The substances like C, N, S, P, H and O enter the living body through biogeochemical cycles. The atmospheric carbon (CO2 ) is used by plants during photosynthesis to synthesize carbohydrate. When animals feed upon the plant products, carbon enters into the animal’s body. C, N, S, P, H and O enters the living community through plants. Carbon comes through photosynthesis and nitrogen is obtained through nitrogen-fixing bacteria. Sulphur and Phosphorus are absorbed from the soil. Hydrogen and oxygen are obtained by water. These nutrients are obtained by animals from plants.