Lecture 15: Population Dynamics 2

Question 1

Constant per capita population in

Answer 1

continuous time, exponential growth

Question 2

assumptions for population model for constant per capita, exponential growth

Answer 2

per capita population growth rate is constant
all individuals the same
but births, deaths are happening continuously
λ or r is constant through time.
→ per capita rate of births, immigration, deaths, emigration is constant

Question 3

Exponential population growth occurs:

Answer 3

If births and deaths happen CONTINOUSLY and the rate at which they happen does not change over time

Question 4

r in exponential growth model explains

Answer 4

intristic rate of increase or exponential growth rate
r= birth rate + immigration rate - death rate - emigration rate (all per capita, b + i - d - e)

Question 5

If r > 0 and λ > 0, population is

Answer 5

growing in size

Question 6

If r < 0 and λ <0, population is

Answer 6

decreasing in size

Question 7

If r=0 and λ=1, the population size is

Answer 7

constant

Question 8

Geometric population growth, time is ____ and exponential population growth, time is ______

Answer 8

discrete, continuous

Question 9

Pros of exponential (continuous) population growth

Answer 9

Constant per-capita population growth
Populations quickly grow out of control or extinct
Good null prediction for short time periods, if nothing changes.

Question 10

Population regulation

Answer 10

One or more resources in short supply
Disease and/or parasite transmission rates high at high densities
Predator N increases: attracted by high prey N and time lag in response to high food supply

Question 11

______ can regulate population size

Answer 11

Negative density dependence
(any shape, negative correlation)

Question 12

Negative density dependence

Answer 12

Individuals added to the population have a negative effect on per capita population growth rate
Increases in B, decreases per capita population growth
Decrease in B, increases per capita population growth

Question 13

Negative-density dependence,
Logistic growth

Answer 13

Each individual added to the population has the same
negative effect on per-capita population growth rate

Question 14

Geometric Model
Pop Growth Equation:
All individuals the same?
Per capita pop growth constant?
Discrete/ continuous
Stable population size
Critical parameters
Equilibrium point

Answer 14

Pop Growth Equation:
Nt = N0λ^t
All individuals the same? Yes
Per capita pop growth constant? Yes
Discrete/ continuous: Discrete
Stable population size: No
Critical parameters: λ
Equilibrium point: λ=1

Question 15

Exponential Model
Pop Growth Equation:
All individuals the same?
Per capita pop growth constant?
Discrete/ continuous
Stable population size
Critical parameters
Equilibrium point

Answer 15

Pop Growth Equation:
Nt = N0 * e^rt

All individuals the same? Yes
Per capita pop growth constant? Yes
Discrete/ continuous: continuous
Stable population size: No
Critical parameters: r
Equilibrium point: r=0

Question 16

Logistic (Negative density dependence) Model
Pop Growth Equation:
All individuals the same?
Per capita pop growth constant?
Discrete/ continuous
Stable population size
Critical parameters
Equilibrium point

Answer 16

Pop Growth Equation:
All individuals the same? Yes
Per capita pop growth constant? No, decreasing
Discrete/ continuous: Continuous
Stable population size: Yes
Critical parameters: r, K
Equilibrium point: N=K

Question 17

Positive density dependence Model
Pop Growth Equation:
All individuals the same?
Per capita pop growth constant?
Discrete/ continuous
Stable population size
Critical parameters
Equilibrium point

Answer 17

Pop Growth Equation:
All individuals the same? Yes
Per capita pop growth constant? No, increasing
Discrete/ continuous: Continuous
Stable population size: No
Critical parameters: N0, r, A
Equilibrium point: N=A

Question 18

All models will have equilibrium point and no population growth when

Answer 18

N0=0
When initial population is 0, will stay 0

Question 19

Time lag

Answer 19

time lag refers to the delay between the initial increase in population and the point where the growth rate begins to slow down as the population approaches the carrying capacity of the environment.

This lag occurs because it takes time for factors such as resource limitations, competition, and environmental resistance to affect the population growth.

lead to population cycles

Question 20

Positive density dependence

Answer 20

Any scenario where individual fitness increases with group size
Destabilizing!
Also called Allee effect; inverse density dependence
Increase in B, increases per capita pop growth
Decrease in N, decreases per capita growth

Question 21

What causes positive density dependence?

Answer 21

Mutualisms; fosters growth and benefits as individuals come together for increase density
Difficulty finding mates at low densities
Cooperative social behaviors: individual fitness in higher in groups
Loss of genetic variation in small populations

Question 22

Loss of genetic variation in small populations causes

Answer 22

Inbreeding depression
Ex. Florida Panther restricted to area with human expansion restricted to area, cut off gene flow with another pumas

Question 23

Conservation success story

Answer 23

Since Florida Panther experienced inbreeding depression, introduced 8 new pumas from Texas to reproduce
Still a threat from new roads and human causes

Question 24

Positive density dependence most commonly occurs at

Answer 24

small population sizes

Question 25

Understanding positive density dependence of a species is critical to

Answer 25

its conservation