A great number of species are living in the world.
In order to survive, they must belong to a stable food
chain. For a food chain to be stable, it must keep layers
species. If a species disappears, the food chain breaks,
this can cause serious problems. We humans belong t
food chain, too. According to one scientist, three hundr
trout are needed to support one human for a year. The
trout must consume 90,000 frogs. The frogs must eat 2
million grasshoppers, and the grasshoppers require 1,0
tons of grass. Imagine what will happen to us if all gras
disappears.