Lecture 9: Regulated Population Growth

Question 1

Exponential population growth is where

Answer 1

populations grow continuously and generations overlap
- keeps growing, does not level off
- the intrinsic rate is unaffected
dN/dt = rN

Question 2

Geometric population growth is where

Answer 2

populations grow in discrete time intervals and reproduce synchronously

N t+1 = Lambda(Nt)

Question 3

When lambda is less than 1 and r is less than 0 the population size ____

Answer 3

the population size decreases in size (lambda < 1 r < 0)

Question 4

When lambda is more than 1 and r are is more than 0 the population size ____

Answer 4

the population size increases in size

Question 5

When lambda or r are equal to 0 the population size ____

Answer 5

stay the same or do not change

Question 6

Can real populations grow exponentially? When?

Answer 6

YES:

• colonization of new habitats
• recovery after catastrophe
• pulse of new nutrients
• introduced species

all can cause populations to grow exponentially

Question 7

what does r affect in exponential growth –> dN/dt = rN

Answer 7

how rapidly population size increases. r is constant, it is not affected by N

Question 8

Exponential growth ___ be sustained for long periods of time in a population

Answer 8

CANNOT

Question 9

the logistic population growth model shows us…

what determines K (carrying capacity)?

Answer 9

the per capita rate of population growth approaches zero as the population size nears carrying capacity (K)
- K can be determined by various limiting factors such as space available, food available, etc.

Question 10

What is the equation for the logistic growth model

Answer 10

dN/dt=rN ((K-N)/K)

K-N shows us the number of additional individuals the environment can support
(K-N)/K is the fraction of K that is still available for population growth

Question 11

r selection is …

Answer 11

is selection for life history traits that maximize reproductive success at low density (further from carrying capacity)

Question 12

k selection is …

Answer 12

is selection for life history traits that are advantageous at high population densities (closer to carrying capacity)

Question 13

define density independent populations

Answer 13

populations where birth rate and death rate DO NOT CHANGE with population density

Question 14

define density dependent populations

Answer 14

birth rates and death rates directly or indirectly regulated by population density

Question 15

density independent factors

Answer 15

effects on birth and death rates independent of number of individuals (weather conditions, catastrophes,)

Question 16

density dependent factors

Answer 16

birth, death, dispersal rates change as the density of the population changes (disease, predation, malnutrition)

Question 17

positive vs negative density dependence

Answer 17

positive density dependence is where population growth is facilitated by increased population density.

negative density dependence is where population growth is facilitated by decreased population density.

Question 18

define density dependent mortality

Answer 18

density dependent birth and death rates are an example of negative feedback that regulates population growth.

Question 19

What are the mechanisms of density dependent populations regulation

Answer 19

1. Competition for resources
2. Disease

Question 20

compeition for resources

Answer 20

increasing population density intensifies competition for resources resulting in lower birth rate

Question 21

disease

Answer 21

In dense populations, pathogens can spread more rapidly