The growth rate of a population can be measured with an equation that takes into account the four factors that affect population size:
r= (b + i) - (d + e)
In this equation, r = population growth rate, b = birth rate, i = immigration rate,
d = death rate, and e = emigration rate. We can apply the four factors to our locker
ecosystem example. A small population of fruit flies immigrated into the locker in
search of food. The population increased due to the birth of a new group of fruit flies.
Those flies that did not die when you swatted them in surprise emigrated from the
locker when you threw the apple away.
As part of a long-term elephant study, biologists counted individuals in a population
of elephants each spring. In one year, there were 18 males and 34 females. Over the
following year, each female gave birth, from which 28 offspring survived. Predators
killed 9 elephants. A construction project cleared 50 acres of nearby forested land,
causing 5 males and 19 females to immigrate into the study area. Competition for
females increased, resulting in the emigration of 10 males to a new territory in search
of mates.
SOLVE Find the growth rate of this population. Show your work.