Q: A population ecologist is studying a population of fish using the mark-recapture method. She marks 50 fish in the first sample, then captures 100 fish in the second sample, of which 10 are marked. What is the estimated population size ($$N$$)?

$$N = \frac{50 \times 100}{10} = 500$$

Question 1

Which of the following best describes the difference between abiotic and biotic factors in an ecosystem?

Accepted Answer

Abiotic factors are non-living environmental components such as temperature and soil, while biotic factors are living or related to living things such as plants and animals.

Question 2

A population ecologist is studying a population of fish using the mark-recapture method. She marks 50 fish in the first sample, then captures 100 fish in the second sample, of which 10 are marked. What is the estimated population size ($$N$$)?

Accepted Answer

$$N = \frac{50 	imes 100}{10} = 500$$

Question 3

Which dispersion pattern is most likely observed in a population of animals that defend territories?

Accepted Answer

Uniform

Question 4

Which survivorship curve is characteristic of species that produce many offspring, most of which die young, but a few survive to old age?

Accepted Answer

Type III

Question 5

A country with a population pyramid that is sharply triangular, with a wide base and narrow top, is most likely experiencing:

Accepted Answer

Rapid population growth

Question 6

Which of the following is a key difference between r-selected and K-selected species?

Accepted Answer

K-selected species tend to have longer lifespans and more parental care, while r-selected species mature quickly and have high mortality rates among offspring.

Question 7

Which equation best represents exponential population growth?

Accepted Answer

$$\frac{dN}{dT} = r$$_{max}$$N$$

Question 8

Which of the following is a density-dependent limiting factor?

Accepted Answer

Disease

Question 9

In the classic predator-prey cycle between Canada lynx and snowshoe hare, what is the primary cause of the cyclical population changes?

Accepted Answer

Predator-prey interactions where increases in hare population lead to increases in lynx population, followed by declines in both

Question 10

Which of the following is an example of Batesian mimicry?

Accepted Answer

A non-poisonous king snake resembling a poisonous coral snake

Question 11

Which formula is used to calculate Simpson’s Diversity Index?

Accepted Answer

$$D = 1 - \sum \left( \frac{n}{N} \$$right)^2$$

Question 12

Which of the following best describes the role of a keystone species in an ecosystem?

Accepted Answer

A species that has a disproportionately large effect on community structure relative to its abundance

Question 13

Which process is responsible for the conversion of atmospheric nitrogen ($$N_2) $$into ammonia ($$NH_3) $$usable by plants?

Accepted Answer

Nitrogen fixation

Question 14

Which of the following is a consequence of biological magnification?

Accepted Answer

Increased concentration of toxins such as mercury or DDT in organisms at higher trophic levels

Question 15

Which equation best represents logistic population growth?

Accepted Answer

$$\frac{dN}{dT} = r_{max} \left( \frac{K-N}{K} \right) N$$

Question 16

Which of the following is a primary difference between energy flow and matter cycling in ecosystems?

Accepted Answer

Matter is recycled, while energy flows in one direction and is eventually lost as heat.

Question 17

Which trophic level is responsible for capturing energy from sunlight and converting it into chemical energy?

Accepted Answer

Primary producers (autotrophs)

Question 18

According to the 10% Rule of Energy Transfer, if a primary producer stores 1000 kcal of energy as biomass, how much energy is available to the primary consumer?

Accepted Answer

100 kcal

Question 19

Which of the following is a behavioral response in animals to environmental cues?

Accepted Answer

Migration in response to seasonal changes

Question 20

Which of the following is a physiological response in plants to environmental cues?

Accepted Answer

Growth toward a light source (phototropism)

Ecology: Population and Community Dynamics – Study Notes

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