Campbell Biology

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

Chapter 53

Population Ecology - all with Video Answers

Educators

Chapter Questions

Problem 1

Population ecologists follow the fate of same-age cohorts to
a. determine a population's carrying capacity.
b. determine the birth rate and death rate of each group in a population.
c. determine if a population is regulated by density-dependent processes.
d. determine the factors that regulate the size of a population.

Heidi Ballew

Heidi Ballew

Numerade Educator

Problem 2

A population's carrying capacity
a. may change as environmental conditions change.
b. can be accurately calculated using the logistic growth model.
c. increases as the per capita growth rate ( $r$ ) decreases.
d. can never be exceeded.

Heidi Ballew

Numerade Educator

Problem 3

Scientific study of the population cycles of the snowshoe hare and its predator, the lynx, has revealed that
a. predation is the dominant factor affecting prey population cycling.
b. hares and lynx are so mutually dependent that each species cannot survive without the other.
c. both hare and lynx populations are regulated mainly by abiotic factors.
d. the hare population is $r$ -selected and the lynx population is K-selected.

Heidi Ballew

Numerade Educator

Problem 4

Analyzing ecological footprints reveals that
a. Earth's carrying capacity would increase if per capita meat consumption increased.
b. current demand by industrialized countries for resources is much smaller than the ecological footprint of those countries.
c. it is not possible for technological improvements to increase Earth's carrying capacity for humans.
d. the ecological footprint of the United States is large because per capita resource use is high.

Heidi Ballew

Numerade Educator

Problem 5

Based on current growth rates, Earth's human population in 2015 will be closest to
a. 2 million.
b. 4 billion.
c. 7 billion.
d. 10 billion.

Heidi Ballew

Numerade Educator

Problem 6

The observation that members of a population are uniformly distributed suggests that
a. resources are distributed unevenly.
b. the members of the population are competing for access to a resource.
c. the members of the population are neither attracted to nor repelled by one another.
d. the density of the population is low.

Heidi Ballew

Numerade Educator

Problem 7

According to the logistic growth equation $$\frac{d N}{d t}=r_{\mathrm{inst}} N \frac{(K-N)}{K}$$
a. the number of individuals added per unit time is greatest when $N$ is close to zero.
b. the per capita growth rate $(r)$ increases as $N$ approaches $K$.
c. population growth is zero when $N$ equals $K$.
d. the population grows exponentially when $K$ is small.

Heidi Ballew

Numerade Educator

Problem 8

Which pair of terms most accurately describes life history traits for a stable population of wolves?
a. semelparous; $r$ -selected
b. semelparous; $K$ -selected
c. iteroparous; $r$ -selected
d. iteroparous; $K$ -selected

Heidi Ballew

Numerade Educator

Problem 9

During exponential growth, a population always
a. has a constant, instantaneous per capita growth rate.
b. quickly reaches its carrying capacity.
c. cycles through time.
d. loses some individuals to emigration.

Heidi Ballew

Numerade Educator

Problem 10

Which of the following statements about human population in industrialized countries is incorrect?
a. Life history is $r$ -selected.
b. Average family size is relatively small.
c. The population has undergone the demographic transition.
d. The survivorship curve is Type I.

Heidi Ballew

Numerade Educator

Problem 11

To estimate which age cohort in a population of females produces the most female offspring, you need information about the number of offspring produced per capita within that cohort and the number of individuals alive in the cohort. Make this estimate for Belding's ground squirrels by multiplying the number of females alive at the start of the year (column 2 in Table 53.1) by the average number of female offspring produced per female (column 5 in Table 53.2). Draw a bar graph with female age in years on the $x$ -axis $(0-1,1-2,$ and so on) and total number of female offspring produced for each age cohort on the $y$ -axis. Which cohort of female Belding's ground squirrels produces the most female young?

Heidi Ballew

Numerade Educator

Problem 12

Write a paragraph contrasting the conditions that favor the evolution of semelparous (one-time) reproduction versus iteroparous (repeated) reproduction.

Heidi Ballew

Numerade Educator

Problem 13

You are testing the hypothesis that increased population density of a particular plant species increases the rate at which a pathogenic fungus infects the plant. Because the fungus causes visible scars on the leaves, you can easily determine whether a plant is infected. Design an experiment to test your hypothesis. Describe your experimental and control groups, how you would collect data, and what results you would see if your hypothesis is correct.

Heidi Ballew

Numerade Educator

Problem 14

Many people regard the rapid population growth of less industrialized countries as our most serious environmental problem. Others think that the population growth in industrialized countries, though smaller, is actually a greater environmental threat. What problems result from population growth in (a) less industrialized countries and (b) industrialized nations? Which do you think is a greater threat, and why?

Heidi Ballew

Numerade Educator

Problem 15

In a short essay $(100-150$ words), identify the factor or factors in Figure 53.18 that you think may ultimately be most important for density-dependent population regulation in humans, and explain your reasoning.

Heidi Ballew

Numerade Educator

Problem 16

Locusts (grasshoppers in the family Acrididae) undergo cyclic population outbreaks. Of the mechanisms of density-dependent regulation shown in Figure $53.18,$ choose the two that you think most apply to locust swarms, and explain why.

Heidi Ballew

Numerade Educator