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 ...

The Earth's biodiversity is the result of 4 billion years of evolution — change in the inherited traits of a population of organisms from one generation to the next. Up until about 600 million years ...

Evolution by natural selection is where a trait is weeded out or becomes more common in a population depending on how well the trait helps organisms (living things) survive and reproduce.

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 ...

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 ...

Scientists have long studied the amount of microscopic organisms not just living on humans' skin but also living inside their bodies. While that amount far exceeds the population of Earth ...

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.