CLEP - Biology Ecosystems and Energy Flow Questions and Answers

Question 1

In a terrestrial ecosystem, if the producers (plants) contain 10,000 kcal of energy, approximately how much energy would be available to the secondary consumers?

Accepted Answer

100 kcal

Answer

Energy transfer between trophic levels is inefficient, with only about 10% of the energy from one level being incorporated into the next. Primary consumers (herbivores) would have access to about 1,000 kcal (10% of 10,000). Secondary consumers, which feed on primary consumers, would then have access to about 100 kcal (10% of 1,000).

Question 2

A lake is contaminated with a persistent, fat-soluble pesticide. Which of the following organisms would likely contain the highest concentration of this pesticide in its tissues?

Accepted Answer

A large predatory fish

Answer

This scenario describes biomagnification, where the concentration of a toxin increases at successively higher levels in a food chain. The pesticide is absorbed by phytoplankton, which are eaten by zooplankton, which are eaten by small fish, which are then consumed by the large predatory fish. At each step, the toxin becomes more concentrated, resulting in the highest levels in the apex predator.

Question 3

Which of the following best defines Net Primary Productivity (NPP)?

Accepted Answer

The rate of energy storage as biomass that is available to consumers.

Answer

Gross Primary Productivity (GPP) is the total amount of energy captured by producers via photosynthesis. Producers use some of this energy for their own cellular respiration (R). Net Primary Productivity (NPP) is the energy that remains (NPP = GPP - R) and is stored as new biomass, making it available to the herbivores in the ecosystem.

Question 4

The process by which certain bacteria convert atmospheric nitrogen gas (N2) into ammonia (NH3), a form usable by plants, is known as:

Accepted Answer

Nitrogen fixation

Answer

Nitrogen fixation is the essential process that converts inert atmospheric nitrogen (N2) into ammonia (NH3) and other nitrogenous compounds that plants can absorb. This is primarily carried out by nitrogen-fixing bacteria, which can be free-living in the soil or live in symbiotic relationships with plants like legumes.

Question 5

Why is a pyramid of energy in an ecosystem always depicted as upright?

Accepted Answer

There is a progressive loss of energy at each successive trophic level.

Answer

The structure of an energy pyramid is dictated by the second law of thermodynamics. As energy flows from one trophic level to the next, a significant portion (around 90%) is lost as metabolic heat. This inefficiency means the total energy available at each successive level is always less than the level below it, resulting in a mandatory upright pyramid shape.

CLEP Practice Test

CLEP Practice Test

CLEP - Biology Ecosystems and Energy Flow Questions and Answers