Chapter 13 - Population Dynamics over Space and Time

Question 1

All populations experience fluctuations over time. Give some reasons for these fluctuations.

Answer 1

Availability of food and nesting sites, predation, competition, disease, parasites, weather or climate.

Question 2

How does body size affect population survival?

Answer 2

Smaller animals reproduce quicker; respond faster to ideal conditions.
Smaller animals have higher SA:V; more affected by negative conditions.
Larger animals maintain homeostasis, more resilient to changed environment.

Question 3

What does unusually high or low numbers of an age group suggest about a population?

Answer 3

The population experienced unusually high birth or death rates in the past.

Question 4

What is overshooting?

Answer 4

When a population grows beyond its carrying capacity.

Question 5

What is a die-off?

Answer 5

A substantial decline in density that typically goes well beyond the carrying capacity.

Question 6

When can an overshoot occur?

Answer 6

When carrying capacity declines from one year to the next.

Question 7

What are population cycles?

Answer 7

Regular oscillation of a population over a longer period of time.

Question 8

What is delayed density dependence?

Answer 8

When density dependence occurs based on a population density at some point in the past.

Question 9

What causes delayed density depedence?

Answer 9

Delay between environmental conditions changing and reproduction.

Question 10

How is the logistic growth model modified for delayed density dependence?

Answer 10

N is now at tau time units in the past.

Question 11

What are damped oscillations?

Answer 11

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

Question 12

What does the delayed density dependence intrinsic growth equation tell us?

Answer 12

Population slows its growth when the population’s size at tau time units in the past approaches the carrying capacity.

Question 13

What happens as time delays increase? What does this mean for the population?

Answer 13

Density dependence is further delayed and the population is more prone to both overshooting and undershooting the carrying capacity.

Question 14

What does a high r value mean in the delayed density dependence intrinsic growth equation?

Answer 14

Can make an overshoot of carrying capacity more likely.

Question 15

What does the amount of cycling in a population experiencing delayed density dependence depend on?

Answer 15

The product of r and tau.

Question 16

What values of rtau indicate damped oscillations in a population?

Answer 16

0.37 <rtau>1.57</rtau>

Question 17

For what value of rtau does no oscillations occur?

Answer 17

rtau<0.37

Question 18

What is a stable limit cycle?

Answer 18

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

Question 19

For what values of rtau does a stable limit cycle occur?

Answer 19

> 1.57

Question 20

What is this graph displaying?

Answer 20

A population approaching the carrying capacity with no oscillations.

Question 21

What is displayed in this graph?

Answer 21

Damped oscillations

Question 22

What is this graph depicting?

Answer 22

Stable limit cycle.

Question 23

What are some possible explanations for delayed density dependence?

Answer 23

• Organisms cans store nutrient and energy reserves
• Time delay in development from one life stage to another

Question 24

Are small or large populations more vulnerable to extinction?

Answer 24

Small

Question 25

What is a deterministic model of populations?

Answer 25

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

Question 26

What is a stochastic model of populations?

Answer 26

A model that incorporates random variation in population growth rate.

Question 27

What makes stochastic models necessary for modelling populations?

Answer 27

Not every individual within a population has the same birth rate or the same probability of dying.

Question 28

What is demographic stocasticity?

Answer 28

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

Question 29

What is environmental stocasticity?

Answer 29

Variation in birth rates and death rates due to random changes in environmental conditions.

Question 30

What are some examples of environmental stoacsticity?

Answer 30

Changes in weather, natural disasters.

Question 31

When is a population more likely to go extinct?

Answer 31

When it randomly experiences years of low birth rates or high death rates.

Question 32

When do metapopulations occur?

Answer 32

When a habitat is fragmented. Can be natural or caused by human disturbance.

Question 33

What is habitat fragmentation?

Answer 33

The process of breaking up a large habitat into smaller habitats.

Question 34

What is this equation? Define each variable.

Answer 34

Basic model of metapopulation dynamics.
p - Proportion of occupied patches when colonization and extinction in metapopulation reach equilibrium.
e - fixed probability of each patch becoming unoccupied
c - fixed probability that each unoccupied patch could become colonized

Question 35

What does the basic model of metapopulation dynamics indicate? How can this be achieved?

Answer 35

Increasing number of occupied patches increases the total number of individuals in the meta population assuming each patch has equal numbers. Achieve this by increasing colonization (corridors) or decreasing extinction (reducing major causes).

Question 36

Are small or large patches more likely to be occupied? Why?

Answer 36

Large; small patches support lower numbers and likely to experience higher rates of extinction.

Question 37

What makes an unoccupied patch more likely to be colonized>

Answer 37

Located close to an occupied patch.

Question 38

What is the rescue effect?

Answer 38

When dispersers supplement a declining subpopulation and thereby prevent the subpopulation from going extinct.