Question

a. consider how energy transfers between trophic levels in the above diagram. a scientist wants to determine how much yellow perch relies on opossum shrimp in a lake as a food source. they first isolate a small group of yellow perch from the pond.
i. identify a reasonable hypothesis that would help guide the scientist to their answer.
ii. identify the dependent variable in your proposed hypothesis.
iii. explain how the results of the experiment might be affected by other influences in the ecosystem.
b. use the food web to identify the following:
i. identify the trophic level represented by green algae, blue - green algae, and flagellates.
ii. identify three species that are intermediate predators (secondary or tertiary consumers) in the marine food web.
iii. describe the effects of removing the green algae species from the marine food web in lake michigan.
c. energy transfers between trophic levels:
i. green algae produces 1,000 grams of biomass, which represents usable chemical energy. describe the approximate amount of energy from that biomass that will transfer from green algae to the native water fleas in the food web.
ii. explain why energy is lost moving from a lower trophic level to a higher trophic level.

Explanation:

Step1: a.i Hypothesis formation

The Yellow Perch's growth rate is directly proportional to the availability of Opossum Shrimp.

Step2: a.ii Dependent - variable identification

The dependent variable is the growth rate of Yellow Perch, as it is expected to change based on the availability of Opossum Shrimp.

Step3: a.iii Ecosystem - influence explanation

Other predators of Yellow Perch could reduce their population, making it seem like they rely less on Opossum Shrimp. Also, other food sources for Yellow Perch might affect their consumption of Opossum Shrimp.

Step4: b.i Trophic - level identification

Green algae, blue - green algae, and flagellates are primary producers, occupying the first trophic level as they produce their own food through photosynthesis.

Step5: b.ii Intermediate - predator identification

Three intermediate predators could be Lake Whitefish, Yellow Perch, and Alewife.

Step6: b.iii Effect of species removal

Removing green algae would reduce the food source for primary consumers like native water fleas. This would lead to a decline in primary - consumer populations, affecting all higher trophic levels that rely on them.

Step7: c.i Energy - transfer calculation

Approximately 10% of the energy is transferred between trophic levels. So if green algae produces 1000 grams of biomass, 100 grams of energy would transfer to native water fleas (1000×0.1 = 100).

Step8: c.ii Energy - loss explanation

Energy is lost as heat during metabolic processes like respiration, and some biomass is not consumed or is indigestible, resulting in less energy being available for the next trophic level.

Answer:

a.i: The Yellow Perch's growth rate is directly proportional to the availability of Opossum Shrimp.
a.ii: The growth rate of Yellow Perch.
a.iii: Other predators of Yellow Perch could reduce their population, and other food sources for Yellow Perch might affect their consumption of Opossum Shrimp.
b.i: Primary producers (first trophic level).
b.ii: Lake Whitefish, Yellow Perch, Alewife.
b.iii: It would reduce the food source for primary consumers, leading to a decline in primary - consumer populations and affecting higher trophic levels.
c.i: 100 grams.
c.ii: Energy is lost as heat during metabolic processes and due to unconsumed or indigestible biomass.