When several food chains come together, they are called
an animal chain
a food web
nature
an environmental chain

a food web

Explanation:

nteraction between biotic and abiotic components constitutes an ecosystem. In any ecosystem, energy flows through the food chain. A food chain is a chain of producers and different consumers. In any ecosystem, there are many food chains operate at a time which are interlinked. The network of different food chains operate in an ecosystem is called a food web. In the food web, producers and consumers are interlined. For example, in a grassland ecosystem insects are eaten by frogs and by birds, frogs are eaten by snakes or by birds. Thus, different organisms form the food web among themselves.    

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.