Q: Which equation correctly represents Net Primary Productivity (NPP)?

$$\mathrm{NPP} = \mathrm{GPP} - (\text{cellular respiration} + \text{heat energy loss})$$

Question 1

Which of the following best describes the flow of energy through an ecosystem?

Accepted Answer

Energy enters as sunlight, is converted by producers, and dissipates as heat as it moves through trophic levels.

Question 2

Gross Primary Productivity (GPP) is defined as:

Accepted Answer

The total amount of chemical energy produced by primary producers in an area over a given time period.

Question 3

Which equation correctly represents Net Primary Productivity (NPP)?

Accepted Answer

$$\mathrm{NPP} = \mathrm{GPP} - (	ext{cellular respiration} + 	ext{heat energy loss})$$

Question 4

Why is energy transfer between trophic levels inefficient?

Accepted Answer

Most energy is used for cellular respiration and lost as heat, with only a small fraction available for growth and reproduction.

Question 5

If a grassland ecosystem has a GPP of $$10,000\ \mathrm{$$kcal/m^2$$/year}$$ and loses $$6,000\ \mathrm{$$kcal/m^2$$/year} to $$cellular respiration and heat, what is the NPP?

Accepted Answer

$$4,000\ \mathrm{$$kcal/m^2$$/year}$$

Question 6

Which of the following is a primary consumer in a terrestrial food web?

Accepted Answer

A grasshopper eating grass

Question 7

What is the main ecological role of decomposers in an ecosystem?

Accepted Answer

They recycle nutrients by breaking down dead organic matter, making nutrients available to primary producers.

Question 8

Which of the following best explains why pollutants such as persistent organic pollutants (POPs) become more concentrated at higher trophic levels?

Accepted Answer

Pollutants are biomagnified because they are retained and concentrated as they move up the food chain.

Question 9

In a food web, what would likely happen to the population of primary consumers if the population of top predators suddenly decreased due to disease?

Accepted Answer

Primary consumer populations would likely increase due to reduced predation.

Question 10

Which of the following is an example of bottom-up control in an ecosystem?

Accepted Answer

A decrease in nutrient availability leads to a decline in all trophic levels above primary producers.

Question 11

If only 10% of the energy at one trophic level is transferred to the next, how much energy is available to tertiary consumers from an initial $$10,000\ \mathrm{kcal} in $$primary producers?

Accepted Answer

$$100\ \mathrm{kcal}$$

Question 12

Which of the following would most likely cause a trophic cascade in a forest ecosystem?

Accepted Answer

The removal of a top predator such as wolves

Question 13

Which of the following best describes the difference between food chains and food webs?

Accepted Answer

Food chains are linear sequences of energy flow, while food webs illustrate complex, interconnected feeding relationships.

Question 14

Which of the following factors would most likely increase net primary productivity (NPP) in a terrestrial ecosystem?

Accepted Answer

Increased nutrient availability

Question 15

A scientist observes that after the introduction of a new herbivore, the abundance of primary producers decreases, and secondary consumers also decline. This is an example of:

Accepted Answer

Bottom-up control

Question 16

Which of the following organisms contributes directly to net primary productivity (NPP) in an ecosystem?

Accepted Answer

A tree performing photosynthesis

Question 17

Why are decomposers essential for maintaining high levels of NPP in an ecosystem?

Accepted Answer

They recycle nutrients, making them available for primary producers to grow and reproduce.

Question 18

Which process is responsible for the majority of energy loss between trophic levels?

Accepted Answer

Cellular respiration and heat loss

Question 19

If a pollutant is not metabolized or excreted by primary producers, what is the likely consequence for organisms at higher trophic levels?

Accepted Answer

The pollutant will biomagnify, increasing in concentration at higher trophic levels.

Question 20

In a fully top-down controlled system, what would happen to the abundance of grasses if the wolf population declined?

Accepted Answer

The abundance of grasses would decrease.

Energy Flow and Trophic Dynamics in Ecosystems

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