A population is the number of organisms of the same species that live in a particular geographic area at the same time, with the capability of interbreeding.
For interbreeding to occur, individuals must be able to mate with any other member of a population and produce fertile offspring. However, populations contain genetic variation within themselves, and not all individuals are equally able to survive and reproduce.
Populations can occur on various different scales. A local population can be confined to a spatially small area, i.e., the fish in one pond. However, this locality can operate on a regional, countrywide, island or continental scale; it may even make up the entire species. If individuals of local populations are able to disperse between other local populations, this is called a metapopulation.
Population biology is the study of population characteristics and the factors that affect their size and distribution. The characteristics which are studied include the migratory patterns, the population density, the demographics (the birth and death rates, sex ratio and age distribution), the population genetics, the life history traits and the group dynamics (the interactions within and between populations). Population ecology is the study of how these populations interact with the environment.
Most populations are not stable, fluctuating in size over time (the letter ‘N’ often denotes the number of individuals in a population). The fluctuations are usually in response to changes in the abiotic and biotic factors, which act as limiting factors against indefinite exponential growth of populations. For example, when food resources are plentiful and environmental conditions are favorable, populations may grow. Conversely, when predation is strong, populations may become depleted.
The characteristics of the population can influence how it is affected by certain factors. The effects that density-dependent factors may have on a population are determined by its size; for example, a larger, denser population will be decimated more quickly by the spread of disease than a widely dispersed population. Life history traits, such as the maturation rate and life span, can affect the rate of growth of a population; if individuals mature later, the population will grow more slowly than if they mature relatively young.
Due to the genetic variation within populations, those that are larger are usually more resilient to stochastic changes in their environment or demography. This is because there is a higher chance that a genetic mutation within the gene pool is better adapted to survive in the new situation. If an extreme event occurs, in which a large number of individuals within the population are unable to survive, the remaining individuals with the favored genes will reproduce, thereby increasing the frequency of these genes in the population by genetic drift. This is called a population bottleneck.
Although the individuals who survived the bottleneck are adapted to the new conditions, there is not always a good rate of long-term success for the population. Genetic diversity within the new population is low, and only increases very slowly as mutations occur in each successive generation. This means that the new population is highly vulnerable to further changes to the environment or availability of resources, as well as suffering the consequences of inbreeding such as disease and deformity in offspring. If a bottleneck results in too few individuals (under the minimum viable population size(MVP), there is a considerable risk of extinction after a few generations.
Examples of Populations
There are two traditionally recognized species of elephant, African elephants (Loxodonta Africana) and Asian Elephants (Elephas maximus), although recent research has divided the African elephants into two species: the African bush elephants (Loxodonta africana) and the African forest elephants (Loxodonta cyclotis).
Populations of African elephants are believed to have existed on a continental-wide scale, numbering up to 5 million individuals in the early 1900s. However, due to habitat fragmentation and poaching for their tusks, elephant numbers have suffered severe declines. There are now believed to be around 400,000 remaining African elephants.
Elephant group structure is formed of family units of around 10 individuals, although when elephant families come into contact, they may bond to form larger groups – called ‘herds’ – of up to 100. Each of these herds forms a local population. However, any individual from each species could reproduce with another species member, so the full population of each African species includes all the individuals on the continent.
Within a habitat there can be many different populations; a small-scale example is a lake. A lake may provide a habitat for birds, fish, insects, amphibians and mammals such as otters or rats. Although each species is provided with resources from the lake, their populations are likely to rely on the habitat in unique ways. For fish, land presents an impenetrable barrier for dispersal. Without any way of leaving, an entire population of trout may exist solely within the lake and nowhere else.
Amphibians such as toads may spawn in the lake, and use several nearby lakes within a valley for feeding. However, because they cannot get across mountains, their local population is restricted to the inside of the valley. If environmental conditions within the valley differ from other surrounding valleys, and the toads are isolated from other populations of the same species for long enough, the behavior or morphology of the toad may change sufficiently enough so that it cannot mate with toads outside of the valley. This isolation would drive the process of speciation and thus the formation of new species.
Migrating birds may visit the lake seasonally in order to winter; for part of the year, these birds form a local population. When the birds return from their wintering grounds, they meet with other populations of the same species so that they can breed in larger numbers. It is common for birds of different ages or sexes to migrate at different times or distances, so the population sizes depend on the group demography.
Many species of Salmon are anadromous, which means they are born in fresh water before migrating to the ocean to feed and mature, and return to fresh water to breed.
Salmon tend to return to the same river that they were born in, in order to themselves spawn. Because of this strong desire to ‘home’, salmon usually do not stray far away from their native spawning site, although the dispersal distance depends largely on the particular species.
Because most spawning sites are separated by land or deep water, each group of salmon that are born in a certain spawning site makes up the local population within that site; although the conditions within the routes available for dispersal to other sites are not impossible for the salmon to withstand, they are rarely found to move between sites.
During their time spent at sea, salmon come into contact with salmon from other local populations, even very distant ones. Although there are no barriers to mating between local populations of the same species, the tendency of salmon to return to their natal river greatly reduces gene flow between them. Nonetheless, some individuals do stray from the expected route, either by choice or in error, resulting in some gene flow between populations.
Due to their life history cycle, salmon can be categorized within the metapopulation structure.
- Community – A group consisting of various species, which interact with each other directly or passively, in a common location.
- Species – A group of physically similar individuals, which are capable of reproducing with the outcome of fertile offspring.
- Gene pool – The set of genes present within a population or species.
- Speciation – The formation of new, distinct species.
1. Which of the following scenarios best fits the definition of a population?
A. Five species of frog living in a swamp.
B. All of the sharks swimming off the west coast of Australia.
C. All the individual mountain gorillas living in the dense forest of four national parks in Africa.
D. The birds, bats and monkeys, which live in the rainforest of Ecuador.
Answer to Question #1
C is correct. Although their local populations are separated into four national parks spanning three countries, the mountain gorillas of the national parks in Africa all belong to the same species (Gorilla beringei beringei). The total population of mountain gorillas consists of around 1000 individuals. All the other scenarios involve communities of different species.
2. A population bottleneck occurs when:
A. The numbers of individuals in a group becomes too high.
B. An event causes a significant loss of individuals in a population.
C. Species migrate away from their native population.
D. Two populations merge together to form a new population.
Answer to Question #2
B is correct. A population bottleneck occurs when significant number of individuals are killed. The surviving individuals may reproduce and repopulate or they may go extinct.
3. Small populations are more vulnerable than large ones because:
A. They are more likely to be predated on.
B. They are vulnerable to change because they have a smaller gene pool.
C. They cannot keep each other warm.
Answer to Question #3
B is correct. Larger populations are usually more resilient toward changes in environment than small ones. In a large population it is more likely that some individuals will possess genetic mutations that are favorable under the new conditions and are able to survive and reproduce.
A group of organisms of one species that interbreed and live in the same place at the same time (e.g., human population, the population of apple trees, total population of deer in a forest). It is a subset of total individuals of a species that occupy a certain geographic area in the world.What is the population in definition? ›
Definition of population
1a : the whole number of people or inhabitants in a country or region. b : the total of individuals occupying an area or making up a whole. c : the total of particles at a particular energy level —used especially of atoms in a laser.
A population in biology is a group of organisms living in the same place at the same time. Examples of different populations are humans living in a city, a pack of wild dogs, or a group of salmon.What is the best definition of population? ›
POPULATION. 1. All the inhabitants of a given country or area considered together; the number of inhabitants of a given country or area.What is the difference between population and sample give an example? ›
To summarize: your sample is the group of individuals who participate in your study, and your population is the broader group of people to whom your results will apply. As an analogy, you can think of your sample as an aquarium and your population as the ocean.What is population and types? ›
A discrete assemblage of entities with identifiable characteristics such as people, animals with the objective of analysis and data collection is called a population. It consists of a similar group of species who dwell in a particular geographical location with the capacity to interbreed.What are the 3 types of population? ›
There are generally three types of population pyramids created from age-sex distributions-- expansive, constrictive and stationary.What is the sentence of population? ›
Use “population” in a sentence
The population gradually increased. Rapid population growth is a serious problem in our country. What is the population of France? The population is increasing rapidly.
- Finite Population.
- Infinite Population.
- Existent Population.
- Hypothetical Population.
Populations are all the members of a species that live in a one area. You are part of the human population for your home town. A freshwater pond has multiple populations, including a population of mallard ducks, and a population of cattail plants growing on the edge.
Some examples of this category are all the bass in a lake, all the stray cats in a city, or all the evergreen trees in a forest. Remember, limiting factors can affect the carrying capacity. Different limiting factors, such as natural disasters or competition, can cause a population size to decrease!What is population in social science? ›
The study of population covers not only basic measurements of population change, but also analysis of the roots and ramifications of those changes. Sociologists approach the study of population by focusing on the social processes and implications of demographic change.What is population and its 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.Who defined population for the first time? ›
1. Professor Solar Wayland defined population education for the first time. 2. The human made social traditions, rule, laws, customs, temple; religious places, etc are social and cultural aspects.What is an example of a sample? ›
A sample is just a part of a population. For example, let's say your population was every American, and you wanted to find out how much the average person earns. Time and finances stop you from knocking on every door in America, so you choose to ask 1,000 random people. This one thousand people is your sample.What is difference between sample and sampling? ›
A sample is a subset of individuals from a larger population. Sampling means selecting the group that you will actually collect data from in your research. For example, if you are researching the opinions of students in your university, you could survey a sample of 100 students.What are the 3 types of population? ›
There are generally three types of population pyramids created from age-sex distributions-- expansive, constrictive and stationary.What is an example of a sample? ›
A sample is just a part of a population. For example, let's say your population was every American, and you wanted to find out how much the average person earns. Time and finances stop you from knocking on every door in America, so you choose to ask 1,000 random people. This one thousand people is your sample.What is population in social studies? ›
In sociology and population geography, population refers to a group of human beings with some predefined criterion in common, such as location, race, ethnicity, nationality, or religion. Demography is a social science which entails the statistical study of populations.What is population in an ecosystem? ›
In ecology, a population consists of all the organisms of a given species that live in a particular area. The statistical study of populations and how they change over time is called demography.
There are different types of population. They are: Finite Population. Infinite Population.What is importance of population? ›
The population is one of the important factors which helps to balance the environment, the population should in a balance with the means and resources. If the population will be balanced, then all the needs and demand of the people can be easily fulfilled, which helps to preserve the environment of the country.What are the characteristics of population? ›
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.What is a difference example? ›
The result of subtracting one number from another. How much one number differs from another. Example: The difference between 8 and 3 is 5. Subtraction.Which is the best definition of a sample? ›
In research terms a sample is a group of people, objects, or items that are taken from a larger population for measurement. The sample should be representative of the population to ensure that we can generalise the findings from the research sample to the population as a whole.What is the target population example? ›
Examples of a target population are a company's customer base, the population of particular country, the students at a particular university or tenants of a housing association.What is population and types? ›
A discrete assemblage of entities with identifiable characteristics such as people, animals with the objective of analysis and data collection is called a population. It consists of a similar group of species who dwell in a particular geographical location with the capacity to interbreed.What are the 7 characteristics of population? ›
- Characteristics or Qualities of the Population.
- Populace size and Density.
- Populace scattering or spatial dissemination.
- Age structure.
- Natality (rate of birth)
- Mortality (passing rate)
- Population Size and Density: Total size is generally expressed as the number of individuals in a population. ...
- Population dispersion or spatial distribution: ...
- Age structure: ...
- Natality (birth rate): ...
- Mortality (death rate):
Answer and Explanation:
All of the students in your classroom would be an example of a population.
Populations are all the members of a species that live in a one area. You are part of the human population for your home town. A freshwater pond has multiple populations, including a population of mallard ducks, and a population of cattail plants growing on the edge.What is a population of animals? ›
A population is a group of individuals of the same species that live in the same geographic area that interbreed with each other. Many species consist of multiple populations dispersed over a few to many geographic areas.