Instantaneous and finite rates

Charles J. Krebs

A rate is a numerical proportion between two sets of things. For example, the number of rotten apples per bushel might be measured to be six rotten apples per bushel. The number of students failing an examination might be 27 of 350, a failure rate of 7.7 percent. In ecological usage, a rate is usually expressed with a standard time base. Thus if 8 seedlings of 12 die within a year, the mortality rate will be 66.7 percent per year. If a population grows from 100 to 150 within a month, the rate of population increase will be 50 percent per month.

Fonte: Krebs, C. J. 1988. Ecology, 3th ed. NY, Harper.