A plant is a multicellular (eukaryotic) organism and in general, is characterized by leaves, fruits, flowers, stem, trunk, etc. Plants are also (relatively) immobile organisms, as compared to other multicellular organisms, say man, deer, etc. Plants carry out two extremely important functions: food production and oxygen generation. Green plants are the primary producers in the ecosystem. They use the process of photosynthesis to convert solar energy into glucose and in turn to biomass. This biomass is the source of food for all herbivores, who in turn sustain carnivores. The same process also consumes carbon dioxide and produces oxygen, the same gas that is required for aerobic metabolism and is essential to most of the life on this planet. The consumption of carbon dioxide also ensures its levels are kept low in our atmosphere thus decreasing global warming. Plants also serve as the habitat for a large number of birds and animals.