Question 1

Which of the following best describes the difference between energy flow and nutrient cycling in ecosystems?

Accepted Answer

Energy flows in one direction and is eventually lost as heat, while nutrients are recycled through biotic and abiotic components.

Question 2

A fox, as shown in the image, is best classified as which of the following in a typical terrestrial food web?

Accepted Answer

Secondary or tertiary consumer

Question 3

Given the following equation for photosynthesis:

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

What is the primary role of this process in the ecosystem?

Accepted Answer

To convert solar energy into chemical energy stored in sugars

Question 4

If a grassland ecosystem receives 10,000 kcal/m²/year of solar energy, and the gross primary productivity (GPP) is 1,000 kcal/m²/year, what percentage of incoming solar energy is captured by GPP?

Use the formula:

$$	ext{Percentage} = \frac{	ext{GPP}}{	ext{Total incoming solar energy}} 	imes 100$$

Accepted Answer

$$1\%$$

Question 5

Which of the following best explains why there are fewer tertiary consumers than primary producers in most ecosystems?

Accepted Answer

Energy transfer between trophic levels is inefficient, with only about 10% passed on to the next level.

Question 6

Which of the following is a direct human impact on the carbon cycle that contributes to climate change?

Accepted Answer

Burning of fossil fuels, increasing atmospheric $$CO_2$$

Question 7

In the nitrogen cycle, which process is primarily responsible for converting atmospheric $$N_2$$ into a form usable by plants?

Accepted Answer

Nitrogen fixation by bacteria

Question 8

A tropical rainforest has a much higher net primary productivity (NPP) than a desert. Which of the following best explains this difference?

Accepted Answer

Rainforests receive more sunlight and water, supporting greater photosynthetic activity.

Question 9

If a primary producer stores 1,000 kcal of energy, how much energy would you expect to be available to secondary consumers, assuming 10% transfer efficiency at each trophic level?

Accepted Answer

$$10$$ kcal

Question 10

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

Accepted Answer

They recycle nutrients from dead organisms back into the ecosystem.

Question 11

Which of the following scenarios would most likely lead to eutrophication in an aquatic ecosystem?

Accepted Answer

Agricultural runoff containing excess nitrogen and phosphorus

Question 12

Which of the following is NOT a major abiotic reservoir for nutrients in an ecosystem?

Accepted Answer

Animals

Question 13

If the net primary productivity (NPP) of an ecosystem is 4,680 kcal/m²/year and the gross primary productivity (GPP) is 10,400 kcal/m²/year, what is the energy lost to respiration?

Use the formula:

$$	ext{Respiration} = 	ext{GPP} - 	ext{NPP}$$

Accepted Answer

$$5,720$$ kcal/m²/year

Question 14

Which of the following best explains the latitudinal biodiversity gradient (energy hypothesis)?

Accepted Answer

There are more species near the equator because higher NPP provides more energy to support more species.

Question 15

Which of the following is a correct sequence of energy flow through a terrestrial food web?

Accepted Answer

Sun → primary producer → primary consumer → secondary consumer

Question 16

Which process in the carbon cycle is directly responsible for removing $$CO_2$$ from the atmosphere?

Accepted Answer

Photosynthesis

Question 17

Which of the following would most likely decrease the capacity of an ecosystem to absorb atmospheric $$CO_2$$?

Accepted Answer

Deforestation

Question 18

Which of the following best describes the 'pyramid of productivity' in ecosystems?

Accepted Answer

It shows that energy decreases at higher trophic levels due to inefficiency of transfer.

Question 19

Which of the following is a likely consequence of disrupting the nitrogen cycle through excessive fertilizer use?

Accepted Answer

Eutrophication of aquatic systems

Question 20

Which of the following statements about decomposers is correct?

Accepted Answer

They break down dead organic matter, returning nutrients to the soil.

Energy Flow and Nutrient Cycling in Ecosystems: Food Chains, Food Webs, and Productivity

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