Question

why most if the food chain cinsist of four steps

Answer 1

Most of the food chains have only 4 steps because:-

1. If there is a long food chain then less energy transfer takes place.
2. This lead to the extinction of top carnivore.
3. this create ecological imbalance.
4. So many food chains consist of 4 steps.

Answer 2

because of Ten Percent Law. Energy reduces by 10% when it goes to next Trophic level in food chain. For Example: 

Grass----Grasshopper----Rabit-----Sanke---Eagle 

Eagle will have the least energy. So that is why food chains have only 3-4 Steps.!!