Chapter 53, Problem 53.5CR

Density-dependent factors regulate population growth (pp. 1200-1205)

• ln. density-dependent population regulation, death rates rise a net birth rates fall with increasing density. A birth or death rate that does not vary with density is said to be density independent.

• Density-dependent changes in birth and death rates curb population increase through negative feedback and can eventually stabilize a population near its carrying capacity. Density-dependent limiting factors include intraspecific competition for limited food or space, increased predation, disease. intrinsic physiological factors, and buildup of toxic substances.

• Because changing environmental conditions periodically disrupt them, all populations exhibit some size fluctuations. Many populations undergo regular boom-and-bust cycles that are influenced by complex interactions between biotic and abiotic factors. A metapopulation is a group of populations linked by immigration and emigration.

Give an example of one biotic and one abiotic factor that contribute

to yearly fluctuations in the size of the human population.