Question

why most of food chains consist of four steps?

Answer 1

The food chain consists of the chain in which it tells us that who eats whom. According to 10%law of Lindemann (1942) only 10 % energy could be passed through one trophic level to other so after 4-5 levels the energy which could be passed remains very less thus considered to be negligible
Hope it helps you

Answer 2

1) Most of the food chains are quite short and mostly consists of four steps.

2) This is because only 10% of the energy present in a level transfers to the other level.

3) Remaining energy is dissipated as heat produced during the process of respiration and other ways.

4) We can conclude that the fewer the steps in the food chain, the more energy will be for the species at the top.