Question

why do higher trophic levels in most ecosystems contain less biomass (organisms) than lower trophic levels?

a. only 10% of energy is passed up trophic levels through feeding relationships and less energy means less biomass.

b. the apex predators at the higher trophic levels actually contain more biomass than the producers at the bottom of trophic levels.

c. energy available to organisms on higher trophic levels is large.

d. 90% of energy is passed on through feeding relationships and therefore there is less energy and biomass at higher trophic levels.

Explanation:

To solve this, we analyze each option:

• Option A: The 10% energy transfer rule (only ~10% of energy from one trophic level is passed to the next) means less energy at higher levels, supporting less biomass. This matches ecological energy flow concepts.
• Option B: Apex predators do not have more biomass than producers; producers (lower levels) typically have more biomass. Eliminate B.
• Option C: Energy available at higher trophic levels is less (due to 10% transfer), not large. Eliminate C.
• Option D: The energy transfer is ~10% (not 90%) passed up. So D's energy transfer percentage is incorrect. Eliminate D.

Answer:

A. Only 10% of energy is passed up trophic levels through feeding relationships and less energy means less biomass.