Summary
All the individuals of one species living in the same area at the same time.
In depth
Populations are defined by species and area. Key traits: size, density, dispersion (clumped, uniform, random), birth and death rates, immigration and emigration. Change = (births + immigration) - (deaths + emigration).
Population size is estimated through sampling. Birth and death rates determine growth. Demography uses life tables.
Key idea: a population is defined by interbreeding and shared geography.
Demography tracks births, deaths, immigration and emigration: the change in population size equals births plus immigration minus deaths and emigration. Populations have a structure by age and sex, and a geographic range, with density varying within it. Population ecologists use life tables and matrix models to project growth.
Human population passed 8 billion in 2022, having doubled from 4 billion in about 48 years (1974 to 2022); growth rate has fallen from a peak of about 2.1 percent in the 1960s to about 0.9 percent. Fertility decline following the demographic transition is the main reason.
Example: counting wolves on Isle Royale since 1958 is one of the longest predator-prey studies, showing booms and crashes.
Frequently asked questions
What is Population?
All the individuals of one species living in the same area at the same time.
Which area of biology covers Population, and how advanced is it?
Population is one of the 54 topics in Ecology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Age Structure, Carrying Capacity, Landscape Ecology.
Can you give an example of Population?
A wolf pack population within Yellowstone.
What should I learn before Population?
Population is a Beginner topic, so no earlier topic is required. Other Beginner topics in Ecology that pair well with it include Ecology, Ecosystem, Biotic and Abiotic Factors.
What topics are related to Population?
The closest topics to Population are Age Structure, Carrying Capacity, Landscape Ecology, Population Density. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Population?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Population. To practise the whole of Ecology, use the Ecology quiz.
How is Population different from Age Structure?
Population: All the individuals of one species living in the same area at the same time. Age Structure: The distribution of ages in a population, which predicts future growth. Read both side by side and note what each one explains.
How should I study Population step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Age Structure and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.