A food chain has only two or three levels. because the food chain has to connect one to another one. so food chain has only two or three levels. but food web has more.

Answer:

Because so much energy is lost to life processes.

Explanation:

As you progress through each trophic, each organism on that level loses energy gained from the previous trophic. 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:

MovementRespirationSensitivity

GrowthReproductionExcretionNutrition

This means that each time, energy is wasted and lost from the food chain. More than four trophics would result in so much energy being lost from the initial trophic (producer), that it would be largely pointless! This is shown very well in the diagram below:

Food chain consists of only 3 or 4 steps as food chain is the chain of animals which haves 3 or 4 types known as:producers,primary consumers,secondary consumers,tertiary consumers.

becoz due to 10% law there is transfer of only 10% of energy to the next trophic levels hence the levels are limited .