Chapter 5 age structure A population?s age structure?the proportions of individuals at various ages?can have a strong effect on how rapidly it increases or decreases in size. biotic potential Species vary in their biotic potential or capacity for population growth under ideal conditions. carrying capacity (K) Together, biotic potential and environmental resistance determine the carrying capacity (K): the maximum population of a given species that a particular habitat can sustain indefinitely without being degraded. coevolution