Question 1

Which statement best explains why matter can be recycled in ecosystems but energy cannot?

Accepted Answer

Matter is conserved and cycled through biogeochemical processes, while energy is lost as heat at each transfer and cannot be reused.

Question 2

Which of the following is an example of an open system in the context of ecosystems?

Accepted Answer

A forest ecosystem that exchanges both energy (sunlight) and matter (water, nutrients) with its surroundings.

Question 3

Which process is primarily responsible for the transfer of energy from primary producers to higher trophic levels in a food chain?

Accepted Answer

Consumption of primary producers by herbivores.

Question 4

In deep sea hydrothermal vent ecosystems, which is the primary energy source for autotrophic organisms?

Accepted Answer

Chemical energy from oxidation of inorganic compounds such as H$$_2S $$and FeS$$_2.$$

Question 5

Which equation correctly represents the net primary productivity (NPP) of an ecosystem?

Accepted Answer

$$NPP = GPP - R$$

Question 6

A food web diagram shows arrows from grass to rabbit and from rabbit to fox. What do these arrows represent?

Accepted Answer

The direction of energy and nutrient transfer from grass to rabbit to fox.

Question 7

Why is energy transfer between trophic levels in a food chain typically inefficient?

Accepted Answer

Energy is lost as heat during cellular respiration and not all biomass is consumed by the next trophic level.

Question 8

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

Accepted Answer

Decomposers break down dead organic matter, releasing carbon back into the atmosphere or soil.

Question 9

Which statement about autotrophs is correct?

Accepted Answer

Autotrophs use external energy sources to synthesize carbon compounds from simple inorganic substances.

Question 10

In a cave ecosystem where sunlight does not reach, which process is most likely to support primary production?

Accepted Answer

Chemosynthesis using high-energy minerals.

Question 11

Which of the following is a correct definition of a carbon sink?

Accepted Answer

A reservoir that stores more carbon than it releases.

Question 12

Which process is responsible for the release of energy in both autotrophs and heterotrophs?

Accepted Answer

Cellular respiration.

Question 13

A pyramid of biomass in a marine ecosystem is inverted. What does this indicate about the relationship between primary producers and consumers?

Accepted Answer

Consumers have more total biomass than primary producers at any given time.

Question 14

Which of the following equations represents the gross primary productivity (GPP) of an ecosystem?

Accepted Answer

$$GPP = NPP + R$$

Question 15

Which of the following is NOT a reason for the reduction in energy availability at each successive trophic level?

Accepted Answer

Complete recycling of energy by decomposers.

Question 16

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

Accepted Answer

They obtain organic molecules from other organisms through various feeding mechanisms.

Question 17

Which of the following is a correct statement about the carbon cycle?

Accepted Answer

Carbon is transferred between the atmosphere, organisms, soil, and oceans through various processes.

Question 18

Which process allows chemosynthetic bacteria to produce organic compounds in the absence of sunlight?

Accepted Answer

Oxidation of inorganic compounds such as H$$_2S.$$

Question 19

If the gross primary productivity (GPP) of a grassland is 2000 g m$$^{-2} yr$^{-1}$$ and the respiration (R) is 1200 g m$$^{-2} yr$^{-1}$$, what is the net primary productivity (NPP)?

Accepted Answer

$$NPP = 800 g m$^{-2} yr$^{-1}$$

Question 20

Which of the following best explains why higher trophic organisms do not have more energy available to sustain themselves?

Accepted Answer

Most energy is lost as heat and only a small fraction is transferred to the next trophic level.

Ecosystem Energy Flow, Food Chains, and the Carbon Cycle

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