Q: Which equation correctly represents net primary productivity (NPP)?

$$\text{NPP} = \text{GPP} - R$$

Q: If the gross primary productivity (GPP) of a plant community is 2000 kJ/m²/year and the energy used for respiration (R) is 1200 kJ/m²/year, what is the net primary productivity (NPP)?

$$\text{NPP} = 800\ \text{kJ/m}^2/\text{year}$$

Question 1

Which of the following best describes an ecosystem?

Accepted Answer

Multiple communities (biotic) living in an area plus abiotic components (air, water, climate, soil) linked by nutrient and energy flow.

Question 2

Autotrophs are essential to ecosystems because they:

Accepted Answer

Transform the energy in sunlight into the chemical energy stored in sugars.

Question 3

Which equation correctly represents net primary productivity (NPP)?

Accepted Answer

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

Question 4

Why are autotrophs inefficient at capturing incoming solar energy?

Accepted Answer

Pigments absorb only a fraction of available light wavelengths, photosynthetic rates drop in winter, and stomata close in dry conditions.

Question 5

If the gross primary productivity (GPP) of a plant community is 2000 kJ/m²/year and the energy used for respiration (R) is 1200 kJ/m²/year, what is the net primary productivity (NPP)?

Accepted Answer

$$	ext{NPP} = 800\ 	ext{kJ/m}^2/	ext{year}$$

Question 6

Which factor most limits the rate at which nutrients move through an ecosystem?

Accepted Answer

The decomposition of organic material by decomposers/detritivores.

Question 7

In the context of energy transfer between trophic levels, what does the '10 percent rule' refer to?

Accepted Answer

10% of the energy at one trophic level is transferred to the next level.

Question 8

Which of the following would most likely result in higher energy transfer efficiency between trophic levels?

Accepted Answer

Presence of ectothermic consumers.

Question 9

Biomagnification occurs when:

Accepted Answer

Pollutants become more concentrated as they move up the food chain.

Question 10

A persistent organic pollutant like toxaphene is found in high concentrations in Arctic food chains, even though it was never used there. This is best explained by:

Accepted Answer

Biomagnification through multiple trophic levels.

Question 11

Which of the following best explains why net primary productivity (NPP) is generally higher on land than in the sea?

Accepted Answer

Water absorbs many wavelengths of light, reducing photosynthesis in marine environments.

Question 12

Which factor is most likely to limit productivity in a terrestrial ecosystem located near the poles?

Accepted Answer

Low sunlight and cold temperatures.

Question 13

In a boreal forest, why does organic matter build up in the uppermost soil layer?

Accepted Answer

Cold conditions limit metabolic rates of decomposers.

Question 14

In the miniature ecosystem of a bromeliad, what effect do predatory insects have on nutrient cycling?

Accepted Answer

They increase nitrogen availability by consuming detritivores and leaving fecal pellets rich in nitrogen.

Question 15

Which of the following is NOT a factor that can limit productivity in an ecosystem?

Accepted Answer

Abundance of tertiary consumers.

Question 16

A food web contains four trophic levels. If a persistent pollutant is present in the primary producers at a concentration of 1 ng/g, what would you expect the concentration to be in the top consumer, assuming a tenfold increase at each level?

Accepted Answer

$$1000\ 	ext{ng/g}$$

Question 17

Which process is responsible for the cycling of nutrients but not the flow of energy in ecosystems?

Accepted Answer

Decomposition by bacteria, archaea, and fungi.

Question 18

Which of the following would most likely increase the rate of nutrient cycling in a tropical ecosystem?

Accepted Answer

High temperature and precipitation.

Question 19

If a primary producer has a net primary productivity (NPP) of 1000 g/m²/year, and only 10% of this is transferred to primary consumers, how much biomass is available to secondary consumers?

Accepted Answer

$$10\ 	ext{g/m}^2/	ext{year}$$

Question 20

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

Accepted Answer

Energy flows and is lost as heat, while nutrients cycle among organisms and the abiotic environment.

Ecosystems and Global Ecology: Energy Flow, Productivity, and Nutrient Cycling

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