the activity are accessible to students in physical science and environmental science courses.

McGrew, Ralph

2015-04-01

14

Black Hole Instabilities and Exponential Growth  

E-print Network

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.

Kartik Prabhu; Robert M. Wald

2015-01-12

15

Mutant number distribution in an exponentially growing population  

NASA Astrophysics Data System (ADS)

We present an explicit solution to a classic model of cell-population growth introduced by Luria and Delbrück (1943 Genetics 28 491–511) 70 years ago to study the emergence of mutations in bacterial populations. In this model a wild-type population is assumed to grow exponentially in a deterministic fashion. Proportional to the wild-type population size, mutants arrive randomly and initiate new sub-populations of mutants that grow stochastically according to a supercritical birth and death process. We give an exact expression for the generating function of the total number of mutants at a given wild-type population size. We present a simple expression for the probability of finding no mutants, and a recursion formula for the probability of finding a given number of mutants. In the ‘large population-small mutation’ limit we recover recent results of Kessler and Levine (2014 J. Stat. Phys. doi:10.1007/s10955-014-1143-3) for a fully stochastic version of the process.

Keller, Peter; Antal, Tibor

2015-01-01

16

Modeling Population Growth and Extinction  

ERIC Educational Resources Information Center

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,…

Gordon, Sheldon P.

2009-01-01

17

Teaching Exponential Growth and Decay: Examples from Medicine  

ERIC Educational Resources Information Center

A treatment of exponential growth and decay is sketched which does not require knowledge of calculus, and hence, it can be applied to many cases in the biological and medical sciences. Some examples are bacterial growth, sterilization, clearance, and drug absorption. (DF)

Hobbie, Russell K.

1973-01-01

18

Exponential order statistic models of software reliability growth  

NASA Technical Reports Server (NTRS)

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.

Miller, D. R.

1985-01-01

19

Black Hole Instabilities and Exponential Growth  

E-print Network

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 $...

Prabhu, Kartik

2015-01-01

20

ON UNIFORM EXPONENTIAL GROWTH FOR SOLVABLE GROUPS  

E-print Network

. the ball of radius n centered at the identity in G for the word metric. Le* *t C be the set of all make a connection between slow growth and the Lehmer conjectur* *e. Dedicated to G . Assume that is symmetric (* *i.e. s 2 ) s-1 2 ), contains the identity e, and let G = G

Breuillard, Emmanuel

21

Population growth (annual %)  

NSDL National Science Digital Library

Data set and map pertaining to population growth for all countries as an annual percentage. The World Bank specifies population growth as a World Development Indicator (WDI) -- the statistical benchmark that helps measure the progress of development.

World Bank

22

Exponential energy growth in adiabatically changing Hamiltonian systems.  

PubMed

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. PMID:25679558

Pereira, Tiago; Turaev, Dmitry

2015-01-01

23

Exponential energy growth in adiabatically changing Hamiltonian systems  

NASA Astrophysics Data System (ADS)

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.

Pereira, Tiago; Turaev, Dmitry

2015-01-01

24

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

E-print Network

Critical Mutation Rate Has an Exponential Dependence on Population Size in Haploid and Diploid that are both fit and robust. At high mutation rates, individuals with greater mutational robustness can capable of determining the relationship between population size, the critical mutation rate at which

Channon, Alastair

25

Population Growth in Yeasts  

NSDL National Science Digital Library

This lesson is the second of two that explore cellular respiration and population growth in yeasts. In the first lesson, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arose during the first lesson and its associated activity, students in this lesson work in small groups to design experiments that determine how environmental factors affect yeast population growth.

Engineering K-PhD Program,

26

Exponential energy growth in adiabatically changing Hamiltonian Systems  

E-print Network

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.

Tiago Pereira; Dmitry Turaev

2014-10-07

27

Population Growth Curves  

NSDL National Science Digital Library

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.

Bio-Inspired Technology and Systems (BITS) RET,

28

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.

29

Some Similarities between the Spread of an Infectious Disease and Population Growth  

NSDL National Science Digital Library

A simple simulation demonstrates how spread of an infectious disease can result in exponential increase in the number of infected individuals. Discussion questions and a graphing activity develop an understanding of exponential and logistic population growth.

Jennifer Doherty

30

Population Growth, Technology, and the Environment  

NSDL National Science Digital Library

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).

National Science Teachers Association (NSTA)

2008-09-30

31

Growth rate determination of heterogeneous microbial population in swine manure.  

PubMed

The effect of manure concentration on the growth of the heterogeneous microbial population under batch condition was studied. Four manure concentrations were used in the study. The dehydrogenase activity was used as a measure of the active biomass in the manure. The chemical oxygen demand test was used to measure the change in organic material caused by biological activities. The growth curve of the heterogeneous microbial population in swine manure was essentially similar to that of a pure culture grown batchwise in that it had the four principle phases: lag, exponential growth, stationary, and death. The exponential growth phase followed a diauxic growth pattern. High concentration of manure had an inhibitory effect on the microbial growth. Manure diluted less than 1:3 (manure:water) depressed the specific growth rate of the microbial population. PMID:2802598

Ghaly, A E; Kok, R; Ingrahm, J M

1989-10-01

32

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

NSDL National Science Digital Library

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.

James J. Rutledge

33

Pairwise Comparisons of Mitochondrial DNA Sequences in Stable and Exponentially Growing Populations  

Microsoft Academic Search

We consider the distribution of pairwise sequence differences of mitochondrial DNA or of other nonrecombining portions of the genome in a population that has been of constant size and in a population that has been growing in size exponentially for a long time. We show that, in a population of constant size, the sample distribution of pairwise differences will typically

Montgomery Slatkin; Rr Hudson

1991-01-01

34

Population Growth: Crisis and Challenge.  

ERIC Educational Resources Information Center

The proceedings of this first annual symposium on population growth considers the consequences of this growth, along with possible means of regulation. Topics of speeches include: Population Outlook in Asia (Irene Taeuber); Malnutrition is a Problem of Ecology (Paul Gyorgy); The Leisure Explosion (E. H. Storey); Effects of Pollution on Population

Beaton, John R., Ed.; Doberenz, Alexander R., Ed.

35

Population growth, poverty and health.  

PubMed

One of the most popular explanations for the many problems that face Africa is population growth. Africa's population has doubled since 1960. Africa has the highest fertility rate in the world and the rate of population growth is higher than in any other region. At the same time, Africa faces a social and economic situation that is viewed by many as alarming. Among the problems that devastate Africa is that of persistent poor health. Africa has lower life expectancy, higher mortality rates and is affected by more disease and illness conditions than any other region. Focusing on sub-Saharan Africa, this paper examines the relationship between population growth, poverty and poor health. While most analyses have focused on population growth as an original cause of poverty and underdevelopment, this paper argues that while both population growth and poor health play a significant role in exacerbating the problem of poverty, they are themselves primary consequences of poverty rather than its cause. PMID:9225412

Kibirige, J S

1997-07-01

36

U.S. Population Growth.  

ERIC Educational Resources Information Center

This autoinstructional lesson deals with the study of man and his environment. No previous experience or learning in this field is required. Emphasis is placed on analysis of population growth and the impact population growth and trends have on natural resource depletion. The behavioral objectives (five) are listed. The study guide for the…

Dillner, Harry

37

Analysis of the lag phase to exponential growth transition by incorporating inoculum characteristics.  

PubMed

During the last decade, individual-based modelling (IbM) has proven to be a valuable tool for modelling and studying microbial dynamics. As each individual is considered as an independent entity with its own characteristics, IbM enables the study of microbial dynamics and the inherent variability and heterogeneity. IbM simulations and (single-cell) experimental research form the basis to unravel individual cell characteristics underlying population dynamics. In this study, the IbM framework MICRODIMS, i.e., MICRObial Dynamics Individual-based Model/Simulator, is used to investigate the system dynamics (with respect to the model and the system modelled). First, the impact of the time resolution on the simulation accuracy is discussed. Second, the effect of the inoculum state and size on emerging individual dynamics, such as individual mass, individual age and individual generation time distribution dynamics, is studied. The distributions of individual characteristics are more informative during the lag phase and the transition to the exponential growth phase than during the exponential phase. The first generation time distributions are strongly influenced by the inoculum state. All inocula with a pronounced heterogeneity, except the inocula starting from a uniform distribution, exhibit commonly observed microbial behaviour, like a more spread first generation time distribution compared to following generations and a fast stabilisation of biomass and age distributions. PMID:21511125

Verhulst, A J; Cappuyns, A M; Van Derlinden, E; Bernaerts, K; Van Impe, J F

2011-06-01

38

Weak extinction versus global exponential growth of total mass for superdiffusions  

E-print Network

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

Song, Renming

39

Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 1; Analysis  

NASA Technical Reports Server (NTRS)

Extensive slow-crack-growth (SCG) analysis was made using a primary exponential crack-velocity formulation under three widely used load configurations: constant stress rate, constant stress, and cyclic stress. Although the use of the exponential formulation in determining SCG parameters of a material requires somewhat inconvenient numerical procedures, the resulting solutions presented gave almost the same degree of simplicity in both data analysis and experiments as did the power-law formulation. However, the fact that the inert strength of a material should be known in advance to determine the corresponding SCG parameters was a major drawback of the exponential formulation as compared with the power-law formulation.

Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

2002-01-01

40

Reduced Heme Levels Underlie the Exponential Growth Defect of the Shewanella oneidensis hfq Mutant  

PubMed Central

The RNA chaperone Hfq fulfills important roles in small regulatory RNA (sRNA) function in many bacteria. Loss of Hfq in the dissimilatory metal reducing bacterium Shewanella oneidensis strain MR-1 results in slow exponential phase growth and a reduced terminal cell density at stationary phase. We have found that the exponential phase growth defect of the hfq mutant in LB is the result of reduced heme levels. Both heme levels and exponential phase growth of the hfq mutant can be completely restored by supplementing LB medium with 5-aminolevulinic acid (5-ALA), the first committed intermediate synthesized during heme synthesis. Increasing expression of gtrA, which encodes the enzyme that catalyzes the first step in heme biosynthesis, also restores heme levels and exponential phase growth of the hfq mutant. Taken together, our data indicate that reduced heme levels are responsible for the exponential growth defect of the S. oneidensis hfq mutant in LB medium and suggest that the S. oneidensis hfq mutant is deficient in heme production at the 5-ALA synthesis step. PMID:25356668

Mezoian, Taylor; Hunt, Taylor M.; Keane, Meaghan L.; Leonard, Jessica N.; Scola, Shelby E.; Beer, Emma N.; Perdue, Sarah; Pellock, Brett J.

2014-01-01

41

Population Explosion: Modeling Phage Growth  

NSDL National Science Digital Library

How is the relationship between phages and their bacterial hosts like that of predators and prey? How does this relationship differ? What are the factors that contribute to phage production in the cell? What can the phage concentration in a high titer lysate tell us about both of these populations? We can investigate these questions and more with an Excel spreadsheet model for phage growth. * explore a multiple parameter model of population growth in bacteriophages that demonstrates interdependence with the population of bacterial hosts

Jean Douthwright (Beloit College; Biology)

2006-05-20

42

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

USGS Publications Warehouse

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.

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

1979-01-01

43

Target population growth: zero.  

PubMed

The Fifth Session of the Fourth National Council of the China Family Planning Association held in Beijing on December 13, 1999, focused on how to control the number of people in China and improve their quality of life. Family planners also explored ways to decrease the number of babies with birth defects and maternal mortality rate. During the meeting, Zhang Weiqing, minister of the State Family Planning Commission, expressed that they are optimistic about keeping the Chinese population under 1.3 billion before the 21st century. He added that top attention should be paid to providing family planning service (sexual and reproductive counseling) for unmarried young people, laid-off workers, and the transient population in urban areas. In Shenzhen, a special economic zone, 854 family planning offices have been established among 2.8 million temporary residents, these agencies, many of which are led by temporary residents themselves. Lastly, Zhang announced that a draft national law on population and family planning has been finished and the law is expected to be enacted in 3 years. PMID:12295907

2000-02-01

44

Food production and population growth.  

PubMed

Governments have frequently ignored the issue of population consumption exceeding the rates of renewal of natural resources. At the UN Conference on the Environment and Development in Rio de Janeiro, the issue of population growth was ignored in the agenda and action plan. In 1974, the UN World Population Conference suggested population stability would be possible if standards of living were raised. Industrialized nations spent half a century of active interference with the stability of global populations and failed to slow growth. 27 countries, mainly in tropical and subtropical zones, have an average cereal yield of under 1 ton per hectare, when improved seed and basic minimum fertilizer could yield 2 tons per hectare. Efforts to increase yields by the Consultative Group for International Agricultural research in 13 international centers resulted in global annual increases of about 50 million tons of grain (wheat and rice). Rainfed agriculture did not benefit as much because of climatic conditions. Where varieties of triticale, sorghum, millet, groundnuts, chick peas, cowpeas, beans, and cassava have helped increase food production, population growth has outstripped the gains. Agricultural fertilizers have been unfairly blamed for soil nutrient losses. Because of the age structure of population, the expected population growth can only be addressed through development of higher yields, new strains resistant to disease, and fertilizers. Slow release phosphates for tropical soils are needed. Shortages of domestic fuel divert much needed farmyard manure and composted crop residues. About 400 million tons of dung are thus wasted annually; food grain harvests are thus reduced by 14 million tons. About 50% of the 1133 million poorest people will live in Asia and another 25% will live in Sub-Saharan Africa, living on a total degraded area of 1219 million hectares. Imbalance between food supply and population need to be addressed on an effective international scale. PMID:12319217

Pereira, H C

1993-07-01

45

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

PubMed

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

Alexander, Tal; Natarajan, Priyamvada

2014-09-12

46

Making a stand: five centuries of population growth in colonizing populations of Pinus ponderosa.  

PubMed

The processes underlying the development of new populations are important for understanding how species colonize new territory and form viable long-term populations. Life-history-mediated processes such as Allee effects and dispersal capability may interact with climate variability and site-specific factors to govern population success and failure over extended time frames. We studied four disjunct populations of ponderosa pine in the Bighorn Basin of north-central Wyoming to examine population growth spanning more than five centuries. The study populations are separated from continuous ponderosa pine forest by distances ranging from 15 to >100 km. Strong evidence indicates that the initial colonizing individuals are still present, yielding a nearly complete record of population history. All trees in each population were aged using dendroecological techniques. The populations were all founded between 1530 and 1655 cal yr CE. All show logistic growth patterns, with initial exponential growth followed by a slowing during the mid to late 20th century. Initial population growth was slower than expectations from a logistic regression model at all four populations, but increased during the mid-18th century. Initial lags in population growth may have been due to strong Allee effects. A combination of overcoming Allee effects and a transition to favorable climate conditions may have facilitated a mid-18th century pulse in population growth rate. PMID:22764493

Lesser, Mark R; Jackson, Stephen T

2012-05-01

47

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

PubMed Central

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

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

2015-01-01

48

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

49

Molecular basis for the explanation of the exponential growth of polyelectrolyte multilayers  

NASA Astrophysics Data System (ADS)

The structure of poly(L-lysine) (PLL)/hyaluronan (HA) polyelectrolyte multilayers formed by electrostatic self-assembly is studied by using confocal laser scanning microscopy, quartz crystal microbalance, and optical waveguide lightmode spectroscopy. These films exhibit an exponential growth regime where the thickness increases exponentially with the number of deposited layers, leading to micrometer thick films. Previously such a growth regime was suggested to result from an "in" and "out" diffusion of the PLL chains through the film during buildup, but direct evidence was lacking. The use of dye-conjugated polyelectrolytes now allows a direct three-dimensional visualization of the film construction by introducing fluorescent polyelectrolytes at different steps during the film buildup. We find that, as postulated, PLL diffuses throughout the film down into the substrate after each new PLL injection and out of the film after each PLL rinsing and further after each HA injection. As PLL reaches the outer layer of the film it interacts with the incoming HA, forming the new HA/PLL layer. The thickness of this new layer is thus proportional to the amount of PLL that diffuses out of the film during the buildup step, which explains the exponential growth regime. HA layers are also visualized but no diffusion is observed, leading to a stratified film structure. We believe that such a diffusion-based buildup mechanism explains most of the exponential-like growth processes of polyelectrolyte multilayers reported in the literature.

Picart, C.; Mutterer, J.; Richert, L.; Luo, Y.; Prestwich, G. D.; Schaaf, P.; Voegel, J.-C.; Lavalle, P.

2002-10-01

50

On Uniform Exponential Growth for Linear Groups Alex Eskin*, Shahar Mozesyand Hee Ohz  

E-print Network

On Uniform Exponential Growth for Linear Groups Alex Eskin*, Shahar generated group. Given a finite set of generators S of , t* *he word length lS(fl) for an element fl 2 writing the final version of the paper we have learned from J. Wilson * *that he has recently

Eskin, Alex

51

Uniform Uniform Exponential Growth of Subgroups of the Mapping Class Group  

Microsoft Academic Search

Let Mod(S) denote the mapping class group of a compact, orientable surface S. We prove that finitely generated subgroups of Mod(S) which are not virtually abelian have uniform exponential growth with minimal growth rate bounded below by a constant depending\\u000a only, and necessarily, on S. For the proof, we find in any such subgroup explicit free group generators which are

Johanna Mangahas

2010-01-01

52

Cellular Respiration and Population Growth  

NSDL National Science Digital Library

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.

2014-09-18

53

Nutrition, Development, and Population Growth  

ERIC Educational Resources Information Center

Focuses on the problem of malnutrition in developing countries through a description of its interrelationships with human development, national economies, economic growth and income, agricultural advances, the crisis in infant feeding practices, new foods, and the population dilemma. Outlines possible future policy directions to significantly…

Berg, Alan

1973-01-01

54

Population Growth: Family Planning Programs.  

ERIC Educational Resources Information Center

These proceedings of the second annual symposium on population growth bring together speeches and panel discussions on family planning programs. Titles of speeches delivered are: Communicating Family Planning (Mrs. Jean Hutchinson); Effects of New York's Abortion Law Change (Dr. Walter Rogers); The Law and Birth Control, Sterilization and Abortion…

Doberenz, Alexander R., Ed.; Taylor, N. Burwell G., Ed.

55

Population growth and foreign policy.  

PubMed

Australian foreign policy is examined in light of the population issue and its relationships to its developing Asian neighbors. Rapid population growth has been a 20th-century phenomenon. In the ESCAP region, almost all governments are anxious to reduce growth rates and welcome international assistance for population programs. The motivation of these governments seems to be both political and economic. Asian countries do not share the view expressed at Bucharest by Latin American and African representatives that high population growth rates are not a problem. Results of national family planning programs in 16 developing Asian countries are assessed. Major fertility decline has only occurred so far in the most prosperous of these countries. Future fertility trends are hard to predict. Present inadequate knowledge of the determinants of human fertility and limited knowledge regarding fertility limitation techniques hamper progress in population reduction. Australia has aided these countries in demographic training and data collection. For both economic and humanitarian reasons, this aid should be extended to program implementation. PMID:12309219

Flood, P J

1978-04-01

56

A magnetosome-associated cytochrome MamP is critical for magnetite crystal growth during the exponential growth phase.  

PubMed

Magnetotactic bacteria use a specific set of conserved proteins to biomineralize crystals of magnetite or greigite within their cells in organelles called magnetosomes. Using Magnetospirillum magneticum AMB-1, we examined one of the magnetotactic bacteria-specific conserved proteins named MamP that was recently reported as a new type of cytochrome c that has iron oxidase activity. We found that MamP is a membrane-bound cytochrome, and the MamP content increases during the exponential growth phase compared to two other magnetosome-associated proteins on the same operon, MamA and MamK. To assess the function of MamP, we overproduced MamP from plasmids in wild-type (WT) AMB-1 and found that during the exponential phase of growth, these cells contained more magnetite crystals that were the same size as crystals in WT cells. Conversely, when the heme c-binding motifs within the mamP on the plasmid was mutated, the cells produced the same number of crystals, but smaller crystals than in WT cells during exponential growth. These results strongly suggest that during the exponential phase of growth, MamP is crucial to the normal growth of magnetite crystals during biomineralization. PMID:25048532

Taoka, Azuma; Eguchi, Yukako; Mise, Shingo; Oestreicher, Zachery; Uno, Fumio; Fukumori, Yoshihiro

2014-09-01

57

Population growth can be checked.  

PubMed

Since independence, India's population size has doubled. The rate of growth was 2.5% during 1971-81, an increase from the rate of 2.15% observed during the 1951-61 period. The increase indicated that efforts to decrease population growth have not succeeded. The implications with respect to food, housing, clothing, education, and health facilities, which are fundamental to improving the physical quality of life, are severe. This demographic trend is a serious impediment to progress. The population growth is due to a constant birthrate and a sharp decline in mortality. Reducing the birthrate is necessary to reduce the rate of growth. An attitudinal change adopting the norm of family limitation should be encouraged through propaganda, socioeconomic programs, and religious and cultural organizations. Other measures to bring about a decline in the birthrate include: increasing the marriage age, and expanding educational and employment opportunities for women and girls. These measures will require substantial effort and time. Incentives may show more immediate effects. Monetary incentives are not desired because of the possibility of misuse. However the government could assume responsibility for the education and guarantee employment of children of couples who have only one child, and provide free education to children of couples with only 2 children. These incentives are not likely to be misused, can be available to all segments of the population, and involve no immediate large financial burden on the government. In addition, scholarships to the Harijan students should be limited to 2 per family. If these measures are accepted, they could quickly reduce the birth rate. PMID:12311944

Shukla, J P

58

Estimation of population growth or decline in genetically monitored populations.  

PubMed Central

This article introduces a new general method for genealogical inference that samples independent genealogical histories using importance sampling (IS) and then samples other parameters with Markov chain Monte Carlo (MCMC). It is then possible to more easily utilize the advantages of importance sampling in a fully Bayesian framework. The method is applied to the problem of estimating recent changes in effective population size from temporally spaced gene frequency data. The method gives the posterior distribution of effective population size at the time of the oldest sample and at the time of the most recent sample, assuming a model of exponential growth or decline during the interval. The effect of changes in number of alleles, number of loci, and sample size on the accuracy of the method is described using test simulations, and it is concluded that these have an approximately equivalent effect. The method is used on three example data sets and problems in interpreting the posterior densities are highlighted and discussed. PMID:12871921

Beaumont, Mark A

2003-01-01

59

Exponential growth of ``snow molds'' at sub-zero temperatures: an explanation for high beneath-snow  

E-print Network

Exponential growth of ``snow molds'' at sub-zero temperatures: an explanation for high beneath-snow of the beneath-snow respiratory flux in cold-winter ecosys- tems. The most common, but still untested hypothesis to explain exponential kinetics and high Q10 values as beneath-snow soils warm from -3 to 0°C

Schmidt, Steven K.

60

Power Law Versus Exponential Form of Slow Crack Growth of Advanced Structural Ceramics: Dynamic Fatigue  

NASA Technical Reports Server (NTRS)

The life prediction analysis based on an exponential crack velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress-rate ("dynamic fatigue") and preload testing at ambient and elevated temperatures. The data fit to the strength versus In (stress rate) relation was found to be very reasonable for most of the materials. It was also found that preloading technique was equally applicable for the case of slow crack growth (SCG) parameter n > 30. The major limitation in the exponential crack velocity formulation, however, was that an inert strength of a material must be known priori to evaluate the important SCG parameter n, a significant drawback as compared to the conventional power-law crack velocity formulation.

Choi, Sung R.; Gyekenyesi, John P.

2002-01-01

61

The communalisation of population growth.  

PubMed

It is politically dangerous to attribute birth rates to religion. Some propaganda proposes the following myths: that Hindus have only 1 wife and Muslims many; that Islam forbids family planning and Hinduism does not; that Muslims have a higher birth rate; and that there will be more Muslims in India soon. Statistical evidence is supplied to refute these claims. In fact, the rate of polygynous marriage is 5.80% among Hindus and 5.73% among Muslims, which means Muslims have a lower incidence. Islam "fatwas" allow temporary methods of contraception, but forbids abortions and sterilizations. Contraceptive use in Muslim countries such as Turkey, Egypt, and Indonesia is generally high. Fertility when cross-classified by religion and urban and rural residence or by monthly expenditures per capita shows that religion is not the significant variable. Socioeconomic factors do affect fertility, but there is a mix of socioeconomic groups among both Hindus and Muslims. Indian population growth projections indicate that Hindus will outnumber Muslims. Fertility decline has been significant in both urban and rural Muslim communities. A comparison of the Malabar region of Kerala and Uttar Pradesh shows Malabar with a 40% Muslim population and a lower birth rate than Uttar Pradesh with a 15% Muslim population. The conclusion is that the evidence does not support the myths; religion is not a primary determining factor. PMID:12286353

Rao, M

1993-02-01

62

Postdiffusion of oligo-peptide within exponential growth multilayer films for localized peptide delivery.  

PubMed

The multilayers of poly(L-lysine) (PLL) and hyaluronic acid (HA) were constructed by alternating deposition of PLL at high pH and HA at low pH. The exponential growth of the multilayer was proved to be amplified by increasing the pH difference between the two deposition solutions. The exponential growth multilayers of PLL/HA assembled at different pH were utilized as reservoirs for loading a trans-activating transcriptional factor (TAT) peptide. The confocal laser scanning microscopy (CLSM) results indicated that the FITC-labeled TAT could diffuse throughout the exponentially growing PLL/HA film. The amount of peptide embedded within multilayer could be adjusted by both multilayer assembly pH and the TAT loading pH. Compared with (PLL/HA 6.5/6.5)5 multilayer (PLL/HA a/b means that the multilayer film was constructed by using PLL at pH a and HA at pH b), the (PLL/HA 9.5/2.9)5 film can be loaded with more TAT peptide at the same loading pH 6.5. The excess of positively charged TAT peptide within (PLL/HA 9.5/2.9)5 film could not only be ascribed to its extraordinary thickness but also be attributed to its uncompensated negative charge density enhanced by the pH difference between film buildup and peptide loading process. Increasing of the TAT loading pH from 6.5 to 9.5, which increases the pH difference between multilayer assembly and peptide loading process, enhances the uncompensated charge density within (PLL/HA 9.5/2.9)5 film and elevates the peptide density from 13.8 to 25.0 microg/cm2. Compared with direct layer-by-layer assembly of TAT and HA, the postdiffusion of TAT into (PLL/HA 9.5/2.9)5 film was loaded much more peptide. The postdiffusion of peptide into a rapid growth multilayer can be more favorable to load and sustainedly release functional oligo-peptide. The cell culture results indicated that the TAT embedded within the film maintained the ability to traverse across the Hep G2 cell membrane. The functionalized (PLL/HA 9.5/2.9)5 TAT 9.5 film was more efficient than the equivalent amount of free TAT peptide in the TAT uptake test. The postdiffusion of oligo-peptide within an exponential growth multilayer can serve as an effective approach for localized and sustained peptide delivery. PMID:19736942

Wang, Xuefei; Ji, Jian

2009-10-01

63

Population Dynamics of Metastable Growth-Rate Phenotypes  

PubMed Central

Neo-Darwinian evolution has presented a paradigm for population dynamics built on random mutations and selection with a clear separation of time-scales between single-cell mutation rates and the rate of reproduction. Laboratory experiments on evolving populations until now have concentrated on the fixation of beneficial mutations. Following the Darwinian paradigm, these experiments probed populations at low temporal resolution dictated by the rate of rare mutations, ignoring the intermediate evolving phenotypes. Selection however, works on phenotypes rather than genotypes. Research in recent years has uncovered the complexity of genotype-to-phenotype transformation and a wealth of intracellular processes including epigenetic inheritance, which operate on a wide range of time-scales. Here, by studying the adaptation dynamics of genetically rewired yeast cells, we show a novel type of population dynamics in which the intracellular processes intervene in shaping the population structure. Under constant environmental conditions, we measure a wide distribution of growth rates that coexist in the population for very long durations (>100 generations). Remarkably, the fastest growing cells do not take over the population on the time-scale dictated by the width of the growth-rate distributions and simple selection. Additionally, we measure significant fluctuations in the population distribution of various phenotypes: the fraction of exponentially-growing cells, the distributions of single-cell growth-rates and protein content. The observed fluctuations relax on time-scales of many generations and thus do not reflect noisy processes. Rather, our data show that the phenotypic state of the cells, including the growth-rate, for large populations in a constant environment is metastable and varies on time-scales that reflect the importance of long-term intracellular processes in shaping the population structure. This lack of time-scale separation between the intracellular and population processes calls for a new framework for population dynamics which is likely to be significant in a wide range of biological contexts, from evolution to cancer. PMID:24312571

Braun, Erez

2013-01-01

64

Comparing growth patterns among field populations of cereal aphids reveals factors  

E-print Network

Comparing growth patterns among field populations of cereal aphids reveals factors limiting species of aphids that may become serious pests. With increasing abundance, the proportion of a particular species in the total aphid population may remain constant, suggesting a density-independent exponential

Kratochvíl, Lukas

65

Population growth rates: issues and an application.  

PubMed Central

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

Godfray, H Charles J; Rees, Mark

2002-01-01

66

Intensification of ?-poly(L: -malic acid) production by Aureobasidium pullulans ipe-1 in the late exponential growth phase.  

PubMed

?-Poly(malic acid) (PMLA) has attracted industrial interest because this polyester can be used as a prodrug or for drug delivery systems. In PMLA production by Aureobasidium pullulans ipe-1, it was found that PLMA production was associated with cell growth in the early exponential growth phase and dissociated from cell growth in the late exponential growth phase. To enhance PMLA production in the late phase, different fermentation modes and strategies for controlling culture redox potential (CRP) were studied. The results showed that high concentrations of produced PMLA (above 40 g/l) not only inhibited PMLA production, but also was detrimental to cell growth. Moreover, when CRP increased from 57 to 100 mV in the late exponential growth phase, the lack of reducing power in the broth also decreased PMLA productivity. PMLA productivity could be enhanced by repeated-batch culture to maintain cell growth in the exponential growth phase, or by cell-recycle culture with membrane to remove the produced PMLA, or by maintaining CRP below 70 mV no matter which kind of fermentation mode was adopted. Repeated-batch culture afforded a high PMLA concentration (up to 63.2 g/l) with a productivity of 1.15 g l(-1) h(-1). Cell-recycle culture also confirmed that PMLA production by the strain ipe-1 was associated with cell growth. PMID:22395899

Cao, Weifeng; Luo, Jianquan; Zhao, Juan; Qiao, Changsheng; Ding, Luhui; Qi, Benkun; Su, Yi; Wan, Yinhua

2012-07-01

67

Human population and atmospheric carbon dioxide growth dynamics: Diagnostics for the future  

NASA Astrophysics Data System (ADS)

We analyze the growth rates of human population and of atmospheric carbon dioxide by comparing the relative merits of two benchmark models, the exponential law and the finite-time-singular (FTS) power law. The later results from positive feedbacks, either direct or mediated by other dynamical variables, as shown in our presentation of a simple endogenous macroeconomic dynamical growth model describing the growth dynamics of coupled processes involving human population (labor in economic terms), capital and technology (proxies by CO2 emissions). Human population in the context of our energy intensive economies constitutes arguably the most important underlying driving variable of the content of carbon dioxide in the atmosphere. Using some of the best databases available, we perform empirical analyses confirming that the human population on Earth has been growing super-exponentially until the mid-1960s, followed by a decelerated sub-exponential growth, with a tendency to plateau at just an exponential growth in the last decade with an average growth rate of 1.0% per year. In contrast, we find that the content of carbon dioxide in the atmosphere has continued to accelerate super-exponentially until 1990, with a transition to a progressive deceleration since then, with an average growth rate of approximately 2% per year in the last decade. To go back to CO2 atmosphere contents equal to or smaller than the level of 1990 as has been the broadly advertised goals of international treaties since 1990 requires herculean changes: from a dynamical point of view, the approximately exponential growth must not only turn to negative acceleration but also negative velocity to reverse the trend.

Hüsler, A. D.; Sornette, D.

2014-10-01

68

Hispanic Population Growth and Rural Income Inequality  

ERIC Educational Resources Information Center

We analyze the relationship between Hispanic population growth and changes in U.S. rural income inequality from 1990 through 2000. Applying comparative approaches used for urban areas we disentangle Hispanic population growth's contribution to inequality by comparing and statistically modeling changes in the family income Gini coefficient across…

Parrado, Emilio A.; Kandel, William A.

2010-01-01

69

A perspective on population growth in India.  

PubMed

Population growth is heralded as a major problem of India; it will determine to a large extent the living conditions of people for decades to come. This paper analyzes the interrelated issues of population growth stabilization, the magnitude of necessary efforts to provide basic essentials to the growing population, and the impact upon the environment. Estimates of population projections are presented, based on the optimistic but probable assumption that India could reach reproductive level fertility in the period 2000-05. If sustained thereafter, the country's population would stabilize around the year 2100 at 1420 million people. In the mean time, the absolute increase of population in the next 2-3 decades will be greater than at present. The effect of population growth on cities and the living conditions of the city dwellers is reviewed and it is pointed out that it is in developing countries where population growth is the primary force producing large urban centers. Population growth presents problems with respect to employment opportunities. The predicted flood of manpower cannot be totally absorbed by the organized sector; it is argued that the agricultural sector is the only one which can help the country during this period of high population growth. To support this large and rising population, India will need to rapidly increase its average crop yields 2-3 times the present level for a modest improvement process. The expected population growth will also have consequences on environmental deterioration and water supply contamination. Finally, progress on human development lines has been taking place in India, but achievements to date are uneven. It is stressed that a national concerted effort is required to achieve such goals. PMID:12179091

Singh, H

1982-01-01

70

How population growth affects linkage disequilibrium.  

PubMed

The "LD curve" relates the linkage disequilibrium (LD) between pairs of nucleotide sites to the distance that separates them along the chromosome. The shape of this curve reflects natural selection, admixture between populations, and the history of population size. This article derives new results about the last of these effects. When a population expands in size, the LD curve grows steeper, and this effect is especially pronounced following a bottleneck in population size. When a population shrinks, the LD curve rises but remains relatively flat. As LD converges toward a new equilibrium, its time path may not be monotonic. Following an episode of growth, for example, it declines to a low value before rising toward the new equilibrium. These changes happen at different rates for different LD statistics. They are especially slow for estimates of [Formula: see text], which therefore allow inferences about ancient population history. For the human population of Europe, these results suggest a history of population growth. PMID:24907258

Rogers, Alan R

2014-08-01

71

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

ERIC Educational Resources Information Center

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…

Peck, Jennifer Marks

1974-01-01

72

Population growth and development planning in Africa.  

PubMed

Some of the consequences of rapid population growth and their implications for the economic development of the Africa region in the 1980s are outlined. The total population of Africa was estimated to be 412 million in 1976, or 10.2% of the total world population of 4044 million. Population density of the region is comparatively low, but the crude density measure of 14 persons per square kilometer in 1977 obscures the very high percentage of Africa's land which is desert or otherwise not arable. Continued high fertility rates in the region coupled with substantial decline in mortality rates especially for infants and children has resulted in Africa having a youthful population. The growth of cities due primarily to rural-urban migration is 1 of the most pressing problems of the region. Some countries in the region maintain pronatalist policies because they have a small population and regard population growth as a stimulus to the socioeconomic development effort. Few countries such as Kenya, Mauritius, Egypt, and Morocco consider rapid population growth a constraint on their development efforts and are now implementing national policies which aim at reducing the rate of growth of their populations. Population problems in Africa arise mainly from the fact that additions to the population needing education, housing, employment and to be fed adequately are increasing at a rate far more than most African countries can cope with. To illustrate the potential impact of population factors on development, the potential relationships between population and health, education, food supply, labor force supply and employment are analyzed. PMID:12263333

1980-12-01

73

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

E-print Network

847Parkyn et al.--Crayfish growth and population dynamics Growth and population dynamics of crayfish Paranephrops planifrons in streams within native forest and pastoral land uses STEPHANIE M. PARKYN Zealand Abstract Population dynamics of crayfish (Paranephrops planifrons White) in streams draining

Waikato, University of

74

26 CHAPTER 2. METHODS FOR SOLVING FIRST ORDER ODES 2.4 Applications (Exponential Growth/Decay)  

E-print Network

is growing and if r Bacteria Counts) Escherichia coli (E. Coli.32 minutes. #12;2.4. APPLICATIONS (EXPONENTIAL GROWTH/DECAY) 29 2.4.3 Financial Models Money invested at interest generally grows in proportion to the amount of money that is invested (principal). Example 2

Previte, Joseph P.

75

Population Growth and CO2 Emissions  

NSDL National Science Digital Library

Shows the projected growth in CO2 emissions through 2100. Shows the potential levels of atmospheric CO2 with slowing population growth, rapid technological change, both, or neither. Shows that either will substantially lower the carbon footprint of human activity, but that both are needed for sustainable levels of Carbon emissions.

AAAS Atlas of Population and Environment

76

Stochastic population growth in spatially heterogeneous environments.  

PubMed

Classical ecological theory predicts that environmental stochasticity increases extinction risk by reducing the average per-capita growth rate of populations. For sedentary populations in a spatially homogeneous yet temporally variable environment, a simple model of population growth is a stochastic differential equation dZ(t) = ?Z(t)dt + ?Z(t)dW(t), t ? 0, where the conditional law of Z(t+?t)-Z(t) given Z(t) = z has mean and variance approximately z ??t and z²?²?t when the time increment ?t is small. The long-term stochastic growth rate lim(t??) t?¹ log Z(t) for such a population equals ? ? ?²/2 . Most populations, however, experience spatial as well as temporal variability. To understand the interactive effects of environmental stochasticity, spatial heterogeneity, and dispersal on population growth, we study an analogous model X(t) = (X¹(t) , . . . , X(n)(t)), t ? 0, for the population abundances in n patches: the conditional law of X(t+?t) given X(t) = x is such that the conditional mean of X(i)(t+?t) ? X(i)(t) is approximately [x(i)?(i) + ?(j) (x(j) D(ji) ? x(i) D(i j) )]?t where ?(i) is the per capita growth rate in the ith patch and D(ij) is the dispersal rate from the ith patch to the jth patch, and the conditional covariance of X(i)(t+?t)? X(i)(t) and X(j)(t+?t) ? X(j)(t) is approximately x(i)x(j)?(ij)?t for some covariance matrix ? = (?(ij)). We show for such a spatially extended population that if S(t) = X¹(t)+· · ·+ X(n)(t) denotes the total population abundance, then Y(t) = X(t)/S(t), the vector of patch proportions, converges in law to a random vector Y(?) as t ? ?, and the stochastic growth rate lim(t??) t?¹ log S(t) equals the space-time average per-capita growth rate ?(i)?(i)E[Y(i)(?)] experienced by the population minus half of the space-time average temporal variation E[?(i,j) ?(i j)Y(i)(?) Y(j)(?)] experienced by the population. Using this characterization of the stochastic growth rate, we derive an explicit expression for the stochastic growth rate for populations living in two patches, determine which choices of the dispersal matrix D produce the maximal stochastic growth rate for a freely dispersing population, derive an analytic approximation of the stochastic growth rate for dispersal limited populations, and use group theoretic techniques to approximate the stochastic growth rate for populations living in multi-scale landscapes (e.g. insects on plants in meadows on islands). Our results provide fundamental insights into "ideal free" movement in the face of uncertainty, the persistence of coupled sink populations, the evolution of dispersal rates, and the single large or several small (SLOSS) debate in conservation biology. For example, our analysis implies that even in the absence of density-dependent feedbacks, ideal-free dispersers occupy multiple patches in spatially heterogeneous environments provided environmental fluctuations are sufficiently strong and sufficiently weakly correlated across space. In contrast, for diffusively dispersing populations living in similar environments, intermediate dispersal rates maximize their stochastic growth rate. PMID:22427143

Evans, Steven N; Ralph, Peter L; Schreiber, Sebastian J; Sen, Arnab

2013-02-01

77

Population Genetics and Economic Growth  

Microsoft Academic Search

This paper builds an age-structural model of human population genetics in which agents are endowed with a high-dimensional genome that determines their cognitive and physical characteristics. Young adults optimally search for a marriage partner, work for firms, consume goods, save for old age and, if married, decide how many children to have. Applying the fundamental genetic operations, children receive genetic

Paul J. Zak; Kwang Woo Park

2000-01-01

78

Population Genetics and Economic Growth  

Microsoft Academic Search

This paper builds an age-structured model of human population genetics in which explicit individual choices drive the dynamics via sexual selection. In the model, agents are endowed with a high-dimensional genome that determines their cognitive and physical characteristics. Young adults optimally search for a marriage partner, work for firms, consume goods, save for old age and, if married, decide how

Paul J. Zak; Kwang Woo Park

2002-01-01

79

The Cultural Divide: Exponential Growth in Classical 2D and Metabolic Equilibrium in 3D Environments  

PubMed Central

Introduction Cellular metabolism can be considered to have two extremes: one is characterized by exponential growth (in 2D cultures) and the other by a dynamic equilibrium (in 3D cultures). We have analyzed the proteome and cellular architecture at these two extremes and found that they are dramatically different. Results Structurally, actin organization is changed, microtubules are increased and keratins 8 and 18 decreased. Metabolically, glycolysis, fatty acid metabolism and the pentose phosphate shunt are increased while TCA cycle and oxidative phosphorylation is unchanged. Enzymes involved in cholesterol and urea synthesis are increased consistent with the attainment of cholesterol and urea production rates seen in vivo. DNA repair enzymes are increased even though cells are predominantly in Go. Transport around the cell – along the microtubules, through the nuclear pore and in various types of vesicles has been prioritized. There are numerous coherent changes in transcription, splicing, translation, protein folding and degradation. The amount of individual proteins within complexes is shown to be highly coordinated. Typically subunits which initiate a particular function are present in increased amounts compared to other subunits of the same complex. Summary We have previously demonstrated that cells at dynamic equilibrium can match the physiological performance of cells in tissues in vivo. Here we describe the multitude of protein changes necessary to achieve this performance. PMID:25222612

Kanlaya, Rattiyaporn; Borkowski, Kamil; Schwämmle, Veit; Dai, Jie; Joensen, Kira Eyd; Wojdyla, Katarzyna; Carvalho, Vasco Botelho; Fey, Stephen J.

2014-01-01

80

Living bacteria rheology: population growth, aggregation patterns and cooperative behaviour under different shear flows  

E-print Network

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 -- 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 both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the two strains follow different and rich behaviours, with no counterpart in the optical density or in the population's colony forming units measurements. While the viscosity of strain COL 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 ...

Patricio, P; Portela, R; Sobral, R G; Grilo, I R; Cidade, T; Leal, C R

2014-01-01

81

Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 2; Constant Stress Rate Experiments  

NASA Technical Reports Server (NTRS)

The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress rate and preload testing at ambient and elevated temperatures. The data fit to the relation of strength versus the log of the stress rate was very reasonable for most of the materials. Also, the preloading technique was determined equally applicable to the case of slow-crack-growth (SCG) parameter n greater than 30 for both the power-law and exponential formulations. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important SCG parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

2002-01-01

82

Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 3; Constant Stress and Cyclic Stress Experiments  

NASA Technical Reports Server (NTRS)

The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on advanced structural ceramics tested under constant stress and cyclic stress loading at ambient and elevated temperatures. The data fit to the relation between the time to failure and applied stress (or maximum applied stress in cyclic loading) was very reasonable for most of the materials studied. It was also found that life prediction for cyclic stress loading from data of constant stress loading in the exponential formulation was in good agreement with the experimental data, resulting in a similar degree of accuracy as compared with the power-law formulation. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important slow-crack-growth (SCG) parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

2002-01-01

83

Critical Mutation Rate Has an Exponential Dependence on Population Size Alastair Channon1  

E-print Network

- plications for populations under threat of local extinction. Introduction Biological population sizes can animal species may exist in populations consisting of only hundreds or even fewer than ten individuals

Channon, Alastair

84

Staphylococcus aureus aconitase inactivation unexpectedly inhibits post-exponential-phase growth and enhances stationary-phase survival.  

PubMed

Staphylococcus aureus preferentially catabolizes glucose, generating pyruvate, which is subsequently oxidized to acetate under aerobic growth conditions. Catabolite repression of the tricarboxylic acid (TCA) cycle results in the accumulation of acetate. TCA cycle derepression coincides with exit from the exponential growth phase, the onset of acetate catabolism, and the maximal expression of secreted virulence factors. These data suggest that carbon and energy for post-exponential-phase growth and virulence factor production are derived from the catabolism of acetate mediated by the TCA cycle. To test this hypothesis, the aconitase gene was genetically inactivated in a human isolate of S. aureus, and the effects on physiology, morphology, virulence factor production, virulence for mice, and stationary-phase survival were examined. TCA cycle inactivation prevented the post-exponential growth phase catabolism of acetate, resulting in premature entry into the stationary phase. This phenotype was accompanied by a significant reduction in the production of several virulence factors and alteration in host-pathogen interaction. Unexpectedly, aconitase inactivation enhanced stationary-phase survival relative to the wild-type strain. Aconitase is an iron-sulfur cluster-containing enzyme that is highly susceptible to oxidative inactivation. We speculate that reversible loss of the iron-sulfur cluster in wild-type organisms is a survival strategy used to circumvent oxidative stress induced during host-pathogen interactions. Taken together, these data demonstrate the importance of the TCA cycle in the life cycle of this medically important pathogen. PMID:12379717

Somerville, Greg A; Chaussee, Michael S; Morgan, Carrie I; Fitzgerald, J Ross; Dorward, David W; Reitzer, Lawrence J; Musser, James M

2002-11-01

85

RpoS regulation of gene expression during exponential growth of Escherichia coli K12  

Microsoft Academic Search

RpoS is a major regulator of genes required for adaptation to stationary phase in E. coli. However, the exponential phase expression of some genes is affected by rpoS mutation, suggesting RpoS may also have an important physiological role in growing cells. To test this hypothesis, we examined\\u000a the regulatory role of RpoS in exponential phase using both genomic and biochemical

Tao Dong; Mark G. Kirchhof; Herb E. Schellhorn

2008-01-01

86

Modeling Microbial Growth  

NSDL National Science Digital Library

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

Ethel D. Stanley (Beloit College; Biology)

2006-05-20

87

Disease in changing populations: growth and disequilibrium.  

PubMed

This paper examines simple age-structured models of childhood disease epidemiology, focusing on nonstationary populations which characterize LDCs. An age-structured model of childhood disease epidemiology for nonstationary populations is formulated which incorporates explicit scaling assumptions with respect both to time and to population density. The static equilibrium properties and the dynamic local stability of the model are analyzed, as are the effects of random variability due to fluctuations in demographic structure. We determine the consequences of population growth rate for: the critical level of immunization needed to eradicate an endemic disease, the transient epidemic period, the return time which measures the stability of departures from epidemiological equilibrium, and the power spectrum of epidemiological fluctuations and combined demographic-epidemiological fluctuations. Growing populations are found to be significantly different from stationary ones in each of these characteristics. The policy implications of these findings are discussed. PMID:1808755

Tuljapurkar, S; John, A M

1991-12-01

88

Future Population Growth Trends in California  

E-print Network

Future Population Growth Trends in California Mary Heim Demographic Research Unit California of age Races are Hispanic-exclusive Include Hispanics by race categories #12;STEP 2 - Remove Special 450000 Net Migration California 1970-2040 #12;PHILOSOPHY #12;No major or world wide wars nor natural

Keller, Arturo A.

89

Lesson 30: Exponential Functions  

NSDL National Science Digital Library

Beginning with a formal definition of an exponential function, the lesson then compares the graphs of increasing and decreasing exponential functions. A comparison between exponential and power functions follows, which leads to methods for determining the h value in the power function h(x) = kx^p and the value of the base b in the exponential function f(x) = ab^x. A procedure for solving exponential equations is presented before a population application problem is solved. The lesson concludes with a discussion about using graphs to find approximate solutions to exponential equations.

2011-01-01

90

Finite amplitude folding: transition from exponential to layer length controlled growth  

E-print Network

the linear theory breaks down. A new analytical relationship for amplitude versus strain was derived for strains much larger than the crossover strain. The new relationship agrees well with complete 2D numerical solutions for up to threefold shortening, whereas the exponential solution predicted by the linear theory

Podladchikov, Yuri

91

Slow crack growth of brittle materials with exponential crack-velocity formulation—static fatigue  

Microsoft Academic Search

The life prediction analysis based on an exponential crack-velocity formulation was made and examined using a variety of experimental data on advanced structural ceramics in constant stress (‘static fatigue’ or ‘stress rupture’) testing at ambient and elevated temperatures. The data fit to the relation between ln (time to failure) versus applied stress was be very reasonable for most of the

S. R. Choi; N. N. Nemeth; J. P. Gyekenyesi

2005-01-01

92

Energy and fluxes of thermal runaway electrons produced by exponential growth of streamers during the stepping of lightning leaders and in transient luminous events  

Microsoft Academic Search

In the present paper, we demonstrate that the exponential expansion of streamers propagating in fields higher than the critical fields for stable propagation of streamers of a given polarity leads to the exponential growth of electric potential differences in streamer heads. These electric potential differences are directly related to the energy that thermal runaway electrons can gain once created. Using

Sebastien Celestin; Victor P. Pasko

2011-01-01

93

A new mechanistic growth model for simultaneous determination of lag phase duration and exponential growth rate and a new Belehdradek-type model for evaluating the effect of temperature on growth rate  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new mechanistic growth model was developed to describe microbial growth under isothermal conditions. The new mathematical model was derived from the basic observation of bacterial growth that may include lag, exponential, and stationary phases. With this model, the lag phase duration and exponen...

94

Maximum likelihood estimation of population growth rates based on the coalescent.  

PubMed Central

We describe a method for co-estimating 4Nemu (four times the product of effective population size and neutral mutation rate) and population growth rate from sequence samples using Metropolis-Hastings sampling. Population growth (or decline) is assumed to be exponential. The estimates of growth rate are biased upwards, especially when 4Nemu is low; there is also a slight upwards bias in the estimate of 4Nemu itself due to correlation between the parameters. This bias cannot be attributed solely to Metropolis-Hastings sampling but appears to be an inherent property of the estimator and is expected to appear in any approach which estimates growth rate from genealogy structure. Sampling additional unlinked loci is much more effective in reducing the bias than increasing the number or length of sequences from the same locus. PMID:9584114

Kuhner, M K; Yamato, J; Felsenstein, J

1998-01-01

95

[Models of economic theory of population growth].  

PubMed

"The economic theory of population growth applies the opportunity cost approach to the fertility decision. Variations and differentials in fertility are caused by the available resources and relative prices or by the relative production costs of child services. Pure changes in real income raise the demand for children or the total amount spent on children. If relative prices or production costs and real income are affected together the effect on fertility requires separate consideration." (SUMMARY IN ENG) PMID:12268788

Von Zameck, W

1987-01-01

96

Population growth makes waves in the distribution of pairwise genetic differences.  

PubMed

Episodes of population growth and decline leave characteristic signatures in the distribution of nucleotide (or restriction) site differences between pairs of individuals. These signatures appear in histograms showing the relative frequencies of pairs of individuals who differ by i sites, where i = 0, 1, .... In this distribution an episode of growth generates a wave that travels to the right, traversing 1 unit of the horizontal axis in each 1/2u generations, where u is the mutation rate. The smaller the initial population, the steeper will be the leading face of the wave. The larger the increase in population size, the smaller will be the distribution's vertical intercept. The implications of continued exponential growth are indistinguishable from those of a sudden burst of population growth Bottlenecks in population size also generate waves similar to those produced by a sudden expansion, but with elevated uppertail probabilities. Reductions in population size initially generate L-shaped distributions with high probability of identity, but these converge rapidly to a new equilibrium. In equilibrium populations the theoretical curves are free of waves. However, computer simulations of such populations generate empirical distributions with many peaks and little resemblance to the theory. On the other hand, agreement is better in the transient (nonequilibrium) case, where simulated empirical distributions typically exhibit waves very similar to those predicted by theory. Thus, waves in empirical distributions may be rich in information about the history of population dynamics. PMID:1316531

Rogers, A R; Harpending, H

1992-05-01

97

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

ERIC Educational Resources Information Center

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…

Kent, Mary Mederios

98

Cursorial spiders retard initial aphid population growth at low densities  

E-print Network

Cursorial spiders retard initial aphid population growth at low densities in winter wheat K technique that revealed species-specific aphid consump- tion rates with a factorial field experiment on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment

Illinois at Chicago, University of

99

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

E-print Network

how the intrinsic rate of exponential population growth, , and the carrying capacity,rmax K, depend for aerobic eukaryotes, including algae, protists, insects, zooplankton, fishes, and mammals, support capacity or equilibrium density of popu- lations should decrease with increasing body size and increasing

Brown, James H.

100

Living bacteria rheology: population growth, aggregation patterns and cooperative behaviour under different shear flows  

E-print Network

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 -- 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 both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the two strains follow different and rich behaviours, with no counterpart in the optical density or in the population's colony forming units measurements. While the viscosity of strain COL 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 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 behaviours, 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, obtained with oscillatory shear, exhibit power-law behaviours whose exponent are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant have complex behaviours, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. These behaviours reflect nevertheless the bacteria growth stage.

P. Patricio; P. L. Almeida; R. Portela; R. G. Sobral; I. R. Grilo; T. Cidade; C. R. Leal

2014-03-06

101

Living bacteria rheology: Population growth, aggregation patterns, and collective behavior under different shear flows  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

102

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

USGS Publications Warehouse

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.

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

2006-01-01

103

Modeling the growth of individuals in plant populations: local density variation in a strand population of Xanthium strumarium (Asteraceae).  

PubMed

We studied the growth of individual Xanthium strumarium plants growing at four naturally occurring local densities on a beach in Maine: (1) isolated plants, (2) pairs of plants ?1 cm apart, (3) four plants within 4 cm of each other, and (4) discrete dense clumps of 10-39 plants. A combination of nondestructive measurements every 2 wk and parallel calibration harvests provided very good estimates of the growth in aboveground biomass of over 400 individual plants over 8 wk and afforded the opportunity to fit explicit growth models to 293 of them. There was large individual variation in growth and resultant size within the population and within all densities. Local crowding played a role in determining plant size within the population: there were significant differences in final size between all densities except pairs and quadruples, which were almost identical. Overall, plants growing at higher densities were more variable in growth and final size than plants growing at lower densities, but this was due to increased variation among groups (greater variation in local density and/or greater environmental heterogeneity), not to increased variation within groups. Thus, there was no evidence of size asymmetric competition in this population. The growth of most plants was close to exponential over the study period, but half the plants were slightly better fit by a sigmoidal (logistic) model. The proportion of plants better fit by the logistic model increased with density and with initial plant size. The use of explicit growth models over several growth intervals to describe stand development can provide more biological content and more statistical power than "growth-size" methods that analyze growth intervals separately. PMID:21680325

Weiner, J; Kinsman, S; Williams, S

1998-11-01

104

Population growth rate and its determinants: an overview.  

PubMed Central

We argue that population growth rate is the key unifying variable linking the various facets of population ecology. The importance of population growth rate lies partly in its central role in forecasting future population trends; indeed if the form of density dependence were constant and known, then the future population dynamics could to some degree be predicted. We argue that population growth rate is also central to our understanding of environmental stress: environmental stressors should be defined as factors which when first applied to a population reduce population growth rate. The joint action of such stressors determines an organism's ecological niche, which should be defined as the set of environmental conditions where population growth rate is greater than zero (where population growth rate = r = log(e)(N(t+1)/N(t))). While environmental stressors have negative effects on population growth rate, the same is true of population density, the case of negative linear effects corresponding to the well-known logistic equation. Following Sinclair, we recognize population regulation as occurring when population growth rate is negatively density dependent. Surprisingly, given its fundamental importance in population ecology, only 25 studies were discovered in the literature in which population growth rate has been plotted against population density. In 12 of these the effects of density were linear; in all but two of the remainder the relationship was concave viewed from above. Alternative approaches to establishing the determinants of population growth rate are reviewed, paying special attention to the demographic and mechanistic approaches. The effects of population density on population growth rate may act through their effects on food availability and associated effects on somatic growth, fecundity and survival, according to a 'numerical response', the evidence for which is briefly reviewed. Alternatively, there may be effects on population growth rate of population density in addition to those that arise through the partitioning of food between competitors; this is 'interference competition'. The distinction is illustrated using a replicated laboratory experiment on a marine copepod, Tisbe battagliae. Application of these approaches in conservation biology, ecotoxicology and human demography is briefly considered. We conclude that population regulation, density dependence, resource and interference competition, the effects of environmental stress and the form of the ecological niche, are all best defined and analysed in terms of population growth rate. PMID:12396508

Sibly, Richard M; Hone, Jim

2002-01-01

105

Circadian rhythm and cell population growth  

E-print Network

Molecular circadian clocks, that are found in all nucleated cells of mammals, are known to dictate rhythms of approximately 24 hours (circa diem) to many physiological processes. This includes metabolism (e.g., temperature, hormonal blood levels) and cell proliferation. It has been observed in tumor-bearing laboratory rodents that a severe disruption of these physiological rhythms results in accelerated tumor growth. The question of accurately representing the control exerted by circadian clocks on healthy and tumour tissue proliferation to explain this phenomenon has given rise to mathematical developments, which we review. The main goal of these previous works was to examine the influence of a periodic control on the cell division cycle in physiologically structured cell populations, comparing the effects of periodic control with no control, and of different periodic controls between them. We state here a general convexity result that may give a theoretical justification to the concept of cancer chronothera...

Clairambault, Jean; Lepoutre, Thomas

2010-01-01

106

FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER  

E-print Network

FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER LAURENCE D. MUELLER of population growth were determined for 26 populations of Drosophila melanogaster maintained in the serial for genotypesof Drosophila melanogaster homo- zygous for whole second chromosomes sampled from nature. The net

Rose, Michael R.

107

Self-Regulated Population Growth Continuous time t Overlapping Generations  

E-print Network

/Density; t 0 Identical Individuals Unstructured Population No Interspecific Interactions Explicit Growth of Change in N(t); Function of N(t) Only Finite Resources Constrain Per-capita Growth Intraspecific Competition N/N(t) = > 0, for 0

Caraco, Thomas

108

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, that is similar to bacterial growth in a chemostat predicts that the fraction of the population lagging behind in space in terms of their gene expression and growth.5,7,8 Bacterial colonies on hard surfaces typically

109

PERSPECTIVES Allometric growth, life-history invariants and population energetics  

E-print Network

, efficiency, life-history invariants, metabo- lism, population energetics, production, scaling. Ecology specific organisms or systems. Indeed, in many cases, context dependent and historically contingent factors, growth, and life history ultimately govern the energy transformations of populations and communities

Kerkhoff, Andrew J.

110

Development of Populations 177 6.6 Growth of Populations with Sexual Reproduction  

E-print Network

Development of Populations 177 6.6 Growth of Populations with Sexual Reproduction G. Alsmeyer In Section 5.9, we studied the effect of sexual reproduction on criticality and ex- tinction risk-negative Alsmeyer G (2005). Growth of Populations with Sexual Reproduction. In: Branching Processes: Variation

Alsmeyer, Gerold

111

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

E-print Network

LETTER Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa disjunct populations of Pinus ponderosa that were initially established by long-distance dispersal. Keywords Allee effects, intrinsic population growth, long-distance dispersal, parentage, Pinus ponderosa

Hui, Bowen

112

U.S. Population Growth: Prospects and Policy.  

ERIC Educational Resources Information Center

The Commission on Population Growth and the American Future concluded that zero population growth (ZPG) is in the best interest of the United States. To achieve ZPG in the future, the United States must keep fertility and net immigration relatively low. Practical problems are discussed. (RM)

McFalls, Joseph A., Jr.; And Others

1984-01-01

113

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

PubMed

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

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

2011-05-01

114

Soil science, population growth and food production: some historical developments  

Microsoft Academic Search

The world’s population has doubled since 1960. Currently, the developing world accounts for about 95% of the population growth\\u000a with Africa as the world’s fastest growing continent. The growing population has many implications but most of all it requires\\u000a an increase in agricultural production to meet food demand. Soil science has a long tradition of considering the growth in\\u000a food

Alfred E. Hartemink

2007-01-01

115

POPULATION GROWTH AND RAPID URBANIZATION IN AFRICA: IMPLICATIONS FOR SUSTAINABILITY  

Microsoft Academic Search

The realties of rapid urbanization and population growth in Africa are objectively patent with the realities of diversity of challenges, constraints and threats to service delivery in urban centres. Urban centres are attraction centres for rural population and, through multiplier effects, population sizes continue to grow concomitant with the demand for the services (hospitals, schools, industrial and commercial zones, security,

Innocent Chirisa

116

The influence of nonrandom mating on population growth.  

PubMed

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

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

2013-07-01

117

BIOTIC INFLUENCES AFFECTING POPULATION GROWTH OF  

E-print Network

of Chlorella and Nitz8chia _ Growth curve and division rate of Chlorella _ Growth curve and division rate in conditioned media _ Inhibitory effect o~ Chlorella of Nitz8chia-conditioned medium _ Inhibitory effect on Nitz8chia of Chlorella-condit,ioned medium _ Inhibitory effects of filtrate from conditioned media

118

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

ERIC Educational Resources Information Center

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…

Groth, Edward, III

119

Bounded Population Growth: A Curve Fitting Lesson.  

ERIC Educational Resources Information Center

Presents two mathematical methods for fitting the logistic curve to population data supplied by the U.S. Census Bureau utilizing computer algebra software to carry out the computations and plot graphs. (JKK)

Mathews, John H.

1992-01-01

120

[The fear of numbers or the challenge of population growth?].  

PubMed

Africa, currently one of the least densely populated continents, is growing so rapidly that its population will comprise some 1.5 billion inhabitants around 2020, and Africans will be more numerous than the population of the developed world. Attitudes about Africa's population size vary widely; many educated Africans believe that low density is a greater disadvantage than overpopulation, but most specialists believe the population of the developing world, and of Africa especially, to be too large, the prospects of significant voluntary reduction are dim. The rate of population growth has thus attracted attention as a factor amenable to modification. Africa's demographic transition remains largely in the future. Its case is unique because of the rate of demographic growth and because the phase of rapid growth will apparently continue far longer in Africa than in any other continent. The widening gap between population growth rates and rates of economic development in Africa inspires great pessimism about the future wellbeing of the population. Population officials urge that demographic growth be slowed in order to reduce pressure on economic and ecological resources and to gain time for social and economic development. But despite the consensus of international organizations, such as the UN Fund for Population, on the desirability of slowing population growth to encourage and permit economic growth, there has actually been relatively little progress since the time of Malthus in understanding the relationship between population, development, and the environment. Some recent works suggest that demographic growth has benefits as well as disadvantages, and the net impact on development is uncertain. Demographic pressure is in this view a far more potent force for innovation than is usually recognized. Population is not just an exogenous variable in development, but it is at the heart of the process. There can be no true integration of population into development until the value of human resources everywhere is reaffirmed. The recognition by international organizations that per capita income or other economic indicators alone are not adequate measures of progress is a favorable sign. The failure of structural adjustment programs to attain their stated goals and the new resolve to lessen their effects on the most vulnerable population sectors are also promising. New orientations toward development in which human resources are given greater prominence may be as ideologically inspired as those they replaced, but they have the merit of greater neutrality concerning the content and form of development and they do not accept the process of development in the West as their sole reference. PMID:12317452

Loriaux, M

1991-12-01

121

Mitochondrial DNA and ancient population growth.  

PubMed

In recent years, the study of mitochondrial DNA (mtDNA) variation has entered a new phase with an increasing emphasis on interpretations of demographic, rather than phylogenetic, history. Human mtDNA variation fits a "sudden expansion" model, where the human species expanded rapidly in size during the Late Pleistocene. This paper examines the sudden expansion model with the goal of partitioning total mtDNA diversity in contemporary populations into two components--diversity that existed prior to the population expansion and diversity that arose after the expansion. A method is developed for estimating these components. Analysis of mtDNA diversity within selected human populations shows that 64-80% of mtDNA diversity in contemporary populations arose after the expansion, a consequence of a high mutation rate relative to the number of generations since expansion. The basic model is extended to two components of excess diversity in sub-Saharan Africa--differences in population size before the expansion and differences in the timing of expansion. Results suggest that excess sub-Saharan African mtDNA diversity is due to the combined effects of the sub-Saharan African population being larger in size prior to the expansion and expanding earlier. PMID:9537924

Relethford, J H

1998-01-01

122

ORIGINAL PAPER Overestimates of maternity and population growth rates  

E-print Network

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

Richner, Heinz

123

Diet Quality Limits Summer Growth of Field Vole Populations  

PubMed Central

Marked variation occurs in both seasonal and multiannual population density peaks of northern European small mammal species, including voles. The availability of dietary proteins is a key factor limiting the population growth of herbivore species. The objective of this study is to investigate the degree to which protein availability influences the growth of increasing vole populations. We hypothesise that the summer growth of folivorous vole populations is positively associated with dietary protein availability. A field experiment was conducted over a summer reproductive period in 18 vegetated enclosures. Populations of field voles (Microtus agrestis) were randomised amongst three treatment groups: 1) food supplementation with ad libitum high protein (30% dry weight) pellets, 2) food supplementation with ad libitum low protein (1% dry weight; both supplemented foods had equivalent energy content) pellets, and 3) control (no food supplementation), n?=?6 per treatment. Vole density, survival, demographic attributes and condition indicators were monitored with live-trapping and blood sampling. Highest final vole densities were attained in populations that received high protein supplementation and lowest in low protein populations. Control populations displayed intermediate densities. The survival rate of voles was similar in all treatment groups. The proportion of females, and of those that were pregnant or lactating, was highest in the high protein supplemented populations. This suggests that variation in reproductive, rather than survival rates of voles, accounted for density differences between the treatment groups. We found no clear association between population demography and individual physiological condition. Our results demonstrate that dietary protein availability limits vole population growth during the summer growing season. This suggests that the nutritional quality of forage may be an underestimated source of interannual variation in the density and growth rates of widely fluctuating populations of herbivorous small mammals. PMID:24621513

Forbes, Kristian M.; Stuart, Peter; Mappes, Tapio; Hoset, Katrine S.; Henttonen, Heikki; Huitu, Otso

2014-01-01

124

Contrasting Signatures of Population Growth for Mitochondrial DNA and Y Chromosomes among Human Populations in Africa  

E-print Network

Contrasting Signatures of Population Growth for Mitochondrial DNA and Y Chromosomes among Human the frequency spectrum of polymorphism in the mitochondrial DNA (mtDNA) of many human populations. Similar of their different effective population sizes. This hypothesis predicts thatmitochondrial and Y chromosomal DNA

Watkins, Joseph C.

125

Developmental rates and population growth of insecticide-resistant and susceptible populations of Sitophilus zeamais  

Microsoft Academic Search

Two experiments were carried out to assess the developmental rate and population growth of four populations of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Two of these populations are resistant to pyrethroid insecticides (Jacarezinho and Juiz de Fora), while the other two are susceptible (Bragança Paulista and Sete Lagoas). The first experiment, with progeny removal and assessment every other day, allowed the

Daniel B. Fragoso; Raul Narciso C. Guedes; Luiz A. Peternelli

2005-01-01

126

Population growth overshooting and trade in developing countries  

Microsoft Academic Search

This paper examines a developing economy using a family-optimization model in which the number of children is a normal good.\\u000a Trade liberalization generates two effects: the income effect that increases population growth and the gender wage effect\\u000a that, in the short run, increases, but, in the long run, decreases population growth. With higher income, families invest\\u000a more in capital if

Ulla Lehmijoki; Tapio Palokangas

2009-01-01

127

Curbing population growth in Republic of Korea.  

PubMed

The population of Korea is expected to increase by another 1/4 of the current population by the year 2000 if the government family planning program is successful. Aggravating Korea's demographic situation is the worldwide phenomenon of urban congestion. According to official statistics, Seoul's population increased from only 1 million in 1953 to 8.5 million in 1980, the latest year for which figures are available. While Seoul's population alone accounts for 22.3% of the total population, that of the greater Seoul area comprises 13,542,000 people or 35.5% of Korea's population. Most of the country's best institutions of higher learning are concentrated in Seoul, and in 1979 Seoul accounted for nearly half (47.7%) of the nation's college and graduate students. Seoul is also the center of the country's political, economic and cultural life and provides better employment opportunities than elsewhere in the country. The exodus of young people from rural areas and the growing census figures have triggered fears that the subsequently reduced agricultural productivity would result in a food supply crisis. In an attempt to remedy the demographic disparity between urban and rural areas, the government initiated a 10-year program in 1982 to promote jobs and improve medicare and the educational system in provincial cities. The plan encourages the establishment of factories and other auxiliary facilities outside the Seoul area that are necessary to support the 1988 Seoul Olympics. The program's success remains in question as it requires consistent, determined, and well coordinated efforts on the part of policy makers to curb the historical trend which has been gaining momentum over the past 100 years. 2 approaches have been adopted in the government's efforts to integrate population dynamics into the development process, overseas migration, and planned parenthood. Despite the 1981 liberalization of overseas travel for Koreans, Korean migration overseas is not expected to grow significantly. The planned parenthood program, the major thrust of the government's population policy, has proven to be effective. The average fertility rate of Korean women has declined from 6 in 1960 to 2.7 in 1982. The net population increase had dropped from 2.84% in 1960 to 1.67% in 1980. Over the 1962-81 period, the government spent US$145.5 million on planned parenthood programs. The preference for sons continues despite the government slogan, "stop at two, regardless of sex." Only 41% of women with only 2 daughters practice birth control, compared with 71% of those with only 2 sons. There is also a fertility gap between urban women (2.4) and rural women (3.3). PMID:12312002

Woo-hyun, S

1983-01-26

128

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

ERIC Educational Resources Information Center

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.…

King, Timothy; Kelley, Allen C.

129

Heat and pulsed electric field resistance of pigmented and non-pigmented enterotoxigenic strains of Staphylococcus aureus in exponential and stationary phase of growth  

Microsoft Academic Search

The survival of four enterotoxigenic strains of Staphylococcus aureus (with different pigment content) to heat and to pulsed electric fields (PEF) treatments, and the increase in resistance to both processing stresses associated with entrance into stationary phase was examined. Survival curves to heat (58 °C) and to PEF (26 kV\\/cm) of cells in the stationary and in the exponential phase of growth

G. Cebrián; N. Sagarzazu; R. Pagán; S. Condón; P. Mañas

2007-01-01

130

reproduction and juvenile growth at a cyclic population peak  

Microsoft Academic Search

Summary 1. Snowshoe hare (Lepus americanus (Erxleben)) populations were provided with supplemental food on two study grids in the south-west Yukon to examine the effects of food on reproduction and juvenile growth. 2. Timing of parturition, pregnancy rates, litter sizes, male breeding condition, and juvenile growth rates were measured on two food grids and on two control grids during two

MARK O'DONOGHUE; CHARLES J. KREBS

131

Growth and size structure in a baltic Mytilus edulis population  

Microsoft Academic Search

Since Mytilus edulis L. has very few predators and competitors for space, it has become a biomass dominant in the Baltic proper covering hard substrates from the water surface to more than 30 m depth. In order to investigate the factors controlling size and production in a Baltic M. edulis population, growth was studied by the analysis of annual growth

N. Kautsky

1982-01-01

132

Parameter Estimates in Differential Equation Models for Population Growth  

ERIC Educational Resources Information Center

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,…

Winkel, Brian J.

2011-01-01

133

Switching and Growth for Microbial Populations in Catastrophic Responsive Environments  

E-print Network

the environment is responsive to the microbial population. In our model, microbes switch randomly between twoSwitching and Growth for Microbial Populations in Catastrophic Responsive Environments Paolo Visco states of gene expression, is common among microbes, and may be important in coping with changing

Visco, Paolo - Laboratoire Matière et Systèmes Complexes, Université Paris 7

134

Population Growth and Costs of Education in Developing Countries.  

ERIC Educational Resources Information Center

The study reported in this document attempted to determine the effect of population growth on education costs in developing countries, given various assumptions as to the future trend of fertility and mortality. The population factor was examined along with other factors influencing educational costs, such as the improvement of enrollment ratios,…

Chau, Ta Ngoc; And Others

135

Herbivory: effects on plant abundance, distribution and population growth  

Microsoft Academic Search

Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular

John L. Maron; Elizabeth Crone

2006-01-01

136

Food-dependent individual growth and population dynamics in fishes  

Microsoft Academic Search

It is long since well established that growth and development in fish individuals are heavily dependent on food intake. Yet, this dependence of individual development on food levels has only to a limited extent been taken into consideration when studying fish population and community processes. Using the modelling framework of physiologically structured population models and empirical data for a number

L. Persson; Roos de A. M

2006-01-01

137

Population Blocks.  

ERIC Educational Resources Information Center

Describes an educational game called "Population Blocks" that is designed to illustrate the concept of exponential growth of the human population and some potential effects of overpopulation. The game material consists of wooden blocks; 18 blocks are painted green (representing land), 7 are painted blue (representing water); and the remaining…

Smith, Martin H.

1992-01-01

138

The old age security hypothesis and optimal population growth.  

PubMed

The application of the Samuelson-Diamond overlapping generations framework to the old age security hypothesis indicates that government intervention schemes can influence the relationship between population growth and capital accumulation. The most direct means of optimizing population growth is through taxes or subsidies that relate to the intergenerational transfer of wealth. A pay-as-you-go social security scheme, in which payment is predicated on the number of children the receiver has and is financed by taxes levied on the working population, emerges as the most likely intervention to produce the optimal steady state equilibrium. This system is able to correct any distortions the private sector may build into it. In contrast, a child support system, in which the government subsidizes or taxes workers according to their family size, can guarantee the optimal capital:labor ratio but not the optimal population growth rate. Thus, if the government seeks to decrease the population growth rate, the appropriate intervention is to levy a lump-sum social-security tax on workers and transfer the revenues to the old; the direction should be reversed if the goal is to increase population growth. Another alternative, a lump sum social security system, can guarantee optimal population growth but not a desirable capital:labor ratio. Finally, the introduction of money as a valued commodity into an economy with a high capital:labor ratio will also serve to decrease the population growth rate and solve the intergenerational transfer problem through the private sector without any need for government intervention. PMID:12342694

Bental, B

1989-03-01

139

Population Projections and Growth: Proposals or Porphecies?  

ERIC Educational Resources Information Center

Presents a review charging the Canadian governments with reacting to population projections as if they were public prophecy. Projections throughout 1930-40 are summarized and tabulated as well as those in the years 1950-60 and recent years. (EB)

Taylor, Chris

1974-01-01

140

Prison population growth and crime reduction  

Microsoft Academic Search

The impact of state prison populations on crime is typically estimated by applying the lambda, the individual crime rate, of prisoners or arrestees. We outline the problems with this approach, attempt to reanalyze the widely divergent lambdas derived in past research, and make adjustments necessary to use lambdas for estimating the incapacitation impact. The result is an uncertain estimate of

Thomas B. Marvell; Carlisle E. Moody

1994-01-01

141

Population growth. Its magnitude and implications for development.  

PubMed

A summary of the 1984 World Development Report is provided. The 3 major points stressed in the report were: 1) rapid population growth adversely affects development, 2) governments must adopt policies to reduce fertility, and 3) policies adopted by many countries have effectively reduced fertility. World population growth began accelerating at 0.5%/year in the 18th century, and by 1950 the annual acceleration rate was 2%. Most of the increase in population size is occurring in less developed countries, and this increase is due in part to the recent decline in mortality experienced by these countries. Of the 80 million individuals who will be added to the world's population in 1984, 70 million will be in the developing countries. Since 1965 the population growth rate for developing countries as a group declined from 2.4% to 2%. However, because of the high proportion of younger aged individuals in developing countries, the decline in fertility is expected to level off. According to World Bank population projections, the world population will stabilize at around 11 billion in 2150. During the interium, the population of developing countries will increase from its present level of 3.6 billion to 8.4 billion, and the population of developed countries will increase from 1.2 billion to 1.4 billion. These projections are probably overly optimistic. The adverse impact on development of rapid population growth is due to several factors. 1st, resources which could be used for investment must instead be used to fulfill the consumption needs of an increased number of people. 2nd, increases in the labor force must be absorbed by the agricultural sector, and this reduces agricultural productivity. 3rd, rapid population growth increases management problems. The adaption of policies by governments to reduce fertility is a necessary step in halting population growth. For poor families, children provide economic security. Therefore, governments must act to improve the economic conditions for poor families if they hope to reduce population growth. Education and job opportunities must be expanded and social security provided for the elderly. In the past it was assumed that fertility would only decline when urbanization, industrialization, and income reached a certain level. It is now known that appropriate policies can effectively reduce fertility even in the absence of economic advancement. Fertility declines are more closely related to increases in literacy and life expectancy than to increases in the gross national product. Family planning programs in China, Colombia, Egypt, India, Indonesia, Korea, Sri Lanka, and Tunisia have reduced fertility far below the level normally associated with the income levels prevailing in those countries. PMID:12266357

Birdsall, N

1984-09-01

142

Modelling individual growth and competition in plant populations: growth curves of Chenopodium album at two densities  

Microsoft Academic Search

Summary 1 We modelled the growth in estimated biomass of individuals in experimental popu- lations of Chenopodium album grown at two densities and measured sequentially nine times over 128 days. Competition is modelled by coupling individual growth equations and, within the population, the growth rate of a plant at any point in time is a function of its size to

Christian Damgaard; Jacob Weiner; Hisae Nagashima

2002-01-01

143

Exponential Transducers  

E-print Network

transducers usually process their input from left to right, top­down tree trans­ ducers transform input trees for Top­Down Tree Transducers Frank Drewes ? Department of Computer Science University of Bremen P.O. Box size problem for top­down tree trans­ ducers asks whether the size of output trees grows exponentially

Drewes, Frank

144

Growth dynamics and the evolution of cooperation in microbial populations  

PubMed Central

Microbes providing public goods are widespread in nature despite running the risk of being exploited by free-riders. However, the precise ecological factors supporting cooperation are still puzzling. Following recent experiments, we consider the role of population growth and the repetitive fragmentation of populations into new colonies mimicking simple microbial life-cycles. Individual-based modeling reveals that demographic fluctuations, which lead to a large variance in the composition of colonies, promote cooperation. Biased by population dynamics these fluctuations result in two qualitatively distinct regimes of robust cooperation under repetitive fragmentation into groups. First, if the level of cooperation exceeds a threshold, cooperators will take over the whole population. Second, cooperators can also emerge from a single mutant leading to a robust coexistence between cooperators and free-riders. We find frequency and size of population bottlenecks, and growth dynamics to be the major ecological factors determining the regimes and thereby the evolutionary pathway towards cooperation. PMID:22355791

Cremer, Jonas; Melbinger, Anna; Frey, Erwin

2012-01-01

145

Population growth and the development of a central place system  

NASA Astrophysics Data System (ADS)

This paper describes the spatial and functional evolution of a central place system as market conditions change with population growth. Utilizing a partial equilibrium optimization model, we examine the spatial response of two economic sectors to increases in market populations resulting from natural increase and migration. Response in both sectors is conditioned by threshold demand, with factor prices also affecting one of the sectors. As the central place system evolves it exhibits spatial and functional characteristics that are initially consistent with a Löschian landscape, then a Christallerian landscape at higher populations, while at even larger populations Krugman’s landscape emerges.

Cromley, Robert G.; Hanink, Dean M.

2008-12-01

146

TOPICAL PROBLEMS: The phenomenological theory of world population growth  

NASA Astrophysics Data System (ADS)

Of all global problems world population growth is the most significant. Demographic data describe this process in a concise and quantitative way in its past and present. Analysing this development it is possible by applying the concepts of systems analysis and synergetics, to work out a mathematical model for a phenomenological description of the global demographic process and to project its trends into the future. Assuming self-similarity as the dynamic principle of development, growth can be described practically over the whole of human history, assuming the growth rate to be proportional to the square of the number of people. The large parameter of the theory and the effective size of a coherent population group is of the order of 105 and the microscopic parameter of the phenomenology is the human lifespan. The demographic transition — a transition to a stabilised world population of some 14 billion in a foreseeable future — is a systemic singularity and is determined by the inherent pattern of growth of an open system, rather than by the lack of resources. The development of a quantitative nonlinear theory of the world population is of interest for interdisciplinary research in anthropology and demography, history and sociology, for population genetics and epidemiology, for studies in evolution of humankind and the origin of man. The model also provides insight into the stability of growth and the present predicament of humankind, and provides a setting for discussing the main global problems.

Kapitza, Sergei P.

1996-01-01

147

Population Growth, (Per Capita) Economic Growth, and Poverty Reduction in Uganda: A brief Summary of Theory and Evidence  

E-print Network

to these projections, Uganda's population is expected to reach 103.2 million people in 2050. This projection is based, population growth will still be over 2% per year in 2045- 50 and Uganda's population is projectedPopulation Growth, (Per Capita) Economic Growth, and Poverty Reduction in Uganda: A brief Summary

Krivobokova, Tatyana

148

Section 3.1. Population Ch. 3.1. Population Growth  

E-print Network

the ever increasing size of the human population and its relation with the natural resources upon which upon which humans depend for their well-being and found that 60% were being degraded or used services. Population growth itself, however, remains an insufficient explanation of relations between

Lopez-Carr, David

149

A model of northern pintail productivity and population growth rate  

USGS Publications Warehouse

Our objective was to synthesize individual components of reproductive ecology into a single estimate of productivity and to assess the relative effects of survival and productivity on population dynamics. We used information on nesting ecology, renesting potential, and duckling survival of northern pintails (Anas acuta) collected on the Yukon-Kuskokvim Delta (Y-K Delta), Alaska, 1991-95, to model the number of ducklings produced under a range of nest success and duckling survival probabilities. Using average values of 25% nest success, 11% duckling survival, and 56% renesting probability from our study population, we calculated that all young in our population were produced by 13% of the breeding females, and that early-nesting females produced more young than later-nesting females. Further, we calculated, on average, that each female produced only 0.16 young females/nesting season. We combined these results with estimates of first-year and adult survival to examine the growth rate (??) of the population and the relative contributions of these demographic parameters to that growth rate. Contrary to aerial survey data, the population projection model suggests our study population is declining rapidly (?? = 0.6969). The relative effects on population growth rate were 0.1175 for reproductive success, 0.1175 for first-year survival, and 0.8825 for adult survival. Adult survival had the greatest influence on ?? for our population, and this conclusion was robust over a range of survival and productivity estimates. Given published estimates of annual survival for adult females (61%), our model suggested nest success and duckling survival need to increase to approximately 40% to achieve population stability. We discuss reasons for the apparent discrepancy in population trends between our model and aerial surveys in terms of bias in productivity and survival estimates.

Flint, P.L.; Grand, J.B.; Rockwell, R.F.

1998-01-01

150

Modeling Bacterial Population Growth from Stochastic Single-Cell Dynamics  

PubMed Central

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

Molina, Ignacio; Theodoropoulos, Constantinos

2014-01-01

151

Population growth and the benefits from optimally priced externalities.  

PubMed

"In this article we show that, considering only economic effects, even if population growth, by natural increase or immigration, increases congestion, pollution, and other forms of external costs, that provided pre-existing citizens own the resources giving rise to the externalities, and provided they efficiently price usage of such, that existing citizens must, in net average terms, be better off with population growth than without it. In simple terms the increased revenues they gain from efficient pricing at increased demand levels will be strictly greater than the monetary value of the increased external costs together with the higher tax costs they incur as consumers of the resources." PMID:12347617

Clarke, H R; Ng Y-k

1995-06-01

152

Switching and Growth for Microbial Populations in Catastrophic Responsive Environments  

PubMed Central

Phase variation, or stochastic switching between alternative states of gene expression, is common among microbes, and may be important in coping with changing environments. We use a theoretical model to assess whether such switching is a good strategy for growth in environments with occasional catastrophic events. We find that switching can be advantageous, but only when the environment is responsive to the microbial population. In our model, microbes switch randomly between two phenotypic states, with different growth rates. The environment undergoes sudden catastrophes, the probability of which depends on the composition of the population. We derive a simple analytical result for the population growth rate. For a responsive environment, two alternative strategies emerge. In the no-switching strategy, the population maximizes its instantaneous growth rate, regardless of catastrophes. In the switching strategy, the microbial switching rate is tuned to minimize the environmental response. Which of these strategies is most favorable depends on the parameters of the model. Previous studies have shown that microbial switching can be favorable when the environment changes in an unresponsive fashion between several states. Here, we demonstrate an alternative role for phase variation in allowing microbes to maximize their growth in catastrophic responsive environments. PMID:20371309

Visco, Paolo; Allen, Rosalind J.; Majumdar, Satya N.; Evans, Martin R.

2010-01-01

153

Switching and growth for microbial populations in catastrophic responsive environments  

E-print Network

Phase variation, or stochastic switching between alternative states of gene expression, is common among microbes, and may be important in coping with changing environments. We use a theoretical model to assess whether such switching is a good strategy for growth in environments with occasional catastrophic events. We find that switching can be advantageous, but only when the environment is responsive to the microbial population. In our model, microbes switch randomly between two phenotypic states, with different growth rates. The environment undergoes sudden "catastrophes", the probability of which depends on the composition of the population. We derive a simple analytical result for the population growth rate. For a responsive environment, two alternative strategies emerge. In the "no switching" strategy, the population maximises its instantaneous growth rate, regardless of catastrophes. In the "switching" strategy, the microbial switching rate is tuned to minimise the environmental response. Which of these strategies is most favourable depends on the parameters of the model. Previous studies have shown that microbial switching can be favourable when the environment changes in an unresponsive fashion between several states. Here, we demonstrate an alternative role for phase variation in allowing microbes to maximise their growth in catastrophic responsive environments.

Paolo Visco; Rosalind J. Allen; Satya N. Majumdar; Martin R. Evans

2010-04-12

154

The chimera of a Muslim population growth rate.  

PubMed

Preliminary results from the 1991 census indicate that overall, the rate of growth of the Muslim population has been 32.8% while that of the Hindu population was 22.8%. However, these data on growth rates by religious communities are not cross-tabulated with their determinants, income and literacy. Organized propaganda harbinging a high rate of Muslim population growth argues that Muslim men tend to have multiple wives and do not practice family planning. As such, Muslims have a higher birth rate than do Hindus and will soon outnumber Hindus in India. Data from official and nonsectarian agencies, however, indicate that polygamy is more common among Hindus than among Muslims and Islam does not prohibit family planning. While the birth rate among Muslims is slightly higher than that of Hindus, the situation is complex and involves socioeconomic determinants of fertility. One study projecting the prevailing growth rates among Hindus and Muslims into the next century indicates that the Muslim population will increase in size far less than will the Hindu population. Muslims will therefore not outnumber Hindus in India. PMID:12347748

Rao, M

1996-01-01

155

The effects of nonmetropolitan population growth on resource management  

Microsoft Academic Search

Studies of nonmetropolitan growth have neglected the effect of changes in the nature of new residents and land?holding size on individual resource management. This study of management of a resource?at?risk shows that deleterious resource management does not follow automatically in the wake of population growth. There is no difference in likelihood of new and long?standing residents to manage resources, although

Louise Fortmann; Lynn Huntsinger

1989-01-01

156

Global analysis of population growth and river water quality  

NASA Astrophysics Data System (ADS)

Human-related pressures on river water quality are a concern of global proportions.. However, little is known about the more specific impact of increasing population on river water quality and how it provides a vital environmental reference for water management. Combining global gridded data on population and river discharge with digitized river networks, we conduct numerical simulations to demonstrate the direct impact of population growth on river water quality. Our model traces the transport, dilution, and degradation of anthropogenic organic matter (BOD) emissions into rivers. Spanning the period from the early 20th century to the present, our analysis indicates that the pressure on downstream river networks markedly increased since the population explosion starting in 1950, especially in developing countries. The ratio of population to river discharge reveals the link between impact severity and dilution capacity. In addition, a denser population is found to be correlated with higher impact severity. Consideration of direct population influences on global river water quality becomes limited as society develops and should be studied as a fundamental reference for human-related river water management. Keywords: Population growth, River water quality, Space-time analysis, Human activities, Water Management

Wen, Yingrong; Schoups, Gerrit; van de Giesen, Nick

2014-05-01

157

Population and prehistory I: Food-dependent population growth in constant environments.  

PubMed

We present a demographic model that describes the feedbacks between food supply, human mortality and fertility rates, and labor availability in expanding populations, where arable land area is not limiting. This model provides a quantitative framework to describe how environment, technology, and culture interact to influence the fates of preindustrial agricultural populations. We present equilibrium conditions and derive approximations for the equilibrium population growth rate, food availability, and other food-dependent measures of population well-being. We examine how the approximations respond to environmental changes and to human choices, and find that the impact of environmental quality depends upon whether it manifests through agricultural yield or maximum (food-independent) survival rates. Human choices can complement or offset environmental effects: greater labor investments increase both population growth and well-being, and therefore can counteract lower agricultural yield, while fertility control decreases the growth rate but can increase or decrease well-being. Finally we establish equilibrium stability criteria, and argue that the potential for loss of local stability at low population growth rates could have important consequences for populations that suffer significant environmental or demographic shocks. PMID:18439637

Lee, Charlotte T; Tuljapurkar, Shripad

2008-06-01

158

Economic growth and population control in preindustrial Japan.  

PubMed

The onset of industrialization in Japan was preceded by a century and a half of very slow population growth, allowing incomes to increase faster than population. It is posited that the Japanese intentionally curtailed their population growth in the 18th and 19th centuries in order to maintain or improve their standard of living. Analysis of the population patterns and growth rates for 4 villages in central Japan indicates that birth rates during this period (Tokugawa period) were between 20-30/1000 and similar at the upper end to birthrates during the Meiji period, suggesting that the concept of a demographic transition may not be applicable to Japan at this time. Death rates were generally slightly below the birthrates, while life expectancy during the last century of the Tokugawa period was in the low 40s. The low rate of population growth was further slowed by famines; however, it is asserted that the number of deaths attributed to famines has been greatly overemphasized. Comparison of population trends in 18th century Tokugawa Japan show remarkable similarities with those in Europe after the onset of industrialization. There are also indications that the villagers followed customs that maximized per capita income. Tight social controls limited who married and at what age, leaving large numbers of unmarried women in the reproductive age group. Although there is no evidence of widespread knowledge of effective birth control measures to prevent conception, infanticide and abortion were widely practiced. It is suggested that the rapidity of Japan's economic growth following the Meiji Restoration is attributable to these unique demographic features. PMID:12339409

Hanley, S B

1983-01-01

159

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

E-print Network

Land Conversion and Recent Trends Forests cover about one-third of the United States and range from recent trends, determi- nants, and projections of forest land conversion in the United States. Examples1 Keywords: Deforestation, development, fragmentation, land-use change, population growth. Forest

Fried, Jeremy S.

160

Population Growth: The Human Dilemma. An NSTA Environmental Materials Guide.  

ERIC Educational Resources Information Center

This annotated bibliography lists more than 100 books about population growth. The books are intended for students in kindergarten through grade 12 and their teachers. The books were selected on the basis of their appropriateness to the interests of classroom teachers and students, and on the basis of readability and accuracy. Most were published…

Fowler, Kathryn Mervine

161

Extreme natural hazards: population growth, globalization and environmental change  

Microsoft Academic Search

Mankind is becoming ever more susceptible to natural disasters, largely as a consequence of population growth and globalization. It is likely that in the future, we will experience several disasters per year that kill more than 10000 people. A calamity with a million casualties is just a matter of time. This situation is mainly a consequence of increased vulnerability. Climate

Herbert E. Huppert; R. Stephen J. Sparks

2006-01-01

162

Circadian rhythm and cell population growth June 17, 2010  

E-print Network

Circadian rhythm and cell population growth June 17, 2010 Jean Clairambault 1 , 2 , St´ephane Gaubert 3 , 4 and Thomas Lepoutre 1 , 5 Abstract Molecular circadian clocks, that are found in all exerted by circadian clocks on healthy and tumour tissue proliferation to explain this phenomenon has

163

Women and Population Growth: Choice beyond Childbearing. Worldwatch Paper 16.  

ERIC Educational Resources Information Center

The paper explores the relationship of women's childbearing attitudes to educational and work opportunities. Program administrators for family planning, educational programs, and national development efforts in developing countries must realize the importance of the social and cultural environment in designing programs to reduce population growth.…

Newland, Kathleen

164

Statistical Properties of New Neutrality Tests Against Population Growth  

Microsoft Academic Search

A number of statistical tests for detecting population growth are described. We compared the statistical power of these tests with that of others available in the literature. The tests evaluated fall into three categories: those tests based on the distribution of the mutation frequencies, on the haplotype distribution, and on the mismatch distribution. We found that, for an extensive variety

Sebastian E. Ramos-Onsins; Julio Rozas

165

Population growth, distribution, and size in Latin America  

E-print Network

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

Lopez-Carr, David

166

Habitat-Specific Population Growth of a Farmland Bird  

PubMed Central

Background To assess population persistence of species living in heterogeneous landscapes, the effects of habitat on reproduction and survival have to be investigated. Methodology/Principal Findings We used a matrix population model to estimate habitat-specific population growth rates for a population of northern wheatears Oenanthe oenanthe breeding in farmland consisting of a mosaic of distinct habitat (land use) types. Based on extensive long-term data on reproduction and survival, habitats characterised by tall field layers (spring- and autumn-sown crop fields, ungrazed grasslands) displayed negative stochastic population growth rates (log ?s: ?0.332, ?0.429, ?0.168, respectively), that were markedly lower than growth rates of habitats characterised by permanently short field layers (pastures grazed by cattle or horses, and farmyards, log ?s: ?0.056, +0.081, ?0.059). Although habitats differed with respect to reproductive performance, differences in habitat-specific population growth were largely due to differences in adult and first-year survival rates, as shown by a life table response experiment (LTRE). Conclusions/Significance Our results show that estimation of survival rates is important for realistic assessments of habitat quality. Results also indicate that grazed grasslands and farmyards may act as source habitats, whereas crop fields and ungrazed grasslands with tall field layers may act as sink habitats. We suggest that the strong decline of northern wheatears in Swedish farmland may be linked to the corresponding observed loss of high quality breeding habitat, i.e. grazed semi-natural grasslands. PMID:18714351

Arlt, Debora; Forslund, Pär; Jeppsson, Tobias; Pärt, Tomas

2008-01-01

167

Demographic modeling of transient amplifying cell population growth.  

PubMed

Quantitative measurement for the timings of cell division and death with the application of mathematical models is a standard way to estimate kinetic parameters of cellular proliferation. On the basis of label-based measurement data, several quantitative mathematical models describing short-term dynamics of transient cellular proliferation have been proposed and extensively studied. In the present paper, we show that existing mathematical models for cell population growth can be reformulated as a specific case of generation progression models, a variant of parity progression models developed in mathematical demography. Generation progression ratio (GPR) is defined for a generation progression model as an expected ratio of population increase or decrease via cell division. We also apply a stochastic simulation algorithm which is capable of representing the population growth dynamics of transient amplifying cells for various inter-event time distributions of cell division and death. Demographic modeling and the application of stochastic simulation algorithm presented here can be used as a unified platform to systematically investigate the short term dynamics of cell population growth. PMID:24245725

Nakaoka, Shinji; Inaba, Hisashi

2014-04-01

168

Philippine laws, regulations back policy to contain population growth.  

PubMed

A recent compilation of population related decrees promulgated since martial law was declared in the Philippines in 1972 indicates that the government may be designing a legal framework encouraging voluntary limitation of family size. The list which was published in an appendix to the 1974-1977 Population Program, reveals that population influencing policies dealing with taxation, maternity benefits, incentive schemes and provision of family planning services by employers are already in effect. Since 1972 tax relief has been restricted to 4 dependents. Paid maternity leave is limited to the first 4 deliveries. Firms with over 300 employees are required to set up family planning clinics, and smaller firms must have infirmary personnel who are trained and certified in the provision of family planning services. Also, the Department of Labor is encouraging employers to develop incentive programs that will encourage workers to use effective family planning methods. The latest population plan also gives top priority to research, calls for targeting information to labor leaders, engaged couples, and out of school youth, and proposes disseminating population and family planning information through residential cooperatives and grass roots organizations. The aim of the current plan is to reduce the birthrate to 35.9 per 100 and the population growth rate to 2.47% by the end of the 4 year period. It is projected that by 1977 58% of the eligible population will be practicing contraception. PMID:12276795

1974-01-01

169

Heat and pulsed electric field resistance of pigmented and non-pigmented enterotoxigenic strains of Staphylococcus aureus in exponential and stationary phase of growth.  

PubMed

The survival of four enterotoxigenic strains of Staphylococcus aureus (with different pigment content) to heat and to pulsed electric fields (PEF) treatments, and the increase in resistance to both processing stresses associated with entrance into stationary phase was examined. Survival curves to heat (58 degrees C) and to PEF (26 kV/cm) of cells in the stationary and in the exponential phase of growth were obtained. Whereas a wide variation in resistance to heat treatments was detected amongst the four strains, with decimal reduction time values at 58 degrees C (D(58 degrees C)) ranging from 0.93 to 0.20 min, the resistance to PEF was very similar. The occurrence of a higher tolerance to heat in stationary phase was coincident with a higher content in carotenoid pigmentation in S. aureus colonies. However, cells of the most heat resistant (pigmented) and the most heat sensitive (non-pigmented) strains in the mid-exponential phase of growth showed similar resistance to heat and to PEF. Therefore the increase in thermotolerance upon entrance into stationary phase of growth was more marked for the pigmented strains. Recovery in anaerobic conditions particularly enhanced survival to heat treatments in a non-pigmented strain. Strain CECT 4630, which possess a deficient sigma B activity, showed low heat resistance, low pigmentation, and reduced increase in thermotolerance in stationary phase. These results indicate that the magnitude of the development of a higher heat resistance in S. aureus in stationary phase is positively related to the carotenoid content of the strain. The development of tolerance to pulsed electric field was less relevant and not linked to the carotenoid content. PMID:17804103

Cebrián, G; Sagarzazu, N; Pagán, R; Condón, S; Mañas, P

2007-09-30

170

Ecology of Increasing Diseases: Population Growth and Environmental Degradation  

Microsoft Academic Search

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

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

171

Math 114 Class 23 Fall 2005 Population Models and Qualitative Analysis  

E-print Network

the population? How well do you think this model would work in capturing the bacterial growth over time? What that track the growth of a population over time; the SIR model we examined some weeks ago is such a model of population growth is known as both exponential growth and Malthus growth. Sketch the function dB/dt versus B

Buckmire, Ron

172

Population, internal migration, and economic growth: an empirical analysis.  

PubMed

The role of population growth in the development process has received increasing attention during the last 15 years, as manifested in the literature in 3 broad categories. In the 1st category, the effects of rapid population growth on the growth of income have been studied with the use of simulation models, which sometimes include endogenous population growth. The 2nd category of the literature is concerned with theoretical and empirical studies of the economic determinants of various demographic rates--most usually fertility. Internal migration and dualism is the 3rd population development category to recieve attention. An attempt is made to synthesize developments in these 3 categories by estimating from a consistent set of data a 2 sector economic demographic model in which the major demographic rates are endogenous. Due to the fact that the interactions between economic and demographic variables are nonlinear and complex, the indirect effects of changes in a particular variable may depend upon the balance of numerical coefficients. For this reason it was felt that the model should be empirically grounded. A brief overview of the model is provided, and the model is compared to some similar existing models. Estimation of the model's 9 behavior equations is discussed, followed by a "base run" simulation of a developing country "stereotype" and a report of a number of policy experiments. The relatively new field of economic determinants of demographic variables was drawn upon in estimating equations to endogenize demographic phenomena that are frequently left exogenous in simulation models. The fertility and labor force participation rate functions are fairly standard, but a step beyong existing literature was taken in the life expectancy and intersectorial migration equations. On the economic side, sectoral savings functions were estimated, and it was found that the marginal propensity to save is lower in agriculture than in nonagriculture. Testing to see the effect of a population's age structure on savings rather than assuming a particular direction as Coale-Hoover and Simon do in their models, it was found that a higher proportion of children compete with savings in agriculture but complement savings in industrial areas. This was consistent with the economic value of children in agricultural and nonagricultural regions of less developed countries. The estimated production functions showed that marginal products of labor were considerably higher in agriculture than in nonagriculture. As with other simulation models, the effect of reducing fertility was to accelerate income growth. Reductions in rural fertility were more equitable and raised the overall level of per capita income more than similar efforts directed to urban areas only. PMID:12264901

Moreland, R S

1982-01-01

173

Growth of rural population in Punjab, 1971-81.  

PubMed

Except for the decade 1941-1951, in which Punjab's population declined because of a huge exchange of population between India and Pakistan and a large loss of life, the decade 1971-1981 was the 1st decade since 1911 to experience a deceleration in the growth rate of the rural population of Punjab, India. The deceleration was due to out-migration to urban areas. The scheduled caste population increased 28.37% between 1971 and 1981, while the nonscheduled caste population increased by only 13.32%, which was considerably below the rate of natural increase. Nonscheduled castes had experienced substantial out-migration because of 1) improved transport and communication facilities which enabled them to move to urban centers; 2) mechanization of main farming operations and easy availability of migrant laborers which lessened the need for family labor; 3) the rise of a relatively mobile younger generation with a high literacy rate; 4) rapidly decreasing land holdings which strengthened the push factor in the countryside; and 5) rising aspirations, especially among the younger generation. In 1981, Sikhs constituted 71.3% of the rural population in Punjab, followed by Hindus (26.51%), Christians (1.25%), and Muslims (.89%). From 1971-1981, Muslims experienced the greatest increase (49.29%). Sikhs grew by 20.74% and Hindus by 9.02%. The Sikhs high growth rate was due to 1) a new technique for counting religious affiliation in which all members of a household are considered the same religion as the head of household and 2) conversion of Hindus to Sikhism. Hindus had a low growth rate because 1) the new method of counting religious affiliation and 2) rural-urban migration. The area with the lowest population increase resulted from industrialists and other nonagriculturists buying farmland, causing the agriculturists to move away to less desirable land. Conclusions are 1) the sharp rural-urban division along religious lines should be lessened, 2) Sikhs' lag in urbanization and upward mobility should be decreased, and 3) nonagriculturalists should be prevented from buying farm land from peasants along main roads and around urban centers. PMID:12179031

Gill, M S

1987-01-01

174

Population growth and food supply in sub-Saharan Africa.  

PubMed

It is argued in this article that sub-Saharan Africa, given its present institutions and endowments of capital and technology, is already dangerously close to overpopulation. The rapid growth of its population projected for the next decades will greatly increase human misery and depress economic development. Specifically, rapid population growth will have disastrous effects on the region's ability to increase exports and provide people with food. There must be a search for new ways in which these effects could be mitigated. In sub-Saharan Africa fertility either continues to be very high or is increasing, in part due to some decline in traditional practices that reduce fertility, such as prolonged breastfeeding. This situation and the expectation of declining mortality imply that African population growth may increase further. Currently, population in sub-Saharan Africa is about half that of India and a third of China. There are 2 main reasons why reduced fertility in the next few decades is unlikely in sub-Saharan Africa as a whole: Africa has low literacy, high infant and child mortality, and low urbanization; and average African fertility rates may even increase for the next 20 years or so. The question that arises is what are the implications of continuing and rapid population growth for the African food supply. The region's cereal production is largely restricted to 4 grains, i.e., millet, sorghum, maize, and rice. The volume of grain production is less, by weight, than 60% of the production of roots and tubers. There are 2 main differences between the output of these crops in sub-Saharan Africa and the rest of the world: yields/hectare are lower in Africa than in elsewhere; and yields have generally been decreasing or largely constant in Africa. The low productivity has several causes. Today, population pressure has brought diminishing returns to traditional agriculture in much of the Sahel and the savanna, in parts of East Africa, Southern Africa, and parts of the West African forest belt. There is also the absence of the Green Revolution, i.e., the use of new high yielding seeds and new technologies in agriculture that has led to marked increases in yields in most other parts of the world. A totally different and more productive agriculture might evolve if African governments were to fundamentally change their vision. Existing production technology could allow substantial increases in the yields of many crops if some basic changes were made in the policies affecting agriculture. A way to achieve such change would be to make farming profitable. The effect of population growth in diminishing returns to agriculture also lends urgency to the need for family planning. Generally, population policy in Africa badly needs strengthening. PMID:12264271

Meerman, J; Cochrane, S H

1982-09-01

175

Deer Population  

NSDL National Science Digital Library

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.

Maryland Virtual High School

176

Theoretical Population Biology 69 (2006) 181191 The ideal free distribution and bacterial growth on two substrates  

E-print Network

Theoretical Population Biology 69 (2006) 181­191 The ideal free distribution and bacterial growth population growth rate. For batch bacterial growth, the model predicts that as the concentration is good. For bacterial growth in the chemostat, the model predicts that at low dilution rates bacteria

Krivan, Vlastimil

177

Growth in an English population from the Industrial Revolution.  

PubMed

The rapid urbanization of the Industrial Revolution in 18th-19th century England presented new health challenges. Our aim is to investigate using English skeletal remains whether the living conditions for an urban working class group in the Industrial Revolution negatively impacted upon their skeletal growth compared with a population from a rural agrarian parish. The Industrial Revolution skeletal material is from St Martin's Churchyard, Birmingham (SMB), West Midlands. It dates primarily from the first half of the nineteenth century when Birmingham was a major manufacturing center. The rural group is from Wharram Percy (WP), North Yorkshire, and dates from 10th-19th century AD. The methodology involves plotting diaphyseal bone lengths versus dental age for subadults. No overall difference was found between the two populations in bone length-for-age among the 2- to 18-year cohort. However the younger parts of the SMB cohort were smaller than at WP; the opposite was true of the older parts of the cohort. Growth rate, as inferred from crosssectional data, appeared greater at SMB than at WP. The only result consistent with expectations is the larger bone dimensions in young children from WP, but this likely reflects prolonged breastfeeding at WP not differences in urban and rural environments. That the deleterious health effects that we know accompanied the major transition in human society from a rural agrarian to an urban industrialized living environment should be little manifest in skeletal endochondral growth data is discouraging for those who would use such methodology to monitor health in earlier populations. PMID:18186509

Mays, S; Brickley, M; Ives, R

2008-05-01

178

Development Planning and Population Growth and Redistribution in the Republic of Iraq.  

ERIC Educational Resources Information Center

Utilizing the 1947, 1957, and l965 census data and the 1970 preliminary population count, the relationship between population growth and redistribution and development planning in Iraq was examined. Trends in rural-urban population growth, migration, and population redistribution were examined as they pertained to the socioeconomic development…

El Attar, M. E.; Salman, A. D.

179

Colonization, population growth, and nesting success of Black Oystercatchers following a seismic uplift  

USGS Publications Warehouse

We present data on the colonization of Middleton Island, Alaska, by Black Oystercatchers (Haematopus bachmani) following the creation of an extensive rocky intertidal zone after the Alaskan earthquake of 1964. The first pair of oystercatchers was detected in 1976, and it was another 5 years before the population increased to three pairs. Oystercatcher numbers increased steadily thereafter, with a population explosion occurring in the 1990s. By 2002, there were 171 territorial pairs on the island. The total number of birds increased from two in 1976 to 718 in 2002. Breeding-pair densities on Middleton Island are the highest recorded for any portion of Alaska, averaging more than 5 pairs per km of shoreline in 2002. Nesting success in 2001 and 2002 was greater (83% or more of the eggs laid hatched) than that reported for any other population of oystercatchers in Alaska or along the Pacific Coast. We attribute this exponential growth rate and exceptionally high reproductive success to the large area of available and suitable habitat, the low number of avian predators and the complete lack of mammalian predators, low rate of nest loss to high tides and storm surges, and a low level of human disturbance. We propose nominating Middleton Island as a regional Western Hemisphere Shorebird Reserve Network site because a high percentage of the world's and region's population of Black Oystercatchers resides there during the breeding season. Further, since Middleton Island may be the single most important site in Alaska for Black Oystercatchers, we suggest it be protected from future development.

Gill, V.A.; Hatch, S.A.; Lanctot, Richard B.

2004-01-01

180

Analytical approximations for a population growth model with fractional order  

NASA Astrophysics Data System (ADS)

In this paper, we apply the homotopy analysis method (HAM) to solve the fractional Volterra's model for population growth of a species in a closed system. This technique is extended to give solutions for nonlinear fractional integro-differential equations. The whole HAM solution procedure for nonlinear fractional differential equations is established. Further, the accurate analytical approximations are obtained for the first time, which are valid and convergent for all time t. This indicates the validity and great potential of the homotopy analysis method for solving nonlinear fractional integro-differential equations.

Xu, Hang

2009-05-01

181

Herbivory: effects on plant abundance, distribution and population growth  

PubMed Central

Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant life-history types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant–consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics. PMID:17002942

Maron, John L; Crone, Elizabeth

2006-01-01

182

Population growth and land use in Nepal: "the great turnabout".  

PubMed

Historically, Nepal has demonstrated a "great turnabout" trend, in which initial immigration from the lowland areas to the mountains has been replaced by accelerating migration from the hills to the plains. The reason for this reversal has been a rapid growth in population within the confines of limited availability of potentially cultivable land. Given Nepal's slow economic development, the overwhelming majority of increases in population have to be accommodated within the agricultural sector, on which 83% of Nepal's households are dependent. Fundamental land use issues in Nepal include rapid achievement of the final limit of land suitability for cultivation and the speed at which land can be brought into cultivation. The Government of Nepal has developed the objectives of increased food production to provide a satisfactory diet for the population, increased per capita income, improved regional balance in income and development, conservation of natural resources such as land and forests, and overall development of the economy through income generation, export earnings, and release of agricultural labor to other sectors. 3 perspective studies have identified a number of policies and programs that could bring Nepal closer to these goals. These studies analyzed potential land use development, agricultural production, and food availability by the year 2005. Most essential is the need to intensify land use not only in crop agriculture, but also grasslands and forest use. Land must be allocated to uses that represent the most productive use of that land without being degrading. Technologies are available for land use in each of the main types of uses--crop agriculture, livestock, and forests--that can provide protection against land degradation. Finally, irrigation is a key element in raising agricultural output. Close cooperation between the government and the people is crucial for the success of the task of finding a balance between population growth and its demand for services of the land. PMID:12281524

Hrabovszky, J P; Miyan, K

1987-08-01

183

[Environmental pollution and population growth in Latin America].  

PubMed

3 factors are always involved in causation of infectious disease: the causal organism, an adverse environment, and nutritional status. As knowledge of degenerative and mental illnesses advances, their relationship to environmental problems becomes clearer. Health in the human being as in all living things is the product of ecological equilibrium. In countries with high mortality rates, the majority of deaths occur in the early years of life. Countries enjoying low mortality rates are those that have protected themselves against environmental deterioration. The Roman civilization, the 1st to have large cities, built aqueducts to protect the water supply from contamination. With the disappearance of the Roman Empire the concern for purity of the water supply also disappeared, and the cities of the Middle Ages became breeding grounds for epidemics. In the early 19th century John Snow demonstrated the role of water in the transmission of cholera and thereafter the concern with potable water and sewage disposal was reborn. The Industrial Revolution eventually allowed sufficient accumulation of wealth to permit improved nutrition. Environmental sanitation and improved food supply produced a new ecological equilibrium, and Western Europe began to have lower and lower mortality rates. Paralleling the decline in deaths a new spirit of responsible parenthood and delayed marriage was lowering birth rates. Population growth, which never exceeded 1%, had the additional escape valve of emigration to America and Australia. The true cause of environmental degradation is man. When human beings were few their contaminants were readily obsorbed by the environment, but as they proliferate the environment is increasingly unable to absorb their pollution by natural processes. Industrial fumes, deforestation, and polluted rivers are only the symptoms of contamination. In the developed countries, technological innovations minimizing industrial pollution and lower population growth are helping to combat environmental degradation, but in Latin America, population control has not yet taken hold and antipollution measures are not implemented because of their high cost. High fertility has always characterized Latin American since colonial days, but until the 20th century it was balanced by high mortality. Largely because of the progressive control of disease, the population increased from some 87 million in 1920 to 212 million by 1960, and may arrive at 650 million by 2000. In just 30 years Latin America was able to reduce mortality to under 10/1000, a process requiring 300 years in the developed world. In Latin America mortality reduction was achieved by medical means and not by environmental improvements. Despite the obious problems caused by rapid population growth, most governments in the region persist in supporting pronatalist policies and legislation. PMID:12313223

Viel, B

1983-01-01

184

Metabolic profiling and flux analysis of MEL-2 human embryonic stem cells during exponential growth at physiological and atmospheric oxygen concentrations.  

PubMed

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

Turner, Jennifer; Quek, Lake-Ee; Titmarsh, Drew; Krömer, Jens O; Kao, Li-Pin; Nielsen, Lars; Wolvetang, Ernst; Cooper-White, Justin

2014-01-01

185

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

PubMed Central

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

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

2014-01-01

186

Lesson 33: Applications of Exponential Functions  

NSDL National Science Digital Library

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.

2011-01-01

187

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

PubMed Central

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 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

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

2014-01-01

188

World population growth, family planning, and American foreign policy.  

PubMed

The US decision since the 1960s to link foreign policy with family planning and population control is noteworthy for its intention to change the demographic structure of foreign countries and the magnitude of the initiative. The current population ideologies are part of the legacy of 19th century views on science, morality, and political economy. Strong constraints were placed on US foreign policy since World War II, particularly due to presumptions about the role of developing countries in Cold War ideology. Domestic debates revolved around issues of feminism, birth control, abortion, and family political issues. Since the 1960s, environmental degradation and resource depletion were an added global dimension of US population issues. Between 1935 and 1958 birth control movements evolved from the ideologies of utopian socialists, Malthusians, women's rights activists, civil libertarians, and advocates of sexual freedom. There was a shift from acceptance of birth control to questions about the role of national government in supporting distribution of birth control. Immediately postwar the debates over birth control were outside political circles. The concept of family planning as a middle class family issue shifted the focus from freeing women from the burdens of housework to making women more efficient housewives. Family planning could not be taken as a national policy concern without justification as a major issue, a link to national security, belief in the success of intervention, and a justifiable means of inclusion in public policy. US government involvement began with agricultural education, technological assistance, and economic development that would satisfy the world's growing population. Cold War politics forced population growth as an issue to be considered within the realm of foreign policy and diplomacy. US government sponsored family planning was enthusiastic during 1967-74 but restrained during the 1980s. The 1990s has been an era of redefinition of the issues and increased divisiveness among environmentalists, feminists, and population control advocates. The current justification of US population program assistance is based on concern for the health of women and children. Future changes will be dependent on ideology, theology, and political philosophy. PMID:12346346

Sharpless, J

1995-01-01

189

Defining and explaining tropical deforestation: shifting cultivation and population growth in colonial Madagascar (1896-1940).  

PubMed

The case study of deforestation in Madagascar demonstrated how deforestation is a complex phenomenon that reflects interconnections between land-based resources, human groups, and global political economy; specifically, there is a link between changing land use practices affecting shifting cultivation and tropical deforestation. The general development model of exponential population growth and shifting cultivation causing deforestation and environmental degradation is too simplified, places undue blame on the victims, and isolates shifting cultivation practices from the reality of land use patterns in specific places at specific times. Problematic also is the way definition, delimitation, and discussion of environmental problems shapes possible solutions. This analysis suggests a theoretical view that links reconstructed regional geography with political ecology. The assertion is that deforestation is historically based on multiple social processes within Madagascar. Land use practices and resource access decisions during the colonial period affected land management and degradation. The colonial state policy played a role in the destruction of tropical flora by fire, shifting cultivation, and grazing, and the responses of Europeans and Malagasys. Context and multiplicity of motivations and practices were key. A review was presented of reconstructed regional geography and political ecology and global tropical deforestation. The description of the political economy of deforestation during colonial times focused on the movement of population into the forests after 1896 and French annexation. Famine resulted. Shifting cultivation laws were passed between 1881 and 1913, due to the desire for rational forest resource management. Ecologically and socially these rules were difficult to enforce; there were resistance due to the threat of the elimination of subsistence living for wage work. Destructive logging practices and forest product extraction after 1921 are described. During 1900-1941, population was below or at replacement level, but the government still blamed Malagasys. Shifting cultivation meant different things to the subsistence farmers, the state, and international agencies. Denial of context promotes an ideology of repression, fuels fear and prejudice, and promotes the wrong solutions. PMID:12318844

Jarosz, L

1993-10-01

190

Population.  

ERIC Educational Resources Information Center

In an effort to help meet the growing interest and concern about the problems created by the rapid growth of population, The International Planned Parenthood Federation has prepared this booklet with the aim of assisting the study of the history and future trends of population growth and its impact on individual and family welfare, national,…

International Planned Parenthood Federation, London (England).

191

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

PubMed Central

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

Attwood, Stephen W.; Upatham, E. Suchart

2013-01-01

192

Growth Kinetics of Listeria monocytogenes in Broth and Beef Frankfurters– Determination of Lag Phase Duration and Exponential Growth Rate under Isothermal Conditions  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this research was to develop a new kinetic model to describe the isothermal growth of microorganisms. The new model was tested with Listeria monocytogenes in broth and frankfurters, and compared with two commonly used models - Baranyi and modified Gompertz models. Bias factor (BF)...

193

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

Microsoft Academic Search

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

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

194

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

Microsoft Academic Search

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

Barry Sinervo

1990-01-01

195

Bluegill Recruitment, Growth, Population Size Structure, and Associated Factors in Minnesota Lakes  

Microsoft Academic Search

To better understand the differences among populations of bluegill Lepomis macrochirus, we analyzed the relationships between bluegill recruitment, growth, population size structure, and associated factors from approximately 2,600 Minnesota lakes. Potential explanatory variables for our models included bluegill year-class strength, growth, population size structure, the relative abundance and mean weight of predator species, physical and chemical characteristics of lakes, summer

Cynthia M. Tomcko; Rodney B. Pierce

2005-01-01

196

World Population, 1970–2009: A Perspective on Nearly Four Decades of Growth  

Microsoft Academic Search

:This review article provides one professional geographer's view of some of the major dilemmas that population growth has created for us during the past four decades. During that time, Earth's population grew by just over three billion, a number that is nearly ten times the current population of the United States. Arguably, that growth has come with some price tags

Gary Peters

2011-01-01

197

World Population, 1970–2009: A Perspective on Nearly Four Decades of Growth  

Microsoft Academic Search

This review article provides one professional geographer's view of some of the major dilemmas that population growth has created for us during the past four decades. During that time, Earth's population grew by just over three billion, a number that is nearly ten times the current population of the United States. Arguably, that growth has come with some price tags

Gary Peters

2011-01-01

198

The Escherichia coli FIS protein is not required for the activation of tyrT transcription on entry into exponential growth.  

PubMed Central

The Escherichia coli DNA bending protein factor for inversion stimulation (FIS), is neither necessary nor responsible for the stimulation of transcription from the wild type promoter for the tyrT operon (encoding a species of tyrosine tRNA) that occurs upon resumption of exponential growth. This conclusion is unexpected given that the regulatory element required for optimal transcription of tyrT contains three binding sites for FIS protein. In addition, it is in apparent conflict with reports from other laboratories which have described FIS-dependent activation of the stable RNA promoters rrnB P1 and thrU(tufB) in vivo. However, tyrT transcription is stimulated in a FIS-dependent manner both in vivo and in vitro when promoter function is impaired by mutation of the promoter itself or by the addition of the polymerase effector guanosine 5'-diphosphate 3'-diphosphate. These conditions, which expose a requirement for activation of stable RNA synthesis by FIS, suggest that FIS serves an adaptive role permitting high levels of stable RNA transcription on nutritional shift-up when RNA polymerase levels are depleted. In principle such a mechanism could confer a significant selective advantage thus accounting for the conservation of FIS binding sites in the regulatory regions of stable RNA promoters. Images PMID:7685276

Lazarus, L R; Travers, A A

1993-01-01

199

An allometric scaling relation based on logistic growth of cities  

E-print Network

The relationships between urban area and population size have been empirically demonstrated to follow the scaling law of allometric growth. This allometric scaling is based on exponential growth of city size and can be termed "exponential allometry", which is associated with the concepts of fractals. However, both city population and urban area comply with the course of logistic growth rather than exponential growth. In this paper, I will present a new allometric scaling based on logistic growth to solve the abovementioned problem. The logistic growth is a process of replacement dynamics. Defining a pair of replacement quotients as new measurements, which are functions of urban area and population, we can derive an allometric scaling relation from the logistic processes of urban growth, which can be termed "logistic allometry". The exponential allometric relation between urban area and population is the approximate expression of the logistic allometric equation when the city size is not large enough. The prop...

Chen, Yanguang

2013-01-01

200

An assessment of bird habitat quality using population growth rates  

USGS Publications Warehouse

Survival and reproduction directly affect population growth rate (lambda) making lambda a fundamental parameter for assessing habitat quality. We used field data, literature review, and a computer simulation to predict annual productivity and lambda for several species of landbirds breeding in floodplain and upland forests in the Midwestern United States. We monitored 1735 nests of 27 species; 760 nests were in the uplands and 975 were in the floodplain. Each type of forest habitat (upland and floodplain) was a source habitat for some species. Despite a relatively low proportion of regional forest cover, the majority of species had stable or increasing populations in all or some habitats, including six species of conservation concern. In our search for a simple analog for lambda, we found that only adult apparent survival, juvenile survival, and annual productivity were correlated with lambda; daily nest survival and relative abundance estimated from point counts were not. Survival and annual productivity are among the most costly demographic parameters to measure and there does not seem to be a low-cost alternative. In addition, our literature search revealed that the demographic parameters needed to model annual productivity and lambda were unavailable for several species. More collective effort across North America is needed to fill the gaps in our knowledge of demographic parameters necessary to model both annual productivity and lambda. Managers can use habitat-specific predictions of annual productivity to compare habitat quality among species and habitats for purposes of evaluating management plans.

Knutson, M.G.; Powell, L.A.; Hines, R.K.; Friberg, M.A.; Niemi, G.J.

2006-01-01

201

Logistic Growth Logistic growth is a simple model for predicting the size y(t) of a population as a  

E-print Network

Logistic Growth Logistic growth is a simple model for predicting the size y(t) of a population the differential equation y (t) = by(t) Logistic growth adds one more wrinkle to this model. It assumes available to each member decreases. This in turn causes the net birth rate b to decrease. In the logistic

Feldman, Joel

202

Population growth and a sustainable environment. The Machakos story.  

PubMed

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

Mortimore, M; Tiffen, M

1994-10-01

203

Recognizing Exponential Growth. Classroom Notes  

ERIC Educational Resources Information Center

Two heuristic and three rigorous arguments are given for the fact that functions of the form Ce[kx], with C an arbitrary constant, are the only solutions of the equation dy/dx=ky where k is constant. Various of the proofs in this self-contained note could find classroom use in a first-year calculus course, an introductory course on differential…

Dobbs, David E.

2004-01-01

204

Exponential Growth through Pattern Exploration  

ERIC Educational Resources Information Center

Participants at the Summer Institute Pattern Exploration: Integration Math and Science in the Middle Grades used and developed a method treat arithmetic, algebra and geometry as one entity. The use of iterative geometric constructions is seen to reinforce the concepts of exponents, ratios and algebraic expressions for the nth stage of the…

Brown, Betty

2005-01-01

205

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 ...

206

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

PubMed

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

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

2012-01-22

207

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

PubMed Central

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

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

2012-01-01

208

Population growth enhances the mean fixation time of neutral mutations and the persistence of neutral variation.  

PubMed

A fundamental result of population genetics states that a new mutation, at an unlinked neutral locus in a randomly mating diploid population, has a mean time of fixation of ?4N(e) generations, where N(e) is the effective population size. This result is based on an assumption of fixed population size, which does not universally hold in natural populations. Here, we analyze such neutral fixations in populations of changing size within the framework of the diffusion approximation. General expressions are derived for the mean and variance of the fixation time in changing populations. Some explicit results are given for two cases: (i) the effective population size undergoes a sudden change, representing a sudden population expansion or a sudden bottleneck; (ii) the effective population changes linearly for a limited period of time and then remains constant. Additionally, a lower bound for the mean time of fixation is obtained for an effective population size that increases with time, and this is applied to exponentially growing populations. The results obtained in this work show, among other things, that for populations that increase in size, the mean time of fixation can be enhanced, sometimes substantially so, over 4N(e,0) generations, where N(e,0) is the effective population size at the time the mutation arises. Such an enhancement is associated with (i) an increased probability of neutral polymorphism in a population and (ii) an enhanced persistence of high-frequency neutral variation, which is the variation most likely to be observed. PMID:22426878

Waxman, D

2012-06-01

209

Population Growth Enhances the Mean Fixation Time of Neutral Mutations and the Persistence of Neutral Variation  

PubMed Central

A fundamental result of population genetics states that a new mutation, at an unlinked neutral locus in a randomly mating diploid population, has a mean time of fixation of ?4Ne generations, where Ne is the effective population size. This result is based on an assumption of fixed population size, which does not universally hold in natural populations. Here, we analyze such neutral fixations in populations of changing size within the framework of the diffusion approximation. General expressions are derived for the mean and variance of the fixation time in changing populations. Some explicit results are given for two cases: (i) the effective population size undergoes a sudden change, representing a sudden population expansion or a sudden bottleneck; (ii) the effective population changes linearly for a limited period of time and then remains constant. Additionally, a lower bound for the mean time of fixation is obtained for an effective population size that increases with time, and this is applied to exponentially growing populations. The results obtained in this work show, among other things, that for populations that increase in size, the mean time of fixation can be enhanced, sometimes substantially so, over 4Ne,0 generations, where Ne,0 is the effective population size at the time the mutation arises. Such an enhancement is associated with (i) an increased probability of neutral polymorphism in a population and (ii) an enhanced persistence of high-frequency neutral variation, which is the variation most likely to be observed. PMID:22426878

Waxman, D.

2012-01-01

210

Extrapolating Growth Reductions in Fish to Changes in Population Extinction Risks: Copper and Chinook Salmon  

Microsoft Academic Search

Fish commonly respond to stress, including stress from chemical exposures, with reduced growth. However, the relevance to wild populations of subtle and sometimes transitory growth reductions may not be obvious. At low-level, sustained exposures, Cu is one substance that commonly causes reduced growth but little mortality in laboratory toxicity tests with fish. To explore the relevance of growth reductions under

Christopher A. Mebane; David L. Arthaud

2010-01-01

211

Populations  

NSDL National Science Digital Library

This chapter introduces population as a group of the same kind of organisms in a given space at a given time. The activities in this section will provide students with the opportunity to define population, estimate populations in a community, and count and compare populations within a community. Students will gain the knowledge in describing plant and animal populations living in a community. They will also experiment with plant populations to control growth and development, not to mention discuss the effects of abiotic conditions on a community.

Janet R. Galle

2005-01-01

212

Giving Exponential Functions a Fair Shake  

ERIC Educational Resources Information Center

This article details an exploration of exponential decay and growth relationships using M&M's and dice. Students collect data for mathematical models and use graphing calculators to make sense of the general form of the exponential functions. (Contains 10 figures and 2 tables.)

Wanko, Jeffrey J.

2005-01-01

213

In Bacillus subtilis LutR is part of the global complex regulatory network governing the adaptation to the transition from exponential growth to stationary phase.  

PubMed

The lutR gene, encoding a product resembling a GntR-family transcriptional regulator, has previously been identified as a gene required for the production of the dipeptide antibiotic bacilysin in Bacillus subtilis. To understand the broader regulatory roles of LutR in B. subtilis, we studied the genome-wide effects of a lutR null mutation by combining transcriptional profiling studies using DNA microarrays, reverse transcription quantitative PCR, lacZ fusion analyses and gel mobility shift assays. We report that 65 transcriptional units corresponding to 23 mono-cistronic units and 42 operons show altered expression levels in lutR mutant cells, as compared with lutR(+) wild-type cells in early stationary phase. Among these, 11 single genes and 25 operons are likely to be under direct control of LutR. The products of these genes are involved in a variety of physiological processes associated with the onset of stationary phase in B. subtilis, including degradative enzyme production, antibiotic production and resistance, carbohydrate utilization and transport, nitrogen metabolism, phosphate uptake, fatty acid and phospholipid biosynthesis, protein synthesis and translocation, cell-wall metabolism, energy production, transfer of mobile genetic elements, induction of phage-related genes, sporulation, delay of sporulation and cannibalism, and biofilm formation. Furthermore, an electrophoretic mobility shift assay performed in the presence of both SinR and LutR revealed a close overlap between the LutR and SinR targets. Our data also revealed a significant overlap with the AbrB regulon. Together, these findings reveal that LutR is part of the global complex, interconnected regulatory systems governing adaptation of bacteria to the transition from exponential growth to stationary phase. PMID:24196425

Irigül-Sönmez, Öykü; Köro?lu, Türkan E; Öztürk, Bü?ra; Kovács, Ákos T; Kuipers, Oscar P; Yazgan-Karata?, Ayten

2014-02-01

214

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

PubMed

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

Ab Ghani, Nurul Izza; Merilä, Juha

2015-01-01

215

Population divergence in compensatory growth responses and their costs in sticklebacks  

PubMed Central

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

Ab Ghani, Nurul Izza; Merilä, Juha

2015-01-01

216

The alternative sigma factor SigB of Corynebacterium glutamicum modulates global gene expression during transition from exponential growth to stationary phase  

PubMed Central

Background Corynebacterium glutamicum is a gram-positive soil bacterium widely used for the industrial production of amino acids. There is great interest in the examination of the molecular mechanism of transcription control. One of these control mechanisms are sigma factors. C. glutamicum ATCC 13032 has seven putative sigma factor-encoding genes, including sigA and sigB. The sigA gene encodes the essential primary sigma factor of C. glutamicum and is responsible for promoter recognition of house-keeping genes. The sigB gene codes for the non-essential sigma factor SigB that has a proposed role in stress reponse. Results The sigB gene expression was highest at transition between exponential growth and stationary phase, when the amount of sigA mRNA was already decreasing. Genome-wide transcription profiles of the wild-type and the sigB mutant were recorded by comparative DNA microarray hybridizations. The data indicated that the mRNA levels of 111 genes are significantly changed in the sigB-proficient strain during the transition phase, whereas the expression profile of the sigB-deficient strain showed only minor changes (26 genes). The genes that are higher expressed during transition phase only in the sigB-proficient strain mainly belong to the functional categories amino acid metabolism, carbon metabolism, stress defense, membrane processes, and phosphorus metabolism. The transcription start points of six of these genes were determined and the deduced promoter sequences turned out to be indistinguishable from that of the consensus promoter recognized by SigA. Real-time reverse transcription PCR assays revealed that the expression profiles of these genes during growth were similar to that of the sigB gene itself. In the sigB mutant, however, the transcription profiles resembled that of the sigA gene encoding the house-keeping sigma factor. Conclusion During transition phase, the sigB gene showed an enhanced expression, while simultaneously the sigA mRNA decreased in abundance. This might cause a replacement of SigA by SigB at the RNA polymerase core enzyme and in turn results in increased expression of genes relevant for the transition and the stationary phase, either to cope with nutrient limitation or with the accompanying oxidative stress. The increased expression of genes encoding anti-oxidative or protection functions also prepares the cell for upcoming limitations and environmental stresses. PMID:17204139

Larisch, Christof; Nakunst, Diana; Hüser, Andrea T; Tauch, Andreas; Kalinowski, Jörn

2007-01-01

217

Population Growth and Demographic Structure. Proceedings of the United Nations Expert Group Meeting on Population Growth and Demographic Structure (Paris, France, November 16-20, 1992).  

ERIC Educational Resources Information Center

This volume contains the report and recommendations of the United Nations-sponsored meeting on population growth and demographic structure which was held in Paris, November 1992. Materials in the volume can serve as useful tools for future research on the relations between population, environment, and development and further the work of the United…

United Nations, New York, NY. Dept. of Economic and Social Affairs.

218

Increasing population growth by asymmetric segregation of a limiting resource during cell division  

E-print Network

Increasing population growth by asymmetric segregation of a limiting resource during cell division of dividing cells, thereby increasing population growth. Molecular Systems Biology (2013) 9, 656; published cells which were born in rich conditions, before the shift. Mother cells continue to divide multiple

Barkai, Naama

219

THE EFFECT OF NATURAL VARIABILITY OF LIFE-HISTORY PARAMETERS ON ANCHOVY AND SARDINE POPULATION GROWTH  

Microsoft Academic Search

The northern anchovy (Engradis movdax) and Pa- cific sardine (Savdinops sagax) populations were modeled with a stage-based matrix to examine how natural variation of life-history parameters affects per capita growth. In the model northern anchovy (Engradis movdax) population, the greatest change in growth results from natural variation in the duration of, and the instantaneous mortality rate of, the early and

JOHN L. BUTLER; PAUL E. SMITH; N. CHYAN-HUE

1993-01-01

220

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

E-print Network

RESEARCH ARTICLE Open Access Population growth of Mexican free-tailed bats (Tadarida brasiliensis colonies of Mexican free-tailed bats (Tadar- ida brasiliensis mexicana) are some of the largest and most population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed

Russell, Amy L.

221

Asymmetries in population growth regulated by intraspecific competition: Empirical studies and model tests  

Microsoft Academic Search

The linearity assumption in the logistic model of population growth is violated for nearly all organisms. Two simple models, the ?-logistic and the ?-Ricker, are shown to account for asymmetric patterns of population growth for 27 species of Drosophila and for a variety of other organisms, where the data were derived from the literature. These models are developed so as

Mark J. Pomerantz; William R. Thomas; Michael E. Gilpin

1980-01-01

222

Genetic variability in a population of arbuscular mycorrhizal fungi causes variation in plant growth  

E-print Network

and diversity. Effects of within-AMF species or within-population variation on plant growth have received less, genetic diversity, Glomus intraradices, intraspecific variation, plant growth, population, symbiosis and increase plant diversity (Grime et al. 1987; Newsham et al. 1995; Smith & Read 1997). Inoculation

Alvarez, Nadir

223

Growth rates and size at metamorphosis of high elevation populations of Ambystoma tigrinum  

Microsoft Academic Search

The role of temperature in determining the alternative life history sequences in high elevation populations of Ambystoma tigrinum is given a physiological base. Growth rates of larval populations increase with increased average pond temperatures whereas sizes of the larvae at metamorphosis decrease with increased average pond temperatures. This results in a negative correlation between growth rate and size at metamorphosis

John R. Bizer

1978-01-01

224

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

PubMed

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

Sinervo, B

1990-06-01

225

Taking Exception. Reduced mortality leads to population growth: an inconvenient truth.  

PubMed

Reduced mortality has been the predominant cause of the marked global population growth over the last 3/4 of a century. While improved child survival increases motivation to reduce fertility, it comes too little and too late to forestall substantial population growth. And, beyond motivation, couples need effective means to control their fertility. It is an inconvenient truth that reducing child mortality contributes considerably to the population growth destined to compromise the quality of life of many, particularly in sub-Saharan Africa. Vigorous child survival programming is of course imperative. Wide access to voluntary family planning can help mitigate that growth and provide many other benefits. PMID:25276571

Shelton, James D

2014-05-01

226

Whither the global population problem  

Microsoft Academic Search

Growth of the human population has been underway for thousands of years and was never a problem until recently. It is now expanding exponentially, and today global population stands at nearly 6 billion with 97 million being added each year. Currently, overpopulation has led to serious social and environmental problems such as poverty, overcrowded slums, crime, terrorism, pollution of air

Roy O. Greep

1998-01-01

227

Habitat heterogeneity affects population growth in goshawk Accipiter gentilis  

Microsoft Academic Search

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

Oliver Kruger; Jan Lindstrom

2001-01-01

228

Recent Population Growth and Change among Asian-Americans.  

ERIC Educational Resources Information Center

Data from the 1990 Census and recent Current Population Survey reports are used to describe population change among Asian-Americans. Comparisons are made between Asian-Americans and the general non-Asian population and among Asian-Americans, focusing on four subgroups: Chinese, Filipinos, Japanese, and Koreans. Specific features examined in…

Vann, Barbara H.; Ryu, Jai P.

229

Composite waves for a cell population system modelling tumor growth and invasion  

E-print Network

Composite waves for a cell population system modelling tumor growth and invasion Min Tang Nicolas coefficient . The right hand side (, ) is the growth term; it expresses that cells divide freely, thus The recent biomechanical theory of cancer growth considers solid tumors as liquid-like materials comprising

Paris-Sud XI, Université de

230

POPULATION AND COMMUNITY ECOLOGY Growth and Survival of Invasive Aedes albopictus Larvae on  

E-print Network

POPULATION AND COMMUNITY ECOLOGY Growth and Survival of Invasive Aedes albopictus Larvae oak. The linear model for the growth rate (deÞned by larval head width) showed a positive slope. In the persimmon oak combination, as the ratio of persimmon to oak increased, the growth rates of the larvae

231

Examining Perceptions of Rapid Population Growth in North and South Gondar Zones, Northwest Ethiopia  

Microsoft Academic Search

Ethiopia is one of the most populous countries in Africa and ranks second only to Nigeria. Rapid population growth has hampered the country's development, making the eradication of extreme poverty and hunger difficult. This study which had two components—quantitative and qualitative—was aimed at exploring the perceptions of women and other social groups on the prevailing population pressures. The quantita- tive

Getu Degu Alene; Alemayehu Worku

2009-01-01

232

Life-History and Spatial Determinants of Somatic Growth Dynamics in Komodo Dragon Populations  

PubMed Central

Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world’s largest lizard the Komodo dragon (Varanus komodoensis). The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs) and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species. PMID:23028983

Laver, Rebecca J.; Purwandana, Deni; Ariefiandy, Achmad; Imansyah, Jeri; Forsyth, David; Ciofi, Claudio; Jessop, Tim S.

2012-01-01

233

Life-history and spatial determinants of somatic growth dynamics in Komodo dragon populations.  

PubMed

Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world's largest lizard the Komodo dragon (Varanus komodoensis). The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs) and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species. PMID:23028983

Laver, Rebecca J; Purwandana, Deni; Ariefiandy, Achmad; Imansyah, Jeri; Forsyth, David; Ciofi, Claudio; Jessop, Tim S

2012-01-01

234

Current and Future Dynamics of the Red-Cockaded Woodpecker Population Inhabiting the Savannah River National Environmental Research Park: Managing For Population Growth  

SciTech Connect

Research aimed to study the dynamics of the SRS population of Red-Cockaded woodpecker and compare to those of other populations to identify factors limiting population growth; recruitment clusters were evaluated to determine what properties of individual cavity trees, surrounding habitat and the surrounding landscape might limit occupancy through natural dispersal. A spatial simulation model was used to project expected dispersal rates and population growth under current conditions and compare those estimates to observed dispersal and population growth. Red cockaded woodpecker populations at SRS are stable considering size. Research reveals that closer placement of recruitment clusters to active territories would produce higher growth rates while decreasing management intensity.

Walters, J.R.; Taylor, T.B.; Daniels, S.J.; Crowder, L.B.; Pridd, J.A.

2001-01-01

235

Understanding contributions of cohort effects to growth rates of fluctuating populations.  

PubMed

1. Understanding contributions of cohort effects to variation in population growth of fluctuating populations is of great interest in evolutionary biology and may be critical in contributing towards wildlife and conservation management. Cohort-specific contributions to population growth can be evaluated using age-specific matrix models and associated elasticity analyses. 2. We developed age-specific matrix models for naturally fluctuating populations of stoats Mustela erminea in New Zealand beech forests. Dynamics and productivity of stoat populations in this environment are related to the 3-5 year masting cycle of beech trees and consequent effects on the abundance of rodents. 3. The finite rate of increase (lambda) of stoat populations in New Zealand beech forests varied substantially, from 1.98 during seedfall years to 0.58 during post-seedfall years. Predicted mean growth rates for stoat populations in continuous 3-, 4- or 5-year cycles are 0.85, 1.00 and 1.13. The variation in population growth was a consequence of high reproductive success of females during seedfall years combined with low survival and fertility of females of the post-seedfall cohort. 4. Variation in population growth was consistently more sensitive to changes in survival rates both when each matrix was evaluated in isolation and when matrices were linked into cycles. Relative contributions to variation in population growth from survival and fertility, especially in 0-1-year-old stoats, also depend on the year of the cycle and the number of transitional years before a new cycle is initiated. 5. Consequently, management strategies aimed at reducing stoat populations that may be best during one phase of the beech seedfall cycle may not be the most efficient during other phases of the cycle. We suggest that management strategies based on elasticities of vital rates need to consider how population growth rates vary so as to meet appropriate economic and conservation targets. PMID:17714273

Wittmer, Heiko U; Powell, Roger A; King, Carolyn M

2007-09-01

236

Four centuries of British economic growth: the roles of technology and population  

Microsoft Academic Search

Using long historical data for Britain over the period 1620–2006, this paper seeks to explain the importance of innovative\\u000a activity, population growth and other factors in inducing the transition from the Malthusian trap to the post-Malthusian growth\\u000a regime. Furthermore, the paper tests the ability of two competing second-generation endogenous growth models to account for\\u000a the British growth experience. The results

Jakob B. Madsen; James B. Ang; Rajabrata Banerjee

2010-01-01

237

Climatic change and Chinese population growth dynamics over the last millennium  

Microsoft Academic Search

The climate–population relationship has long been conceived. Although the topic has been repeatedly investigated, most of\\u000a the related works are Eurocentric or qualitative. Consequently, the relationship between climate and population remains ambiguous.\\u000a In this study, fine-grained temperature reconstructions and historical population data sets have been employed to statistically\\u000a test a hypothesized relationship between temperature change and population growth (i.e., cooling

Harry F. Lee; Lincoln Fok; David D. Zhang

2008-01-01

238

Review of "Going Exponential: Growing the Charter School Sector's Best"  

ERIC Educational Resources Information Center

This Progressive Policy Institute report argues that charter schools should be expanded rapidly and exponentially. Citing exponential growth organizations, such as Starbucks and Apple, as well as the rapid growth of molds, viruses and cancers, the report advocates for similar growth models for charter schools. However, there is no explanation of…

Garcia, David

2011-01-01

239

Population Growth and Policies in Mega-Cities. Sao Paulo.  

ERIC Educational Resources Information Center

This document is one in a series of studies that focus on the population policies and plans of a number of mega-cities in developing countries. The object of the series is to examine the formulation, implementation, and evaluation of the population policies of mega-cities from a broad perspective, emphasizing the reciprocal links between…

United Nations New York, NY. Dept. of Economic and Social Information and Policy Analysis.

240

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

ERIC Educational Resources Information Center

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…

Siegler, Theodore R.

241

Attached growth of Sphaerotilus and mixed populations in a continuous-flow apparatus.  

PubMed

The effects of NH(4)Cl concentration, organic nitrogen compounds, glucose concentration, dissolved oxygen concentration, and flow rate on the attached growth of pure cultures of Sphaerotilus natans and of a mixed population in a continuous-flow apparatus are described. Low concentrations of NH(4)Cl and oxygen, and high flow rates resulted in attached populations that were dominated by Sphaerotilus. The conditions that allowed maximal attached growth in pure culture did not correspond to the conditions that promoted attached growth of Sphaerotilus in a mixed population. PMID:4877499

Dias, F F; Dondero, N A; Finstein, M S

1968-08-01

242

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

PubMed

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

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

2012-11-01

243

Calculating second derivatives of population growth rates for ecology and evolution  

PubMed Central

1. Second derivatives of the population growth rate measure the curvature of its response to demographic, physiological or environmental parameters. The second derivatives quantify the response of sensitivity results to perturbations, provide a classification of types of selection and provide one way to calculate sensitivities of the stochastic growth rate. 2. Using matrix calculus, we derive the second derivatives of three population growth rate measures: the discrete-time growth rate ?, the continuous-time growth rate r = log ? and the net reproductive rate R0, which measures per-generation growth. 3. We present a suite of formulae for the second derivatives of each growth rate and show how to compute these derivatives with respect to projection matrix entries and to lower-level parameters affecting those matrix entries. 4. We also illustrate several ecological and evolutionary applications for these second derivative calculations with a case study for the tropical herb Calathea ovandensis.

Shyu, Esther; Caswell, Hal

2014-01-01

244

POPULATION ECOLOGY Divergent compensatory growth responses within species  

E-print Network

; 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

Hutchings, Jeffrey A.

245

An Exceptional Exponential Function  

ERIC Educational Resources Information Center

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…

Curgus, Branko

2006-01-01

246

Nutrition, Population Growth and the Industrial Revolution in England  

Microsoft Academic Search

Argues that the improvements in nutritional status of the English population in the 1730s was instrumental in the demographic and industrial revolution that started a generation later when those birth cohorts reached adulthood.

John Komlos

247

Population growth of Yellowstone grizzly bears: uncertainty and future monitoring  

E-print Network

(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

Harris, Richard B.

248

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

PubMed Central

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

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

2013-01-01

249

Population Growth and Affluence: The Fissioning of Human Society. Caltech Population Program Occasional Papers, Series 1, Number 9.  

ERIC Educational Resources Information Center

This paper compares population growth and affluence in developed nations in which per capita income and consumption have been relatively high, and in developing nations in which per capita income and consumption have been relatively low. The paper is one in a series of occasional publications intended to increase understanding of the…

Brown, Harrison

250

Survival, Recruitment, and Population Growth Rate of an Important Mesopredator: The Northern Raccoon  

PubMed Central

Populations of mesopredators (mid-sized mammalian carnivores) are expanding in size and range amid declining apex predator populations and ever-growing human presence, leading to significant ecological impacts. Despite their obvious importance, population dynamics have scarcely been studied for most mesopredator species. Information on basic population parameters and processes under a range of conditions is necessary for managing these species. Here we investigate survival, recruitment, and population growth rate of a widely distributed and abundant mesopredator, the northern raccoon (Procyon lotor), using Pradel’s temporal symmetry models and >6 years of monthly capture-mark-recapture data collected in a protected area. Monthly apparent survival probability was higher for females (0.949, 95% CI?=?0.936–0.960) than for males (0.908, 95% CI?=?0.893–0.920), while monthly recruitment rate was higher for males (0.091, 95% CI?=?0.078–0.106) than for females (0.054, 95% CI?=?0.042–0.067). Finally, monthly realized population growth rate was 1.000 (95% CI?=?0.996–1.004), indicating that our study population has reached a stable equilibrium in this relatively undisturbed habitat. There was little evidence for substantial temporal variation in population growth rate or its components. Our study is one of the first to quantify survival, recruitment, and realized population growth rate of raccoons using long-term data and rigorous statistical models. PMID:24901349

Troyer, Elizabeth M.; Cameron Devitt, Susan E.; Sunquist, Melvin E.; Goswami, Varun R.; Oli, Madan K.

2014-01-01

251

Survival, recruitment, and population growth rate of an important mesopredator: the northern raccoon.  

PubMed

Populations of mesopredators (mid-sized mammalian carnivores) are expanding in size and range amid declining apex predator populations and ever-growing human presence, leading to significant ecological impacts. Despite their obvious importance, population dynamics have scarcely been studied for most mesopredator species. Information on basic population parameters and processes under a range of conditions is necessary for managing these species. Here we investigate survival, recruitment, and population growth rate of a widely distributed and abundant mesopredator, the northern raccoon (Procyon lotor), using Pradel's temporal symmetry models and >6 years of monthly capture-mark-recapture data collected in a protected area. Monthly apparent survival probability was higher for females (0.949, 95% CI = 0.936-0.960) than for males (0.908, 95% CI = 0.893-0.920), while monthly recruitment rate was higher for males (0.091, 95% CI = 0.078-0.106) than for females (0.054, 95% CI = 0.042-0.067). Finally, monthly realized population growth rate was 1.000 (95% CI = 0.996-1.004), indicating that our study population has reached a stable equilibrium in this relatively undisturbed habitat. There was little evidence for substantial temporal variation in population growth rate or its components. Our study is one of the first to quantify survival, recruitment, and realized population growth rate of raccoons using long-term data and rigorous statistical models. PMID:24901349

Troyer, Elizabeth M; Cameron Devitt, Susan E; Sunquist, Melvin E; Goswami, Varun R; Oli, Madan K

2014-01-01

252

[The relationships between population growth and environment: from doctrinal to empirical].  

PubMed

This work provides a brief review of changing attitudes toward population growth, the environment, and economic development, and summarizes the major theoretical doctrines concerning the interrelations between rapid population growth and environmental damage and results of research on the topic. The general optimism about the prospects for progress in the Southern hemisphere of the 1950s and 1960s gave way to greater skepticism and recognition of problems in the 1970s. The creation of the UN Population Fund in 1969 and the UN Environmental Program in 1972 reflected increasing concern in the international community about demographic growth and environmental degradation in the south. Economic and social conditions appeared to worsen in the 1980s, with the recession and structural adjustment programs having a disproportionate impact on the most destitute. New integrating concepts and paradigms including that of sustainable development arose in this context of profound crisis in many Third World economics and societies. The most widely accepted position on the connection between population growth and environmental degradation since the late 1970s has been a nuanced neo-Malthusian approach which sees demographic pressure not as the direct cause of environmental problems, but as an aggravating factor. The slowing of population growth is viewed as 1 element in an overall strategy that also includes encouragement of development and elimination of poverty. The extreme positions that rapid population growth is the major cause of environmental degeneration or that population growth has little actual effect on the environment have been largely abandoned. The impact of population growth on the environment can be analyzed at the global, regional, or local level. On the global level, there is agreement that 2 major factors responsible for environmental deterioration are the model of economic development followed in the Northern countries and the poverty of much of the population in the Southern countries. Quantitative studies have been unable to demonstrate at the global level that demographic growth has a primordial effect on the environment. The ecological consequences of poverty cannot be reduced without attacking poverty itself, of which high fertility is but 1 aspect. A growing but still insufficient number of smaller scale studies suggest that demographic growth is not always the major element in environmental damage or in preventable exhaustion of resources. Specific studies are needed on well-defined populations in order to unravel the effects of population growth and other factors. The approach should be systemic and transdisciplinary, depending on a less fragmented vision of reality than that reflected in traditional disciplinary boundaries. PMID:12343873

Tabutin, D; Thiltges, E

1992-01-01

253

A heterogeneous population model for the analysis of bacterial growth kinetics  

Microsoft Academic Search

A two-compartment, heterogeneous population model (HPM) was derived using the simulation software SB ModelMaker© to describe the growth of Listeria monocytogenes in bacteriological media at 5–35 °C. The model assumed that, at time t = 0, the inoculum was distributed between two distinct compartments, Non-Growing and Growing, and that growth could be described by four parameters: initial total cell population

R. C. McKellar

1997-01-01

254

Flower Power: Sunflowers as a Model for Logistic Growth  

ERIC Educational Resources Information Center

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,…

Fernandez, Eileen; Geist, Kristi A.

2011-01-01

255

A Non-phenomenological Model of Competition and Cooperation to Explain Population Growth Behaviors.  

PubMed

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

Ribeiro, Fabiano L

2015-03-01

256

Deletion of the Escherichia coli pseudouridine synthase gene truB blocks formation of pseudouridine 55 in tRNA in vivo, does not affect exponential growth, but confers a strong selective disadvantage in competition with wild-type cells.  

PubMed Central

Previous work from this laboratory (Nurse et al., RNA, 1995, 1:102-112) established that TruB, a pseudouridine (psi) synthase from Escherichia coli, was able to make psi55 in tRNA transcripts but not in transcripts of full-length or fragmented 16S or 23S ribosomal RNAs. By deletion of the truB gene, we now show that TruB is the only protein in E. coli able to make psi55 in vivo. Lack of TruB and psi55 did not affect the exponential growth rate but did confer a strong selective disadvantage on the mutant when it was competed against wild-type. The negative selection did not appear to be acting at either the exponential or stationary phase. Transformation with a plasmid vector conferring carbenicillin resistance and growth in carbenicillin markedly increased the selective disadvantage, as did growth at 42 degrees C, and both together were approximately additive such that three cycles of competitive growth sufficed to reduce the mutant strain to approximately 0.2% of its original value. The most striking finding was that all growth effects could be reversed by transformation with a plasmid carrying a truB gene coding for a D48C mutation in TruB. Direct analysis showed that this mutant did not make psi55 under the conditions of the competition experiment. Therefore, the growth defect due to the lack of TruB must be due to the lack of some other function of the protein, possibly an RNA chaperone activity, but not to the absence of psi55. PMID:11142385

Gutgsell, N; Englund, N; Niu, L; Kaya, Y; Lane, B G; Ofengand, J

2000-01-01

257

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

USGS Publications Warehouse

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.

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

2007-01-01

258

Population growth of Mexican free-tailed bats (Tadarida brasiliensis mexicana) predates human agricultural activity  

PubMed Central

Background Human activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although many species have suffered population declines, increased population fragmentation, or even extinction in connection with these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed to the widespread expansion of agriculture in North America following European settlement. Colonies of T. b. mexicana are extremely large (~106 individuals) and, in the modern era, major agricultural insect pests form an important component of their food resource. It is thus hypothesized that the growth of these insectivorous bat populations was coupled to the expansion of agricultural land use in North America over the last few centuries. Results We sequenced one haploid and one autosomal locus to determine the rate and time of onset of population growth in T. b. mexicana. Using an approximate Maximum Likelihood method, we have determined that T. b. mexicana populations began to grow ~220 kya from a relatively small ancestral effective population size before reaching the large effective population size observed today. Conclusions Our analyses reject the hypothesis that T. b. mexicana populations grew in connection with the expansion of human agriculture in North America, and instead suggest that this growth commenced long before the arrival of humans. As T. brasiliensis is a subtropical species, we hypothesize that the observed signals of population growth may instead reflect range expansions of ancestral bat populations from southern glacial refugia during the tail end of the Pleistocene. PMID:21457563

2011-01-01

259

Molecular-Level Variation Affects Population Growth in a Butterfly Metapopulation  

PubMed Central

The dynamics of natural populations are thought to be dominated by demographic and environmental processes with little influence of intraspecific genetic variation and natural selection, apart from inbreeding depression possibly reducing population growth in small populations. Here we analyse hundreds of well-characterised local populations in a large metapopulation of the Glanville fritillary butterfly (Melitaea cinxia), which persists in a balance between stochastic local extinctions and recolonisations in a network of 4,000 discrete habitat patches. We show that the allelic composition of the glycolytic enzyme phosphoglucose isomerase (Pgi) has a significant effect on the growth of local populations, consistent with previously reported effects of allelic variation on flight metabolic performance and fecundity in the Glanville fritillary and Colias butterflies. The strength and the sign of the molecular effect on population growth are sensitive to the ecological context (the area and spatial connectivity of the habitat patches), which affects genotype-specific gene flow and the influence of migration on the dynamics of local populations. The biological significance of the results for Pgi is underscored by lack of any association between population growth and allelic variation at six other loci typed in the same material. In demonstrating, to our knowledge for the first time, that molecular variation in a candidate gene affects population growth, this study challenges the perception that differential performance of individual genotypes, leading to differential fitness, is irrelevant to population dynamics. These results also demonstrate that the spatial configuration of habitat and spatial dynamics of populations contribute to maintenance of Pgi polymorphism in this species. PMID:16620151

Saccheri, Ilik

2006-01-01

260

Exponential splines: A survey  

SciTech Connect

Herein, we discuss a generalization of the semiclassical cubic spline known in the literature as the exponential spline. In actuality, the exponential spline represents a continuum of interpolants ranging from the cubic spline to the linear spline. A particular member of this family is uniquely specified by the choice of certain {open_quotes}tension{close_quotes} parameters. We first outline the theoretical underpinnings of the exponential spline. This development roughly parallels the existing theory for cubic splines. The primary extension lies in the ability of the exponential spline to preserve convexity and monotonicity present in the data. We next discuss the numerical computation of the exponential spline. A variety of numerical devices are employed to produce a stable and robust algorithm. An algorithm for the selection of tension parameters that will produce a shape preserving approximant is developed. A sequence of selected curve-fitting examples are presented which clearly demonstrate the advantages of exponential splines over cubic splines. We conclude with a consideration of the broad spectrum of possible uses of exponential splines in the applications. Our primary emphasis is on computational fluid dynamics although the imaginative reader will recognize the wider generality of the techniques developed.

McCartin, B.J.

1996-12-31

261

SUITABILITY OF SELECTED CROPS AND SOIL FOR GARDEN SYMPHYLAN (SYMPHYLA, SCUTIGERELLIDAE: SCUTIGERELLA IMMACULATA NEWPORT) POPULATION GROWTH  

Technology Transfer Automated Retrieval System (TEKTRAN)

The suitability of selected crops and soil for garden symphylan (Scutigerella immaculata Newport) population growth was studied in the laboratory and field. In the laboratory, we measured the population increase of S. immaculata after 8 w from a starting density of 35 in pots of spinach (Spinacia o...

262

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

E-print Network

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

Mitchell, Mike

263

Establishment and Seedling Growth of Big Bluestem and Switchgrass Populations Divergently Selected for Seedling Tiller Number  

Microsoft Academic Search

development, plant growth, and field establishment of big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum tional stage, that period of flux between the two stages, is L.) populations that were developed by divergent selection for seed- when seedling failure is most likely. A selection criterion ling tiller number while selecting for high shoot weight. Six populations that theoretically integrates

Alexander J. Smart; Lowell E. Moser; Kenneth P. Vogel

2003-01-01

264

Global health action on a crowded Earth: Bay Area perspectives on population growth,  

E-print Network

Global health action on a crowded Earth: Bay Area perspectives on population growth, environment, and political instability--we must continue finding innovative ways to achieve global health goals. Population to booming metropolises, there is a need for transdisciplinary and collaborative global health action

Derisi, Joseph

265

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...

266

November 2003 / Vol. 53 No. 11 BioScience 1069 Human population growth and increased water  

E-print Network

November 2003 / Vol. 53 No. 11 BioScience 1069 Articles Human population growth and increased water area for potential expansion of human populations, often have more challenging water resource problems lost because of over- pumping and subsequentsaltwater intrusion (e.g.,Hunterand Arbona 1995

Benstead, Jon

267

Ecology of Children’s Growth: An Example from Transitional Populations of the Brazilian Amazon  

Microsoft Academic Search

The intense environmental and social changes taking place in Amazonia make this a key area for health studies of populations transitioning to a cosmopolitan lifestyle and market economy. Caboclos are among those populations. They comprise the majority of rural Brazilian Amazon peoples. At present there is limited information about their patterns of growth and health. In this paper, anthropometric data

Hilton P. Silva; Douglas E. Crews

2006-01-01

268

On the structure-bounded growth processes in plant populations.  

PubMed

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

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

2010-07-01

269

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

PubMed Central

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

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

2014-01-01

270

World Bank Atlas: Population, Per Capita Product and Growth Rates.  

ERIC Educational Resources Information Center

The ninth edition of the World Bank Atlas shows estimates of population, gross national product, and per capita production of 189 countries and territories for 1972. The data presented in the atlas are the result of the work of the World Bank Group whose major purpose is to provide both financial and technical assistance and to improve the living…

World Bank, Washington, DC.

271

Localization and Extinction of Bacterial Populations under Inhomogeneous Growth Conditions  

Microsoft Academic Search

The transition from localized to systemic spreading of bacteria, viruses, and other agents is a fundamental problem that spans medicine, ecology, biology, and agriculture science. We have conducted experiments and simulations in a simple one-dimensional system to determine the spreading of bacterial populations that occurs for an inhomogeneous environment under the influence of external convection. Our system consists of a

Anna L. Lin; Bernward A. Mann; Gelsy Torres-Oviedo; Bryan Lincoln; Josef Käs; Harry L. Swinney

2004-01-01

272

Impact of Population Growth on Food Supplies and Environment  

Microsoft Academic Search

As the world population continues to grow geometrically, great pressure is being placed on arable land, water, energy, and biological resources to provide an adequate supply of food while maintaining the integrity of our ecosystem. According to the World Bank and the United Nations, from 1 to 2 billion humans are now malnourished, indicating a combination of insufficient food, low

David Pimentel; Xuewen Huang; Ana Cordova; Marcia Pimentel

1997-01-01

273

Exponential Cardassian Universe  

E-print Network

The expectation of explaining cosmological observations without requiring new energy sources is forsooth worthy of investigation. In this letter, a new kind of Cardassian models, called exponential Cardassian models, for the late-time universe are investigated in the context of the spatially flat FRW universe scenario. We fit the exponential Cardassian models to current type Ia supernovae data and find they are consistent with the observations. Furthermore, we point out that the equation-of-state parameter for the effective dark fluid component in exponential Cardassian models can naturally cross the cosmological constant divide $w=-1$ that observations favor mildly without introducing exotic material that destroy the weak energy condition.

Dao-jun Liu; Chang-bo Sun; Xin-zhou Li

2006-01-25

274

Population growth of Mexican free-tailed bats ( Tadarida brasiliensis mexicana ) predates human agricultural activity  

Microsoft Academic Search

Background  Human activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although\\u000a many species have suffered population declines, increased population fragmentation, or even extinction in connection with\\u000a these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population\\u000a growth in an insectivorous bat (Tadarida brasiliensis mexicana) can

Amy L Russell; Murray P Cox; Veronica A Brown; Gary F McCracken

2011-01-01

275

Rapid population growth and fragile environments: the sub-Saharan African and south Asian experience.  

PubMed

Case studies of the world's two poorest regions, sub-Saharan Africa and South Asia, were used to illustrate the compromised standard of living of the poor and environmental damage due to continued rapid population growth. The conclusion was that the livelihoods of the poor should not be endangered for preserving the living standards of richer people. Nations must not ignore the challenges of reducing population growth as fast as can be achieved. The transitional period over the next 50 years is the main concern, because population growth rates will be slowing. Rural population growth is expected to decline from 60% of total population growth in South Asia to 7% between 2000 and 2025; similarly the decline in sub-Saharan Africa would be from 50% to 15%. Over the past 30 years, food production in South Asia has kept pace with population growth. Sub-Saharan Africa has adopted food importation to meet demand. African problems are a low resource base, faster population growth, and the fact that governments and individuals are too poor to maintain soil fertility. Long-term studies of how much soil depletion will occur are not available for these regions, and local area studies are not as pessimistic. Transition policies are needed to put "people first in terms of engineered or directed population and ecological change." The six main issues are the following: 1) the Brundtland Commission appropriately identified poverty as the main cause and effect of environmental degradation because of the threat to survival; 2) the verdict is still out about whether food production will keep pace with population growth through economic growth and investment in agriculture; 3) empirical research is needed to examine local social and regulatory institutions and the possibility of reinforcing these mechanisms rather than instituting central controls; 4) central coercion or modernizing economic policies can destroy local level controls; 5) famine is a complex ecological phenomenon and the product of political mismanagement and civil disorder; 6) deforestation is as important an issue as protection of the livelihoods of forest populations. Case studies were provided for Ekiti district of Nigeria, the West and East African Savannahs, Karnataka state in South India, arid South Asia, and Nepal. The protection of the most fragile environments subject to population pressure can be managed with respect for human dignity through general economic development and external assistance. PMID:8154727

Caldwell, J C; Caldwell, P

1994-02-18

276

Population and prehistory I: Food-dependent population growth in constant environments  

Microsoft Academic Search

We present a demographic model that describes the feedbacks between food supply, human mortality and fertility rates, and labor availability in expanding populations, where arable land area is not limiting. This model provides a quantitative framework to describe how environment, technology, and culture interact to influence the fates of preindustrial agricultural populations. We present equilibrium conditions and derive approximations for

Charlotte T. Lee; Shripad Tuljapurkar

2008-01-01

277

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

ERIC Educational Resources Information Center

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…

Goudy, Willis

2002-01-01

278

Exponential Graphing Using Technology  

NSDL National Science Digital Library

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.

Cheryl Gaynr

2012-07-27

279

Increased population growth rate in invasive polyploid Centaurea stoebe in a common garden.  

PubMed

Biological invasions are inherently demographic processes, but trait differences between native and introduced genotypes are rarely linked to population growth rates. Native European Centaurea stoebe occurs as two cytotypes with different life histories (monocarpic diploids, polycarpic tetraploids); however, only tetraploids have been found in its introduced range in North America. In a common garden experiment using artificial populations, we compared the demographic performance of the three geo-cytotypes in the presence and absence of a specialist herbivore using periodic matrix models. We found no difference in population growth rate between the two European cytotypes and no significant effects of herbivory in all geo-cytotypes. However, there was a pronounced increase in population growth rate for North American compared with European tetraploids due to increased seed production and juvenile establishment. These results suggest that genetic drift or rapid evolution, rather than pre-adaptation through polyploidy may explain the invasion success of tetraploids. PMID:22727026

Hahn, Min A; Buckley, Yvonne M; Müller-Schärer, Heinz

2012-09-01

280

Population growth rate determinants for Arbacia: Evaluating ecological relevance of toxicity test endpoints  

SciTech Connect

A population dynamics model for the sea urchin, Arbacia punctulata, was recently developed incorporating life stage endpoints frequently measured in acute and chronic toxicity studies. Model elasticity analysis was used to demonstrate that population growth rate was influenced most by adult survival and least by early life stage success, calling into question the ecological relevance of results from standardized Arbacia fertilization and larval development toxicity tests. Two approaches were used to continue this evaluation. Actual and hypothetical dose-response curves for toxicant exposures over multiple life stages were used to evaluate contributions to population growth rate of stage-specific toxicant effects. Additionally, relationships between critical life stages were developed from laboratory data for Arbacia. The results of this analysis underscore the importance of understanding both endpoint sensitivity to toxicants and sensitivity of population growth rate to test endpoints in determining the ecological relevance of toxicity tests results.

Nacci, D.; Gleason, T.; Munns, W.R. Jr. [Environmental Protection Agency, Narragansett, RI (United States). Environmental Research Lab.

1995-12-31

281

The changing face of the Australian population: growth in centenarians.  

PubMed

At the time of the 2006 Census, there were 3154 centenarians in Australia, 797 men (25%) and 2357 women (75%). This number is expected to increase to 12,000 by 2020. In Australia we are experiencing a demographic transition in which the proportions of people in the oldest age groups are increasing while the proportions in the youngest age groups are decreasing. Centenarians are the fastest growing age segment of the Australian population. Their numbers have increased by 8.5% per year over the past 25 years. In 2006, they represented 0.12% (3154/2,644,469) of the population aged 65 years and over. More than half of centenarians live in private dwellings, with 27% of men and 14% of women living on their own. Government policies are starting to address the issues of an ageing population, including provisions for financial support, improved access to medical services, and appropriate housing and transport facilities. However, we need specific social, medical and financial estimates of the impact of living to 100 years and beyond. PMID:18558896

Richmond, Robyn L

2008-06-16

282

An Unusual Exponential Graph  

NASA Astrophysics Data System (ADS)

This paper is an addition to the series of papers on the exponential function begun by Albert Bartlett. In particular, we ask how the graph of the exponential function y =e-t/? would appear if y were plotted versus ln t rather than the normal practice of plotting ln y versus t. In answering this question, we find a new way to interpret the mean life (or time constant) ? using such a linear-log graph.

Syed, M. Qasim; Lovatt, Ian

2014-05-01

283

An Unusual Exponential Graph  

ERIC Educational Resources Information Center

This paper is an addition to the series of papers on the exponential function begun by Albert Bartlett. In particular, we ask how the graph of the exponential function y = e[superscript -t/t] would appear if y were plotted versus ln t rather than the normal practice of plotting ln y versus t. In answering this question, we find a new way to…

Syed, M. Qasim; Lovatt, Ian

2014-01-01

284

Strongly exponential symmetric spaces  

E-print Network

We study the exponential map of connected symmetric spaces and characterize, in terms of midpoints and of infinitesimal conditions, when it is a diffeomorphism, generalizing the Dixmier-Saito theorem for solvable Lie groups. We then give a geometric characterization of the (strongly) exponential solvable symmetric spaces as those spaces for which every triangle admits a unique double triangle. This work is motivated by Weinstein's quantization by groupoids program applied to symmetric spaces.

Yannick Voglaire

2014-04-06

285

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

USGS Publications Warehouse

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.

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

2011-01-01

286

[Effect of the population density on growth and regeneration in the snail Achatina fulica].  

PubMed

In the laboratory, the growth rate of the giant African snail Achatina fulica, as estimated by the weight and shell length was shown to decrease when the population density increased from 10 to 60 snails/m2 of the total terrarium area for five months. In the second experiment, when the population density increased from 48 to 193 snails/m2, the growth rate had already decreased by six weeks. In the groups with a high population density the feeding behavior was weakened, expressed by a greater amount of nonconsumed food, according to visual observations, than in the groups with lower population densities. At the population density of 10 to 60 snails/m2, the proliferative activity in the course of the optic tentacle regeneration, as expressed by the mitotic index, did not differ reliably within five months. In the second experiment, the mitotic indices at the population densities of 96 and 193 snails/m2 within 1.5 months exceeded that of 48 snails/m2. Recommendations are given concerning the population density from the viewpoint of commercial growth of the snails. It was proposed that, based on the analysis of the mechanism underlying the inhibition of feeding behavior in populations with extra high densities, one may develop a new approach to the production of chemical agents to control land snails as agricultural pests. PMID:11042956

Sidel'nikov, A P; Stepanov, I I

2000-01-01

287

Genetic parameter estimation in seedstock Swine population for growth performances.  

PubMed

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

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

288

On the relationship between population growth and social and economic development.  

PubMed

China's population has grown rapidly since 1949, reaching a size of 1,008,170,000 by 1982. Rapid population growth has been encouraged by a high birth rate coupled with low mortality, traditional preference for sons, and the incorrect assumption that man is only a producer and not a consumer. Rapid population growth directly decreases economic development while producing a rapidly increasing labor force requiring an increase in the number of jobs available. Population growth has already reduced arable land from 3 MN in 1949 to 1.5 MN at present and can also cause sanitation and pollution problems. Only by adopting family plnning and the 1 child family can China gradually slow population growth to correspond with economic development; then the state will be able to improve health care and education and, therefore, population quality. China's population policy is not one of NeoMalthusianism, which advocates birth control and late marriage, and assumes the existence of a capitalist system and does not apply to communist systems. Malthus may have attempted to absolve the nourgeoisie from all blame by aiming his preaching against blind reproduction at the poor; he thought that overpopulation would be reduced by pestilence, war, and famine. Protecting capitalism motivated Malthus and other capitalists, but the Chinese want to promote economic development. Marx has refuted Malthus' views on population. While Chinese population policy and NeoMalthusianism agree on advocating birth control and late marriage, their underlying philosophies are different. The author supports laws and policies on fertility and family planning, and feels that population scientists must be involved in all aspects--study, propaganda, and education--relating to family planning. PMID:12313980

Xu, D

1983-01-01

289

Population growth and the enclosure movement in Ankole, Uganda.  

PubMed

There is a rush for people to fence their land in West and East Ankole, Uganda, and fenced fields now represent close to 15% of the total land area and 30% of the area that is used for grazing. Since fencing is allowed only after a person is in possession of a valid land title, the acceptance of this innovation means the acceptance of noncustomary tenurial arrangements in the area. This paper contends that the primary drive of the fencing movement is insecurity about land. This insecurity is the outcome of the rapid increase of both the human and livestock population of the area. Discussion covers the land and the people, contemporary land tenure systems, the enclosure movement, land pressure, and the rise of modern pastoralism. The 2 districts of West and East Ankole comprise a total land area of 16,182 km; roughly 1000 km of this is classified as forest and game reserve. In general a typical landholding of an individual in West Ankole is about 2 hectares and is roughly equally divided between perennial and annual crops. Land in Ankole is either privately held or is vested in the Public Land Commission. Privately held land falls into 2 major categories: land can be surveyed, registered, and then granted as either freehold or leasehold. Freehold land in Ankole is of 3 main types: grants or freehold land can be made out to each of the religious sects in the area; grants of freehold land can be made to individuals out of what is commonly referred to as "Mailo" land; privately held land under lease from the Uganda Public Land Commission, or prior to independence from the British Crown. The bulk of Ankole land is held under what is commonly referred to as customary tenure. Under this arrangement, all the land is vested in the Uganda Public Land Commission, which acts as an umbrella under whose protection land is freely used as the customs of the Banyankore stipulate. Over the past decade, Ankole has experienced a marked increase in its human population. The population increased from 530,000 in 1959 to more than 1 million in 1974. Migration as well as natural increase has been a significant factor. The rapid increase of population in Ankole has resulted in considerable densities in several localities. Due to increases both in the human and livestock populations, incidents of land pressure in the area have become quite common. Several people feel insecure about land. Individuals who have ample land around them are fencing it since this is the way that fields can go fallow and pasturage ensured. In most instances fencing is being carried out on land where signs of effective ownership do not exist. There is also a realization that through segregated grazing that better quality animals can be obtained. PMID:12265055

Muwonge, J W

1978-01-01

290

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

PubMed

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

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

2013-06-01

291

Growth and population size of crayfish in headwater streams: individual-and higher-level consequences of  

E-print Network

Growth and population size of crayfish in headwater streams: individual- and higher evaluate the individual- and population-level effects of acidification on crayfish (Cambarus bartonii stream pH and crayfish growth rates. Growth rates were always higher in circumneutral reaches than

Keeley, Ernest R.

292

The influence of prey consumption and demographic stochasticity on population growth rate of Isle Royale wolves Canis lupus  

Microsoft Academic Search

The relationship between the rates of prey capture and predator population growth is a fundamental aspect of predation, yet it is rarely measured for vertebrate predators. For the isolated wolf population on Isle Royale, annual variation in kill rate explains 22% of the variation in wolf population growth rate. From the slope of this relationship, we estimate that the production

John A. Vucetich; Rolf O. Peterson

2004-01-01

293

Population growth and development of the psocid Liposcelis brunnea Motschulsky (Psocoptera: Liposcelididae) 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 Liposcelis brunnea Motschulsky. L. brunnea did not survive at 43% RH, while populations increased from 22.5-32.5°C and 55 -75% RH. Interestingly, we found L. brunnea population growth ...

294

Slow protein fluctuations explain the emergence of growth phenotypes and persistence in clonal bacterial populations  

E-print Network

One of the most challenging problems in microbiology is to understand how a small fraction of microbes that resists killing by antibiotics can emerge in a population of genetically identical cells, the phenomenon known as persistence or drug tolerance. Its characteristic signature is the biphasic kill curve, whereby microbes exposed to a bactericidal agent are initially killed very rapidly but then much more slowly. Here we relate this problem to the more general problem of understanding the emergence of distinct growth phenotypes in clonal populations. We address the problem mathematically by adopting the framework of the phenomenon of so-called weak ergodicity breaking, well known in dynamical physical systems, which we extend to the biological context. We show analytically and by direct stochastic simulations that distinct growth phenotypes can emerge as a consequence of slow-down of stochastic fluctuations in the expression of a gene controlling growth rate. In the regime of fast gene transcription, the system is ergodic, the growth rate distribution is unimodal, and accounts for one phenotype only. In contrast, at slow transcription and fast translation, weakly non-ergodic components emerge, the population distribution of growth rates becomes bimodal, and two distinct growth phenotypes are identified. When coupled to the well-established growth rate dependence of antibiotic killing, this model describes the observed fast and slow killing phases, and reproduces much of the phenomenology of bacterial persistence. The model has major implications for efforts to develop control strategies for persistent infections.

Andrea Rocco; Andrzej M. Kierzek; Johnjoe McFadden

2013-10-31

295

The contributions of age and sex to variation in common tern population growth rate.  

PubMed

1. The decomposition of population growth rate into contributions from different demographic rates has many applications, ranging from evolutionary biology to conservation and management. Demographic rates with low variance may be pivotal for population persistence, but variable rates can have a dramatic influence on population growth rate. 2. In this study, the mean and variance in population growth rate (lambda) is decomposed into contributions from different ages and demographic rates using prospective and retrospective matrix analyses for male and female components of an increasing common tern (Sterna hirundo) population. 3. Three main results emerged: (1) subadult return was highly influential in prospective and retrospective analyses; (2) different age-classes made different contributions to variation in lambda: older age classes consistently produced offspring whereas young adults performed well only in high quality years; and (3) demographic rate covariation explained a significant proportion of variation in both sexes. A large contribution to lambda did not imply a large contribution to its variation. 4. This decomposition strengthens the argument that the relationship between variation in demographic rates and variation in lambda is complex. Understanding this relationship and its consequences for population persistence and evolutionary change demands closer examination of the lives, and deaths, of the individuals within populations within species. PMID:17032370

Ezard, T H G; Becker, P H; Coulson, T

2006-11-01

296

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

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…

Mahar, Dennis J., Ed.; And Others

297

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

Microsoft Academic Search

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

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

2009-01-01

298

The impact of population change on the growth of mega-cities.  

PubMed

The population dynamics of population growth in mega-cities and the contributions of migration to urban growth are described. The policy implications are identified as the need for a continued emphasis on fertility declines, because reductions will have a beneficial effect on reducing the pace of growth of mega-cities. The short-term goal of policy should be to provide urban contraceptive services to female migrants, who should be targeted specifically as a special group. Natural increase will be the main source of growth of mega-cities, and women who migrated during the 1990s will be a part of that natural increase. Reductions in population growth will make it easier for governments to provide services and to manage the large population size in mega-cities, which will continue to exist as long as economic activities are centralized and economic development promotes urbanization and spatial concentration. The emergence of mega-cities with populations of many millions has been a recent and increasing phenomena. The largest cities in 1980 were Tokyo with 16.9 million followed by New York City with 15.6 million. By 1990, the largest mega-cities were Mexico City with 20.2 million, Tokyo with 18.1 million, Sao Paulo with 17.4 million, and New York with 16.2 million. By the year 2000, the expectation is that Mexico City will have 25.6 million, Sao Paulo 22.1 million, Tokyo 19.0 million, Shanghai 17.0 million, and New York 16.8 million. The rankings will change, but the pattern clearly reflects the growth of mega-cities in developing countries. The age structure of urban populations is conducive to population growth. The main component of urban growth in Asia has been migration. Age structure changes have affected migration and will continue to affect fertility in mega-cities. Mega-cities will attract a young population because of the tourist and personnel services sectors which employ large numbers of young people, because of the demand for educated workers who tend to be younger, and because of enhanced opportunities for education. In Asia, economic policies encourage high levels of female labor force participation. PMID:12288070

Guest, P

1994-03-01

299

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

USGS Publications Warehouse

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.

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

2003-01-01

300

Energetics and growth kinetics of a deep Prochlorococcus spp. population in the Arabian Sea  

NASA Astrophysics Data System (ADS)

During the US JGOFS process studies in the Arabian Sea (1995), secondary fluorescence maxima (SFM) were observed frequently at the oxic-anoxic interface at the extreme base of the euphotic zone. These secondary peaks were most prominent during the early NE monsoon in the central oligotrophic portion of the Arabian Sea, although they were spatially and temporally variable. Based on high performance liquid chromatography (HPLC) and flow cytometry analyses, SFM were determined to be populated almost exclusively by the marine cyanobacterium Prochlorococcus spp. While SFM were about half the magnitude of primary fluorescence peaks, chlorophyll a biomass was typically an order of magnitude less than at the primary maxima (although total chlorophyll ( a+ b) differed only by a factor of two). Photosynthesis versus irradiance response curves revealed an efficient population adapted to extremely low light (˜0.02-0.05% surface irradiance) largely through increased light absorption capabilities. A theoretical spectral irradiance absorption efficiency model based on available spectral irradiance, individual cell properties, and bulk particulate spectral absorption also supports a well-adapted low-light population. Deck-incubated C-14 uptake as well as dilution growth experiments revealed instantaneous growth rates on the order of ?=0.01 d -1. However, additional in situ observations suggest SFM populations may be more dynamic than the growth rates estimates from shipboard bottle incubations predict. We advance four hypotheses for the regulation of SFM populations including: (1) reduced loss rates, (2) discontinuous environmental conditions, (3) enhanced sub-oxic growth, and (4) physical mechanisms.

Johnson, Z.; Landry, M. L.; Bidigare, R. R.; Brown, S. L.; Campbell, L.; Gunderson, J.; Marra, J.; Trees, C.

1999-08-01

301

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

PubMed Central

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

2014-01-01

302

Growth rates in a wild primate population: ecological influences and maternal effects  

Microsoft Academic Search

Growth rate is a life-history trait often linked to various fitness components, including survival, age of first reproduction, and fecundity. Here we present an analysis of growth-rate variability in a wild population of savannah baboons ( Papio cynocephalus). We found that relative juvenile size was a stable individual trait during the juvenile period: individuals generally remained consistently large-for-age or small-for-age

Jeanne Altmann; Susan C. Alberts

2005-01-01

303

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

Microsoft Academic Search

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

Christopher R. Webster; Michael A. Jenkins

2008-01-01

304

Nutritional Status and Growth in Pediatric Crohn's Disease: A Population-Based Study  

Microsoft Academic Search

OBJECTIVES:Growth retardation and malnutrition are major features of pediatric Crohn's disease (CD). We examined nutritional and growth parameters from diagnosis to maximal follow-up in a population-based pediatric cohort, and we determined predictive factors.METHODS:A total of 261 patients (156 boys, 105 girls) with onset of CD before the age of 17 were identified from 1988 to 2004 through the EPIMAD registry

Francis Vasseur; Corinne Gower-Rousseau; Gwenola Vernier-Massouille; Jean Louis Dupas; Veronique Merle; Beatrice Merlin; Eric Lerebours; Guillaume Savoye; Jean Louis Salomez; Antoine Cortot; Jean Frederic Colombel; Dominique Turck

2010-01-01

305

Temperature-dependent population growth of three species of stored product mites (Acari: Acaridida)  

Microsoft Academic Search

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions.\\u000a In this study we investigated the effect of temperature, ranging from 5 to 35°C, on the population growth of three important\\u000a mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of

Gamila Aspaly; Vaclav Stejskal; Stano Pekár; Jan Hubert

2007-01-01

306

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

Microsoft Academic Search

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

Anders Henrik Sirén

2007-01-01

307

Demography, population growth, and population policy in China: a brief history from 1940 to the present.  

PubMed

For some 3 decades after the founding of the People's Republic of China, Chinese studies have had to life with the paradoxical situation in which the abundance of population on the mainland, ever increasing in number predictably and inexorably, was couples with a scarcity of data about the nature and patterns of demographic change, ever harder to come by. As increasing amounts of new demographic data from China, sometimes produced jointly between Chinese and foreign researchers, become available, it is clear that previous methods, technics, and styles of analyses habituated by 3 decades of minimal data from China will become inadequate and obsolete. In 1957 Ma Yinchu put forth 3 main proposals for population control: 1) to conduct another national census to gain more demographic statistics, 2) to advocate widespread public education to inform people of the importance and practical knowledge of birth control combined with propaganda on the disadvantages of early marriages and the benefits of late marriage, and 3) family planning, by popular use of contraception, is the most effective method for population control. It is argued that 1) the years 1950-1958 consisted of a period of fermentation and preparation, 2) the post-leap years, 1959-1965, constituted a period of trial implementation of emerging policies, 3) 1966-1971 was an uncontrolled period, and 4) only the years after 1971 may be viewed as a period during which serious implementation took place. Overall, the selections in this volume are intended to inform both China scholars and social scientists interested in recent developments in Chinese population studies. PMID:12314766

Chu, D S

1984-01-01

308

Population growth and social change: a note on rural society.  

PubMed

Changing social conditons, particularly in rural areas, often create a feeling of normlessness. For such major changes as family limitation to be accepted in rural India, those involved must understand the total social change which will be necessary. In rural areas today the desire for motherhood is a matter of being accepted. A barren woman suffers social ostracism; folk tales tell of even animals refusing to eat a meal prepared by a barren woman. A women with a large family is particularly respected, especially if they are well provided for. The other reasons given for having large numbers of children are family survival, care in old age, increase in family income, to get more share in the property, to follow the community pattern, and to make the home happier. There is a rationale for most of these. High infant and child mortality account for the family survival, The only security the parents have is the children. More children increase the family share in a joint-family land-holding. Raising the age at marriage for girls has often been suggested as a population control measure, but what is the girl to do until 19? Rural parents do not feel their obligations to their daughter have been discharged until she is married and it is the parents who are blamed if no arrangments have been made. The idea of her becoming educated is not socially acceptable and rural boys are reluctant to marry educated girls. India's values pertaining to divorce, widow remarriage, and abortion are already undergoing change. Migration to the cities is bringing about change. Looking to the cities may bring about modernization, but the fact that the young men are the ones moving away is leading a lack of leadership in the villages. To bring about the social conditions favorable to modernization agriculture should be modernized, reducing the need for labor; factories should be built in rural areas to take up this slack in agricultural employment, and perhaps it would become acceptable for girls to work in them; rising expectations should be encouraged; and efforts should be made to encourage better diet, better child care, education, and other factors which would lead to a small family norm. When family planning programs are introduced in the context of total social change, chances of success are greater. PMID:12333661

Barnabas, A P

1974-01-01

309

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

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…

McNicoll, Geoffrey

310

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...

311

Impacts of breeder loss on social structure, reproduction and population growth in a social canid.  

PubMed

The importance of individuals to the dynamics of populations may depend on reproductive status, especially for species with complex social structure. Loss of reproductive individuals in socially complex species could disproportionately affect population dynamics by destabilizing social structure and reducing population growth. Alternatively, compensatory mechanisms such as rapid replacement of breeders may result in little disruption. The impact of breeder loss on the population dynamics of social species remains poorly understood. We evaluated the effect of breeder loss on social stability, recruitment and population growth of grey wolves (Canis lupus) in Denali National Park and Preserve, Alaska using a 26-year dataset of 387 radiocollared wolves. Harvest of breeding wolves is a highly contentious conservation and management issue worldwide, with unknown population-level consequences. Breeder loss preceded 77% of cases (n = 53) of pack dissolution from 1986 to 2012. Packs were more likely to dissolve if a female or both breeders were lost and pack size was small. Harvest of breeders increased the probability of pack dissolution, likely because the timing of harvest coincided with the breeding season of wolves. Rates of denning and successful recruitment were uniformly high for packs that did not experience breeder loss; however, packs that lost breeders exhibited lower denning and recruitment rates. Breeder mortality and pack dissolution had no significant effects on immediate or longer term population dynamics. Our results indicate the importance of breeding individuals is context dependent. The impact of breeder loss on social group persistence, reproduction and population growth may be greatest when average group sizes are small and mortality occurs during the breeding season. This study highlights the importance of reproductive individuals in maintaining group cohesion in social species, but at the population level socially complex species may be resilient to disruption and harvest through strong compensatory mechanisms. PMID:25041127

Borg, Bridget L; Brainerd, Scott M; Meier, Thomas J; Prugh, Laura R

2014-07-01

312

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

USGS Publications Warehouse

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.

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

2006-01-01

313

Growth rates and variances of unexploited wolf populations in dynamic equilibria  

USGS Publications Warehouse

Several states have begun harvesting gray wolves (Canis lupus), and these states and various European countries are closely monitoring their wolf populations. To provide appropriate perspective for determining unusual or extreme fluctuations in their managed wolf populations, we analyzed natural, long-term, wolf-population-density trajectories totaling 130 years of data from 3 areas: Isle Royale National Park in Lake Superior, Michigan, USA; the east-central Superior National Forest in northeastern Minnesota, USA; and Denali National Park, Alaska, USA. Ratios between minimum and maximum annual sizes for 2 mainland populations (n?=?28 and 46 yr) varied from 2.5–2.8, whereas for Isle Royale (n?=?56 yr), the ratio was 6.3. The interquartile range (25th percentile, 75th percentile) for annual growth rates, Nt+1/Nt, was (0.88, 1.14), (0.92, 1.11), and (0.86, 1.12) for Denali, Superior National Forest, and Isle Royale respectively. We fit a density-independent model and a Ricker model to each time series, and in both cases we considered the potential for observation error. Mean growth rates from the density-independent model were close to 0 for all 3 populations, with 95% credible intervals including 0. We view the estimated model parameters, including those describing annual variability or process variance, as providing useful summaries of the trajectories of these populations. The estimates of these natural wolf population parameters can serve as benchmarks for comparison with those of recovering wolf populations. Because our study populations were all from circumscribed areas, fluctuations in them represent fluctuations in densities (i.e., changes in numbers are not confounded by changes in occupied area as would be the case with populations expanding their range, as are wolf populations in many states).

Mech, L. David; Fieberg, John

2015-01-01

314

Demographic, mechanistic and density-dependent determinants of population growth rate: a case study in an avian predator.  

PubMed Central

Identifying the determinants of population growth rate is a central topic in population ecology. Three approaches (demographic, mechanistic and density-dependent) used historically to describe the determinants of population growth rate are here compared and combined for an avian predator, the barn owl (Tyto alba). The owl population remained approximately stable (r approximately 0) throughout the period from 1979 to 1991. There was no evidence of density dependence as assessed by goodness of fit to logistic population growth. The finite (lambda) and instantaneous (r) population growth rates were significantly positively related to food (field vole) availability. The demographic rates, annual adult mortality, juvenile mortality and annual fecundity were reported to be correlated with vole abundance. The best fit (R(2) = 0.82) numerical response of the owl population described a positive effect of food (field voles) and a negative additive effect of owl abundance on r. The numerical response of the barn owl population to food availability was estimated from both census and demographic data, with very similar results. Our analysis shows how the demographic and mechanistic determinants of population growth rate are linked; food availability determines demographic rates, and demographic rates determine population growth rate. The effects of food availability on population growth rate are modified by predator abundance. PMID:12396509

Hone, Jim; Sibly, Richard M

2002-01-01

315

El Niño drives timing of breeding but not population growth in the song sparrow (Melospiza melodia).  

PubMed

Increasing evidence suggests that climate change affects the timing of breeding in birds, but there is less evidence to show how such changes affect the population dynamics of birds overall. Over the past 43 years, song sparrows (Melospiza melodia) on Mandarte Island, British Columbia, Canada have not shown an advance in breeding date in response to global warming. However, this population did show considerable annual variation in timing of breeding correlated with the El Niño Southern Oscillation. Birds bred earlier in warmer El Niño years and later in colder La Niña years. Early breeding strongly increased reproductive output. However, annual variation in timing of breeding had little effect on population growth, perhaps because the population is strongly regulated by the rate of recruitment by juveniles. The juvenile recruitment rate declined with increasing population density but showed little response to climate. These findings suggest that populations will vary in response to climate change depending on how climate affects the demographic parameters that contribute most to population growth. PMID:12960365

Wilson, Scott; Arcese, Peter

2003-09-16

316

Rapid Population Growth and Rural Community Change: A Focus on Land Use Issues.  

ERIC Educational Resources Information Center

Land use controls are often a major point of conflict between recent migrants and long-term residents of rapidly growing communities. Such conflict was noted in a case study of a rural community undergoing rapid population growth. The revision of a comprehensive land use plan for the community provided the opportunity to evaluate citizen…

Garkovich, Lorraine

317

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

Microsoft Academic Search

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

D. Gibson; J. B. Jones

1993-01-01

318

Native and Introduced Populations of Smallmouth Bass Differ in Concordance between Climate and Somatic Growth  

Microsoft Academic Search

We characterized the association between climate and somatic growth in 125 North American populations of smallmouth bass Micropterus dolomieu. Using multivariate techniques (i.e., principal components and Procrustes analyses), we found an overall significant concordance between eight climate variables (cloud cover, frost frequency, precipitation, mean air temperature, minimum air temperature, maximum air temperature, mean summer air temperature, and growing degree-days above

Erin S. Dunlop; Brian J. Shuter

2006-01-01

319

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

E-print Network

of Hydrology and Water Resources College of Science This project was made possible by the University of Arizona. Management of our finite water supplies is extremely important for sustaining and growing cities within supply in Tucson, Arizona within the next 30 years ("Update to Water Plan", 2008). Population growth

Fay, Noah

320

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...

321

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...

322

Water relations and root growth of two populations of Gutierrezia sarothrae  

Microsoft Academic Search

We hypothesise that genotypic differences in transpiration and root growth in the southern and northern populations of Gutierrezia sarothrae are driven by growing season vapour pressure deficit (VPD) and that ecotypic differentiations are linked to corresponding variations in tissue and leaf water relations. Seedlings from an Idaho (ID) and a Texas (TX) seed source were grown either in an open

Changgui Wan; Ronald E Sosebee; Bobby L McMichael

1998-01-01

323

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

Microsoft Academic Search

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

Peter A. Biro; John R. Post

2008-01-01

324

Hydrocarbon Leaching, Microbial Population, and Plant Growth in Soil Amended with Petroleum  

Microsoft Academic Search

Two samples of oily waste organics (OWO) from petroleum wells were added to heath soils from Tierra del Fuego, Argentina, and the effects on hydrocarbon leaching, microbial population, and plant growth were studied. These mixtures and a control soil were subjected to four deionized water leachates. For each leachate, total petroleum hydrocarbons (TPH), aliphatic hydrocarbons (ALH), aromatic hydrocarbons (ARH) with

Rodolfo E. Mendoza

1998-01-01

325

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

Microsoft Academic Search

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

Christine Robitschek

2003-01-01

326

236 Branching Processes: Variation, Growth, and Extinction of Populations 7.6 Modeling Measles Outbreaks  

E-print Network

236 Branching Processes: Variation, Growth, and Extinction of Populations 7.6 Modeling Measles of pathogens with a reproduc- tive number smaller than one, using the epidemiology of measles as an example. We.6.2 The epidemiology of measles Measles is caused by the measles virus. It is transmitted on close contact via airborne

327

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

E-print Network

Modeling circadian clock-cell cycle interaction effects on cell population growth rates R. El, Byblos, P.O.Box 36, Byblos, Lebanon Abstract The circadian clock and the cell cycle are two tightly coupled oscillators. Recent analytical studies have shown counter-intuitive effects of circadian gating

Boyer, Edmond

328

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

E-print Network

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

Smith, Steven E.

329

Population Growth. Understanding Global Change: Earth Science and Human Impacts. Global Change Instruction Program.  

ERIC Educational Resources Information Center

The Global Change Instruction Program was designed by college professors to fill a need for interdisciplinary materials on the emerging science of global change. This instructional module concentrates on interactions between population growth and human activities that produce global change. The materials are designed for undergraduate students…

Jacobsen, Judith E.

330

REGIONAL VARIATION IN FERTILITY, MORTALITY AND POPULATION GROWTH IN ETHIOPIA, 1970-1981  

Microsoft Academic Search

This paper studies regional and temporal variation in age at marriage, fertility, mortality and population growth in Ethiopia. The data thas was used for this study was obtained from the 1970 and 1981 demographic surveys conducted by the Central Statistics Office of Ethiopia. Even though scientific methods of data collection were adopted, the final report was not free from errors

ASMEROM KIDANE

1990-01-01

331

Effects of resistance genes and insecticidal seed treatments on soybean aphid population growth and development  

E-print Network

1 Effects of resistance genes and insecticidal seed treatments on soybean aphid population growth Lafayette, IN, 47907, USA. Introduction Soybean aphid (Aphis glycines) is an introduced pest first reported. 2004). Heavy infestation of aphids causes distortion of leaves, reduction of seed pods and yield loss

Ginzel, Matthew

332

Growth and competitive effects of Centaurea stoebe populations in response to simulated nitrogen deposition.  

PubMed

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

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

2012-01-01

333

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

PubMed Central

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

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

2012-01-01

334

Uncertainty in Population Growth Rates: Determining Confidence Intervals from Point Estimates of Parameters  

PubMed Central

Background Demographic models are widely used in conservation and management, and their parameterisation often relies on data collected for other purposes. When underlying data lack clear indications of associated uncertainty, modellers often fail to account for that uncertainty in model outputs, such as estimates of population growth. Methodology/Principal Findings We applied a likelihood approach to infer uncertainty retrospectively from point estimates of vital rates. Combining this with resampling techniques and projection modelling, we show that confidence intervals for population growth estimates are easy to derive. We used similar techniques to examine the effects of sample size on uncertainty. Our approach is illustrated using data on the red fox, Vulpes vulpes, a predator of ecological and cultural importance, and the most widespread extant terrestrial mammal. We show that uncertainty surrounding estimated population growth rates can be high, even for relatively well-studied populations. Halving that uncertainty typically requires a quadrupling of sampling effort. Conclusions/Significance Our results compel caution when comparing demographic trends between populations without accounting for uncertainty. Our methods will be widely applicable to demographic studies of many species. PMID:21049049

Devenish Nelson, Eleanor S.; Harris, Stephen; Soulsbury, Carl D.; Richards, Shane A.; Stephens, Philip A.

2010-01-01

335

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

PubMed

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

Howat, Peter; Stoneham, Melissa

2011-12-01

336

Cell Growth and Size Homeostasis in Silico  

NASA Astrophysics Data System (ADS)

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.

Hu, Yucheng; Zhu, Tianqi

2014-03-01

337

Exponential random graph models  

E-print Network

Nowadays, exponential random graphs (ERGs) are among the most widely-studied network models. Different analytical and numerical techniques for ERG have been developed that resulted in the well-established theory with true predictive power. An excellent basic discussion of exponential random graphs addressed to social science students and researchers is given in [Anderson et al., 1999][Robins et al., 2007]. This essay is intentionally designed to be more theoretical in comparison with the well-known primers just mentioned. Given the interdisciplinary character of the new emerging science of complex networks, the essay aims to give a contribution upon which network scientists and practitioners, who represent different research areas, could build a common area of understanding.

Fronczak, Agata

2012-01-01

338

Population growth, agricultural intensification, induced innovation and natural resource sustainability: An application of neoclassical growth theory  

Microsoft Academic Search

Using a simple neoclassical type growth model including both man-made and natural capital as inputs to production, the theoretical basis for a U-shaped relationship between agricultural intensification and farm household investment in renewable resource capital is established. As development of technology, infrastructure, or markets increase the relative return to investment in man-made capital over natural capital, resource depletion occurs as

John L. Pender

1998-01-01

339

Light disappears rapidly (exponentially)  

E-print Network

#12;#12;#12;#12;Light disappears rapidly (exponentially) with depth At the same time, the color of the light shifts #12;#12;#12;#12;· Euphotic zone ­ plentiful light ­ 0-100 m (about) · Dysphotic zone ­ very, very little light ­ 100-1000 m (about) · Aphotic zone ­ no light ­ below 1000 m #12;Sunlight in Water

Kudela, Raphael M.

340

[The population growth in the city of Beijing and our present tasks (author's transl)].  

PubMed

Concern for the rapid population growth since 1949 of China's second largest city, Beijing, is discussed in terms of population control, migration, and rises in the productive development of the city. From 1949 to 1963 the natural rate of population increased from 7.5 to 35.3%; however, after the introduction of a birth control program in 1971, the natural increase of population declined to 4.02% in 1977. From 1949-1978, the average birth rate was 145,000/year while the average death rate was 46,500/year, leaving the annual average increase in population at 98,000. The natural population increased by 2,340,000 from 1949-1978. The massive population growth since 1949 affected the economic development of the city as well as the country. Cultivated land near Beijing increased from 1949-1952, but because of urban development the land for cultivation decreased by 1,527,000 market acres from that available in 1949 (7,965,000 market acres). Population density increased from 430 persons/ square kilometer in 1962 to 506 persons/ square kilometer in 1978. From 1953 to 1978, production and consumption rates fluctuated with a net balance of only 2020 million catties in the 26 years, causing the need for products to be imported from other areas of the country. Unemployment is exacerbated by the lack of jobs and increasing numbers of people. Transportation problems also have developed. New efforts are being made to inform people of population control by the Beijing Population Association begun in 1979, because Beijing's population will continue to increase until 1989 due to the baby boom years during the fifties which created a 2nd boom in the late 1970s as well as the lack of education on population control. Other programs are being developed to, 1) educate people on economical measures of reducing the population, 2) promote governmental departments to improve birth control programs by means of social security services, child health agencies, and nursing schools, 3) propagandize eugenics and genetic education to enhance the population, and 4) reinforce the propaganda on birth control and technical guidance. PMID:12311025

Qian, L J; Xu, B; Huang, S Y

1980-04-01

341

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

PubMed Central

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

Biro, Peter A.; Post, John R.

2008-01-01

342

Population growth and physiological characteristics of microalgae in a miniaturized bioreactor during space flight  

NASA Astrophysics Data System (ADS)

A strain of microalgae ( Anabaena siamensis) had been cultured in a miniaturized bioreactor during a retrievable satellite flight for 15 days. By means of remote sensing equipment installed in the satellite, we gained the growth curve of microalgae population in space every day in real time. The curve indicated that the growth of microalgae in space was slower than the control on ground. Inoculation of the retrieved microalgae culture showed that the growth rate was distinctively higher than ground control. But after several generations, both cultures indicated similar growth rates. Those data showed that algae can adapt to space environment easily which may be valuable for designing more complex bioreactor and controlled ecological life support system in future experiment.

Wang, Gaohong; Chen, Haofeng; Li, Genbao; Chen, Lanzhou; Li, Dunhai; Hu, Chunxiang; Chen, Kun; Liu, Yongding

2006-03-01

343

The Influence of Damselfly Naiads, Phytoplankton, and Selected Physicochemical Factors on the Population Growth of Daphnia schødleri  

Microsoft Academic Search

The effect of selected biotic and abiotic factors on the population growth rate of Daphnia schødleri was studied over a five month period in a wetland ecosystem. Among the factors studied, only the density of damselfly naiads with head capsule width greater than 2.0 mm was significantly correlated with D. schødleri's population growth rate. The presence of small and medium

Timothy D. Johnson; Joseph C. Coughlan; Fred W. Rabe

1986-01-01

344

Population Growth in New Hampshire during the Nineteenth and Twentieth Centuries. Studies in New England Geography, Number 1.  

ERIC Educational Resources Information Center

This paper traces the shifts in New Hampshire's state and county population during the nineteenth and twentieth centuries, focusing on the growth of urban centers and industry. From 1790 to 1840 most of New Hampshire's population growth was agricultural despite the beginnings of industrialization and urbanization. These processes greatly…

Hobart, Christine L.

345

The intrinsic growth rate as a predictor of population viability under climate warming.  

PubMed

1. Lately, there has been interest in using the intrinsic growth rate (rm) to predict the effects of climate warming on ectotherm population viability. However, because rm is calculated using the Euler-Lotka equation, its reliability in predicting population persistence depends on whether ectotherm populations can achieve a stable age/stage distribution in thermally variable environments. Here, we investigate this issue using a mathematical framework that incorporates mechanistic descriptions of temperature effects on vital rates into a stage-structured population model that realistically captures the temperature-induced variability in developmental delays that characterize ectotherm life cycles. 2. We find that populations experiencing seasonal temperature variation converge to a stage distribution whose intra-annual pattern remains invariant across years. As a result, the mean annual per capita growth rate also remains constant between years. The key insight is the mechanism that allows populations converge to a stationary stage distribution. Temperature effects on the biochemical processes (e.g. enzyme kinetics, hormonal regulation) that underlie life-history traits (reproduction, development and mortality) exhibit well-defined thermodynamical properties (e.g. changes in entropy and enthalpy) that lead to predictable outcomes (e.g. reduction in reaction rates or hormonal action at temperature extremes). As a result, life-history traits exhibit a systematic and predictable response to seasonal temperature variation. This in turn leads to temporally predictable temperature responses of the stage distribution and the per capita growth rate. 3. When climate warming causes an increase in the mean annual temperature and/or the amplitude of seasonal fluctuations, the population model predicts the mean annual per capita growth rate to decline to zero within 100 years when warming is slow relative to the developmental period of the organism (0.03-0.05°C per year) and to become negative, causing population extinction, well before 100 years when warming is fast (e.g. 0.1°C per year). The Euler-Lotka equation predicts a slower decrease in rm when warming is slow and a longer persistence time when warming is fast, with the deviation between the two metrics increasing with increasing developmental period. These results suggest that predictions of ectotherm population viability based on rm may be valid only for species with short developmental delays, and even then, only over short time-scales and under slow warming regimes. PMID:23926903

Amarasekare, Priyanga; Coutinho, Renato M

2013-11-01

346

Native insect herbivory limits population growth rate of a non-native thistle.  

PubMed

The influence of native fauna on non-native plant population growth, size, and distribution is not well documented. Previous studies have shown that native insects associated with tall thistle (Cirsium altissimum) also feed on the leaves, stems, and flower heads of the Eurasian congener C. vulgare, thus limiting individual plant performance. In this study, we tested the effects of insect herbivores on the population growth rate of C. vulgare. We experimentally initiated invasions by adding seeds at four unoccupied grassland sites in eastern Nebraska, USA, and recorded plant establishment, survival, and reproduction. Cumulative foliage and floral herbivory reduced C. vulgare seedling density, and prevented almost any reproduction by C. vulgare in half the sites. The matrix model we constructed showed that this herbivory resulted in a reduction of the asymptotic population growth rate (?), from an 88% annual increase to a 54% annual decline. These results provide strong support for the hypothesis that indigenous herbivores limit population invasion of this non-native plant species into otherwise suitable grassland habitat. PMID:24402131

Eckberg, James O; Tenhumberg, Brigitte; Louda, Svata M

2014-05-01

347

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

USGS Publications Warehouse

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.

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

2006-01-01

348

Growth in Percutaneous Coronary Intervention Capacity Relative to Population and Disease Prevalence  

PubMed Central

Background The access to and growth of percutaneous coronary intervention (PCI) has not been fully explored with regard to geographic equity and need. Economic factors and timely access to primary PCI provide the impetus for growth in PCI centers, and this is balanced by volume standards and the benefits of regionalized care. Methods and Results Geospatial and statistical analyses were used to model capacity, growth, and access of PCI hospitals relative to population density and myocardial infarction (MI) prevalence at the state level. Longitudinal data were obtained for 2003–2011 from the American Hospital Association, the U.S. Census, and the Centers for Disease Control and Prevention (CDC) with geographical modeling to map PCI locations. The number of PCI centers has grown 21.2% over the last 8 years, with 39% of all hospitals having interventional cardiology capabilities. During the same time, the US population has grown 8.3%, from 217 million to 235 million, and MI prevalence rates have decreased from 4.0% to 3.7%. The most densely concentrated states have a ratio of 8.1 to 12.1 PCI facilities per million of population with significant variability in both MI prevalence and average distance between PCI facilities. Conclusions Over the last decade, the growth rate for PCI centers is 1.5× that of the population growth, while MI prevalence is decreasing. This has created geographic imbalances and access barriers with excess PCI centers relative to need in some regions and inadequate access in others. PMID:24166491

Langabeer, James R.; Henry, Timothy D.; Kereiakes, Dean J.; DelliFraine, Jami; Emert, Jamie; Wang, Zheng; Stuart, Leilani; King, Richard; Segrest, Wendy; Moyer, Peter; Jollis, James G.

2013-01-01

349

The Effects of Population Density on Juvenile Growth Rate in White-Tailed Deer  

NASA Astrophysics Data System (ADS)

Animal body size is driven by habitat quality, food availability, and nutrition. Adult size can relate to birth weight, to length of the ontogenetic growth period, and/or to the rate of growth. Data requirements are high for studying these growth mechanisms, but large datasets exist for some game species. In North America, large harvest datasets exist for white-tailed deer ( Odocoileus virginianus), but such data are collected under a variety of conditions and are generally dismissed for ecological research beyond local population and habitat management. We contend that such data are useful for studying the ecology of white-tailed deer growth and body size when analyzed at ordinal scale. In this paper, we test the response of growth rate to food availability by fitting a logarithmic equation that estimates growth rate only to harvest data from Fort Hood, Texas, and track changes in growth rate over time. Results of this ordinal scale model are compared to previously published models that include additional parameters, such as birth weight and adult weight. It is shown that body size responds to food availability by variation in growth rate. Models that estimate multiple parameters may not work with harvest data because they are prone to error, which renders estimates from complex models too variable to detect interannual changes in growth rate that this ordinal scale model captures. This model can be applied to harvest data, from which inferences about factors that influence animal growth and body size (e.g., habitat quality and nutritional availability) can be drawn.

Barr, Brannon; Wolverton, Steve

2014-10-01

350

The effects of population density on juvenile growth rate in white-tailed deer.  

PubMed

Animal body size is driven by habitat quality, food availability, and nutrition. Adult size can relate to birth weight, to length of the ontogenetic growth period, and/or to the rate of growth. Data requirements are high for studying these growth mechanisms, but large datasets exist for some game species. In North America, large harvest datasets exist for white-tailed deer (Odocoileus virginianus), but such data are collected under a variety of conditions and are generally dismissed for ecological research beyond local population and habitat management. We contend that such data are useful for studying the ecology of white-tailed deer growth and body size when analyzed at ordinal scale. In this paper, we test the response of growth rate to food availability by fitting a logarithmic equation that estimates growth rate only to harvest data from Fort Hood, Texas, and track changes in growth rate over time. Results of this ordinal scale model are compared to previously published models that include additional parameters, such as birth weight and adult weight. It is shown that body size responds to food availability by variation in growth rate. Models that estimate multiple parameters may not work with harvest data because they are prone to error, which renders estimates from complex models too variable to detect interannual changes in growth rate that this ordinal scale model captures. This model can be applied to harvest data, from which inferences about factors that influence animal growth and body size (e.g., habitat quality and nutritional availability) can be drawn. PMID:25148782

Barr, Brannon; Wolverton, Steve

2014-10-01

351

Spatially Directed Guidance of Stem Cell Population Migration by Immobilized Patterns of Growth Factors  

PubMed Central

We investigated how engineered gradients of exogenous growth factors, immobilized to an extracellular matrix material, influence collective guidance of stem cell populations over extended time (>1 day) and length (>1 mm) scales in vitro. Patterns of low-to-high, high-to-low, and uniform concentrations of heparin-binding epidermal growth factor-like growth factor were inkjet printed at precise locations on fibrin substrates. Proliferation and migration responses of mesenchymal stem cells seeded at pattern origins were observed with time-lapse video microscopy and analyzed using both manual and automated computer vision-based cell tracking techniques. Based on results of established chemotaxis studies, we expected that the low-to-high gradient would most effectively direct cell guidance away from the cell source. All printed patterns, however, were found to direct net collective cell guidance with comparable responses. Our analysis revealed that collective “cell diffusion” down a cell-to-cell confinement gradient originating at the cell starting lines and not the net sum of directed individual cell migration up a growth factor concentration gradient is the principal driving force for directing mesenchymal stem cell population outgrowth from a cell source. These results suggest that simple uniform distributions of growth factors immobilized to an extracellular matrix material may be as effective in directing cell migration into a wound site as more complex patterns with concentration gradients. PMID:21272933

Miller, Eric D.; Li, Kang; Kanade, Takeo; Weiss, Lee E.; Walker, Lynn M.; Campbell, Phil G.

2011-01-01

352

Spatially directed guidance of stem cell population migration by immobilized patterns of growth factors.  

PubMed

We investigated how engineered gradients of exogenous growth factors, immobilized to an extracellular matrix material, influence collective guidance of stem cell populations over extended time (>1 day) and length (>1 mm) scales in vitro. Patterns of low-to-high, high-to-low, and uniform concentrations of heparin-binding epidermal growth factor-like growth factor were inkjet printed at precise locations on fibrin substrates. Proliferation and migration responses of mesenchymal stem cells seeded at pattern origins were observed with time-lapse video microscopy and analyzed using both manual and automated computer vision-based cell tracking techniques. Based on results of established chemotaxis studies, we expected that the low-to-high gradient would most effectively direct cell guidance away from the cell source. All printed patterns, however, were found to direct net collective cell guidance with comparable responses. Our analysis revealed that collective "cell diffusion" down a cell-to-cell confinement gradient originating at the cell starting lines and not the net sum of directed individual cell migration up a growth factor concentration gradient is the principal driving force for directing mesenchymal stem cell population outgrowth from a cell source. These results suggest that simple uniform distributions of growth factors immobilized to an extracellular matrix material may be as effective in directing cell migration into a wound site as more complex patterns with concentration gradients. PMID:21272933

Miller, Eric D; Li, Kang; Kanade, Takeo; Weiss, Lee E; Walker, Lynn M; Campbell, Phil G

2011-04-01

353

Loss of foundation species increases population growth of exotic forbs in sagebrush steppe.  

PubMed

The invasion and spread of exotic plants following land disturbance threatens semiarid ecosystems. In sagebrush steppe, soil water is scarce and is partitioned between deep-rooted perennial shrubs and shallower-rooted native forbs and grasses. Disturbances commonly remove shrubs, leaving grass-dominated communities, and may allow for the exploitation of water resources by the many species of invasive, tap-rooted forbs that are increasingly successful in this habitat. We hypothesized that exotic forb populations would benefit from increased soil water made available by removal of sagebrush, a foundation species capable of deep-rooting, in semiarid shrub-steppe ecosystems. To test this hypothesis, we used periodic matrix models to examine effects of experimental manipulations of soil water on population growth of two exotic forb species, Tragopogon dubius and Lactuca serriola, in sagebrush steppe of southern Idaho, USA. We used elasticity analyses to examine which stages in the life cycle of T. dubius and L. serriola had the largest relative influence on population growth. We studied the demography of T. dubius and L. serriola in three treatments: (1) control, in which vegetation was not disturbed, (2) shrubs removed, or (3) shrubs removed but winter-spring recharge of deep-soil water blocked by rainout shelters. The short-term population growth rate (Lambda) of T. dubius in the shrub-removal treatment was more than double that of T. dubius in either sheltered or control treatments, both of which had limited soil water. All L. serriola individuals that emerged in undisturbed sagebrush plots died, whereas Lambda of L. serriola was high (Lambda > 2.5) in all shrub-removal plots, whether they had rainout shelters or not. Population growth of both forbs in all treatments was most responsive to flowering and seed production, which are life stages that should be particularly reliant on deep-soil water, as well as seedling establishment, which is important to most plant populations, especially during invasion. These data indicate the importance of native species, in this case the dominant shrub, in influencing soil resources and restricting population growth of exotic plants. These results argue that management of invasive plants should focus not only on removal of nonnatives, but also on reestablishment of important native species. PMID:21049877

Prevéy, Janet S; Germino, Matthew J; Huntly, Nancy J

2010-10-01

354

Body downsizing caused by non-consumptive social stress severely depresses population growth rate.  

PubMed

Chronic social stress diverts energy away from growth, reproduction and immunity, and is thus a potential driver of population dynamics. However, the effects of social stress on demographic density dependence remain largely overlooked in ecological theory. Here we combine behavioural experiments, physiology and population modelling to show in a top predator (pike Esox lucius) that social stress alone may be a primary driver of demographic density dependence. Doubling pike density in experimental ponds under controlled prey availability did not significantly change prey intake by pike (i.e. did not significantly change interference or exploitative competition), but induced a neuroendocrine stress response reflecting a size-dependent dominance hierarchy, depressed pike energetic status and lowered pike body growth rate by 23 per cent. Assuming fixed size-dependent survival and fecundity functions parameterized for the Windermere (UK) pike population, stress-induced smaller body size shifts age-specific survival rates and lowers age-specific fecundity, which in Leslie matrices projects into reduced population rate of increase (lambda) by 37-56%. Our models also predict that social stress flattens elasticity profiles of lambda to age-specific survival and fecundity, thus making population persistence more dependent on old individuals. Our results suggest that accounting for non-consumptive social stress from competitors and predators is necessary to accurately understand, predict and manage food-web dynamics. PMID:19923130

Edeline, Eric; Haugen, Thrond O; Weltzien, Finn-Arne; Claessen, David; Winfield, Ian J; Stenseth, Nils Chr; Vøllestad, L Asbjørn

2010-03-22

355

Rapid population growth. Effects on the social infrastructures of southern Africa.  

PubMed

Southern Africa's high rate of population growth and widespread poverty have serious implications for the region's social infrastructure. Large increases in the school-age population have undermined efforts to improve the quality of education since all resources are directed toward expansion of availability. To achieve a teacher-pupil ratio of 1:40 at the primary level and 1:35 at the secondary level, an estimated additional 50,000 classrooms would be required. Also jeopardized by high fertility is access to health services, safe water, and sanitation. In Mozambique, for example, where only 30% of the population has access to health services, the under-five years mortality rate is 297/1000 live births and the physician-population ratio is 1:37,970. Substandard housing, homelessness, congestion, deteriorating public services, pollution, and crime dominate urban areas. The single most effective intervention to reduce population growth in Southern Africa is female education. Women without a secondary education bear an average of seven children; if 40% of women attend secondary school, this drops to three children. Thus, governments must make gender equality a central focus of development planning and ensure that women are participants in this process. Property and inheritance laws that serve to increase the economic need for early marriage should be eliminated. Public health programs, including family planning, must be expanded. Finally, women's organizations should be strengthened and urged to foster female empowerment. PMID:12346213

Smith, J D

1995-01-01

356

Population Growth of Pratylenchus penetrans on Winter Cover Crops Grown in the Pacific Northwest  

PubMed Central

Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass × sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest. PMID:19270948

Forge, T. A.; Ingham, R. E.; Kaufman, D.; Pinkerton, J. N.

2000-01-01

357

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

PubMed Central

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

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

2010-01-01

358

Quadratic exponential vectors  

SciTech Connect

We give a necessary and sufficient condition for the existence of a quadratic exponential vector with test function in L{sup 2}(R{sup d}) intersection L{sup {infinity}}(R{sup d}). We prove the linear independence and totality, in the quadratic Fock space, of these vectors. Using a technique different from the one used by Accardi et al. [Quantum Probability and Infinite Dimensional Analysis, Vol. 25, p. 262, (2009)], we also extend, to a more general class of test functions, the explicit form of the scalar product between two such vectors.

Accardi, Luigi; Dhahri, Ameur [Volterra Center, University of Roma Tor Vergata, Via Columbia 2, 00133 Roma (Italy)

2009-12-15

359

Determining Individual Variation in Growth and Its Implication for Life-History and Population Processes Using the Empirical Bayes Method  

PubMed Central

The differences in demographic and life-history processes between organisms living in the same population have important consequences for ecological and evolutionary dynamics. Modern statistical and computational methods allow the investigation of individual and shared (among homogeneous groups) determinants of the observed variation in growth. We use an Empirical Bayes approach to estimate individual and shared variation in somatic growth using a von Bertalanffy growth model with random effects. To illustrate the power and generality of the method, we consider two populations of marble trout Salmo marmoratus living in Slovenian streams, where individually tagged fish have been sampled for more than 15 years. We use year-of-birth cohort, population density during the first year of life, and individual random effects as potential predictors of the von Bertalanffy growth function's parameters k (rate of growth) and (asymptotic size). Our results showed that size ranks were largely maintained throughout marble trout lifetime in both populations. According to the Akaike Information Criterion (AIC), the best models showed different growth patterns for year-of-birth cohorts as well as the existence of substantial individual variation in growth trajectories after accounting for the cohort effect. For both populations, models including density during the first year of life showed that growth tended to decrease with increasing population density early in life. Model validation showed that predictions of individual growth trajectories using the random-effects model were more accurate than predictions based on mean size-at-age of fish. PMID:25211603

Vincenzi, Simone; Mangel, Marc; Crivelli, Alain J.; Munch, Stephan; Skaug, Hans J.

2014-01-01

360

Determining individual variation in growth and its implication for life-history and population processes using the empirical Bayes method.  

PubMed

The differences in demographic and life-history processes between organisms living in the same population have important consequences for ecological and evolutionary dynamics. Modern statistical and computational methods allow the investigation of individual and shared (among homogeneous groups) determinants of the observed variation in growth. We use an Empirical Bayes approach to estimate individual and shared variation in somatic growth using a von Bertalanffy growth model with random effects. To illustrate the power and generality of the method, we consider two populations of marble trout Salmo marmoratus living in Slovenian streams, where individually tagged fish have been sampled for more than 15 years. We use year-of-birth cohort, population density during the first year of life, and individual random effects as potential predictors of the von Bertalanffy growth function's parameters k (rate of growth) and L? (asymptotic size). Our results showed that size ranks were largely maintained throughout marble trout lifetime in both populations. According to the Akaike Information Criterion (AIC), the best models showed different growth patterns for year-of-birth cohorts as well as the existence of substantial individual variation in growth trajectories after accounting for the cohort effect. For both populations, models including density during the first year of life showed that growth tended to decrease with increasing population density early in life. Model validation showed that predictions of individual growth trajectories using the random-effects model were more accurate than predictions based on mean size-at-age of fish. PMID:25211603

Vincenzi, Simone; Mangel, Marc; Crivelli, Alain J; Munch, Stephan; Skaug, Hans J

2014-09-01

361

APPLICATION OF ELASTICITY ANALYSES AND PERTURBATION SIMULATIONS IN DETERMINING STRESSOR IMPACTS ON POPULATION GROWTH RATE AND EXTINCTION RISK  

EPA Science Inventory

Population structure and life history strategies are determinants of how populations respond to stressor-induced impairments in individual-level responses, but a consistent and holistic analysis has not been reported. Effects on population growth rate were modeled using five theo...

362

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

Microsoft Academic Search

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,

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

363

Nerve growth cone lamellipodia contain two populations of actin filaments that differ in organization and polarity  

PubMed Central

The organization and polarity of actin filaments in neuronal growth cones was studied with negative stain and freeze-etch EM using a permeabilization protocol that caused little detectable change in morphology when cultured nerve growth cones were observed by video- enhanced differential interference contrast microscopy. The lamellipodial actin cytoskeleton was composed of two distinct subpopulations: a population of 40-100-nm-wide filament bundles radiated from the leading edge, and a second population of branching short filaments filled the volume between the dorsal and ventral membrane surfaces. Together, the two populations formed the three- dimensional structural network seen within expanding lamellipodia. Interaction of the actin filaments with the ventral membrane surface occurred along the length of the filaments via membrane associated proteins. The long bundled filament population was primarily involved in these interactions. The filament tips of either population appeared to interact with the membrane only at the leading edge; this interaction was mediated by a globular Triton-insoluble material. Actin filament polarity was determined by decoration with myosin S1 or heavy meromyosin. Previous reports have suggested that the polarity of the actin filaments in motile cells is uniform, with the barbed ends toward the leading edge. We observed that the actin filament polarity within growth cone lamellipodia is not uniform; although the predominant orientation was with the barbed end toward the leading edge (47-56%), 22-25% of the filaments had the opposite orientation with their pointed ends toward the leading edge, and 19-31% ran parallel to the leading edge. The two actin filament populations display distinct polarity profiles: the longer filaments appear to be oriented predominantly with their barbed ends toward the leading edge, whereas the short filaments appear to be randomly oriented. The different length, organization and polarity of the two filament populations suggest that they differ in stability and function. The population of bundled long filaments, which appeared to be more ventrally located and in contact with membrane proteins, may be more stable than the population of short branched filaments. The location, organization, and polarity of the long bundled filaments suggest that they may be necessary for the expansion of lamellipodia and for the production of tension mediated by receptors to substrate adhesion molecules. PMID:1447299

1992-01-01

364

Models for optimal harvest with convex function of growth rate of a population  

SciTech Connect

Two models for growth of a population, which are described by a Cauchy problem for an ordinary differential equation with right-hand side depending on the population size and time, are investigated. The first model is time-discrete, i.e., the moments of harvest are fixed and discrete. The second model is time-continuous, i.e., a crop is harvested continuously in time. For autonomous systems, the second model is a particular case of the variational model for optimal control with constraints investigated in. However, the prerequisites and the method of investigation are somewhat different, for they are based on Lemma 1 presented below. In this paper, the existence and uniqueness theorem for the solution of the discrete and continuous problems of optimal harvest is proved, and the corresponding algorithms are presented. The results obtained are illustrated by a model for growth of the light-requiring green alga Chlorella.

Lyashenko, O.I.

1995-12-10

365

Getting the timing right: antler growth phenology and sexual selection in a wild red deer population  

Microsoft Academic Search

There has been growing interest in the determinants of the annual timing of biological phenomena, or phenology, in wild populations,\\u000a but research on vertebrate taxa has primarily focused on the phenology of reproduction. We present here analyses of the phenology\\u000a of the annual growth of a secondary sexual characteristic, antlers in red deer (Cervus elaphus) males. The long-term individual-based data

Michelle N. Clements; Tim H. Clutton-Brock; Steve D. Albon; Josephine M. Pemberton; Loeske E. B. Kruuk

2010-01-01

366

Comparisons of Sex-Specific Growth and Weight–Length Relationships in Minnesota Black Crappie Populations  

Microsoft Academic Search

We examined differences in sex-specific growth and weight–length relationships for five Minnesota populations of black crappies Pomoxis nigromaculatus. Male black crappies typically grew slightly faster than females, but observed differences in mean total lengths (TLs) at age were always 15 mm or less and were typically less than 10 mm. We detected few differences in log10(weight)–log10(TL) regressions between sexes, and

Daniel A. Isermann; Andrew L. Thompson; Philip J. Talmage

2010-01-01

367

AGRICULTURAL ADJUVANTS: ACUTE MORTALITY AND EFFECTS ON POPULATION GROWTH RATE OF DAPHNIA PULEXAFTER CHRONIC EXPOSURE  

Microsoft Academic Search

Abstract—Acute and chronic toxicity of eight agricultural adjuvants (Bond t, Kinetict, Plyact, R-11t, Silwet L-77t, Sylgard 309t, X-77t, and WaterMaxxt )t oDaphnia pulex were evaluated with 48-h acute lethal concentration estimates (LC50) and a 10-d population growth-rate measurement, the instantaneous rate of increase (ri). Based on LC50, the order of toxicity was R-11 . X- 77 5 Sylgard 309 5

JOHN D. STARK; W ILLIAM K. WALTHALL

2003-01-01

368

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

Microsoft Academic Search

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

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

2001-01-01

369

Fetal Growth and Risk of Stillbirth: A Population-Based Case–Control Study  

PubMed Central

Background Stillbirth is strongly related to impaired fetal growth. However, the relationship between fetal growth and stillbirth is difficult to determine because of uncertainty in the timing of death and confounding characteristics affecting normal fetal growth. Methods and Findings We conducted a population-based case–control study of all stillbirths and a representative sample of live births in 59 hospitals in five geographic areas in the US. Fetal growth abnormalities were categorized as small for gestational age (SGA) (<10th percentile) or large for gestational age (LGA) (>90th percentile) at death (stillbirth) or delivery (live birth) using population, ultrasound, and individualized norms. Gestational age at death was determined using an algorithm that considered the time-of-death interval, postmortem examination, and reliability of the gestational age estimate. Data were weighted to account for the sampling design and differential participation rates in various subgroups. Among 527 singleton stillbirths and 1,821 singleton live births studied, stillbirth was associated with SGA based on population, ultrasound, and individualized norms (odds ratio [OR] [95% CI]: 3.0 [2.2 to 4.0]; 4.7 [3.7 to 5.9]; 4.6 [3.6 to 5.9], respectively). LGA was also associated with increased risk of stillbirth using ultrasound and individualized norms (OR [95% CI]: 3.5 [2.4 to 5.0]; 2.3 [1.7 to 3.1], respectively), but not population norms (OR [95% CI]: 0.6 [0.4 to 1.0]). The associations were stronger with more severe SGA and LGA (<5th and >95th percentile). Analyses adjusted for stillbirth risk factors, subset analyses excluding potential confounders, and analyses in preterm and term pregnancies showed similar patterns of association. In this study 70% of cases and 63% of controls agreed to participate. Analysis weights accounted for differences between consenting and non-consenting women. Some of the characteristics used for individualized fetal growth estimates were missing and were replaced with reference values. However, a sensitivity analysis using individualized norms based on the subset of stillbirths and live births with non-missing variables showed similar findings. Conclusions Stillbirth is associated with both growth restriction and excessive fetal growth. These findings suggest that, contrary to current practices and recommendations, stillbirth prevention strategies should focus on both severe SGA and severe LGA pregnancies. Please see later in the article for the Editors' Summary PMID:24755550

Bukowski, Radek; Hansen, Nellie I.; Willinger, Marian; Reddy, Uma M.; Parker, Corette B.; Pinar, Halit; Silver, Robert M.; Dudley, Donald J.; Stoll, Barbara J.; Saade, George R.; Koch, Matthew A.; Rowland Hogue, Carol J.; Varner, Michael W.; Conway, Deborah L.; Coustan, Donald; Goldenberg, Robert L.

2014-01-01

370

Effect of Microstructure on Population Growth Parameters of Escherichia coli in Gelatin-Dextran Systems  

PubMed Central

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

Boons, Kathleen; Noriega, Estefanía; Van den Broeck, Rob; David, Charlotte C.; Hofkens, Johan

2014-01-01

371

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

PubMed Central

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

Picard, Nicolas; Liang, Jingjing

2014-01-01

372

Matrix models for size-structured populations: unrealistic fast growth or simply diffusion?  

PubMed

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 i to class i + 1, ? 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

Picard, Nicolas; Liang, Jingjing

2014-01-01

373

Dynamics and forecasting of population growth and urban expansion in Srinagar City - A Geospatial Approach  

NASA Astrophysics Data System (ADS)

The urban areas of developing countries are densely populated and need the use of sophisticated monitoring systems, such as remote sensing and geographical information systems (GIS). The urban sprawl of a city is best understood by studying the dynamics of LULC change which can be easily generated by using sequential satellite images, required for the prediction of urban growth. Multivariate statistical techniques and regression models have been used to establish the relationship between the urban growth and its causative factors and for forecast of the population growth and urban expansion. In Srinagar city, one of the fastest growing metropolitan cities situated in Jammu and Kashmir State of India, sprawl is taking its toll on the natural resources at an alarming pace. The present study was carried over a period of 40 years (1971-2011), to understand the dynamics of spatial and temporal variability of urban sprawl. The results reveal that built-up area has increased by 585.08 % while as the population has increased by 214.75 %. The forecast showed an increase of 246.84 km2 in built-up area which exceeds the overall carrying capacity of the city. The most common conversions were also evaluated.

Farooq, M.; Muslim, M.

2014-11-01

374

Estimation of contributions to population growth: a reverse-time capture-recapture approach  

USGS Publications Warehouse

We consider methods for estimating the relative contributions of different demographic components, and their associated vital rates, to population growth. We identify components of the population at time i (including a component for animals not in the population at i). For each such component we ask the following question: 'What is the probability that an individual randomly selected from the population at time i + 1 was a member of this component at i?' The estimation methods for these probabilities ((i) are based on capture-recapture studies of marked animal populations and use reverse-time modeling. We consider several different sampling situations and present example analyses for meadow voles, Microtus pennsylvanicus. The relationship between these (i parameters and elasticities (and other parameters based on projection matrix asymptotics) is noted and discussed. We conclude by suggesting that model-based asymptotics be viewed as demographic theory and that direct estimation approaches be used to test this theory with data from sampled populations with marked animals.

Nichols, J.D.; Hines, J.E.; Lebreton, J.D.; Pradel, R.

2000-01-01

375

Local environment and density-dependent feedbacks determine population growth in a forest herb.  

PubMed

Linking spatial variation in environmental factors to variation in demographic rates is essential for a mechanistic understanding of the dynamics of populations. However, we still know relatively little about such links, partly because feedbacks via intraspecific density make them difficult to observe in natural populations. We conducted a detailed field study and investigated simultaneous effects of environmental factors and the intraspecific density of individuals on the demography of the herb Lathyrus vernus. In regression models of vital rates we identified effects associated with spring shade on survival and growth, while density was negatively correlated with these vital rates. Density was also negatively correlated with average individual size in the study plots, which is consistent with self-thinning. In addition, average plant sizes were larger than predicted by density in plots that were less shaded by the tree canopy, indicating an environmentally determined carrying capacity. A size-structured integral projection model based on the vital rate regressions revealed that the identified effects of shade and density were strong enough to produce differences in stable population sizes similar to those observed in the field. The results illustrate how the local environment can determine dynamics of populations and that intraspecific density may have to be more carefully considered in studies of plant demography and population viability analyses of threatened species. We conclude that demographic approaches incorporating information about both density and key environmental factors are powerful tools for understanding the processes that interact to determine population dynamics and abundances. PMID:25224800

Dahlgren, Johan P; Ostergård, Hannah; Ehrlén, Johan

2014-12-01

376

Life-history correlates of maximum population growth rates in marine fishes.  

PubMed Central

Theory predicts that populations of animals with late maturity, low fecundity, large body size and low body growth rates will have low potential rates of population increase at low abundance. If this is true, then these traits may be used to predict the intrinsic rate of increase for species or populations, as well as extinction risks. We used life-history and population data for 63 stocks of commercially exploited fish species from the northeast Atlantic to test relationships between life-history parameters and the rate of population increase at low abundance. We used cross-taxonomic analyses among stocks and among species, and analyses that accounted for phylogenetic relationships. These analyses confirmed that large-bodied, slow-growing stocks and species had significantly lower rates of recruitment and adult production per spawning adult at low abundance. Furthermore, high ages at maturity were significantly correlated with low maximum recruit production. Contrary to expectation, fecundity was significantly negatively related to recruit production, due to its positive relationship with maximum body size. Our results support theoretical predictions, and suggest that a simply measured life-history parameter can provide a useful tool for predicting rates of recovery from low population abundance. PMID:12427316

Denney, Nicola H; Jennings, Simon; Reynolds, John D

2002-01-01

377

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

PubMed

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

Leta, Samson; Mesele, Frehiwot

2014-01-01

378

The impact of population growth on environment: the debate heats up.  

PubMed

A proposed framework, which was introduced at the 1989 meetings of the American Association for the Advancement of Science, included political constraints as well as population growth as a proximate cause with potentially important impacts on the environment in Paul and Ann Ehrlich's well-known PAT equation. PAT limitations are identified as the 1.2 billion people caught in the debt-poverty trap, less developed countries' balance of payments deficits, and "distortionary factors" that undermined economic incentives and contributed to mismanagement of resources. Such factors could be keeping farm prices low and have an impact on deterring use of environmentally sound traditional agricultural practices. Mismanagement of public lands occurs when large commercial enterprises or large scale mechanization displace population onto marginal or less productive lands. Intergroup warfare is a new form impacting on the environment. In Burma loggers are authorized to clear cut large tracts of teak forests in order to ferret out Karen guerrillas. Over 15 million refugees were thus displaced and forced to live in encampments that require trees for shelter, firewood for survival, and overgrazing of livestock. Social and economic environments are also undermined by "dependency" factors such as trade protectionism, brain drain, and limited foreign aid. The Group of 77 Non-Aligned Developing Countries proposed that discussions of the links between population and the environment be omitted from the agenda of the 1994 UN Conference on Population and Development. Basic clarifications are needed to distinguish ultimate versus proximate factors and current versus future concerns. The debate ignores distribution patterns, migration, or changing age structures. The debate blames unjustifiably rapid population growth as the ultimate cause of global environmental degradation and links population growth to a host of other social problems such as famine and refugees, while ignoring civil unrest. The evidence suggests that population limitation will probably prevent environmental degradation in poor, resource constrained countries from getting worse. Resource conservation will remain unaffected. The World Bank proposes National Environmental Action Plans or the Cleaver Schreiber proposal for a "nexus strategy" for balancing food supply and population in Africa. PMID:12290504

Shaw, R P

1992-02-01

379

Age, growth, and population structure of the smooth clam Callista chione in the eastern Adriatic Sea  

NASA Astrophysics Data System (ADS)

The age, growth, and population structure of the smooth clam Callista chione were determined from samples collected by hydraulic dredge and SCUBA at four locations in the eastern Adriatic during 2007 and 2008. The age of 436 clam shells was determined from internal growth lines present in shell sections, and the timing of growth line formation was ascertained from monthly collections of clams to occur between August and September when sea water temperatures were maximal. In addition, age of 30 older individuals was verified with acetate peels of polished and etched shell sections. Differences were apparent in the age structure and growth rates of clams collected from the four locations studied. Von Bertalanffy growth (VBG) curves obtained for clams from these locations were L t = 72.4 (1-e-0.25(t - 2.68)) (Rab Island), L t = 74.5 (1-e-0.15(t + 0.57)) (Pag Bay), L t = 79.3 (1-e-0.34(t - 0.97)) (Cetina estuary), and L t = 82.5 (1-e-0.11(t + 2.88)) (Kaštela Bay). The age of the clams ranged between 3 and 44 years; median clam ages were similar at three of the four locations (14, 12, and 12 years, respectively), but was significantly lower in the Cetina estuary (4 years). The VBG growth constants recorded from clams were within the range of values obtained for this species by previous authors. The observed local differences in population structure indicate different levels of exploitation and illustrate the need to establish long-term strategies for a sustainable exploitation of smooth clams in the Croatian Adriatic.

Ezgeta-Bali?, Daria; Peharda, Melita; Richardson, Christopher A.; Kuzmani?, Marina; Vrgo?, Nedo; Isajlovi?, Igor

2011-12-01

380

Anatomy of a bottleneck: diagnosing factors limiting population growth in the Puerto Rican parrot  

USGS Publications Warehouse

The relative importance of genetic, demographic, environmental, and catastrophic processes that maintain population bottlenecks has received little consideration. We evaluate the role of these factors in maintaining the Puerto Rican Parrot (Amazona vittata) in a prolonged bottleneck from 1973 through 2000 despite intensive conservation efforts. We first conduct a risk analysis, then examine evidence for the importance of specific processes maintaining the bottleneck using the multiple competing hypotheses approach, and finally integrate these results through a sensitivity analysis of a demographic model using life-stage simulation analysis (LSA) to determine the relative importance of genetic, demographic, environmental, and catastrophic processes on population growth. Annual population growth has been slow and variable (1.0 6 5.2 parrots per year, or an average k?1.05 6 0.19) from 16 parrots (1973) to a high of 40-42 birds (1997-1998). A risk analysis based on population prediction intervals (PPI) indicates great risk and large uncertainty, with a range of 22?83 birds in the 90% PPI only five years into the future. Four primary factors (reduced hatching success due to inbreeding, failure of adults to nest, nest failure due to nongenetic causes, and reduced survival of adults and juveniles) were responsible for maintaining the bottleneck. Egghatchability rates were low (70.6% per egg and 76.8% per pair), and hatchability increased after mate changes, suggesting inbreeding effects. Only an average of 34% of the population nested annually, which was well below the percentage of adults that should have reached an age of first breeding (41-56%). This chronic failure to nest appears to have been caused primarily by environmental and/or behavioral factors, and not by nest-site scarcity or a skewed sex ratio. Nest failure rates from nongenetic causes (i.e., predation, parasitism, and wet cavities) were low (29%) due to active management (protecting nests and fostering captive young into wild nests), diminishing the importance of nest failure as a limiting factor. Annual survival has been periodically reduced by catastrophes (hurricanes), which have greatly constrained population growth, but survival rates were high under non-catastrophic conditions. Although the importance of factors maintaining the Puerto Rican Parrot bottleneck varied throughout the 30-year period of study, we determined their long-term influence using LSA simulations to correlate variation in demographic rates with variation in population growth (k). The bottleneck appears to have been maintained primarily by periodic catastrophes (hurricanes) that reduced adult survival, and secondarily by environmental and/or behavioral factors that resulted in a failure of many adults to nest. The influence of inbreeding through reduced hatching success played a much less significant role, even when additional effects of inbreeding on the production and mortality of young were incorporated into the LSA. Management actions needed to speed recovery include (1) continued nest guarding to minimize the effects of nest failure due to nongenetic causes; (2) creating a second population at another location on the island --a process that was recently initiated--to reduce the chance that hurricane strikes will cause extinction; and (3) determining the causes of the low percentage of breeders in the population and ameliorating them, which would have a large impact on population growth.

Beissenger, S.R.; Wunderle, J.M., Jr.; Meyers, J.M.; Saether, B.-E.; Engen, S.

2008-01-01

381

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

NASA Astrophysics Data System (ADS)

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;

Bagan, H.; Yamagata, Y.

2012-12-01

382

Integrating physiological and biomechanical drivers of population growth over environmental gradients on coral reefs.  

PubMed

Coral reefs exhibit marked spatial and temporal variability, and coral reef organisms exhibit trade-offs in functional traits that influence demographic performance under different combinations of abiotic environmental conditions. In many systems, trait trade-offs are modelled using an energy and/or nutrient allocation framework. However, on coral reefs, differences in biomechanical vulnerability have major demographic implications, and indeed are believed to play an essential role in mediating species coexistence because highly competitive growth forms are vulnerable to physical dislodgment events that occur with high frequency (e.g. annual summer storms). Therefore, an integrated energy allocation and biomechanics framework is required to understand the effect of physical environmental gradients on species' demographic performance. However, on coral reefs, as in most ecosystems, the effects of environmental conditions on organisms are measured in different currencies (e.g. lipid accumulation, survival and number of gametes), and thus the relative contributions of these effects to overall capacity for population growth are not readily apparent. A comprehensive assessment of links between the environment and the organism, including those mediated by biomechanical processes, must convert environmental effects on individual-level performance (e.g. survival, growth and reproduction) into a common currency that is relevant to the capacity to contribute to population growth. We outline such an approach by considering the population-level performance of scleractinian reef corals over a hydrodynamic gradient, with a focus on the integrating the biomechanical determinants of size-dependent coral colony dislodgment as a function of flow, with the effects of flow on photosynthetic energy acquisition and respiration. PMID:22357590

Madin, Joshua S; Hoogenboom, Mia O; Connolly, Sean R

2012-03-15

383

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

PubMed Central

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

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

2004-01-01

384

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

PubMed Central

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

Nicolè, Florence; Jacquemyn, Hans; Tuljapurkar, Shripad

2013-01-01

385

Examining perceptions of rapid population growth in North and South Gondar zones, northwest Ethiopia.  

PubMed

Ethiopia is one of the most populous countries in Africa and ranks second only to Nigeria. Rapid population growth has hampered the country's development, making the eradication of extreme poverty and hunger difficult. This study which had two components--quantitative and qualitative--was aimed at exploring the perceptions of women and other social groups on the prevailing population pressures. The quantitative study involved 3,512 women aged 15-49 years. The qualitative study consisted of five focus-group discussions and six key-informant interviews. Over 90% of women (n = 3,512) who participated in the quantitative study and nearly all the focus-group discussants and interviewees (n = 39) felt that something should be done to keep the population from growing too fast. Most (over 90%) participants approved of the Government passing a law regarding the maximum number of children that a couple should have. It is, therefore, timely for the responsible bodies to exert maximum effort and commitment in responding to the emerging attitudes of the people by making the population problem a priority. PMID:20099762

Alene, Getu Degu; Worku, Alemayehu

2009-12-01

386

National Health Expenditure Growth in the 1980's: An Aging Population, New Technologies, and Increasing Competition  

PubMed Central

Health care spending in the United States more than tripled between 1971 and 1981, increasing from $83 billion to $287 billion. This growth in health sector spending substantially outpaced overall growth in the economy, averaging 13.2 percent per year compared to 10.5 percent for the gross national product (GNP). By 1981, one out of every ten dollars of GNP was spent on health care, compared to one out of every thirteen dollars of GNP in 1971. If current trends continue and if present health care financing arrangements remain basically unchanged, national health expenditures are projected to reach approximately $756 billion in 1990 and consume roughly 12 percent of GNP. The focal issue in health care today is cost and cost Increases. The outlook for the 1980's is for continued rapid growth but at a diminished rate. The primary force behind this moderating growth is projected lower inflation. However, real growth rates are also expected to moderate slightly. The chief factors influencing the growth of health expenditures in the eighties are expected to be aging of the population, new medical technologies, increasing competition, restrained public funding, growth in real income, increased health manpower, and a deceleration in economy-wide inflation. Managers, policy makers and providers in the health sector, as in all sectors, must include in today's decisions probable future trends. Inflation, economic shocks, and unanticipated outcomes of policies over the last decade have intensified the need for periodic assessments of individual industries and their relationship to the macro economy. This article provides such an assessment for the health care industry. Baseline current-law projections of national health expenditures are made to 1990. PMID:10309852

Freeland, Mark S.; Schendler, Carol Ellen

1983-01-01

387

Translating effects of inbreeding depression on component vital rates to overall population growth in endangered bighorn sheep.  

PubMed

Evidence of inbreeding depression is commonly detected from the fitness traits of animals, yet its effects on population growth rates of endangered species are rarely assessed. We examined whether inbreeding depression was affecting Sierra Nevada bighorn sheep (Ovis canadensis sierrae), a subspecies listed as endangered under the U.S. Endangered Species Act. Our objectives were to characterize genetic variation in this subspecies; test whether inbreeding depression affects bighorn sheep vital rates (adult survival and female fecundity); evaluate whether inbreeding depression may limit subspecies recovery; and examine the potential for genetic management to increase population growth rates. Genetic variation in 4 populations of Sierra Nevada bighorn sheep was among the lowest reported for any wild bighorn sheep population, and our results suggest that inbreeding depression has reduced adult female fecundity. Despite this population sizes and growth rates predicted from matrix-based projection models demonstrated that inbreeding depression would not substantially inhibit the recovery of Sierra Nevada bighorn sheep populations in the next approximately 8 bighorn sheep generations (48 years). Furthermore, simulations of genetic rescue within the subspecies did not suggest that such activities would appreciably increase population sizes or growth rates during the period we modeled (10 bighorn sheep generations, 60 years). Only simulations that augmented the Mono Basin population with genetic variation from other subspecies, which is not currently a management option, predicted significant increases in population size. Although we recommend that recovery activities should minimize future losses of genetic variation, genetic effects within these endangered populations-either negative (inbreeding depression) or positive (within subspecies genetic rescue)-appear unlikely to dramatically compromise or stimulate short-term conservation efforts. The distinction between detecting the effects of inbreeding depression on a component vital rate (e.g., fecundity) and the effects of inbreeding depression on population growth underscores the importance of quantifying inbreeding costs relative to population dynamics to effectively manage endangered populations. PMID:22070275

Johnson, Heather E; Mills, L Scott; Wehausen, John D; Stephenson, Thomas R; Luikart, Gordon

2011-12-01

388

Temperature-dependent population growth of three species of stored product mites (Acari: Acaridida).  

PubMed

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions. In this study we investigated the effect of temperature, ranging from 5 to 35 degrees C, on the population growth of three important mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of mites was observed after 3 weeks of cultivation, or after 6 weeks for those kept at low temperatures (5, 10, 12.5, and 15 degrees C). The rate of increase was calculated for each temperature and species. The obtained data were fitted with polynomial models. The mite population growth rates increased with increasing moderate temperatures until 25 degrees C, when r ( m )-values were 0.179, 0.177 and 0.190 for A. siro, A. ovatus and T. putrescentiae, respectively. The lower development threshold was 10.2 degrees C in all three species. Estimated upper temperature threshold was higher in T. putrescentiae (49 degrees C) than in A. siro and A. ovatus (38 degrees C). Simulation of the rate of population increase under ideal conditions, using real temperature records obtained from Czech grain stores, showed that the pest mite populations increase only during 3.5 months within a typical 9-month storage season in Central Europe. These results indicate that control of mites, be it chemical, physical or biological, is recommended during the months when allergens and pests are produced, i.e. from September to mid November and in May. PMID:17479350

Aspaly, Gamila; Stejskal, Vaclav; Pekár, Stano; Hubert, Jan

2007-01-01

389

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

PubMed

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

Ockinger, Erik; Nilsson, Sven G

2010-07-01

390

Influence of projected ocean warming on population growth potential in two North Atlantic copepod species  

NASA Astrophysics Data System (ADS)

Copepods of the genera Pseudocalanus and Centropages play an important role in the North Atlantic ecosystems and have distinctive spatial and temporal patterns depending on physiological adaptation to different environmental conditions. To examine the possible impact of climate change on these biogeographic patterns, potential population growth rate was computed for each species using IPCC projections of sea surface temperature together with chlorophyll distributions from SeaWiFS climatology and published laboratory data on temperature and food-dependent life-history parameters. The results indicate that the predicted temperature increase throughout the North Atlantic will cause temporal and spatial shifts in copepod species population growth potential. The Centropages population is projected to increase in mid-latitudinal shelf areas, e.g. the Gulf of Maine and the North Sea, due to shorter generation times and a longer growing season, while Pseudocalanus is predicted to be less abundant in these regions after 2050. These shifts potentially have a significant impact on the future demographics of pelagic fish species for which the copepods are the major food source.

Stegert, Christoph; Ji, Rubao; Davis, Cabell S.

2010-10-01

391

THE IMPACT OF HISPANIC POPULATION GROWTH ON THE OUTLOOK OF AFRICAN AMERICANS  

PubMed Central

We know too little about the effects of immigration on black Americans. If prior research yields mixed evidence about immigration’s consequences for the objective well-being of African Americans, it is silent about effects of immigration on blacks’ subjective well-being. To fill that void, this paper assesses the impact of the expanding Hispanic population on black Americans from a social psychological perspective. We ask whether blacks’ self-reported distress, social distrust, or attitudes toward Hispanics and immigrants are affected by the size of the local Hispanic population or by the percentage growth in local Hispanic residents. Answers come from responses of non-Hispanic black participants in the 1998–2002 General Social Surveys, linked to 1990 and 2000 census data. Contrary to pessimistic claims, most social psychological outcomes, including measures of economic distress, manifest no impact of local Hispanic numbers. The four exceptions, significant effects of local Hispanic population share or percentage growth evenly split in valence, underscore the complexity of recent immigration’s effects on African Americans. PMID:25242830

Taylor, Marylee C.; Schroeder, Matthew B.

2014-01-01

392

The petroleum exponential (again)  

NASA Astrophysics Data System (ADS)

The U.S. production and reserves of liquid and gaseous petroleum have declined since 1960, at least in the lower 48 states. This decline stems from decreased discovery rates, as predicted by M. King Hubbert in the mid-1950's. Hubbert's once unpopular views were based on statistical analysis of the production history of the petroleum industry, and now, even with inclusion of the statistical perturbation caused by the Prudhoe Bay-North Alaskan Slope discovery (the largest oil field ever found in the United States), it seems clear again that production is following the exponential curve to depletion of the resource—to the end of the ultimate yield of petroleum from wells in the United States.In a recent report, C. Hall and C. Cleveland of Cornell University show that large atypical discoveries, such as the Prudhoe Bay find, are but minor influences on what now appears to be the crucial intersection of two exponentials [Science, 211, 576-579, 1981]: the production-per-drilled-foot curve of Hubbert, which crosses zero production no later than the year 2005; the other, a curve that plots the energy cost of drilling and extraction with time; that is, the cost-time rate of how much oil is used to drill and extract oil from the ground. The intersection, if no other discoveries the size of the Prudhoe Bay field are made, could be as early as 1990, the end of the present decade. The inclusion of each Prudhoe-Bay-size find extends the year of intersection by only about 6 years. Beyond that point, more than one barrel of petroleum would be expended for each barrel extracted from the ground. The oil exploration-extraction and refining industry is currently the second most energy-intensive industry in the U.S., and the message seems clear. Either more efficient drilling and production techniques are discovered, or domestic production will cease well before the end of this century if the Hubbert analysis modified by Hall and Cleveland is correct.

Bell, Peter M.

393

Variation in age-structured vital rates of a long-lived raptor: Implications for population growth  

Microsoft Academic Search

Age-structured variation in multiple vital-rates is a fundamental determinant of population growth, with important implications for conservation management. However, for many long-lived vertebrates such as birds of prey, such variation has been usually examined in shorter-lived species. Here, we investigate the pattern of age-related variation in fitness components and its repercussions on population growth for a migratory raptorial bird, the

Fabrizio Sergio; Giacomo Tavecchia; Julio Blas; Lidia López; Alessandro Tanferna; Fernando Hiraldo

2011-01-01

394

Phase Space Interpretation of Exponential Fermi Acceleration  

E-print Network

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.

Benno Liebchen; Robert Büchner; Christoph Petri; Fotis K. Diakonos; Florian Lenz; Peter Schmelcher

2011-07-18

395

IKVAV regulates ERK1/2 and Akt signalling pathways in BMMSC population growth and proliferation  

PubMed Central

Objectives The molecular mechanism of bone marrow mesenchymal stem cell (BMMSC) population growth and proliferation, induced by Isoleucyl-lysyl-valyl-alanyl-valine (IKVAV), was explored in this study. Materials and methods IKVAV peptides were synthesized by the solid-phase method. Influence of IKVAV on BMMSC population growth and proliferation were investigated by assays of CCK-8, flow cytometry, real-time PCR and western blotting. Results IKVAV peptide was found to induce proliferation and proliferating cell nuclear antigen (PCNA) synthesis of BMMSC in a dose- and time-dependent manner. Cell cycle analysis showed that the proportion of IKVAV-treated BMMSC in S phase in was higher than controls. Western blot results suggested that mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signalling pathways were activated by IKVAV by enhancing phosphorylation levels of ERK1/2 and Akt in the BMMSCs. Meanwhile, phosphorylation levels of ERK1/2 and Akt were partially blocked by ERK1/2 inhibitor (PD98059) and Akt inhibitor (wortmannin), respectively. Conclusions Our results demonstrated that IKVAV stimulated BMMSC population growth and proliferation by activating MAPK/ERK1/2 and PI3K/Akt signalling pathways. This study is the first to reveal an enhancement effect of IKVAV peptide on BMMSC at the signal transduction level, and the outcome could provide experimental evidence for application of IKVAV-grafted scaffolds in the field of BMMSC-based tissue engineering. PMID:24617901

Li, B; Qiu, T; Zhang, P; Wang, X; Yin, Y; Li, S

2014-01-01

396

Phylogenetic prediction of the maximum per capita rate of population growth  

PubMed Central

The maximum per capita rate of population growth, r, is a central measure of population biology. However, researchers can only directly calculate r when adequate time series, life tables and similar datasets are available. We instead view r as an evolvable, synthetic life-history trait and use comparative phylogenetic approaches to predict r for poorly known species. Combining molecular phylogenies, life-history trait data and stochastic macroevolutionary models, we predicted r for mammals of the Caniformia and Cervidae. Cross-validation analyses demonstrated that, even with sparse life-history data, comparative methods estimated r well and outperformed models based on body mass. Values of r predicted via comparative methods were in strong rank agreement with observed values and reduced mean prediction errors by approximately 68 per cent compared with two null models. We demonstrate the utility of our method by estimating r for 102 extant species in these mammal groups with unknown life-history traits. PMID:23720545

Fagan, William F.; Pearson, Yanthe E.; Larsen, Elise A.; Lynch, Heather J.; Turner, Jessica B.; Staver, Hilary; Noble, Andrew E.; Bewick, Sharon; Goldberg, Emma E.

2013-01-01

397

Climate change and population growth in Timor Leste: implications for food security.  

PubMed

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

Molyneux, Nicholas; da Cruz, Gil Rangel; Williams, Robert L; Andersen, Rebecca; Turner, Neil C

2012-12-01

398

Increasing population growth by asymmetric segregation of a limiting resource during cell division  

PubMed Central

We report that when budding yeast are transferred to low-metal environment, they adopt a proliferation pattern in which division is restricted to the subpopulation of mother cells which were born in rich conditions, before the shift. Mother cells continue to divide multiple times following the shift, generating at each division a single daughter cell, which arrests in G1. The transition to a mother-restricted proliferation pattern is characterized by asymmetric segregation of the vacuole to the mother cell and requires the transcription repressor Whi5. Notably, while deletion of WHI5 alleviates daughter cell division arrest in low-zinc conditions, it results in a lower final population size, as cell division rate becomes progressively slower. Our data suggest a new stress-response strategy, in which the dilution of a limiting cellular resource is prevented by maintaining it within a subset of dividing cells, thereby increasing population growth. PMID:23591772

Avraham, Nurit; Soifer, Ilya; Carmi, Miri; Barkai, Naama

2013-01-01

399

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

PubMed

Stochastic matrix projection models are widely used to model age- or stage-structured populations with vital rates that fluctuate randomly over time. Practical applications of these models rest on qualitative properties such as the existence of a long term population growth rate, asymptotic log-normality of total population size, and weak ergodicity of population structure. We show here that these properties are shared by a general stochastic integral projection model, by using results in (Eveson in D. Phil. Thesis, University of Sussex, 1991, Eveson in Proc. Lond. Math. Soc. 70, 411-440, 1993) to extend the approach in (Lange and Holmes in J. Appl. Prob. 18, 325-344, 1981). Integral projection models allow individuals to be cross-classified by multiple attributes, either discrete or continuous, and allow the classification to change during the life cycle. These features are present in plant populations with size and age as important predictors of individual fate, populations with a persistent bank of dormant seeds or eggs, and animal species with complex life cycles. We also present a case-study based on a 6-year field study of the Illyrian thistle, Onopordum illyricum, to demonstrate how easily a stochastic integral model can be parameterized from field data and then applied using familiar matrix software and methods. Thistle demography is affected by multiple traits (size, age and a latent "quality" variable), which would be difficult to accommodate in a classical matrix model. We use the model to explore the evolution of size- and age-dependent flowering using an evolutionarily stable strategy (ESS) approach. We find close agreement between the observed flowering behavior and the predicted ESS from the stochastic model, whereas the ESS predicted from a deterministic version of the model is very different from observed flowering behavior. These results strongly suggest that the flowering strategy in O. illyricum is an adaptation to random between-year variation in vital rates. PMID:17123085

Ellner, Stephen P; Rees, Mark

2007-02-01

400

Beaver-mediated methane emission: The effects of population growth in Eurasia and the Americas.  

PubMed

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

Whitfield, Colin J; Baulch, Helen M; Chun, Kwok P; Westbrook, Cherie J

2015-02-01

401

Population growth and development in the Third World: the neocolonial context.  

PubMed

Less developed countries (LDCs) that were colonies of other nations continued operating under the same social and political structures set up by the former ruling nations. The small minority of elites in the LDCs held on to the power acquired during colonial times. In order to preserve their political and financial status after independence, they maintained their close linkages to the capitalist nations and their multinational corporations (MNCs). The elites did not generally have popular support, however. These capitalist nations and their commercial interests continue to dictate most LDCs development process which supports the financial interests of the MNCs and the local elites and not those of the majority, the poor. The poor realize that they are trapped and unable to break away from the economic and political structures, therefore, to assure some form of security, they have many children which exacerbates their poverty. Yet population control policies based on Malthusian theory and those that rely on such undimensional, technical approaches as family planning alone cannot cure the multidimensional social problems of high population growth and poverty. Neither the Malthusian nor Marxist theories totally explain the situation in the LDCs or even provide workable solutions. Research on population and development in LDCs needs to address both the Malthusian concern for the problems posed by high growth rates and the Marxist critique of class struggle in development trends. To eliminate the trap of poverty and dependent economies, each country must design its own remedies based on its history, culture, and geography and alter the prevailing social, economic, and political power structures in favor of the poor. 6 propositions that must be modified to each nation's particular problems and needs are presented to guide LDCs in formulating or reformulating policies to alleviate the problems of population and poverty. PMID:12342352

Patterson, J G; Shrestha, N R

1988-01-01

402

Bushmeat poaching reduces the seed dispersal and population growth rate of a mammal-dispersed tree.  

PubMed

Myriad tropical vertebrates are threatened by overharvest. Whether this harvest has indirect effects on nonhunted organisms that interact with the game species is a critical question. Many tropical birds and mammals disperse seeds. Their overhunting in forests can cause zoochorous trees to suffer from reduced seed dispersal. Yet how these reductions in seed dispersal influence tree abundance and population dynamics remains unclear. Reproductive parameters in long-lived organisms often have very low elasticities; indeed the demographic importance of seed dispersal is an open question. We asked how variation in hunting pressure across four national parks with seasonal forest in northern Thailand influenced the relative abundance of gibbons, muntjac deer, and sambar deer, the sole dispersers of seeds of the canopy tree Choerospondias axillaris. We quantified how variation in disperser numbers affected C. axillaris seed dispersal and seedling abundance across the four parks. We then used these data in a structured population model based on vital rates measured in Khao Yai National Park (where poaching pressure is minimal) to explore how variation in illegal hunting pressure might influence C. axillaris population growth and persistence. Densities of the mammals varied strongly across the parks, from relatively high in Khao Yai to essentially zero in Doi Suthep-Pui. Levels of C. axillaris seed dispersal and seedling abundance positively tracked mammal density. If hunting in Khao Yai were to increase to the levels seen in the other parks, C. axillaris population growth rate would decline, but only slightly. Extinction of C. axillaris is a real possibility, but may take many decades. Recent and ongoing extirpations of vertebrates in many tropical forests could be creating an extinction debt for zoochorous trees whose vulnerability is belied by their current abundance. PMID:19544729

Brodie, Jedediah F; Helmy, Olga E; Brockelman, Warren Y; Maron, John L

2009-06-01

403

Thyroxine affects behavioral thermoregulation but not growth rate among populations of the western fence lizard ( Sceloporus occidentalis )  

Microsoft Academic Search

We investigated whether thyroxine influences hatchling growth rate of the western fence lizard (Sceloporus occidentalis) throught its effects on thermoregulatory behaviors. We reared control and thyroxine-injected hatchlings from three populations of S. occidentalis that differ in growth rate in a thermal gradient. We also measured the daily changes in body temperature and activity level (proportion of time spent out of

B. Sinervo; K. D. Dunlap

1995-01-01

404

Dynamics of harvested populations of the tropical understory herb Aechmea magdalenae in old-growth versus secondary forests  

Microsoft Academic Search

The prevalence of secondary forests is increasing across tropical landscapes, but the effects of these environments on the population dynamics of understory species and on their capacity to regenerate after harvest remains poorly documented. We compare the population dynamics of the understory bromeliad, Aechmea magdalenae, between old-growth and secondary rainforests in Southeast Mexico. A. magdalenae is a non-timber forest product

T. Ticktin; P. Nantel

2004-01-01

405

Measurement of the intraspecific variation in population growth rate under controlled conditions in the clonal parthenogen Daphnia magna  

Microsoft Academic Search

Clones of parthenogenetically reproducing females of Daphnia magna were developed from females derived from the same wild population. Significant differences were found between the population growth rates of such clones under controlled conditions. Such variation showed no clear relationship to electrophoretic differences at the GOT and esterase-1 loci between the clones. The extent to which such variation represents fitness variation

J. F. Y. Brookfield

1984-01-01

406

On the Matrix Exponential Function  

ERIC Educational Resources Information Center

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.

Hou, Shui-Hung; Hou, Edwin; Pang, Wan-Kai

2006-01-01

407

Euler's number II: Complex exponentials  

NSDL National Science Digital Library

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.

2013-06-21

408

Function Estimation Employing Exponential Splines  

NASA Astrophysics Data System (ADS)

We introduce and discuss the use of the exponential spline family for Bayesian nonparametric function estimation. Exponential splines span the range of shapes between the limiting cases of traditional cubic spline and piecewise linear interpolation. They are therefore particularly suited for problems where both, smooth and rapid function changes occur.

Dose, V.; Fischer, R.

2005-11-01

409

World population and energy growth: Impact on the Caribbean and the roles of energy efficiency improvements and renewable energies  

SciTech Connect

This paper briefly describes population and energy use trends and their consequences, particularly to the Caribbean region. Historical trends for transitional countries show a decrease in population growth rate as annual per capita commercial energy use increases. If trends continue, an increase in per capita energy will be important to stabilizing populations of transitional countries. Energy efficiency improvements, the role of fossil energy, and the use of alternative energy sources in Caribbean nations are briefly discussed. 6 refs., 3 figs.

Sheffield, J.

1997-06-01

410

Some socio-economic aspects of population growth in the USSR.  

PubMed

This summarizes population trends in the U.S.S.R. since the early 19 00's. On August 9, 1973, the population topped 250 million, almost precisely double that of Russia at the time of the 1st general census in 1897. Since 1922 it had increased by more than 84%. Russia has suffered more population loss in wars than any other country in modern times. The First World War, the Civil War, and the Second World War took a toll of more than 30 million, more than 20 million during the Second World War alone. The extent of these loses can be judged from the following: between 1897 and 1913 the population of Russia increased at the rate of 1.55% per annum or 34.6 million; if this had continued the population would have been at least 182.8 million by the end of 1922. As it was, the population was 136.1 million by 1922 and the hypothetical 182.8 million was not reached until 1952. More than 4/5 of today's population have been born since the October Revolution. Only 43 million were born before the revolution and only 7.5 were born in the last century. The economic base has grown much more rapidly than the population. For the period 1940-1972 the population increased 1.27 times, national income 9.51 times, fixed assets, 8.76 times, industrial production, 13.65 times, agricultural output, 2.14 times, and capital investment 14.52 times. The birthrate has been falling since World War 1 but total population growth has increased steadily. Birthrates have declined from 45.5/1000 in 1913 to 17.8/1000 in 1972 and a slight upturn is seen. It is expected that the birthrate will continue to increase slightly, then stabilize. Much of the population increase has come from significantly reduced mortality rates. 1st and 2nd children now account for 71% of all births. Family allowances, child care, free health care, and other social benefits encourage births while high employment levels for women, a shortage of men in the marriageable age ranges, and late marriages tend to depress the birthrate. The shortage of men is directly the result of the losses during World War 2. Employment opportunities have changed dramatically. The country has gone from a primarily agricultural nation to one in which 80% of the people are working class wage or salary earners. The current problem is closing the urban-rural gap and equalizing population density. 3/5 of the people are town-dwellers. To fight declining population in the villages and in the areas of Siberia and the Far East, new towns and new industrial and cultural centers are being established such as Bratsk, Ust-Ilim, Norilsk, and others. PMID:12307196

Simchera, V

1974-01-01

411

Water scarcity in the tropical Andes: population growth outweighs climate change  

NASA Astrophysics Data System (ADS)

Globally, water resources for cities are under increasing stress. Two main stressors are climate change and population growth, but evaluating their relative impact is difficult, especially because of the complex topology of water supply. This is especially true in the tropical Andes, which is a region with strong climatic gradients and topographical limits to water resources. In this study we present an evaluation of both stressors on water resources in a geospatial framework to identify gradients in water availability that may lead to conflicts over water use. We focus on 4 major cities in, or receiving water from the tropical Andes. A multi-model dataset of 19 climate models is used as input for a regional water balance model. Per capita water availability is evaluated along topographic gradients for the present, and for future scenarios of population growth and climate change. In all cases, the median projection of climate change suggests a relatively limited impact on water availability but uncertainties are large. Despite these uncertainties, we find that the expected demographic changes are very likely to outpace the impact of climate change on water availability and should therefore be the priority for local policy making. However, distinctive geospatial patterns characterize the supply systems of the studied cities, highlighting the need to analyse the topology of water supply within an ecosystem services context. Our approach is flexible enough to be extended to other regions, stressors and water resources topologies.

Buytaert, W.; De Bièvre, B.

2012-12-01

412

Genetic diversity of different populations and improved growth in the F1 hybrids in the swimming crab (Portunus trituberculatus).  

PubMed

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

Gao, B Q; Liu, P; Li, J; Wang, Q Y; Li, X P

2014-01-01

413

Population trends, growth, and movement of bigmouth buffalo, Ictiobus cyprinellus, in Lake Oahe, 1963-70  

USGS Publications Warehouse

The bigmouth buffalo, Ictiobus cyprinellus, is the most important commercial species in Lake Oahe, a reservoir in the upper Missouri River. The population was dominated by three strong year classes (1959, 1960, and 1962). Estimated population in the fall of 1964 was 540,000 fish of the combined 1959-60 year classes and 5 million of the 1962 year class (equivalent to 81 kg per hectare). Abundance declined irregularly during 1964-70. Annual landings of these two dominant groups during 1965-70 ranged from 149 to 271 metric tons. The total landings during the period amounted to about 151,800 fish of the 1959-60 year classes and 313,000 fish of the 1962 year class. Growth rate was high during the first few years of impoundment and then declined. Males and females grew at about the same rate for the first 4 yr of life, but females were longer and heavier than males at ages V-VIII. At these ages, fish of the 1962 year class were about 10% shorter and 36% lighter than those of the 1959 year class. Growth of tagged and untagged fish was similar. The number of females per male increased with age. Age at maturity increased slightly as growth rate declined. Movement of marked fish was extensive and the recapture of marked fish was directly related to size of fish, location of release, and subsequent fishing pressure; 44% were recaptured downstream from the point of release, and 38% upstream. Females showed a stronger tendency to move downstream than males. Maximum distance traveled was 380 km and maximum rate of travel was 6.4 km per day. Successful reproduction appeared to be associated with flooding of shoreline vegetation during spring and early summer. Inasmuch as little such flooding is expected in the future, annual landings of bigmouth buffalo will probably continue to decline sharply.

Moen, Thomas E.

1974-01-01

414

Population dynamics and growth of the bivalve Choromytilus meridionalis (Kr.) at different tidal levels  

NASA Astrophysics Data System (ADS)

Settlement, growth and reproductive output of a population of Choromytilus meridionalis have been monitored at different shore levels at Bailey's Cottage, False Bay, South Africa. Settlement was irregular, occurring at 4- to 6-year intervals, and confined to the sublittoral and lower littoral of rocky areas. Spat settled on the existing mussel bed and adjacent clean rock surfaces. Continual migration of young mussels up the shore took place during the first 1 to 1·5 years of growth until an even distribution up to 0·5 m above L.W.S. was achieved. Juveniles displaced older individuals by moving between them and forcing them off the rocks so that the majority of the adult population were eliminated from the bed within the first year after spat settlement. Mortality in individual cohorts was largely caused by strong wave action and competition for space. The density of individuals within the mussel bed was closely related to mean shell length. Growth rates varied with habitat and declined markedly with increasing height above L.W.S. Sexual maturity was attained at approximately 20 mm and reproductive output rose from 5 kJ year -1 at this length to 80 kJ year -1 at 100 mm shell length. Since packing densities were much higher in smaller individuals the annual gamete output assessed on an area basis, remained fairly constant as the mussels grew, and averaged 1392 g m -2 year -1 dry weight (31 320 kJ m -2 year -1). Energy expended as gonad output exceeded that due to mortality by a factor of 10.

Griffiths, Roberta J.

1981-01-01

415

Population dynamics of Gluconacetobacter diazotrophicus in sugarcane cultivars and its effect on plant growth.  

PubMed

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

Muñoz-Rojas, J; Caballero-Mellado, J

2003-11-01

416

Socially informed random walks: incorporating group dynamics into models of population spread and growth.  

PubMed

Simple correlated random walk (CRW) models are rarely sufficient to describe movement of animals over more than the shortest time scales. However, CRW approaches can be used to model more complex animal movement trajectories by assuming individuals move in one of several different behavioural or movement states, each characterized by a different CRW. The spatial and social context an individual experiences may influence the proportion of time spent in different movement states, with subsequent effects on its spatial distribution, survival and fecundity. While methods to study habitat influences on animal movement have been previously developed, social influences have been largely neglected. Here, we fit a 'socially informed' movement model to data from a population of over 100 elk (Cervus canadensis) reintroduced into a new environment, radio-collared and subsequently tracked over a 4-year period. The analysis shows how elk move further when they are solitary than when they are grouped and incur a higher rate of mortality the further they move away from the release area. We use the model to show how the spatial distribution and growth rate of the population depend on the balance of fission and fusion processes governing the group structure of the population. The results are briefly discussed with respect to the design of species reintroduction programmes. PMID:18270158

Haydon, Daniel T; Morales, Juan M; Yott, Adelle; Jenkins, Deborah A; Rosatte, Rick; Fryxell, John M

2008-05-01

417

Histopathology of Growth Anomaly Affecting the Coral, Montipora capitata: Implications on Biological Functions and Population Viability  

PubMed Central

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

Burns, John H. R.; Takabayashi, Misaki

2011-01-01

418

Vascular endothelial growth factor-A is associated with chronic mountain sickness in the Andean population.  

PubMed

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

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

2014-06-01

419

Correlations between age, phenotype, and individual contribution to population growth in common terns.  

PubMed

There have been numerous reports of changes in phenology, which are frequently attributed to environmental change. Age-dependent change in phenotypic traits, fledgling production, and the timing of events in the life cycle is also widespread. This means that changes in the age structure of a population could generate changes in phenology, which may be incorrectly attributed to environmental change or microevolution. Here, estimates of selection for arrival date, arrival mass, and laying date are compared when age is and is not corrected for. This is achieved using long-term individual-based data collected from a breeding colony of Common Terns (Sterna hirundo) and a novel fitness measure: individual contributions to population growth. The failure to correct for age generated deceptive estimates of selection in eight out of nine comparisons. In six out of nine comparisons, the direction of selection differed between age-corrected and uncorrected estimates. Persistent individual differences were detected: individuals remained within the same part of the phenotype distribution throughout life. The age-corrected estimates of selection were weak and explained little variation in fitness, suggesting that arrival date, arrival mass, and laying date are not under intense selection in this population. These results also demonstrate the importance of correcting for age when identifying factors associated with changes in seabird phenology. PMID:18027753

Ezard, Thomas H G; Becker, Peter H; Coulson, Tim

2007-10-01

420

Effects of wind energy production on growth, demography, and survivorship of a Desert Tortoise (Gopherus agassizii) population in Southern California with comparisons to natural populations  

USGS Publications Warehouse

We studied a Desert Tortoise (Gopherus agassizii) population at a large wind energy generation facility near Palm Springs, California over six field seasons from 1997 to 2010. We compared growth and demographic parameters to populations living in less disturbed areas; as well as populations of the closely-related and newly-described G. morafkai elsewhere in the Sonoran Desert of Arizona. We marked 69 individuals of all size classes and estimated a population size of 96 tortoises, or about 15.4/km2. Growth rates for males were lower than reported elsewhere, although maximum body size was larger. The smallest female with shelled eggs was 221 mm and males mature at over 200 mm. Mean male size was greater than that of females. The adult sex ratio was not significantly different from unity. Size frequency histograms were similar over time and when compared to most, but not all, G. morafkai populations in the Sonoran Desert. For a cohort of adult females, we estimated mortality at 8.4% annually due, in part, to site operations. This value was low in comparison to many other populations during the same time period. Other than possible differences in growth rate of males and the high survivorship of females, there appear to be few differences between this population and those in more natural areas. The high productivity of food plants at the site and its limited public access may contribute to the overall stability of the population. However, the effects of utility-scale renewable energy development on tortoises in other, less productive, areas are unknown. Additional research (especially controlled and replicated before and after studies) is urgently needed to address this deficiency because of forecasted expansion of utility-scale renewable energy development in the future.

Lovich, J.E.; Ennen, J.R.; Madrak, S.; Meyer, K.; Loughran, C.; Bjurlin, C.; Arundel, T.; Turner, W.; Jones, C.; Groenendaal, G.M.

2011-01-01

421

Long-term analysis of survival, fertility, and population growth rate of black bears in North Carolina  

USGS Publications Warehouse

We estimated survival, fertility, and realized and asymptotic population growth rates from 1981 to 2002 for a protected population of black bears (Ursus americanus) in the southern Appalachian Mountains. We used Akaike's information criterion to assess the time interval for averaging observations that was best for estimating vital rates for our study, given our yearly sample sizes. The temporal symmetry approach allowed us to directly assess population growth and to address all losses and gains to the population by using only capture data, offering an alternative to the logistically intensive collection of reproductive data. Models that averaged survival and fertility across 5- and 7-year time intervals were best supported by our data. Studies of black bear populations with annual sample sizes similar to ours should be of at least 5 years in duration to estimate vital rates reliably, and at least 10 years in duration to evaluate changes in population growth rate (??). We also hypothesized that survival would not track changes in ?? because ?? is influenced by both survival and fertility. The 5-year model supported our hypothesis, but the 7-year model did not. Where long-term dynamics of large, relatively stable bear populations are of interest, monitoring survival is likely to be sufficient for evaluating trends in ??. For rapidly changing, small populations, however, failure to incorporate fertility into assessments of ?? could be misleading. ?? 2005 American Society of Mammalogists.

Brongo, L.L.; Mitchell, M.S.; Grand, J.B.

2005-01-01

422

Effects of habitat characteristics on the growth of carrier population leading to increased spread of typhoid fever: a model.  

PubMed

In this paper, a non-linear model is proposed and analyzed to study the effects of habitat characteristics favoring logistically growing carrier population leading to increased spread of typhoid fever. It is assumed that the cumulative density of habitat characteristics and the density of carrier population are governed by logistic models; the growth rate of the former increases as the density of human population increases. The model is analyzed by stability theory of differential equations and computer simulation. The analysis shows that as the density of the infective carrier population increases due to habitat characteristics, the spread of typhoid fever increases in comparison with the case without such factors. PMID:24857178

Shukla, J B; Goyal, Ashish; Singh, Shikha; Chandra, Peeyush

2014-06-01

423

Modeling effects of cadmium on population growth of Palaemonetes pugio: results of a full life cycle exposure.  

PubMed

In an 8-month laboratory experiment, Palaemonetes pugio (grass shrimp) were exposed to aqueous cadmium (free cadmium ion concentrations of 1.51 or 2.51 microg Cd(2+)/L) for an entire life cycle, from larva to reproductive adult and through to production of second-generation larva. Individual-level effects on survival, life stage duration, and reproduction were measured, and population growth was projected using two models: a stage-based matrix model and a z-transformed life cycle graph analysis. Adult survival was significantly reduced at 2.51 microg Cd(2+)/L, but cadmium exposure had no effects on survival or stage duration of embryos, larvae, or juveniles. Survival of second-generation larvae was unaffected by maternal exposure. Brood size was reduced by 27% at 1.51 microg Cd(2+)/L and by 36% at 2.51 microg Cd(2+)/L. The percent of females in the population that was gravid was approximately 50% lower at 2.51 microg Cd(2+)/L, compared to controls. Both population models projected a dose-dependent decrease in population growth rate (lambda), up to a 12% reduction at 2.51 microg Cd(2+)/L, which can be attributed mainly to contributions from reproductive effects. Elasticity analysis revealed that population growth rate was most sensitive to changes in survival of juveniles and adults. However, lethal effects of cadmium made only a small contribution to the effect on population growth rate. Even though both models project positive growth (lambda>1) of grass shrimp populations exposed to low concentrations of cadmium, the ability of populations to withstand predation pressure would be compromised. PMID:18456346

Manyin, Teresa; Rowe, Christopher L

2008-06-23

424