What are leaves important?

To a plant, leaves are food producing organs. Leaves "absorb" some of the energy in the sunlight that strikes their surfaces and also take in carbon dioxide from the surrounding air in order to run the metabolic process of photosynthesis. The green color of leaves, in fact, is caused by an abundance of the pigment "chlorophyl" which is the specific chemical agent that acts to capture the sunlight energy needed for photosynthesis. The products of photosynthesis are sugars and polysaccharides. An important "waste product" of photosynthesis is oxygen. To an animal, a leaf may be a food source or a place to live on or under.

Two different types of succession—primary and secondary—have been distinguished. Primary succession occurs in essentially lifeless areas—regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier.