Professionals Who Study And Make Predictions About Human Populations Are Called?

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Professionals Who Study And Make Predictions About Human Populations Are Called
Professionals who study and make predictions about human populations are called demographers.
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What is the study of human population called?

Demography is the statistical study of human populations.
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What are people who specifically study the growth patterns and socioeconomic characteristics of human populations called?

Demographers study how human populations grow, shrink, and change in terms of age and gender compositions using vital statistics about people such as births, deaths, population size, and where people live. Demographers also compare populations in different countries or regions.
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How do scientists predict population sizes?

Components of Population Projections – The population of a country or area grows or declines through the interaction of three demographic factors: fertility, mortality, and migration. To project future population, demographers make assumptions about how the current rates of births, deaths, and immigration and emigration will change in the future.

Based on these assumptions, age- and sex-specific population increases or decreases over a future period are calculated and added to census results or an estimate of the population at the beginning of the period. Each set of projections produced by an organization or government is based on its own set of assumptions about fertility, mortality, and migration, and will likely differ from each other.

Some groups, most notably the UNPD, identify uncertainty in projections by showing estimates of the likelihood that the future population size will fall within a certain range. The UNPD and others also develop multiple projections to reflect several possible scenarios of future levels of fertility and mortality.

Fertility Fertility is expressed as the total fertility rate (TFR), a measure of the number of children on average that a woman will have in her lifetime. (More specifically, the TFR is a measure of how many children women would bear in their lives if the rate of childbearing in a given year remained unchanged across their lives.) Of the three components, fertility often has the largest effect on future population size, especially in developing countries with high birth rates.

Globally, fertility fell during the latter half of the 20th century, and though it has not decreased at the same pace everywhere, today the world’s total fertility rate stands at 2.5 children per woman. Where fertility is high, demographers generally assume that fertility will follow a similar pattern of decline and eventually stabilize in every country at about two children per woman.

  • This level of fertility is referred to as “replacement level” fertility (2.1 children per woman) as couples who have two children merely replace themselves without increasing the size of succeeding generations.
  • One common misunderstanding about population projections is that when fertility declines to replacement level, the population will immediately stop growing.

In previously high-fertility countries, however, population will continue to grow for many decades even after fertility reaches replacement level. Years of high fertility result in a young population age structure, which generates momentum for future population growth as the increasing number of young people begin having children of their own.

  • Brazil, for example, had fertility decline to below-replacement level in the mid-2000s, but the UNPD projects its population to continue growing until mid-century.
  • Not only does fertility decline affect population size, it also profoundly affects age distribution.
  • Declines in fertility result in a growing proportion of elderly, now seen in most developed and many developing countries.

In most developed countries, fertility is now below replacement level, often quite far below. The majority of developing countries, however, still have fertility above replacement level. In the least developed countries, women have on average more than four children.

Additionally, fertility has remained high in most countries of sub-Saharan Africa, often declining slowly or not at all. As such, the fertility assumptions for this region tend to be less reliable. Future population size and age distribution for a country can vary substantially based on when a fertility decline begins, the pace of the decline, and whether the decline continues all the way to replacement fertility or stalls at a higher level.

Because of the possible discrepancy between assumptions and actual trends, the UNPD publishes multiple projections every two years with differing fertility assumptions, including Low, Medium, and High Fertility variants. The Medium Variant, most often cited among the series, assumes a growth in the use of family planning that will result in reductions in fertility in patterns similar to what occurred in other countries.

The Low Variant simply assumes that in each country the TFR is one-half child less than the Medium Variant at most periods in time, while the High Variant assumes that the TFR is one-half child more than the Medium Variant. Under these three variant scenarios, the assumed fertility in Kenya in 2050, for example, would range from 2.2 to 3.2 children per woman—down from 4.6 in 2010.

Kenya’s population totals in 2050 corresponding to these different assumptions about fertility would range from 85 to 110 million (see Figure 1). Another common misunderstanding is that a path of fertility decline is more or less automatic and is continuous, as projections assume.

  • Declines in fertility, however, often depend on increased investments in family planning services, health, and education—particularly for women and girls.
  • Many countries that have not adequately invested in these areas have not experienced the fertility declines assumed in past projections and have had subsequent projections continuously revised upward.

Over one-half of the countries in the Africa region, for example, had their UN population estimates for 2010 revised upward between the 2010 and 2012 revisions, increasing the total population projected for the region under the Medium Variant scenario by 8.8 million.

  • In other cases, countries that have invested adequately have seen fertility decline more rapidly than originally assumed and population projections have been revised downward.
  • Some users incorrectly assume that population levels stabilize in the final year for which a population is projected.
  • For many years, the UNPD developed projections to the year 2050 and some users incorrectly interpreted the numbers to mean that world population growth under the Medium Variant would slow and stabilize in 2050.

More recently the UNPD has developed population projections to 2100, and while the uncertainty in the underlying assumptions grows over time, population growth for the world and in many countries continues well beyond 2050. In fact, in all of the current population projections except the Low Variant, world population continues to grow past 2050. Professionals Who Study And Make Predictions About Human Populations Are Called Mortality Mortality is incorporated into projections by estimating death rates by age group and sex. Where mortality is relatively high and the resulting life expectancy at birth relatively low, changes in mortality play an important role in future population size.

Where mortality is already low and life expectancy has risen, mortality has much less effect. Throughout developing countries, infant mortality has declined substantially over the last several decades; the general assumption underlying population projections for all countries is a continued decline in death rates and an increase in life expectancy.

The HIV pandemic and its substantial impact on mortality in countries with high prevalence created the need to consider the future course of HIV infection and its treatment in mortality assumptions and population projections. In those countries with growing HIV epidemics during the 1990s, death rate assumptions were revised upward in population projections.

Despite the rise in mortality, population growth continued, albeit at a slower rate due to the impact of HIV. Malawi’s population projection for 2050, for example, is 49.7 million, 8.2 million lower than the projection without the impact of HIV on mortality (see Figure 2). Recently, the UN projections show that life expectancies in the seriously affected countries of southern Africa are beginning to rise as a result of slowing the spread of HIV and improving the chances of survival among people living with HIV.

Nonetheless, HIV will have a lasting impact on mortality for several decades: The extent to which HIV affects future mortality will depend on continued investments in both prevention and treatment of the disease. In fact, the UNPD assumes mortality from HIV will continue to decline due to improved access to antiretroviral therapy and fewer new infections. Professionals Who Study And Make Predictions About Human Populations Are Called For many developed countries, low fertility combined with declining mortality among older adults is of considerable interest because of the impact on population aging. For example, the UN projections for many developed countries show the proportion of the population ages 65 and over rising as high as 30 percent to 40 percent by mid-century, an unprecedented development.

  1. Over 90 countries are projected to have life expectancy at age 65 reach 20 years or more by mid-century.
  2. Many people often wonder whether demographers incorporate other possible increases in mortality into projections, such as future conflict, natural disasters, or changing lifestyles like increases in obesity and lack of exercise.

Because of the uncertainty about where conflict and natural disasters might occur, what the impacts might be, and how mortality rates might be affected, demographers do not incorporate such factors into projections. In the case of changing lifestyles, data on the impact on mortality are still largely unavailable or just emerging in most countries and are not yet included in projection assumptions.

  • In general, demographers have not assumed other changes in mortality beyond declining infant mortality, the continued impact of HIV, and increased longevity.
  • Migration International migration can be particularly unpredictable and difficult to incorporate into projection assumptions.
  • Migration flows often result from short-term changes in economic, social, political, or environmental factors that are difficult to anticipate.

Moreover, for many countries, reliable information on the number of immigrants and emigrants is not available. Nonetheless, migration can have a significant effect on population change in specific countries and regions. For many years, the most common pattern of migration has been the movement of people from developing countries to developed countries and from poorer developed countries to wealthier ones.

  1. Populations of countries and regions with low fertility, where deaths exceed births, will decline without net migration gains.
  2. For example, international migration accounted for over one-half of the population growth in developed countries in the 2000s.
  3. The movement of people between developing countries because of economic opportunities, environmental disasters, or political or civil unrest has also altered the demographic landscape.
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Migration assumptions often take into account the experience of countries with historically high immigration, such as the United States. Given its unpredictable nature, however, it is usually assumed that current migration levels will persist for a time and slowly decline.

  • For example, the UNPD assumes that the current estimated annual flow of about 2.6 million people from less developed countries to more developed countries will slowly decrease to about 2.1 million by 2050.
  • But national policies on immigration and the future economic appeal of developed countries could certainly change that figure in either direction.

UNPD assumes net migration will eventually reach zero by 2100 in all countries. This highly unlikely scenario suggests how difficult it is to predict the levels of migration over such a long period.
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How do you predict population growth?

Population Growth Rate It is calculated by dividing the number of people added to a population in a year (Natural Increase + Net In-Migration) by the population size at the start of the year. If births equal deaths and there is zero net migration, the growth rate will be zero.
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What is the study of population biology?

Population biology is a field of study that explores populations and how they interact with their environment. Scientists observe all factors influencing a population within an ecosystem when gathering data about specific populations of interest. Often these observations are vital to decisions made about how to protect a species.
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What is the study of human populations biology?

Human population biology: a viable transdisciplinary science – PubMed Display options Format Abstract PubMed PMID PIP: The development and potential contributions of a transdisciplinary science, Human Population Biology is presented. Human Population Biology is the study of living human beings as aggregate units in an attempt to understand the origins of biological variations within and between units and their functional and behavioral consequences.

  • Objective observations of the characteristics of “other” groups have been recorded since the Classical Greeks.
  • The 1st 1/2 of the 20th century saw the foundation of most of the present day disciplines that are concerned with human beings.
  • Comparative study was undertaken on subdivisions of the species, e.g., psychologists examined differences in neurological or “mental” functions; anthropologists and anatomists detailed morphological descriptions of groups.

Research into the impact of the environment, adaptation and genetic variation due to selective pressure challenged traditional theories and disciplinary boundaries. This research was carried out by practitioners in several disciplines who used common research methodologies.

  1. The social environment was a major inhibitor of the development of research methodologies that utilized between group comparisons.
  2. Correlational approaches that related human morphological variables to the environment, geographical clinical approaches to genetic variation, and experimental studies on nonhuman mammals became popular alternatives.

The structure of Human Population Biology can be examined in terms of its practitioners, theory, methods, and application. Practitioners are identified from an inspection of the authors from 2 journals and surveys of current reserarch interests. The major contributors to the field are anthropologists but well over 50% have other disciplinary affiliations.

  • The theoretical foundation lies with evolutionary theory and is enhanced by sociobiology, and concepts in ecological theory and adaptation adopted from physiology and population genetics.
  • The research strategies, extracted from a limited survey of published articles, are limited.
  • The most frequently used is intragroup analysis using regression or other continuum statistics, followed by intergroup comparisons, e.g., of classes, castes but rarely races.

Most modeling strategies were based on intragroup analysis.1/4 of the research reported described the population. No original experimental manipulations were undertaken. The transdisciplinary nature of Human Population Biology allows its application in multiple areas including nutrition, growth, physical fitness, epidemiology and physical response to the environment and suggests a sound funding base.

Little MA, Garruto RM. Little MA, et al. Hum Biol.2000 Feb;72(1):179-99. Hum Biol.2000. PMID: 10721617 Begossi A. Begossi A. Interciencia.1993 May-Jun;18(3):121-32. Interciencia.1993. PMID: 12345859 Portuguese. Pavlinov IIa. Pavlinov IIa. Zh Obshch Biol.2004 Jul-Aug;65(4):334-66. Zh Obshch Biol.2004. PMID: 15490579 Russian. McDade TW. McDade TW. Am J Phys Anthropol.2003;Suppl 37:100-25. doi: 10.1002/ajpa.10398. Am J Phys Anthropol.2003. PMID: 14666535 Review.

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What refers to the study of population and its characteristics?

Population Characteristics Demography is the study of a population, the total number of people or organisms in a given area. Understanding how population characteristics such as size, spatial distribution, age structure, or the birth and death rates change over time can help scientists or governments make decisions.

For example, knowing how lion populations have increased or decreased over a period of time can help conservationists understand if their protection efforts are effective while knowing how many seniors or children live in a particular neighborhood can shape the type of activities scheduled at the local recreation center.

Select from these resources to teach your students about population characteristics. Biology, Ecology, Geography, Human Geography, Physical Geography : Population Characteristics
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What are the characteristics of the individuals of the population being studied called?

Variables are the characteristics of the individuals in the population.
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What do we call the study of population change and characteristics?

Demography.A. the study of population change and characteristics.
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What are 4 methods that scientists use to determine the size of a population?

‘Wildlife managers use 4 general approaches to estimate population sizes of wildlife: total counts, incomplete counts, indirect counts, and mark-recapture methods ‘(www.cals.ncsu.edu).
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What is the difference between population study and demography?

Population study is concerned with human beings. Demography is the statistical study of the living populations and sub-populations. It can be a very general science that can be applied to any kind of dynamic living population that is one that changes over time or space.
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What are the methods of estimating human population?

Methods of population estimation and projection This section covers:

  • Methods of population estimation and projections
  • Population projections

Population estimates Description 
 Whilst the Census is crucial for resource allocation and planning, because it is carried out only every ten years, other methods are required for planning in the intervening years. Population estimates use census as a baseline, add births, subtract deaths and make allowances for migration.

They can be used for national and local planning. Population estimates are produced annually. In the UK, the Office for National Statistics (ONS) estimates are also used as the basis for capitation-based funding of local authorities and PCTs. Under-estimation can therefore have severe effects on local services.

International migration is now the main driver of population change in the UK. ONS estimates a net inflow of 318,000 in 2014. Migration affects different local communities in different ways and local responses need to be developed. It can affect the makeup of the local population, the local economy, the nature of the jobs that are filled, the speed of turnover and housing occupancy.

If families come with children, there are impacts on the education and child health systems such as immunisation programmes. Overall, migration cuts across many policy and service areas and so is an important public health issue; for example: employment, housing, education, child health, mental health, access to services.

Strengths Crucial for local planning. Wider use locally for housing, education and other planning. Weaknesses Questionable accuracy with regard to internal migration. Data on migration are difficult to obtain, particularly at local level. Some migrant workers may only stay a few months and it is hard to measure change.

  • Mortality (not too difficult to estimate for today’s 25 – 45 year olds)
  • Fertility (much harder to estimate; often a range of high, low and medium fertility levels are used in the projections which are then published as a series)
  • Migration (easy to misjudge as has happened in recent years)

In the UK, the Government Actuary’s Department (GAD) produces ‘full’ population projections by age and sex for the United Kingdom and constituent countries every two years, Special projections can be undertaken in the intervening years, such as estimates by marital status.

ONS uses the national figures to produce sub-national population projections. Data are available, 2 or 3 times in each decade, on the GAD website by age and sex for Government Office Regions, counties, county districts, unitary authorities, and London boroughs, Household projections are undertaken by the Department for Communities and Local Government (CLG).

For London, the Greater London Authority (GLA) creates population projections, which are updated on a yearly basis, both at population and at household levels. In addition to the frequency, GLA projections can differ from ONS versions because they adjust estimates at borough level when ONS mid-year estimates have been found to be not robust.

  • Example
  • In addition to the national and regional projections, the GLA calculates London projections by ethnicity and at ward level.
  • Uses

Longer term planning e.g. care of elderly in 20 years’ time. Planning the level of health and other services locally and nationally.

  1. Weaknesses
  2. Projections lose accuracy the further ahead the planning is attempted.
  3. Capture – Recapture techniques

It often happens that it is not the total population that is of concern but some fraction of unknown size. For example, we may wish to know the numbers of problematic drug users in order to plan service levels, or the numbers of diabetics in an area to estimate the completeness of a register, or the frail elderly who can stay in their own homes with appropriate community support.

In these cases we can draw on techniques developed in the field of ecology. In field studies a sample of the population is taken (say S1), and ‘marked’, then released. After enough time has elapsed for the sample to mingle with the rest of the population a second sample is taken (say S2), and the numbers previously marked (say M) and unmarked (say U) noted.

S2 = M+U. The total population may then be estimated as: S1 *S2/M or S1*(M+U)/M. There are two assumptions here that must hold:

  1. the population must be closed, that is to say of fixed size between the two samples, and
  2. the two samples must be genuinely independent.

This estimate can be made on the basis of two samples only. There is a significant body of literature discussing statistical tools appropriate to larger numbers of samples. In epidemiology, sometimes separate datasets held concurrently are substituted for repeat samplings.

However, someone known to one dataset may be more likely to be known to another than a genuinely random member of the population, and this can be a source of significant bias in estimates, which requires sophisticated statistical techniques to compensate. Catchment populations – the Multiplier Method 
 We may wish to estimate the catchment population served by a particular facility.

Assume we have data on the total number of people using the facility, and survey data that a set fraction comes from an area whose total population (P) is known. From this we can calculate the proportion of P who use the facility, and on this basis calculate a notional overall catchment.

  • Worked example: A fitness centre serves 20,000 people in a season.
  • A survey has shown that approximately half its users live in the local district, half from outside.
  • The population of the local district was 92,000 at the last census.
  • Then the notional total catchment can be estimated as (92,000 / 0.5) = 184,000.
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This method can also be used epidemiologically, for example to estimate injecting drug use, where appropriate data is available. As example of this can be found at,

  • References
  • 1 Crossing borders: Responding to the local challenges of migrant workers, Audit Commission, 2007
  • 2
  • 3
  • © M Goodyear & N Malhotra, 2007, M Goodyear 2016 and S Seager 2018

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What are the 3 methods used to forecast future population?

Arithmetic Progression. Geometric Progression. Iller Bankasi Method. Decreasing Rate of Growth method.
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What models predict population growth?

B. Logistic Population Growth Model – In fact, there is a maximum population capacity, that is,, in a region or an environment; thus, the growth rate in the Malthus model can be slightly altered. When and, the solution tends to a fixed constant, that is,, which is called the environmental capacity.

  • In addition, is the relative growth rate.
  • It can be observed that the relative growth rate decreases as population increases.
  • Assuming that is a quantity that is not affected by the environment and is only related to itself, it is called the intrinsic growth rate and is also known as the coefficient of life.

When, the relative growth rate is 0, and the total population tends to the limit value, Therefore, the logistic growth model can be obtained as follows: Formula () is a Bernoulli equation and can be solved as follows: Based on formula (), if and the total populations during two periods are known, we can obtain the following two equations: The maximum population and the intrinsic growth rate can be obtained from the equations in formula () to predict the total population with the same spacing.

This method uses only three types of data, which do not fully follow the law of population growth. Furthermore, this equation group is a nonlinear equation group, and analytically solving this group is difficult. There are many numerical solutions, and the results may be distorted. The growth model needs to be improved.

The grey prediction model is simple and adaptable. This model can better address sudden changes in the parameters. Through data accumulation processing, the relationships in the data increase, the exponential relationship of a sequence increases, and the randomness of the data decreases.
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Which method is accurate for population forecasting?

Free MPSC AE CE Mains 2019 Official (Paper 1) 100 Questions 200 Marks 120 Mins Explanation: Various methods for population forecasting as suitable for that city, considering the growth pattern, are as follows: 1, Arithmetical increase method :

In this method assumed that the population is increasing at a constant rate. This method is suitable for a large and old city with considerable development.

2. Geometrical increase method (or geometrical progression method):

In this method, the percentage increase in population from decade to decade is assumed to remain constant. This method gives higher values and hence should be applied for a young and rapidly increasing city, but only for a few decades.

3, Incremental increase method :

This method is a modification of arithmetical increase method and it is suitable for an average size town under the normal condition where the growth rate is found to be in increasing order.

4, Logistic curve method:

This method is used when the growth rate of the population due to births, deaths, and migrations takes place under normal situation and it is not subjected to any extraordinary changes like an epidemic, war, earthquake or any natural disaster, etc.

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What do population geneticists study?

Population genetics is the study of variation within populations of individuals, and the forces which shape it. This involves studying changes in the frequencies of genetic variation in populations over space and time. Some of the major forces that shape variation in natural populations are: mutation, selection, migration and random genetic drift.

  1. When a new mutation arises, it may be beneficial to the organism; deleterious (harmful) to the organism; or it may be neutral (have no effect on the fitness of the organism).
  2. Generally, beneficial and deleterious mutations are subject to natural selection, typically leading to increases and decreases in their allele frequency, respectively.

Allele frequencies are also influenced by random genetic drift, This process explains the chance fluctuation in allele frequencies from one generation to another due to independent assortment in meiosis. This is the major force acting on neutral variants.

Map human migration 13 Track the spread and evolution of antimicrobial resistance 14

You can browse population genetics data in Ensembl, Learn more about this in the Population Genetics section our course Ensembl: Browsing chordate genomes,
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What are the two types of Population Studies?

Population Studies – Through Census – The census is carried out to study the population systematically. The first modern census to study the population was conducted in America in 1790. This was followed in Europe in the early 1800s.

The British government started conducting censuses in India between 1862-72. Since 1881, the census has been conducted in India regularly. It was a decennial census, meaning it was conducted once every ten years. Since India gained independence, the census has been conducted once every 10 years, starting from 1951. The last census in India was conducted in 2011. It was supposed to be conducted in 2021, but it was not feasible due to the global pandemic. The Indian census is considered to be the largest in the world.

The various types of population studies are retrospective cohort studies, prospective, case-control studies, cross-sectional studies, and twin studies. Population studies help us to know how far the growth rate of the economy is keeping pace with the growth rate of the population.

The 3 important components of population studies are migration, death, and birth. The 3 types of population pyramids are stationary, constrictive, and expansive. These 3 types of population pyramids are created from age-sex distributions. Population study is generally considered a branch of economy, sociology, and geography.

: Population Studies – An Overview
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What are population ecologists study?

Population ecology The study of spatial and temporal patterns in the abundance and distribution of organisms and of the mechanisms that produce those patterns. Population ecology investigates how and why populations change over time (). In general, species differ dramatically in their average abundance and geographical distributions, and they display a remarkable range of dynamical patterns of abundance over time, including relative constancy, cycles, irregular fluctuations, violent outbreaks, and extinctions.

Thus, the aims of population ecology are threefold: (1) to elucidate general principles explaining dynamic population patterns; (2) to integrate these principles with mechanistic models and evolutionary interpretations of individual life-history tactics, physiology, and behavior, as well as with theories of community and ecosystem dynamics; and (3) to apply these principles to the management and conservation of natural populations.

See also: ; ; ; ; Fig.1 Relationship between prey and predator populations. The abundance curve (population density versus time) for the predator lags behind that of the prey. (Copyright © McGraw Hill) Professionals Who Study And Make Predictions About Human Populations Are Called A population is the total number of individuals of a given biological species found in one place at one time. In practice, ecologists often deal with density (numbers per unit area for land organisms and numbers per unit volume in aquatic systems) or even weight rather than raw numbers.

  1. What may be described as an “individual” depends on the kind of organism and the aim of the scientific inquiry.
  2. In most animals, the life cycle starts with a fertilized egg, passes through a largely irreversible process of coupled growth and differentiation, and ends in a tightly integrated, unitary, adult organism.

Population size can be measured by merely counting adult units and their juvenile progeny. However, in most plants and some colonial animals, growth and differentiation proceed in a modular fashion; in these cases, growth involves the replication of a basic body unit, so a fertilized egg generates a spatially distributed “population” of connected modules.

In general, modular organisms show tremendous plasticity in size and form. There are only four ways that a population can change in size: birth, death, immigration, and emigration. If immigration and emigration are negligible, the population is closed, and the difference between birth and death rates drives its dynamics.

Terrestrial animals on islands often have closed populations. If immigration and emigration are important, however, the population is open, and its abundance may be substantially influenced by spatially distant events. For example, the number of barnacles that are found on a rocky coastline often reflects the density of setting larvae, which in turn is governed by events in offshore waters.

  1. If a population that is under study is found to be highly open, the spatial scale of the study may be too narrowly circumscribed to capture the important mechanisms of its population dynamics.
  2. See also: Populations exhibit a great variety of dynamical patterns, including explosive outbreaks, local extinctions, and regular cycles or relatively constant abundances.

To help describe and explain these patterns, ecologists rely on population models. Simple life cycles and closed populations provide a useful starting point in developing population models. For example, many temperate-zone insects have one annual generation; thus, at any given time, all individuals are at the same stage of life.

Iterations of discrete time-growth models for subsequent generations allow one to project population numbers through time. The theoretical framework of population ecology largely consists of elaborations of basic growth models, including extensions to more complicated life cycles and multiple species.

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In addition, exponential growth has a snowballing effect—for example, the more individuals that there are, the faster that the population grows (if the growth rate is constant). Even low growth rates eventually lead to populations of enormous sizes. Some natural populations show transient phases of exponential growth, particularly in colonizing episodes.

In addition, exponential growth during colonization often involves expansion across space and an increase through time. Thus, immigration and emigration, if appropriate, need to be considered. Population models, when interpreted literally, assume that all members of a population are identical. This is rarely true, though.

Birth and death rates typically vary as a function of age, body weight, and genotype. A great deal of work in population ecology is devoted to elucidating age-specific schedules of mortality and fecundity, using these patterns to predict population growth, and interpreting these patterns in the light of evolutionary theory.

To study age-structured population dynamics, the number of individuals in each age class must be monitored. The two ingredients needed to project changes in population size and age structure are the mortality schedule or survivorship curve, which describes the fraction of newborns surviving to each age, and the fecundity schedule, which describes the rate of female births per female at each age.

It is a formidable task to measure complete fecundity and mortality schedules in natural populations. However, if these schedules are estimated, geometric growth models can be generalized to a matrix model. Moreover, if these schedules are constant, a population will (with rare exceptions) eventually settle into a stable age distribution in which each age class comprises a constant fraction of the total population.

A population in its stable age distribution grows geometrically at a rate of increase uniquely determined from the mortality and fecundity schedules. A population displaced from its stable age distribution may exhibit transient phases of growth or decline, diverging from its long-term growth pattern.

All populations are genetically variable. If different genotypes have different fecundity or mortality schedules, genetic variation can influence population dynamics. Models that simultaneously incorporate changes in genetic composition and population growth can be quite complex.

However, they may be important in describing some populations and are necessary for linking population ecology with evolutionary theory. See also: Populations cannot expand exponentially forever. Often, mortality rates increase or birth rates decrease (or both) as a result of competition for limited resources.

The underlying mechanisms in these cases are called negatively density-dependent factors, which are specific examples of the more general concept of feedback. Alternatively, environmental conditions (for example, climatic shifts) can worsen, leading to population declines.

  • Such causes for variation in birth or death rates are called density-independent factors.
  • Ecologists have long disputed the relative importance of density-dependent and density-independent factors in determining population size.
  • It is likely that both are important, but to differing degrees in different species and environments.

Intriguingly, population regulation by no means implies population stability. In general, a population is stable if it returns to equilibrium following a perturbation. Moreover, many local populations may not be persistent over long periods of time and thus may not be regulated in the usual sense.

  1. For example, open populations, by definition coupled by dispersal with other populations, can become reestablished by immigration following a local extinction.
  2. See also: A useful method for considering the interplay of density-dependent and density-independent factors in determining population size is to plot birth and death rates as functions of density.

The carrying capacity of a population in a given environment is defined to be the largest number of individuals for which the birth rate just matches the death rate (). In general, density-dependent factors are necessary to regulate populations, but density-independent factors must also be considered to understand fully what limits populations to a given value of carrying capacity. Professionals Who Study And Make Predictions About Human Populations Are Called Given that density dependence exists, the mechanisms generating it can be used both to predict the consequences of environmental change for population dynamics and to provide insight into systems where experimental manipulations are difficult. Density dependence often arises from competition, which is said to exist when organisms utilize common limiting resources and thereby negatively affect each other.

There are two principal sorts of competition—namely, interference and exploitative. Interference competition occurs when one individual directly harms another. Interference may be dramatic, as in lethal aggression, or subtle, as when social interactions reduce the time available for gathering resources or increase the risk of predation.

Exploitative competition occurs when one individual consumes a resource, such as food, that otherwise would have been consumed by another individual. Because exploitative competition is mediated indirectly through a shared resource base, it can be more difficult to demonstrate than interference competition.

Negative density dependence may arise from interspecific interactions. A schematic classification of interactions between two species comes from considering the positive (+) or negative (−) effect that individuals of one species have on the growth rate of the other. In interspecific competition, the interaction is (−,−); in mutualism, it is (+,+).

Natural enemies, defined broadly to include predators, herbivores, and parasites, are often engaged in (+,−) relations with their prey or hosts. Most species are potential prey to one or more natural enemies; even top-level carnivores may be beset by parasites.

  • Obviously, competitors and mutualists can dramatically affect the size of a given population and thus must be considered when studying population limitation.
  • However, natural enemies are far more likely to be regulatory agents than are either competitors or mutualists.
  • If two species are competing and one increases in density, the other will decrease.

This will relax the interspecific competition on the first, which can then increase even more. Hence, competitive loops (and similarly mutualist loops) tend to produce positive feedback and will not regulate population growth. By contrast, predator-prey interactions () may produce negative density dependence acting across several time scales on both the predator and prey.

As prey in one habitat patch become more numerous, predators may almost immediately become more active or switch over from other prey types or patches. Predators also may show an intergenerational numerical response to increased prey availability. Because an increase in predator numbers usually decreases prey numbers, this induces delayed density dependence in both the predator and its prey.

See also: In addition to its intrinsic conceptual appeal, population ecology has great practical utility. Control programs for agricultural pests or pathogens that cause human diseases ideally attempt to reduce the intrinsic rate of increase of those organisms to very low values.

Analyses of the population dynamics of infectious diseases have successfully guided the development of vaccination programs. In the exploitation of renewable resources, such as in forestry or fisheries biology, population models are required in order to devise sensible harvesting strategies that maximize the sustainable yield extracted from exploited populations.

Conservation biology is increasingly concerned with the consequences of habitat fragmentation for species preservation. Population models can help characterize minimum viable population sizes below which a species is vulnerable to rapid extinction, and can help guide the development of interventionist policies to save endangered species.
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Which branch of science is the study of populations?

Where do biology graduates work? – biology, study of living things and their vital processes. The field deals with all the physicochemical aspects of life, The modern tendency toward cross-disciplinary research and the unification of scientific knowledge and investigation from different fields has resulted in significant overlap of the field of biology with other scientific disciplines,

Modern principles of other fields— chemistry, medicine, and physics, for example—are integrated with those of biology in areas such as biochemistry, biomedicine, and biophysics, Biology is subdivided into separate branches for convenience of study, though all the subdivisions are interrelated by basic principles.

Thus, while it is custom to separate the study of plants ( botany ) from that of animals ( zoology ), and the study of the structure of organisms ( morphology ) from that of function ( physiology ), all living things share in common certain biological phenomena—for example, various means of reproduction, cell division, and the transmission of genetic material.

Biology is often approached on the basis of levels that deal with fundamental units of life. At the level of molecular biology, for example, life is regarded as a manifestation of chemical and energy transformations that occur among the many chemical constituents that compose an organism. As a result of the development of increasingly powerful and precise laboratory instruments and techniques, it is possible to understand and define with high precision and accuracy not only the ultimate physiochemical organization (ultrastructure) of the molecules in living matter but also the way living matter reproduces at the molecular level.

Especially crucial to those advances was the rise of genomics in the late 20th and early 21st centuries. Cell biology is the study of cells—the fundamental units of structure and function in living organisms. Cells were first observed in the 17th century, when the compound microscope was invented.

  1. Before that time, the individual organism was studied as a whole in a field known as organismic biology; that area of research remains an important component of the biological sciences.
  2. Population biology deals with groups or populations of organisms that inhabit a given area or region.
  3. Included at that level are studies of the roles that specific kinds of plants and animals play in the complex and self-perpetuating interrelationships that exist between the living and the nonliving world, as well as studies of the built-in controls that maintain those relationships naturally.

Those broadly based levels— molecules, cells, whole organisms, and populations—may be further subdivided for study, giving rise to specializations such as morphology, taxonomy, biophysics, biochemistry, genetics, epigenetics, and ecology, A field of biology may be especially concerned with the investigation of one kind of living thing—for example, the study of birds in ornithology, the study of fishes in ichthyology, or the study of microorganisms in microbiology, Professionals Who Study And Make Predictions About Human Populations Are Called Britannica Quiz Biology Bonanza
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Is geography the study of human population?

Population Geography – Key takeaways –

  • Population geography is the study of human populations. This includes their distributions across the world, their density in certain areas, and their movements ( migration ).
  • Population changes are usually influenced by economic, cultural, political, or environmental circumstances. These influences can be explained by push and pull factors,
  • The government uses population geography to make decisions on current and future population needs.
  • Anti-natalist policies are government policies that serve to discourage people from having children. Pronatalist policies are government policies that serve to encourage people to have children.
  • Population geography has important ties to economic, cultural, political, and environmental disciplines.

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What is the difference between population and demography?

Population study is concerned with human beings. Demography is the statistical study of the living populations and sub-populations. It can be a very general science that can be applied to any kind of dynamic living population that is one that changes over time or space.
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