Ecology 6th Edition by Manuel Molles

Exercise 5

Population biologists may refer to abiotic factors, such as temperature and moisture, as density-independent because such factors can affect population processes independently of local population density. At the same time, biotic factors, such as disease and competition, are called density-dependent factors because their effects may be related to local population density. Explain how abiotic factors can influence populations in a way that is independent of local population density. Explain why the influence of a biotic factor is often affected by local population density. Now, explain how the impact of an abiotic factor may also be affected by the local population density, that is, may behave at least partly as a density- dependent factor.