Abundance

Abiotic factors help determine both the abundance of a species—how many individuals are present—and its distribution—where those individuals are found. Each species is adapted to a particular range of conditions. Near its optimum, an organism is more likely to grow, survive and reproduce successfully.

A plant may be common in an open, well-lit area but scarce beneath a tree, while another species may show the opposite pattern. Its distribution describes where it occurs, and its abundance describes how much of it is present.

Abundance tells us how many individuals of a species are present; distribution tells us where they occur. Both may vary across a habitat as conditions such as light, moisture or the presence of other organisms change. Counting every organism is often impractical, so investigators examine samples and use them to estimate numbers in a defined area.

In a field investigation, distribution tells you where a species occurs, while abundance tells you how many there are. A patch of grass might contain daisies across its whole area but have far more in the sunny part than under a tree. To investigate this, first decide which species and area you will study.