Q: A population of deer is growing logistically with a carrying capacity $$K = 500$$ and an intrinsic growth rate $$r = 0.1. If $$the current population size is $$N = 250$$, what is the expected population growth rate at this moment? Use the logistic growth equation: $$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right).$$

$$\frac{dN}{dt} = 0.1 \times 250 \times \left(1 - \frac{250}{500}\right) = 12.5$$

Question 1

A researcher is studying two islands in the Pacific Ocean. Island A is large and close to the mainland, while Island B is small and far from the mainland. According to the Theory of Island Biogeography, which island is expected to have a higher equilibrium number of species, and why?

Accepted Answer

Island A, because its larger size and proximity to the mainland increase immigration and decrease extinction rates.

Question 2

Which of the following best explains why deserts are typically found at 30° latitude north and south of the equator?

Accepted Answer

Descending dry air masses at these latitudes inhibit cloud formation and precipitation.

Question 3

A population of rabbits in a meadow has a per capita growth rate $$r = 0.2$$ per month. If the initial population size is $$N_0 = 100$, what will the population size be after one month, assuming exponential growth and no immigration or emigration? Use the exponential growth equation: N_t$$ = $$N_0$$ $$e^{rt}.$$

Accepted Answer

$$N_1 = 100$$ $$e^{0.2}$$ \approx 122$$

Question 4

Which of the following scenarios best illustrates the concept of a realized niche?

Accepted Answer

A plant species grows in all soil types in a greenhouse but only in sandy soils in the wild due to competition.

Question 5

In a food web, which of the following best describes the flow of energy and cycling of nutrients?

Accepted Answer

Energy flows through the food web and is lost as heat, while nutrients cycle between biotic and abiotic components.

Question 6

A population of deer is growing logistically with a carrying capacity $$K = 500$$ and an intrinsic growth rate $$r = 0.1. If $$the current population size is $$N = 250$$, what is the expected population growth rate at this moment? Use the logistic growth equation: $$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right).$$

Accepted Answer

$$\frac{dN}{dt} = 0.1 	imes 250 	imes \left(1 - \frac{250}{500}ight) = 12.5$$

Question 7

Which of the following is an example of a fitness trade-off in population ecology?

Accepted Answer

A plant species allocates more energy to producing many small seeds rather than a few large seeds.

Question 8

Which of the following best describes the competitive exclusion principle?

Accepted Answer

Two species competing for the same limiting resource cannot coexist indefinitely; one will outcompete the other.

Question 9

A mountain range causes moist air to rise and cool, resulting in precipitation on one side and dry conditions on the other. What is this phenomenon called, and how does it affect biome distribution?

Accepted Answer

Rain shadow effect; it creates deserts on the leeward side of mountains.

Question 10

Which of the following interactions is correctly matched with its effect on the fitness of the two species involved?

Accepted Answer

Mutualism: (+/+)

Question 11

Which of the following best explains why net primary productivity (NPP) is typically higher in tropical rainforests than in tundra biomes?

Accepted Answer

Tropical rainforests receive more sunlight and precipitation, supporting higher rates of photosynthesis.

Question 12

Which of the following is a direct human impact on the nitrogen cycle in ecosystems?

Accepted Answer

Application of synthetic fertilizers increases nitrogen runoff into waterways.

Question 13

A scientist observes that two bird species feed on similar seeds but one species has a slightly larger beak. Over time, the beak sizes diverge further. What evolutionary process is most likely responsible for this pattern?

Accepted Answer

Character displacement due to competition for resources.

Question 14

Which of the following statements about energy transfer in ecosystems is correct?

Accepted Answer

Only about 10% of energy is transferred from one trophic level to the next.

Question 15

Which of the following best describes the difference between exponential and logistic population growth?

Accepted Answer

Exponential growth is density-independent, while logistic growth is density-dependent and limited by carrying capacity.

Question 16

Which of the following is an example of commensalism?

Accepted Answer

Barnacles attaching to a whale, gaining a place to live while the whale is unaffected.

Question 17

If a population's birth rate is 0.05 per individual per year, death rate is 0.03 per individual per year, immigration rate is 0.01 per individual per year, and emigration rate is 0.02 per individual per year, what is the per capita growth rate $$r$$?

Accepted Answer

$$r = (0.05 + 0.01) - (0.03 + 0.02) = 0.01$$

Question 18

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

Accepted Answer

They recycle nutrients from dead organic matter back into the abiotic environment.

Question 19

Which of the following is a likely consequence of asymmetric competition between two species?

Accepted Answer

One species will be excluded from the resource or habitat.

Question 20

Which of the following best explains why ocean currents can influence the climate of coastal regions?

Accepted Answer

Warm ocean currents raise air temperatures and increase precipitation, while cold currents lower air temperatures and reduce precipitation.

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