Question 1

Which of the following best explains why there are typically fewer tertiary consumers than primary consumers in an ecosystem?

Accepted Answer

Energy is lost at each trophic level, so less energy is available to support higher trophic levels.

Question 2

A grassland ecosystem contains grasses, rabbits, snakes, and hawks. If the population of snakes suddenly decreases due to disease, what is the most likely immediate effect on the ecosystem?

Accepted Answer

The grass population will decrease due to increased herbivory.

Question 3

Which equation best represents the logistic growth model for population size $$N$$ over time $$t$$?

Accepted Answer

$$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$$

Question 4

Which of the following is an example of a biotic factor that can limit the carrying capacity of a population?

Accepted Answer

Predation by wolves

Question 5

According to the 10% Rule, if a producer stores 10,000 kcal of energy, how much energy is available to primary consumers?

Accepted Answer

1,000 kcal

Question 6

Sea otters are considered a keystone species in kelp forest ecosystems. What is the most likely consequence of removing sea otters from this ecosystem?

Accepted Answer

A decrease in kelp due to unchecked sea urchin populations.

Question 7

Which statement best describes the Green World Hypothesis?

Accepted Answer

Predators keep herbivore populations in check, allowing plants to thrive.

Question 8

Which of the following best illustrates the first law of thermodynamics as applied to food webs?

Accepted Answer

Energy is transferred from one organism to another, but the total amount remains constant.

Question 9

A population of deer in a forest increases rapidly, then levels off and fluctuates around a certain number. This pattern is best explained by:

Accepted Answer

Logistic growth model

Question 10

Which of the following scenarios is an example of a trophic cascade?

Accepted Answer

The removal of wolves leads to an increase in deer, which then overgraze vegetation.

Question 11

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

Accepted Answer

They recycle nutrients by breaking down dead organic matter.

Question 12

If a food chain consists of grass → grasshopper → frog → snake, which organism is the secondary consumer?

Accepted Answer

Frog

Question 13

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

Accepted Answer

A decrease in nutrients in the soil leads to fewer plants, which reduces herbivore and predator populations.

Question 14

Which of the following is NOT a reason why energy transfer between trophic levels is inefficient?

Accepted Answer

All energy is stored in the bodies of consumers.

Question 15

Which of the following best defines a keystone species?

Accepted Answer

A species whose impact on its community is disproportionately large relative to its abundance.

Question 16

Which of the following is an abiotic factor that could affect the carrying capacity of a population?

Accepted Answer

Temperature

Question 17

If a producer stores 5,000 kcal of energy, how much energy would be available to a tertiary consumer according to the 10% Rule?

Accepted Answer

50 kcal

Question 18

Which of the following best describes a food web?

Accepted Answer

A complex network of interconnected food chains in an ecosystem.

Question 19

Which of the following is a real-world example of a limiting factor causing a population to reach carrying capacity?

Accepted Answer

A population of fish in a lake stops growing because the oxygen levels in the water are too low.

Question 20

Which of the following best explains why there is a limit to the number of trophic levels in an ecosystem?

Accepted Answer

Energy is lost at each trophic level, so eventually there is not enough energy to support additional levels.

Energy Flow and Species Interactions in Ecosystems

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