Biogeography is the study of the patterns of distribution of the world's living organisms. It tries to determine where plants and animals occur, why they occur where they do, and when and how the patterns developed. Bio-geographic patterns are largely determined by climate, geology, soil conditions, and historical events. Individual plant species are generally restricted to particular habitats, but many plants have widely overlapping ecological requirements so that many different kinds grow together in communities.

Impact of Climate

Rainfall has a significant impact on the distribution of plant types. Savannas, steppes, and prairies occur where rainfall patterns result in long, dry periods at certain times of the year. During the dry season, fires often sweep through these areas. Woody plants, with buds for future vegetative growth borne above ground, are killed by the flames. Grasses and other herbaceous plants, whose reproductive buds are produced on underground shoots, and...