Q: A caterpillar eats 200 J of plant material. It assimilates 100 J, uses 67 J for cellular respiration, and produces 33 J of new biomass. What is the caterpillar's production efficiency?

$$\text{Production efficiency} = \frac{33}{100} \times 100\% = 33\%$$

Q: If a grassland receives 100,000 J of sunlight, and the net primary production is 10,000 J, what is the efficiency of energy conversion by primary producers?

$$\frac{10,000}{100,000} \times 100\% = 10\%$$

Question 1

Which of the following best describes the difference between gross primary production (GPP) and net primary production (NPP) in an ecosystem?

Accepted Answer

GPP is the total amount of light energy converted to chemical energy by autotrophs, while NPP is the energy remaining after autotrophs use some for respiration.

Question 2

According to the second law of thermodynamics, what happens to energy as it moves through trophic levels in an ecosystem?

Accepted Answer

Energy is lost as heat at each trophic level, resulting in less energy available to higher trophic levels.

Question 3

A caterpillar eats 200 J of plant material. It assimilates 100 J, uses 67 J for cellular respiration, and produces 33 J of new biomass. What is the caterpillar's production efficiency?

Accepted Answer

$$	ext{Production efficiency} = \frac{33}{100} 	imes 100\% = 33\%$$

Question 4

Which of the following is a limiting nutrient in many terrestrial ecosystems, often addressed by the presence of nitrogen-fixing bacteria in root nodules?

Accepted Answer

Nitrogen

Question 5

In the nitrogen cycle, which process converts atmospheric $$N_2$$ into a form usable by plants?

Accepted Answer

Nitrogen fixation

Question 6

Which of the following best explains why energy transfer between trophic levels is typically only about 10% efficient?

Accepted Answer

Most energy is used for cellular respiration and lost as heat.

Question 7

Which of the following organisms would be considered a detritivore in an ecosystem?

Accepted Answer

A fungus decomposing a dead tree

Question 8

A scientist measures the net ecosystem production (NEP) of a forest and finds it is positive. What does this indicate about the forest?

Accepted Answer

The forest is accumulating more biomass than it is losing.

Question 9

Which of the following is an example of a biogeochemical cycle?

Accepted Answer

The cycling of water between the atmosphere, land, and oceans

Question 10

If a grassland receives 100,000 J of sunlight, and the net primary production is 10,000 J, what is the efficiency of energy conversion by primary producers?

Accepted Answer

$$\frac{10,000}{100,000} 	imes 100\% = 10\%$$

Question 11

Which of the following would most likely increase the rate of decomposition in a forest ecosystem?

Accepted Answer

Higher temperatures and moderate moisture

Question 12

Which process in the water cycle is responsible for moving water from land to the atmosphere?

Accepted Answer

Evapotranspiration

Question 13

A farmer applies nitrogen fertilizer to a field. Which process could result in the loss of nitrogen from the soil to the atmosphere as $$N_2$$ gas?

Accepted Answer

Denitrification

Question 14

Which of the following best describes the role of primary producers in an ecosystem?

Accepted Answer

They convert inorganic energy into organic molecules through photosynthesis.

Question 15

In a terrestrial food chain, which group would have the lowest biomass?

Accepted Answer

Tertiary consumers

Question 16

Which of the following is a consequence of the law of conservation of mass in ecosystems?

Accepted Answer

Nutrients must be recycled through biogeochemical cycles.

Question 17

Which of the following would most likely limit primary production in an estuary?

Accepted Answer

Low nitrogen or phosphorus availability

Question 18

Which of the following best explains why tropical rainforests have high net primary production?

Accepted Answer

They have abundant sunlight, warm temperatures, and high rainfall.

Question 19

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

Accepted Answer

Photosynthesis

Ecosystem Structure, Energy Flow, and Biogeochemical Cycles

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