Question

question 5 chapter 5: the ecological efficiency in a food chain is 20%. the growth rate of predators is half the growth rate of their prey. if the biomass on trophic level 1 is 400, what is the biomass on trophic level 3. select one a. 160 b. 120 c. 64 d. 36

Explanation:

Step1: Calculate biomass at trophic level 2

The ecological efficiency is 20% or 0.2. Biomass at trophic level 1 is 400. To find biomass at trophic level 2, we use the formula: Biomass at level 2 = Biomass at level 1×Ecological - efficiency. So, Biomass at level 2 = 400×0.2 = 80.

Step2: Calculate biomass at trophic level 3

Since the growth rate of predators (trophic level 3) is half of their prey (trophic level 2), and the ecological - efficiency is still 20% for the transfer from level 2 to level 3. First, we find the biomass at level 3 using the ecological - efficiency formula. Biomass at level 3 = Biomass at level 2×0.2. Substituting the value of biomass at level 2 (80), we get Biomass at level 3 = 80×0.2 = 16.

Answer:

16