AP BIOLOGY

Detailed explanation-1: -Immigration describes individuals moving into the population while emigration describes individuals exiting the population. If immigration rates are higher than emigration rates, the population increases, whereas if emigration rates are higher than immigration rates, the population size decreases.

Detailed explanation-2: -When demographers attempt to forecast changes in the size of a population, they typically focus on four main factors: fertility rates, mortality rates (life expectancy), the initial age profile of the population (whether it is relatively old or relatively young to begin with) and migration.

Detailed explanation-3: -Density-dependent limiting factors cause a population’s per capita growth rate to change-typically, to drop-with increasing population density. One example is competition for limited food among members of a population. Density-independent factors affect per capita growth rate independent of population density.