Refers to the food chain relationship between organisms (including animals, plants and microorganisms) that provide food to each other. For example, grass on the grassland provides food for rabbits, rabbits are food for foxes, and foxes are delicious for wolves. But when the wolf dies, the body will be decomposed into nutrients for the grass by inorganic substances, which is the grassland food chain. Therefore, if one species in the food chain is extinct, it may lead to the extinction of other species and eventually lead to the collapse of the entire ecosystem.