Ch.10- Population Growth and dynamics: Logistic Growth

Question 0

Density-independent factors:

Answer 0

When birth and death do not depend on population size(N): [floods, extreme temp.- usually abiotic factors]

Question 1

Limits on population growth

Answer 1

Eventually, a critical resource limits reproduction ( Nesting sites, Food availability

Question 2

Density-dependent factors:

Answer 2

If birth and death increase or decrease with population size: disease, predators- usually biotic factors

Question 3

Logistic growth

Answer 3

• Sigmoidal (S-Shaped) pattern of growth on graph
• It is density-dependent
• assumes population can not grow indefinitely

Question 4

Carrying capacity (K)

Answer 4

The Maximum population size that a habitat can support

Question 5

Behavior of the logistic model

Answer 5

• Grows below K
• Decreases above K
• Remains constant at K

Question 6

Inflection Point

Answer 6

• Separates the accelerating and decelerating phases of population growth
• When N=K/2 -> Maximum possible growth rate

Question 7

Birth Rate with Limited resources

Answer 7

b=(b0)-aN

• This means that as population (N) increases, instantaneous birth rates (b) will decline.
• a is constant measuring the strength of density dependence
• b0 is birth rates w/ unlimited resources

Question 8

Death rate with limiting resources

Answer 8

d=(d0)+cN

• This means that as population (N) increases, instantaneous death rates (d) will increase
• (d0) is death rate w/ unlimited resources
• c is constant measuring the strength of density dependence

Question 9

Logistic Growth Equation

Answer 9

dN/dt= (b-d)N; if (b0-d0)=r and K=((b0)-(d0))/(a+c) then after some algebra the equation comes to

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

Question 10

r- selected species (Maximize)

Answer 10

• evolutionarily adapted to exploit empty niches

- produce many offspring each with a low probability of surviving to adulthood

Question 11

K- selected species (Live at)

Answer 11

• evolutionarily are strong competitors in crowded niches

- invest heavily in few offspring each with high probability of surviving to adulthood

Question 12

Density- independent effects:

Answer 12

• Magnitude of the outcome is not related to population size
• Ex: hurricane, extreme weather, floods
  
  • > Exponential growth

Question 13

Density-dependent effects

Answer 13

• Magnitude of the outcome is related to population size
• Ex: starvation, competition
  
  • > Logistic growth

Question 14

Demography

Answer 14

The quantitative study of populations

Question 15

Effective population size

Answer 15

number of individuals in a population that contribute offspring to the next generation

Question 16

Other Influencing factors: Age Structure

Answer 16

• Rapid growth: more young than old
• zero growth: = pop. size between age groups
• negative growth: more old than young

Question 17

Other influencing factors: Environmental Stochasticity

Answer 17

erratic or unpredictable changes in the environment

Question 18

Other Influencing factors: Delayed density-dependence

Answer 18

growth does not immediately stop once r=K

->very common!

Question 19

Other Influencing factors: Allee effect

Answer 19

• a decrease in the population growth rate as the population density decrease
• Ex: Passenger pigeon-were once the most abundant N. american bird but declined and couldn’t survive in low numbers

Question 20

Other Influencing factors: initial population size

Answer 20

small populations more likely to go extinct by chance

Question 21

Other Influencing factors: Sex ration

Answer 21

• usually 50:50 but not always

- Ex: turtle-sex is determined by temp. (warmer=female) so can have populations that are 90% one sex.