Deck 13: Population Dynamics Over Space and Time

Question 1

Consider a logistic model that includes a time delay in density dependence and exhibits damped oscillations. If the carrying capacity is increased but all other parameters remain the same, which of the following outcomes is most likely?

A) The population will approach carrying capacity without any oscillations.
B) The population will continue to exhibit damped oscillations.
C) The population will oscillate as a stable limit cycle.
D) The population will go extinct.

Answer 1

B

Question 2

Which is TRUE about damped oscillations?
I. They are a pattern of population growth in which a population continues to exhibit large oscillations over time.
II. They are a form of demographic stochasticity.
III. They are expected to occur when $\tau$ = 1.

A) I only
B) II only
C) III only
D) I and II only
E) II and III only

Answer 2

III only

Question 3

Which conclusion does the figure support?

A) Recruitment of all species has been constant.
B) Oak may have had increased recruitment since 1650.
C) White pine may have had decreased recruitment since the late 1700s.
D) Eastern hemlock has had decreased recruitment since 1650.

Answer 3

C

Question 4

Which panel is most likely to indicate a population with a constant environment and no time delays in density dependence?

A) a
B) b
C) c
D) d

Question 5

In the logistic growth model with time delays, the product of r indicates the

A) carrying capacity of a population.
B) extent of oscillations in population size.
C) amount of demographic stochasticity.
D) amount of environmental stochasticity.

Question 6

Consider a logistic model that includes a time delay in density dependence and exhibits damped oscillations. If the intrinsic rate of increase is reduced but all other parameters remain the same, which of the following outcomes is most likely?

A) The overall population will decrease.
B) The overall population will increase.
C) The population will approach carrying capacity without any oscillations.
D) The population will oscillate as a stable limit cycle.

Question 7

In population dynamics following the logistic model, an overshoot occurs when

A) N = $\frac { K } { 2 }$ .
B) N = $\frac { r } { 2 }$ .
C) N > K.
D) N > r.

Question 8

Many species exhibit population cycles with peaks at regular intervals, such as peaks in population size that occur every 6 years. Explain why is it not likely that environmental variation is the underlying cause of these regular cycles. As part of your explanation, include a description of expected differences between changes in population size due to environmental variation and changes in population size due to density-dependent population regulation.

Question 9

Which of the following is an example of delayed density dependence?
I) The per capita growth rate of a coyote population decreases as the number of coyotes increases.
II) The fecundity of two-year-old frogs is based on their density as tadpoles.
III) The number of seeds produced by flowers in the fall depends on the amount of rainfall the previous spring.

A) I only
B) II only
C) III only
D) I and II only
E) II and III only

Question 10

What eventually occurs when the number of individuals in a population exceeds the population's carrying capacity?

A) The number of individuals continues to increase but at a faster rate.
B) The number of individuals continues to increase but at a slower rate.
C) The number of individuals reaches equilibrium and becomes constant.
D) The number of individuals declines.

Question 11

A herd of 25 reindeer was introduced to St. Paul Island in 1911. The line shows the number of reindeer on the island. Which describe(s) the entire figure correctly?
I) The pattern fits the exponential model of population growth.
II) The population experienced an overshoot.
III) The population experienced a die-off.

A) I only
B) II only
C) III only
D) II and III only
E) I, II, and III

Question 12

In the logistic model with delayed density dependence, an increase in the length of the time delay will affect population dynamics by

A) making it more likely that the population approaches K without oscillations.
B) making it more likely that the population will oscillate.
C) decreasing the mean population size.
D) increasing the mean population size.

Question 13

Which trait(s) is/are likely to cause less-stable population fluctuations over time?
I) short generation time
II) small body size
III) high sensitivity to environmental conditions

A) I only
B) II only
C) III only
D) I and II only
E) I, II, and III

Question 14

Which panel illustrates a stable limit cycle?

A) a
B) b
C) c
D) d

Question 15

A population die-off occurs when
I) a species' resources are depleted.
II) an overshoot occurs.
III) carrying capacity is exceeded.

A) I only
B) II only
C) III only
D) II and III only
E) I, II, and III

Question 16

In the logistic growth model that includes delayed density dependence, the term  indicates the

A) strength of density dependence.
B) previous carrying capacity.
C) length of the time delay.
D) current population size.

Question 17

Based on the figure, which year produced an unusually high number of offspring?

A) 1942
B) 1943
C) 1944
D) 1945
E) 1946

Question 18

Delayed density dependence

A) occurs when a population is larger than the carrying capacity.
B) occurs when density dependence is based on population density in the past.
C) is the observation that populations increase and decrease over time.
D) is a form of environmental stochasticity.

Question 19

Consider moose that breed in the fall and give birth in the spring. During breeding, the moose population is below carrying capacity, but once the young moose are born, the moose population far exceeds carrying capacity. This is an example of

A) delayed density dependence.
B) demographic stochasticity.
C) dampened oscillations.
D) rescue effect.

Question 20

Population cycles
I) are increases and decreases of population size occurring at regular time intervals.
II) can be caused by overshooting carrying capacity and subsequent die-offs.
III) indicate that a species is about to become extinct.

A) I only
B) II only
C) III only
D) I and II only
E) II, and III only

Question 21

Which statement correctly identifies the relationship between population size and extinction risk?

A) Small populations are most likely to go extinct.
B) Intermediate-sized populations are most likely to go extinct.
C) Large populations are most likely to go extinct.
D) Population size does not correlate with extinction risk.

Question 22

Which of the following is most likely to explain why Daphnia exhibits greater oscillations in population size than Bosmina?

A) Daphnia exhibits delayed density dependence; Bosmina does not.
B) Bosmina exhibits delayed density dependence; Daphnia does not.
C) Daphnia's carrying capacity is higher than Bosmina's.
D) Daphnia's carrying capacity is lower than Bosmina's.

Question 23

Variation in birth and death rates due to random differences among individuals is

A) overshooting the carrying capacity.
B) demographic stochasticity.
C) environmental stochasticity.
D) habitat fragmentation.

Question 24

The females of a certain species of fish produce on average 1,000 eggs each year. By chance some females produce a few more eggs than average, and others produce slightly fewer eggs than average. This is an example of

A) demographic stochasticity.
B) environmental stochasticity.
C) damped oscillations.
D) population cycles.

Question 25

Consider these two populations, which exhibit variation in population size over time. In which population is the fluctuation most likely due to environmental variation, and in which population is fluctuation most likely due to density dependence? Explain your answer.

Question 26

Variations in birth and death rates due to random changes in environmental conditions are

A) damped oscillations.
B) delayed density dependence.
C) environmental stochasticity.
D) stable limit cycles.

Question 27

Of the following species, which is most likely to exhibit a stable limit cycle or dampened oscillations?

A) a species with limited energy reserves such that resource availability in previous years does not affect its current ability to survive or produce offspring
B) a species whose fecundity in the present year is highly dependent on the amount of rainfall 2 years previous
C) a species whose only food resources for juveniles are limited and juvenile food availability affects adult fecundity and survival
D) a species whose population growth is following the exponential model

Question 28

Two species of mice are similar in many characteristics. However, species A has large fat reserves that increase survival over periods when environmental resources are depleted, while species B has no fat reserves. Which species is more likely to exhibit oscillating population dynamics? Explain your answer.

Question 29

Consider the time series of population sizes in years 1 and 2 for populations a, b, c, and d. If the population size in year 3 is determined by a logistic model with delayed density dependence from a 1-year time lag , r = 1, and K = 10 individuals, which of the following time series of population sizes would lead to an overshoot of the carrying capacity in year 3?

A) year 1, 5 individuals; year 2, 10 individuals
B) year 1, 10 individuals; year 2, 5 individuals
C) year 1, 5 individuals; year 2, 5 individuals
D) year 1, 10 individuals; year 2, 10 individuals

Question 30

Consider a population with the following numbers of individuals over time. year 1: 10
Year 2: 25
Year 3: 30
If the population size in year 4 is determined by a logistic model with delayed density dependence from a 1-year time lag and K = 50 individuals, what value of r would lead the population size to exceed carrying capacity in year 4?

A) r = 0.2
B) r = 0.5
C) r = 1.0
D) r = 2.0

Question 31

Which is an example of demographic stochasticity?
I) increased moose mortality when the population exceeds carrying capacity
II) variation in death rate of mice due to chance differences between individuals
III) increases and decreases in seed production due to changes in rainfall

A) I only
B) II only
C) III only
D) I and II only
E) II and III only

Question 32

Consider four populations of island birds. Each island has a different carrying capacity, and the birds are subject to environmental and demographic stochasticity. Which population is LEAST likely to go extinct?

A) island 1, K = 100
B) island 2, K = 300
C) island 3, K = 900
D) island 4, K = 1,200

Question 33

For populations growing under the logistic growth model with delayed density dependence, which of the following combinations of parameter values is most likely to lead to damped oscillations?

A) r = 0.1; K = 200; $\tau$ = 2
B) r = 0.1; K = 20; $\tau$ = 2
C) r = 0.5; K = 200; $\tau$ = 3
D) r = 1; K =20; $\tau$ = 3

Question 34

Which population model incorporates random variation in population growth?

A) deterministic
B) stochastic
C) stable limit
D) metapopulation

Question 35

Consider a population with the following numbers of individuals over time. year 1: 100
Year 2: 150
Year 3: 200
Year 4: 250
If the population size in year 5 is determined by a logistic model with delayed density dependence, r = 1.1, and K = 200 individuals, what value of $\tau$ would cause the population to decrease from year 4 to year 5?

A) $\tau$ = 0
B) $\tau$ = 1
C) $\tau$ = 2
D) $\tau$ = 3

Question 36

Explain the biological reason that higher intrinsic growth rates and longer delays lead to greater oscillations in population size.

Question 37

A biologist is developing models to describe the population dynamics of the species he studies. Four models are listed. Each model is based on the logistic model, with r equal to 1 and K equal to 100. The initial population size is given by N₀. In which of his models of population growth would the population be most likely to go extinct?

A) deterministic model, N₀ = 5
B) stochastic model, N₀ = 10
C) deterministic model, N₀ = 100
D) stochastic model, N₀ = 150

Question 38

A species of grass is affected by the amount of rainfall in the spring. In years of high rain, the grass survives better than in years of low rain. This is an example of

A) demographic stochasticity.
B) environmental stochasticity.
C) damped oscillations.
D) population cycles.

Question 39

Which is an example of environmental stochasticity?
I) changes in the weather that increase or decrease survival by a small amount
II) variation in individual health that affects likelihood of death
III) forest fires that kill large numbers of individuals every 10 to 50 years

A) I only
B) II only
C) III only
D) I and III only
E) I, II and III

Question 40

Which type of model always includes random variation?

A) stochastic
B) deterministic
C) logistic
D) exponential

Question 41

Which correctly describes metapopulations?
I) They can arise from habitat fragmentation.
II) The frequency of occupied habitats is due to the balance of extinction and colonization.
III) The basic metapopulation model assumes that all patches are equal in quality.

A) I only
B) II only
C) III only
D) II and III only
E) I, II, and III

Question 42

Metapopulations

A) occur when suitable habitat for a species is separated by unsuitable habitat.
B) are populations whose intrinsic rate of increase (r) is greater than 1.
C) are composed of subpopulations that do not go extinct.
D) are small populations likely to go extinct as a result of demographic stochasticity.

Question 43

This figure shows a metapopulation for the California spotted owl. Describe two ways in which this real metapopulation differs from the assumptions of the basic model of metapopulation dynamics,
= (1 - e/c).

Question 44

Human activity can affect metapopulations. In the basic model of metapopulation dynamics, if humans improve the quality (and thus carrying capacity) of subpopulations, the probability of _____ and the proportion of occupied patches _____.

A) extinction increases; decreases
B) extinction decreases; increases
C) colonization increases; increases
D) colonization decreases; decreases

Question 45

When immigrants supplement a declining subpopulation, they prevent the subpopulation from going extinct. This phenomenon is known as

A) a metapopulation.
B) the rescue effect.
C) demographic stochasticity.
D) habitat fragmentation.

Question 46

There are two key predictions about how extinction probability and colonization probability affect metapopulation dynamics. List these predictions and explain how they are illustrated by this figure.

Question 47

Grasslands used to be spread across large portions of North America. However, human land use has separated formerly large, continuous grassland into many smaller isolated patches. This is an example of

A) habitat fragmentation.
B) rescue effect.
C) extinction.
D) dampened oscillations.

Question 48

Which contributed to the decline and extinction of black-footed ferrets?
I) Habitat destruction reduced carrying capacity of ferrets.
II) Lethal diseases like canine distemper killed many ferrets.
III) poisoning of prairie dogs.

A) I only
B) II only
C) III only
D) I and II only
E) I, II, and III

Question 49

Human activity can affect metapopulations. Under the basic model of metapopulation dynamics, when humans make it easier for individuals to travel between patches, the probability of _____ and the proportion of occupied patches _____.

A) extinction increases; decreases
B) extinction increases; increases
C) colonization increases; increases
D) colonization decreases; decreases

Question 50

A group of subpopulations has independent population dynamics over space. This is an example of

A) habitat fragmentation.
B) a metapopulation.
C) the rescue effect.
D) environmental stochasticity.

Question 51

Which of the following contributed to the success of conservation programs that reintroduced ferrets to the wild?

A) Ferrets were introduced into multiple subpopulations.
B) Diseases that kill ferrets were eliminated.
C) Habitat destruction was prevented.
D) Stochastic causes of extinction were removed.

Question 52

Based on the predictions of metapopulation biology, which scenario can be expected to exhibit the largest fraction of occupied habitat patches?

A) small patches isolated from one another
B) large patches isolated from one another
C) large patches close to one another
D) small patches close to one another

Question 53

A species of frog is found separated into many subpopulations living in ponds that are surrounded by agricultural fields. Sometimes one frog subpopulation goes extinct because of disease or environmental stochasticity. Frogs from other subpopulations will occasionally move across fields to recolonize ponds where subpopulations have gone extinct. This is an example of

A) a metapopulation.
B) the rescue effect.
C) a sink population.
D) damped oscillations.

Question 54

Describe how the moose population has been "controlled" on Isle Royale since the early 1900s.

Question 55

Under the basic model of metapopulation dynamics, when the extinction rate is equal to the colonization rate, we predict that the proportion of patches occupied $( \bar p )$ will equal

A) 0.
B) 0.25.
C) 0.50.
D) 0.75.
E) 1.

Question 56

Under the basic model of metapopulation dynamics, which of the following conditions is necessary to prevent the species from going extinct?

A) colonization rate greater than zero
B) colonization rate equal to extinction rate
C) colonization rate less than extinction rate
D) colonization rate greater than extinction rate
E) extinction rate less than 1

Question 57

Which is an example of the rescue effect?
I) A small population of birds maintains a stable population size near carrying capacity.
II) A population of mice in a low-quality habitat persists because of immigration from high-quality habitats.
III) Habitat destruction reduces the quality of an environment and causes a population of lizards to decline every year until they go extinct.

A) I only
B) II only
C) III only
D) I and II
E) II and III

Question 58

Which is an example of a metapopulation?
I) Insects live in isolated patches of forest surrounded by agriculture. Sometimes the population in a patch goes extinct, but eventually the insects recolonize that patch.
II) A species of bird is found in Canada during the summer. In the fall, the species migrates to the Caribbean and spends the winter there. In the spring it returns to Canada.
III) A species of fish lives in a fast-flowing cold river. A dam is constructed on the river, causing the fish to go extinct because of warmer water.

A) I only
B) II only
C) III only
D) I and II
E) II and III

Question 59

Define the three components of the basic model of metapopulation dynamics,
= (1 - e/c). Explain one way in which conservation biologists can affect each of the variables e and c to protect a species.

Question 60

Riverview has 200 individuals, Oak Park has 600 individuals, and Mountainside has 50 individuals. Rank the populations in order from the most likely to go extinct to the least likely. Explain your reasoning.

Question 61

The observation that three species of grouse in Finland all experience natural population cycles every 6-7 years in synchrony is evidence that

A) the species are more closely related than originally thought.
B) the species arose from convergent evolution.
C) the drivers of population cycles can happen over a large area.
D) climate change impacts all species equally.

Question 62

When comparing larger animals to smaller animals we tend to see more stable population sizes in larger animals. What might be a reason this is the case?

A) Larger animals can better respond to (are less impacted by) environmental stochasticity.
B) Smaller animals can better respond to (are less impacted by) environmental stochasticity.
C) Larger animals reproduce more rapidly.
D) Smaller animals reproduce more slowly.

Question 63

When a population is small there is an abundance of resources for all individuals, so the per capita resource availability is high, thus leading to more rapid growth rates (as compared to larger populations). Why then are small populations more likely to go extinct compared to large populations?

A) Large populations are more impacted by stochastic events.
B) Small populations are more impacted by stochastic events.
C) Small populations are impacted by demographic stochasticity and not environmental stochasticity.
D) Small populations are impacted by environmental stochasticity and not demographic stochasticity.

Question 64

A population that exceeds its carrying capacity will

A) immediately die off, reducing its population.
B) level off at its inflection point and then remain at that population level indefinitely.
C) continue to grow until density-dependent diseases increase to such an extent that growth ceases.
D) likely continue to increase for a time but then die back to below the carrying capacity.

Question 65

Which of the following is NOT true about the 1911 St. Paul Island, Alaska, reindeer introduction?

A) The reindeer numbers crashed because they relied on the same food item throughout the entire year.
B) Natural predators did not play a role in controlling reindeer numbers.
C) Habitat fragmentation was not an issue on the island in regard to reindeer numbers.
D) Environmental stochasticity played a role in the decrease in reindeer numbers.

Question 66

That a predator finds itself in an environment with increased prey, yet does not immediately convert the prey consumed in such a resource-rich environment into offspring is the foundation for the idea of

A) overshoot and die-off.
B) delayed density dependence.
C) extinction modeling.
D) metapopulation dynamics.

Question 67

Which of the following is NOT a factor that determines whether a patch is likely to be occupied by a species?

A) size of the patch
B) proximity to other occupied patches
C) resource availability in the patch
D) history of extinction in the patch

Question 68

Vernal pools are ephemeral bodies of water that form in small depressions within the forested landscape during early spring in the northeastern United States (as well as elsewhere). The water in the vernal pools has its origin with winter snowmelt and spring rains. These vernal pools are important breeding grounds for some amphibian species. Describe how environmental stochasticity might influence amphibian populations at vernal pools.

Question 69

Describe what is meant by delayed density dependence.