Population ecology is the study of how populations — of plants, animals, and other organisms — change over time and space and interact with their environment. Populations are groups of ...

A species is a population of organisms that interbreeds and has fertile offspring. Living organisms have descended with modifications from species that lived before them. Natural selection ...

Like all living organisms, humans exploit their surroundings ... hunting and gathering just enough food to stay alive. Population numbers were kept low because of the difficulty of finding food.

When sampling a population, the numbers of organisms are counted within a sample site, and then the results multiplied to estimate the total number in the entire habitat. Large animals and plants ...

Different allelic forms of a single gene can appear and disappear from time to time within a single group of organisms. This means that the gene pool of a population is dynamic and can change at ...

Usually, we think of a population that adapts to changes in a physical environment. Often, however, the pressure to adapt comes from another organism. It can occur between species that are ...