Chapter 53. Population Ecology (Campbell’s Biology, 9e)

Population ecologists are primarily interested in

Understanding how biotic and abiotic factors influence the density, distribution, size, and age structure of populations.

A population is correctly defined as having which of the following characteristics?
I. inhabiting the same general area
II. belonging to the same species
III. possessing a constant and uniform density and dispersion

I and II only

An ecologist recorder 12 white-tailed deer, Odocoileus virginianus, per square mile in one woodlot and 20 per square mile in another woodlot. What was the ecologist comparing?

Density (# of individuals per unit area or volume)

During the spring, you are studying the mice that live in a field near your home. The population density is high, but you realize that you rarely observe any reproductive female mice. This most likely indicates

that you are observing immigrant mice

Uniform spacing patterns in plants such as the creosote bush are most often associated with

competitive interaction between individuals of the same population

Which of the following groups would be most likely to exhibit uniform dispersion?

a) red squirrels, who actively defend territories
b) cattails, which grow primarily at edges of lakes and streams
c) dwarf mistletoes, which parasitize particular species of forest tree
d) moths, in a city at night
e) lake trout, which seek out cold, deep water hight in dissolved oxygen

a) red squirrels, who actively defend territories

To construct a reproductive table for a sexual species, one needs to

a) assess sperm viability for the males in the population
b) keep track of all of the offspring of a cohort.
c) keep track of the females in a cohort
d) keep track of all of the offspring of the females in a cohort
e) analyze the ratio of deaths to births in a cohort

c) keep track of the females in an cohort *cohort: a group of individuals of the same age

Which of the following examples would MOST accurately measure the density of the population being studied?

counting the number of zebras from airplane census observations

Which of the following assumptions have to be made regarding the capture-recapture estimate of population size?

I. Marked and unmarked individuals have the same probability of being trapped.
II. The marked individuals have thoroughly mixed with the population after being marked.
III. No individuals have entered or left the population by immigration or emigration, and no individuals have been added by birth or eliminated by death during the course of the estimate.

I, II, and III

Long-term studies of Belding’s ground squirrels show that immigrants move nearly 2 km from where they are born and become 1%-8% of the males and 0.7-6% of the females in other populations. On an evolutionary scale, why is this significant?

These immigrants provide a source of genetic diversity for the other populations.

Which of the following sets of measurements is the most useful when studying populations?

density, dispersion, and demographics of a population

Which of the following scenarios would provide the MOST legitimate data on population DENSITY?

Count the number of pine trees in several randomly selected 10m X 10m plots and extrapolate this number to the faction of the study area these plots represent

Which of the following is the best example of Uniform Distribution?

Territorial songbirds in a mature forest during mating season

Which of the following choices would most likely promote Random Distribution?

Homogeneous chemical and physical factors in the environment

Which of the following best defines a cohort?

a group of the individuals from the same age group, from birth until they are all dead

Why do some invertebrates, such as lobsters, show a "stair-step" survivorship?

Many invertebrates molt in order to grow, and they are vulnerable to predation during their "soft shell" stage.

Which of the following is the most important assumption for the capture-recapture method to estimate the size of wildlife populations?

Marked individuals have the same probability of being recaptured as unmarked individuals during the recapture phase.

A population of ground squirrels has an annual per capita birth rate of 0.06 and an annual per capita death rate of 0.02. Calculate an estimate of the number of individuals added to (or lost from) a population of 1,000 individuals in one year.

40 individuals added * Per capita (grown rate) = birth rate – death rate 0.06-0.02= 0.04 1,000*0.04=40 Therefore, 40 individuals added

Exponential growth of a population is represented by dN/dt=

rN (rmaxN)

Starting from a single individual, what is the size of a population of bacteria that reproduce by binary fission every 20 minutes at the end of a 2-hour time period? (Assume unlimited resources and no mortality.)

2^6 = 64 *exponential growth: describes population growth in an idealized, unlimited environment; assumes resources are abundant

Which of the following is the equation for zero population growth? (ZPG)

R=b-m *Zero population growth (ZPG) occurs when the per capita birth and death rates are equal (r=0)

In July 2008, the United States had a population of approximately 302,000,000 people. How many Americans were there in July 2009, if the estimated 2008 growth rate was 0.88%?

304,000,000 302,000,0000.0088=2,657,600 302,000,000+2,657,600=304,657,600

In 2008, the population of New Zealand was approximately 4,275,000 people. If the birth rate was 14 births for every 1,000 people, approximately how many births occurred in New Zealand in 2008?

60,000 4,275,000(14/1000) = 59,850

Consider two forests: one is an undisturbed old-growth forest, while the other has recently been logged. In which forest are species likely to experience exponential growth, and why?

Logged, because the disturbed forest affords more resources for increased specific populations to grow

Logistic growth of a population is represented by dN/dt =

rN * (K-N)/K *Carrying capacity (K) is the maximum population size the environment can support *N: population size

As N approaches K for a certain population, which of the following is predicted by the logistic equation?

The growth rate will approach ZERO.

In models of logistic population growth,

the population growth rate slows dramatically as N approaches K.

The Allee effect is used to describe a population that

has become so small that i will have difficulty surviving and reproducing.

Carrying capacity (K) is

the maximum population size that a particular environment can support.

Which of the following causes populations to shift most quickly from an exponential to a logistic population growth?

a) increase birth rate
b) removal of predators
c) decrease death rate
d) competition for resources
e) favorable climactic conditions

d) competition for resources

Which of the following statements about the evolution of life histories is correct?

a) stable environments with limited resources favor r-selected populations
b) K-selected populations are most often found in environments where density-independent factors are important regulators of population size
c) Most populations have both r- and K- selected characteristics that vary under different environmental conditions.
d) The reproductive efforts of r-selected populations are directed at producing just a few offspring with good competitive abilities.
e) K-selective populations rarely approach carrying capacity.

c) Most populations have both r- and K-selected characteristics that vary under different environmental conditions.

Natural selection involves energetic trade-offs between

high survival rates of offspring and the cost of parental care

The three basic variables that make up the life history of an organism are

1) age when reproduction begins, 2) how often reproduction occurs, 3) and how many offspring are produced

Which of the following pairs of reproductive strategies is consistent with energetic trade-off and reproductive success?

Female rabbits that suffer high predation rates may produce several litters per breeding season, and coconuts produce few fruits, but most survive when they encounter proper growing conditions.

Pacific salmon and annual plants are excellent examples of

Semelparous reproduction (Big-bang reproduction)

Which of the following is characteristics of K-selected populations?

a) offspring with good chances of survival
b) many offspring per reproductive episode
c) small offspring
d) a high intrinsic rate of increase
e) early parental reproduction

a) offspring with good chances of survival * K-selected populations: – biotic factors: competition, territoriality, disease, predation, toxic waste build-up – ex) blue whales – K-selected species produce relatively few young over long time spans, and exhibit extensive parental care. This is a good strategy to have in relatively stable environments * r-selected populations: – abiotic factors: weather (major storms, droughts, and wildfires) – ex) white-footed mouse – having lots of offspring at frequent intervals is the best strategy

Which variable define the ecological life history of a species?

the age at which reproduction begins, frequency of reproduction, and the number of offspring for each reproductive episode

Which pattern of reproduction is correctly paired with a species?

iteroparity – elephant *semelparity (big-bang) reproduce once and die: pacific salmon, annual plants *Iteroparity (repeated) produce offspring repeatedly: Oak tree, humans, turtles, elephants, rabbit, polar bear..

Often the growth cycle of one population has an effect on the cycle of another. As moose populations increase, for example, wolf populations also increase. Thus, if we are considering the logistic equation for the wolf population, dN/dt = rN * (K-N)/K
Which of the factors accounts for the effect on the moose population?

K

In which of the following situations would you expect to find the largest number of K-selected individuals?
A) a recently abandoned agricultural field in Ohio
B) the sand dune communities of south Lake Michigan
C) the flora and fauna of a coral reef in the Caribbean
D) South Florida after a hurricane
E) a newly emergent volcanic island

c) the flora and fauna of a coral reef in the Caribbean * K-selected – Biotic factors – Stable environments – Blue whales – Density dependent – competition, territoriality, disease, predation, toxic waste build-up

Which of the following is most likely to contribute to density-dependent regulation of populations?

A) the removal of toxic waste by decomposers
B) intraspecific competition for nutrients
C) earthquakes
D) floods
E) fires

B) intraspecific competition for nutrients * Density-depedent: biotic factors (competition, territoriality, disease, predation, toxic waste build-up)

Why do populations grow more slowly as they approach their carrying capacity?

Density-dependent factors lead to fewer births and increased mortality.

A population of white-footed mice becomes severely overpopulated in a habitat that has been disturbed by human activity. Sometimes INTRINSIC FACTORS cause the population to increase in mortality and lower reproduction rates to occur in reaction to the stress of overpopulation. Which of the following is an example of intrinsic population control?

Females undergo hormonal changes that delay sexual maturation and many individuals suffer depressed immune systems and die due to the stress of overpopulation.

Why is territoriality an adaptive behavior for songbirds maintaining populations at or near their carrying capacity?

Songbird males defend territories commensurate with the size from which they can derive adequate resources for themselves, their mate, and their chicks.

Which of the following could be a density-independent factor limiting human population growth?

A) social pressure for birth control
B) earthquakes
C) plagues
D) famines
E) pollution

B) earthquakes

An ecological footprint is a construct that is useful

for a person living in a DEVELOPED nation to consider to make better choices when using global food and energy resources.

Which of the following was the most significant limiting factor in human population growth in the 20th century?
A) famine
B) non-HIV disease
C) HIV
D) genocide
E) clean water

E) clean water

Which of the following is most key to understanding the demographic transition in human population growth?

voluntary reduction of family size

Why does the 2009 U.S. population continue to grow even though the United States has essentially established a ZPG?
A) emigration
B) immigration
C) better sanitation
D) baby boomer reproduction
E) the 2007-2009 economic recession

B) immigration

Which statement is true with regard to human population growth?

Its rate of growth is slowing.

In terms of demographics, which country is likely to experience the greatest population growth problem over the next ten years?

A) Mexico, because there are fewer pre-reproductive individuals in their population
B) China, whose population is more than a billion, but whose expected fertility rate is 1.8 children
C) Germany, where the growth rate of the population is 0.1% per year
D) United States (2009 population ~ 205,000,000, where 200,000 Americans are added to the population each day)
E) Afghanistan, with a 3.85 annual growth rate

E) Afghanistan, with a 3.85 annual growth rate

To measure the population of lake trout in a 250-hectare lake, 400 individual trout were netted and marked with a fin clip, then returned to the lake. The next week, the lake was netted again, and out of the 200 lake trout that were caught, 50 had fin clips. Using the capture-recapture estimate, the lake trout population size could be closest to which of the following?

1,600

Your friend comes to you with a problem. It seems his shrimp boats aren’t catching nearly as much shrimp as they used to. He can’t understand why because he used to catch all the shrimp he could handle. Each year he added a new boat, and for a long time each boat caught tons of shrimp. As he added more boats, there came a time when each boat caught somewhat fewer shrimp, and now, each boat is catching a lot less shrimp. Which of the following topics might help your friend understand the source of his problem?

density-dependent population regulation and intrinsic characteristics of population growth

Imagine that you are managing a large game ranch. You know from historical accounts that a species of deer used to live there, but they have been extirpated. You decide to reintroduce them. After doing some research to determine what might be an appropriately sized founding population, you do so. You then watch the population increase for several generations, and graph the number of individuals (vertical axis) against the number of generations (horizontal axis). The graph will likely appear as

a "J," increasing with each generation.

Population ecologists follow the fate of same-age cohorts to

determine the birth rate and death rate of each group in a population.

A population’s carrying capacity

may change as environmental conditions change.

Scientific study of the population cycles of the snowshoe hare and its predator, the lynx, has revealed that

multiple biotic and abiotic factors contribute to the cycling of the hare and lynx populations.

Based on current growth rates, Earth’s human population in 2012 will be closest to
A) 2 million.
B) 3 billion.
C) 4 billion.
D) 7 billion.
E) 10 billion.

D) 7 billion.

A recent study of ecological footprints concluded that

the ecological footprint of the United States is large because per capita resource use is high.

The observation that members of a population are uniformly distributed suggests that

the members of the population are competing for access to a resource.

According to the logistic growth equation

population growth is zero when N equals K.

Which pair of terms most accurately describes life history traits for a stable population of wolves?

iteroparous; K-selected

During exponential growth, a population always

grows at its maximum per capita rate.

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.
E) Age distribution is relatively uniform.

A) Life history is r-selected.

For which of the following would it be the easiest to estimate population densities?

Kangaroos
Mice
Guppies
Squirrels
Pine trees

Pine trees

A broad-based pyramid-shaped age structure is characteristic of a population that is

growing rapidly

In the models that describe population growth, r stands for

per capita population growth rate

To determine the density of a rabbit population, you would need to know the number of rabbits and________

the size of the area in which they live * density is the number of individuals of population per unit area