You are here

Population Size and Density

6 April, 2016 - 17:26

Populations are characterized by their population size (total number of individuals) and their population density (number of individuals per unit area). A population may have a large number of individuals that are distributed densely, or sparsely. There are also populations with small numbers of individuals that may be dense or very sparsely distributed in a local area. Population size can affect potential for adaptation because it affects the amount of genetic variation present in the population. Density can have effects on interactions within a population such as competition for food and the ability of individuals to find a mate. Smaller organisms tend to be more densely distributed than larger organisms (Figure 19.2).


Figure 19.2 Australian mammals show a typical inverse relationship between population density and body size. 

As this graph shows, population density typically decreases with increasing body size. Why do you think this is the case?