Question 1

Which statement best describes the flow of energy and cycling of matter in an ecosystem?

Accepted Answer

Energy flows one-way through an ecosystem, while matter cycles within it.

Question 2

According to the first law of thermodynamics, which of the following is true about energy in ecosystems?

Accepted Answer

Energy is transferred or transformed, but not created or destroyed.

Question 3

Which equation correctly represents the relationship between gross primary production (GPP), net primary production (NPP), and respiration (R) in an ecosystem?

Accepted Answer

$$NPP = GPP - R$$

Question 4

A scientist adds nitrogen to a lake and observes a massive increase in algal growth, followed by a decrease in fish populations. What process best explains the decline in fish?

Accepted Answer

Eutrophication led to oxygen depletion due to increased decomposition.

Question 5

Which of the following is an example of an open system in ecology?

Accepted Answer

A forest ecosystem that exchanges energy and matter with its environment.

Question 6

Which group of organisms is primarily responsible for recycling nutrients from dead organic matter back into the ecosystem?

Accepted Answer

Decomposers (detritivores)

Question 7

Why do energy pyramids typically have a broad base and a narrow top?

Accepted Answer

Energy transfer between trophic levels is inefficient, with about 90% lost as heat or waste at each step.

Question 8

Which of the following best describes the role of iron in some marine ecosystems?

Accepted Answer

Iron enrichment can increase primary production in regions where nitrogen and phosphorus are abundant.

Question 9

A restoration ecologist wants to speed up the recovery of a polluted wetland. Which strategy involves using living organisms to remove toxins from the environment?

Accepted Answer

Bioremediation

Question 10

Which of the following is a real-world example of the second law of thermodynamics in an ecosystem?

Accepted Answer

Heat is lost at each trophic level, increasing the entropy of the universe.

Question 11

Which process is responsible for converting atmospheric nitrogen ($$N_2) $$into a form usable by plants?

Accepted Answer

Nitrogen fixation

Question 12

Which of the following adaptations helps plants access limiting nutrients in poor soils?

Accepted Answer

Forming mutualisms with nitrogen-fixing bacteria

Question 13

If a fish population in a lake is declining due to low oxygen levels, which human activity is most likely responsible?

Accepted Answer

Runoff of fertilizers from nearby farms causing eutrophication

Question 14

Which of the following best explains why eating lower on the food chain (e.g., plants instead of meat) is more energy efficient for humans?

Accepted Answer

Less energy is lost as heat and waste when consuming primary producers directly.

Question 15

Which of the following is NOT a key process in the phosphorus cycle?

Accepted Answer

Nitrogen fixation

Question 16

Which of the following best describes the main reservoir for the water cycle?

Accepted Answer

Oceans

Question 17

Which of the following is a correct statement about the conservation of mass in ecosystems?

Accepted Answer

Matter cycles within ecosystems and is neither created nor destroyed.

Question 18

Which of the following would most likely limit primary production in an old, tropical soil?

Accepted Answer

Phosphorus

Question 19

Which of the following best describes the role of decomposers in the carbon cycle?

Accepted Answer

They break down dead organic matter, releasing carbon dioxide through respiration.

Question 20

Which of the following is a likely consequence if detritivores were removed from an ecosystem?

Accepted Answer

Chemical elements would stop cycling between living and nonliving parts of the ecosystem.

Ecosystems and Energy: Dynamics, Productivity, and Nutrient Cycling

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