Question

why are only four or five trophic levels present in each food chain

Answer 1

Any food chain has a maximum of only 4 or 5 trophic levels.This is because according to the 10% law of transfer of energy, only 10% of the energy of any organism at a perticular trophic level is available to another organism at the higher trophic level...So, their is very less energy available for the organism at the 4th or the 5th trophic level...

Answer 2

Each organism on that level loses energy gained from the previous trophic level . This is due to losing energy through wasted material (e.g. bones) and to life processes, 7 of which can be remembered by MRS GREN:

M ovement

R espiration

S ensitivity

G rowth

R eproduction

E xcretion

N utrition

This mean that each time, energy is wasted from the food chain. More than four trophics would result in so much loss in energy from the initial trophic level(producer) to final trophic level (consumer).