Chapter 13 Part 2

Question 1

Density dependence with time delays can cause populations to be

Answer 1

inherently cyclic

Question 2

Populations have an inherent periodicity and tend to fluctuate up and down, although

Answer 2

the time required to complete a cycle differs among species

Question 3

Populations behave like a swinging pendulum, which is

Answer 3

stable when hanging straight up and down

Question 4

Gravity will force the pendulum back to the center, but

Answer 4

momentum causes it to overshoot the center

Question 5

Populations are stable at their carrying capacity

Answer 5

when reductions in population sizes occur, the population responds by growing—often overshooting carrying capacity

Question 6

Overshoots can occur when there is a delay between

Answer 6

the initiation of breeding and the time that offspring are added to the population

Question 7

Population cycles can be modeled by starting with the logistic growth model:

Answer 7

dN/dt = rN [1 - (N/K)]

Question 8

dN/dt

Answer 8

rate of change in population size

Question 9

r

Answer 9

intrinsic growth rate

Question 10

N

Answer 10

current population size at time t

Question 11

K

Answer 11

carrying capacity

Question 12

We can incorporate a delay between

Answer 12

a change in environmental conditions and the time the population reproduces

Question 13

Delayed density dependence

Answer 13

when density dependence occurs based on a population density at some time in the past

Question 14

We can also think about time delays for predators. When predators experience
an increase of prey,

Answer 14

their carrying capacity increases

Question 15

We can also think about time delays for predators. When predators experience
an increase of prey, their carrying capacity increases. However,

Answer 15

it may take
weeks or months for the predators to convert abundant prey into higher
reproductive rates

Question 16

We can also think about time delays for predators. When predators experience
an increase of prey, their carrying capacity increases. However, it may take
weeks or months for the predators to convert abundant prey into higher
reproductive rates.

Answer 16

By this time, the prey may no longer be abundant. The lack of prey will cause
the carrying capacity of the predator to decline just as the predator population
is increasing. In both scenarios, the population experiences a time delay in
density dependence.

Question 17

To incorporate a time delay (τ) into the logistic growth model:

Answer 17

dN/dt = rN [1 - (Nt-t/K)

Question 18

As the time delay increases,

Answer 18

density dependence is delayed and the population is more prone to both overshooting and undershooting K

Question 19

The amount of cycling in a population depends on the product of

Answer 19

r and τ.

Question 20

When rτ < 0.37, the population

Answer 20

approaches carrying capacity without oscillations.

Question 21

When 0.37 < rτ < 1.57, the population

Answer 21

exhibits damped oscillations.

Question 22

Damped oscillations

Answer 22

a pattern of population growth in which the population initially oscillates but the magnitude of the oscillations declines over time

Question 23

When rτ > 1.57, the population

Answer 23

will exhibit a stable limit cycle

Question 24

Stable limit cycle

Answer 24

a pattern of population growth in which the population continues to exhibit large oscillations over time

Question 25

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

Answer 25

The population will continue to exhibit dampened oscillations

Question 26

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

Answer 26

The population will approach carrying capacity without any oscillations.

Question 27

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

Answer 27

making it more likely that the population will oscillate.

Question 28

Delayed density dependence may occur because

Answer 28

the organism can store energy and nutrient reserves

Question 29

When populations are low and food is abundant, the water flea Daphnia galeata

Answer 29

stores surplus energy as lipid droplets.

Question 30

When resources are less abundant, adults use

Answer 30

this stored energy to reproduce

Question 31

Eventually, lipid reserves are used up and

Answer 31

the populations decline to low numbers

Question 32

In contrast, Bosmina longirostris

Answer 32

does not store energy and does not exhibit oscillations in population size

Question 33

Delayed density dependence can occur when there is

Answer 33

a time delay in development from one life stage to another

Question 34

what can cause small populations to go extinct

Answer 34

chance events

Question 35

Small populations are more vulnerable to extinction than

Answer 35

larger populations

Question 36

Although data suggest that small populations are more likely to go extinct, growth models suggest that

Answer 36

small populations should have more rapid growth and be resistant to extinction

Question 37

Although data suggest that small populations are more likely to go extinct, growth models suggest that small populations should have more rapid growth and be resistant to extinction This contradiction can be resolved by incorporating

Answer 37

incorporating random variation of growth rates into growth models.

Question 38

Deterministic model

Answer 38

a model that is designed to predict a result without accounting for random variation in population growth rate

Question 39

Stochastic model

Answer 39

a model that incorporates random variation in population growth rate; assumes that variation in birth and death rates is due to random chance

Question 40

Demographic stochasticity

Answer 40

variation in birth rates and death rates due to random differences among individuals

Question 41

Environmental stochasticity

Answer 41

variation in birth rates and death rates due to random changes in the environmental conditions (e.g., changes in the weather)

Question 42

what populations are more likely to go extinct

Answer 42

populations that randomly experience a string of years with low birth rates or high death rates

Question 43

With time, there is an increased chance of having

Answer 43

a string of bad years

Question 44

Smaller populations are at more risk of extinction if they experience

Answer 44

a string of bad years

Question 45

When we use stochastic models, there is an average growth rate with some variation around that average. The actual growth rate experienced by the modeled population can

Answer 45

take any of the values within the range of this variation

Question 46

When we use stochastic models, there is an average growth rate with some variation around that average. The actual growth rate experienced by the modeled population can take any of the values within the range of this variation. As a result, a population’s growth rate may be

Answer 46

above or below the average growth rate

Question 47

If a population experiences | a string of years with above average growth rates, it will have

Answer 47

faster growth

Question 48

If the population happens to have a string of years with below average growth rates, it will have

Answer 48

slower growth