Question

How does the amount of biomass at the fourth trophic level compare to the amount of biomass at the third troph?

Answer 1

Biomass at the 4th trophic level would be relatively smaller than at a 3rd trophic level.

Explanation:

The best way to think of biomass is to break it down into simpler terms. If we take the mass of let's say a Great White shark and multiplied it by the entire amount of Great White sharks in the same trophic level, we can then calculate biomass .

4th trophic level sharks (let's assume there are 3 of them)

800 kg each, the biomass for sharks in that trophic level would just be 3 sharks x 800 kg = 2400 kg.

3rd trophic level fur seals (let's assume there are 20 of them)

200 kg each, the biomass for fur seals would be 20 fur seals x 200 kg = 4000 kg

And as we continue to go lower and lower, you'll notice a correlation between decreasing body size/mass and increasing population density.

The image below shows a biomass pyramid and a pyramid of numbers for two communities.