Learning Objectives

9.3.1 Describe the factors important to the suitability of habitat for populations and species.

9.3.2 Explain how the distribution and abundance of species can reflect their evolutionary and geologic history.

9.3.3 Describe the role of dispersal and migration in distributing organisms across the landscape.

It is clear from the chameleon example discussed earlier in this chapter that identifying the factors important to species presence is key to understanding their distribution and abundance patterns. Many factors can influence the distributions and abundances of organisms. We'll survey these factors by grouping them into three categories: habitat suitability, historical factors (such as evolutionary history and continental drift), and dispersal.