Modeling Populations

Question 1

What is a model?

Answer 1

Representation of an idea

Question 2

What is a model in ecology?

Answer 2

Formalized conceptualization of ecological processes
Usually quantitative

Question 3

What does birth refer to?

Answer 3

Any process that produces new individuals in a population

Question 4

What are examples of birth?

Answer 4

Eggs laid
Offspring born
Shoots produced
Cell division, mycelial growth
Number of spores

Question 5

What are some causes of death?

Answer 5

Old age, disease, lack of resources, herbivory, predation

Question 6

What is immigration and emigration?

Answer 6

Permanent movements of individuals into a local population and out of a local population

Question 7

What are abiotic modes of dispersal?

Answer 7

Wind, water

Question 8

What are biotic modes of dispersal?

Answer 8

Birds, mammals

Question 9

How do we model population growth?

Answer 9

Nt+1 = Nt + B + I - D - E

Question 10

What happens when [B+I]>[D+E]?

Answer 10

The population grows

Question 11

What happens when [B+I]<[D+E]

Answer 11

The population decreases

Question 12

What is the problem with population growth models?

Answer 12

Absolute values of difficult to compare across populations

Question 13

What do we need to solve the problem with population growth models?

Answer 13

We need per capita values to better compare trends

Question 14

What is the population growth per capita model?

Answer 14

Nt+1=Nt(b+i-d-e)

Question 15

Why is immigration and emigration assumed to be constant?

Answer 15

Because they are difficult to track

Question 16

What are density-dependent factors?

Answer 16

Influenced by population density
Often biotic factors like predators and disease

Question 17

What are density-independent factors?

Answer 17

Do not vary with population density
Often abiotic like floods and extreme temps

Question 18

What is a fecundity schedule?

Answer 18

A tabulation of birthrates for females of different ages in a population

Question 19

What do we use to estimate the rates of change in a population?

Answer 19

Life tables and fecundity schedules

Question 20

What is net reproductive rate (R0)

Answer 20

The average number of offspring produced by a female individual in her lifetime

Question 21

What is the geometric rate of increase (lambda)?

Answer 21

The ratio of the population size at two points in time

Question 22

What is generation time (T)?

Answer 22

The average age within a population at which a female gives birth to her offspring
Can be great than age of first reproduction is female reproduces more than once

Question 23

What is the per capita rate of increase (r)?

Answer 23

Equal to per capita birth rate minus per capita death rate (b-d)

Question 24

Why do we focus on fecundity in females?

Answer 24

It is easier to track maternity than paternity

Question 25

How would you track paternal fecundity?

Answer 25

Would have to analyze paternity using genetic studies which can be time and cost consuming

Question 26

What does R0=1 mean?

Answer 26

Each mother is producing exactly one female offspring to replace the mother (stable population)

Question 27

What does R0=2.4 mean?

Answer 27

Each mother produces 2.4 seeds on average that will replace the mother (population increasing)

Question 28

What is generation time?

Answer 28

Average age at which a female gives birth to her offspring
Average time from mother to daughter

Question 29

What is per capita rate of increase?

Answer 29

Per capita birth rate minus per capita death rate
A measure of population growth
Can be calculated from R0 and T

Question 30

What happens when r<0?

Answer 30

Population is declining

Question 31

What happens when r=0?

Answer 31

Population is stable

Question 32

What happens when r>0?

Answer 32

Population is increasing

Question 33

What is population growth?

Answer 33

Increase in the number of individuals within a population over time

Question 34

How can studying population growth be useful?

Answer 34

Can help to understand factors associated with population increase/decrease
Helps us make predictions about future population size

Question 35

What do geometric and exponential growth models assume?

Answer 35

Unlimited environment
-overabundant resources, density independence

Question 36

What do logistic growth models assume?

Answer 36

Limited environment
-resources can be depleted, density dependence

Question 37

What is a geometric rate of increase?

Answer 37

Ratio of the population size at two points in time
Growth increases by a constant proportion where reproduction is pulsed and generations are non-overlapping

Question 38

What is a J-shaped curve?

Answer 38

Geometric growth is discrete, increased by a fixed ratio
Each successive generation differs in size by a constant ratio

Question 39

What is exponential population growth?

Answer 39

Each successive generation differs in size based on a constant times population size at that moment in time
Produces
Non-pulsed reproduction and overlapping generations J-shaped curve

Question 40

Why do geometric or exponential growth not continue indefinitely?

Answer 40

Resources are not unlimited

Question 41

What is logistic population growth?

Answer 41

If resources become limited, the population growth rate will slow and eventually stop

Question 42

What is the carrying capacity (K)?

Answer 42

The population size at which growth stops
The number of individuals of a particular species that the local environment can support