Q: If a primary producer captures 10,000 J of energy from sunlight, approximately how much energy is available to secondary consumers, assuming a 10% transfer efficiency at each trophic level?

$$10,000 \times 0.1 \times 0.1 = 100 J$$

Question 1

Which of the following best describes an ecosystem?

Accepted Answer

A community of organisms and their physical environment, interconnected by energy flow and cycling of materials.

Question 2

What is the ultimate source of energy for almost all life on Earth?

Accepted Answer

The Sun

Question 3

Which equation correctly represents the process of photosynthesis?

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 4

Which group of organisms is responsible for capturing solar energy and converting it into chemical energy?

Accepted Answer

Autotrophs

Question 5

In an energy pyramid, why is the amount of energy available at each successive trophic level reduced?

Accepted Answer

Energy is lost as metabolic heat and through cellular respiration at each level.

Question 6

If a primary producer captures 10,000 J of energy from sunlight, approximately how much energy is available to secondary consumers, assuming a 10% transfer efficiency at each trophic level?

Accepted Answer

$$10,000 	imes 0.1 	imes 0.1 = 100 J$$

Question 7

Which of the following best defines net primary production (NPP)?

Accepted Answer

The amount of energy stored or incorporated into autotroph body structure after accounting for their metabolic needs.

Question 8

A caterpillar eats 200 J of plant material. It loses 100 J in feces, uses 67 J for cellular respiration, and the rest is used for growth. What is the caterpillar's production efficiency?

Accepted Answer

Question 9

Which of the following is an example of biological magnification?

Accepted Answer

A nondegradable toxin like DDT becomes more concentrated in the tissues of organisms at higher trophic levels.

Question 10

Why is eating lower on the food chain (e.g., being a vegetarian) considered more energy efficient for humans?

Accepted Answer

Because energy transfer between trophic levels is inefficient, and more energy is available at lower levels.

Question 11

Which of the following best describes the role of decomposers in an ecosystem?

Accepted Answer

They extract energy from organic wastes and dead organisms, recycling nutrients.

Question 12

If the standing crop of primary producers in a bog is 809 g/m$$^2$$ and the standing crop of tertiary consumers is 1.5 g/m$$^2$$, what does this indicate about energy transfer in this ecosystem?

Accepted Answer

Most energy is lost as heat or used for metabolic processes at each trophic level.

Question 13

Which of the following is NOT a correct match between organism type and its role in the ecosystem?

Accepted Answer

Producer – Detritivore

Question 14

A food web is more stable than a food chain because:

Accepted Answer

It allows for multiple feeding relationships, providing alternative energy routes.

Question 15

Which of the following best explains why top predators are rare in ecosystems?

Accepted Answer

Energy is lost at each trophic level, so less is available to support top predators.

Question 16

Which process is responsible for the cycling of materials such as carbon and nitrogen in an ecosystem?

Accepted Answer

Decomposition

Question 17

If a toxin is present at 0.000003 ppm in water and increases to 25 ppm in fish-eating birds, what ecological phenomenon does this illustrate?

Accepted Answer

Biological magnification

Question 18

Which of the following statements about energy flow in ecosystems is correct?

Accepted Answer

Energy flows in one direction and is eventually lost as heat.

Question 19

Which of the following would most likely increase the net primary production (NPP) of an ecosystem?

Accepted Answer

Increasing sunlight and nutrient availability for producers

Ecosystem Energy Flow and Trophic Structure

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