Question

why food chain never very long​

Answer 1

Answer:

The chain currently has “ends” because simple plant life is as close to the original energy as an organism can get, and so far there aren't any consumers at a “higher” level than humans. ... Very soon, the total available energy in the universe would have reached maximum entropy, and it would end

Answer 2

Answer:

The chain currently has “ends” because simple plant life is as close to the original energy as an organism can get, and so far there aren’t any consumers at a “higher” level than humans.

Even theoretically, the chain cannot go on forever because each higher level requires increasing the disorder in the lower level by orders of magnitude. Very soon, the total available energy in the universe would have reached maximum entropy, and it would end.

Source: Wikipedia