Question

12 multiple choice 1 point

% of energy is lost to metabolic (bodily) processes, like moving, growing, and healing, as trophic levels get higher in a trophic pyramid.

100
90
50
10
13 multiple choice 3 points
a stable aquatic ecosystem is represented by a four - level food chain: phytoplankton (producer) → zooplankton (primary consumer) → small fish (secondary consumer) → large fish (tertiary consumer). if a new pollutant is introduced that causes a catastrophic, long - term 90% decline in the small fish population, triggering a classic trophic cascade, what is the most likely immediate change to the population sizes of phytoplankton and zooplankton?
phytoplankton population increases; zooplankton population decreases.
both phytoplankton and zooplankton populations will increase.
phytoplankton population decreases; zooplankton population increases.
both phytoplankton and zooplankton populations will decrease.

Explanation:

Step1: Energy transfer in trophic levels

In a trophic pyramid, only about 10% of energy is transferred to the next level. The rest (90%) is lost through metabolic processes like heat production, movement, growth, and healing.

Step1: Analyze the trophic cascade

• Small fish (secondary consumer) decline.
• Large fish (tertiary consumer) that prey on small fish will have less food. But the immediate effect is on the lower levels.
• Zooplankton (primary consumer) are prey for small fish. With fewer small fish, zooplankton population will increase (less predation).
• Phytoplankton (producer) are food for zooplankton. With more zooplankton (increased consumers), phytoplankton population will decrease.

Answer:

90