Q: A population of birds is studied using the mark-recapture method. If 50 birds are initially tagged ($$s = 50$$), 100 birds are captured in the second sample ($$n = 100$$), and 20 of them are tagged ($$x = 20$$), what is the estimated population size ($$N$$)?

$$N = \frac{sn}{x} = \frac{50 \times 100}{20} = 250$$

Question 1

Which of the following best describes the population growth of sea otters reintroduced to Vancouver Island in the 1970s, as shown in the provided graph?

Accepted Answer

The population exhibited exponential growth, resulting in a J-shaped curve.

Question 2

A population of birds is studied using the mark-recapture method. If 50 birds are initially tagged ($$s = 50$$), 100 birds are captured in the second sample ($$n = 100$$), and 20 of them are tagged ($$x = 20$$), what is the estimated population size ($$N$$)?

Accepted Answer

$$N = \frac{sn}{x} = \frac{50 	imes 100}{20} = 250$$

Question 3

Which pattern of dispersion is most likely observed in populations where resources are unevenly distributed and individuals aggregate in patches, as shown in the starfish image?

Accepted Answer

Clumped dispersion

Question 4

In the logistic growth model, what happens to the per capita rate of increase as the population size ($$N) $$approaches the carrying capacity ($$K$$)?

Accepted Answer

It decreases and approaches zero as $$N$$ approaches $$K.$$

Question 5

Given the logistic growth equation $$\frac{dN}{dt} = rN \frac{K-N}{K}$$, what is the population growth rate when $$N = K$$?

Accepted Answer

$$\frac{dN}{dt} = rN \frac{K-N}{K} = rN \frac{K-K}{K} = 0$$

Question 6

Which survivorship curve type is characterized by a constant death rate throughout the organism's life span, as shown in the ground squirrel data?

Accepted Answer

Type II

Question 7

A population of penguins exhibits uniform dispersion. What is the most likely cause of this pattern?

Accepted Answer

Social interactions such as territoriality

Question 8

If a population has a per capita birth rate ($$b) of 0.2 $$and a per capita death rate ($$m) of 0.1$$, what is the per capita rate of increase ($$r$$)?

Accepted Answer

$$r = b - m = 0.2 - 0.1 = 0.1$$

Question 9

Which of the following best explains why some populations overshoot their carrying capacity ($$K) $$before stabilizing?

Accepted Answer

Delayed response to resource limitation

Question 10

In a population, which process adds individuals, and which removes individuals, as illustrated in the bird diagram?

Accepted Answer

Births and immigration add; deaths and emigration remove

Question 11

Which real-world scenario is an example of resource partitioning, allowing similar species to coexist?

Accepted Answer

Different species of lizards occupying distinct vertical levels in a forest

Question 12

What is the main difference between a fundamental niche and a realized niche?

Accepted Answer

A fundamental niche is the niche potentially occupied by a species, while a realized niche is the niche actually occupied due to competition.

Question 13

Which interaction is described as (+/−), where one species benefits and the other is harmed?

Accepted Answer

Predation

Question 14

In the context of community ecology, what is a keystone species?

Accepted Answer

A species that exerts strong control on community structure by its ecological role, not necessarily by abundance

Question 15

According to the energetic hypothesis, why are food chains typically only a few links long?

Accepted Answer

Because only about 10% of energy is transferred to the next trophic level

Question 16

Which type of ecological succession occurs in an area where no soil exists, such as after glacial retreat?

Accepted Answer

Primary succession

Question 17

What does the intermediate disturbance hypothesis predict about species diversity?

Accepted Answer

Moderate levels of disturbance foster greater diversity than high or low levels

Question 18

Which equation represents the Shannon diversity index ($$H) $$used to compare species diversity in a community?

Accepted Answer

$$H = -\sum p_i \ln p_i$$

Question 19

Which of the following is an example of facilitation in a biological community?

Accepted Answer

A black rush making soil more hospitable for other plant species

Population and Community Ecology: Structure, Dynamics, and Interactions

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