Food Chain - Ecosystem
In a food chain, the food energy is transformed from a given source through a series of species, each of which eats the one before itself in the chain. This repeated series of eating and being eaten is always initiated with green plants, which convert radiant energy into chemical energy which is stored in food. A very simple food chain is:
Sun → grass → goat → man
Each transfer a proportion of the food, energy is lost as heat. This limits the number of links or steps in a food chain, usually to four or five. In aquatic ecosystems, microscopic green plants called phytoplankton and algae play the same role as grasses in a pasture or trees in a forest.