Question

What is the reason that a food chain consists of only 3-5 steps ?

Answer 1

As per 10% law of Lindeman (1942), the energy available decreases by 90% with the rise of trophic level. 2000 J of energy available at the producer or T${}_1$ level will provide only 2 J of energy to second order carnivores (T${}_4$) Therefore, an ecosystem cannot have food chains of several steps.