AP Biology Embedded Videos

The desert biome is characterized by low precipitation, a high rate of evaporation (seven to fifty times as much as precipitation), and a wide daily range in temperature. The dramatic temperature fluctuations are the result of low humidity, which allows up to 90 percent of solar radiation to penetrate the atmosphere and heat the ground during the day, then for this accumulated heat to be released back into the atmosphere at night.

Precipitation in deserts, unlike other biomes, is highly irregular. In the Sonoran Desert, rain usually comes in short, sporadic clusters of rainy days three to fifteen times a year. On average, only one to six of these rainfalls is large enough to stimulate plant growth. Thus, Sonoran plants experience long periods of inactivity broken by periods of rapid growth and reproduction.