Density Dependent Growth

Question 1

Why can exponential growth not go on forever

Answer 1

due to finite resources

Question 2

Is density dependence typically positive or negative and why

Answer 2

negative density dependence because the growth rate declines as population density increases (ex. intraspecific competition for limited resources

Question 3

Explain the difference between exponential and logistic growth models
and how does the equation change between the two

Answer 3

exponential = population with unlimited resources and therefore keeps growing bigger and faster (which isnt true)
logistic = population with limited resources or other limited factor, which grows slower as it gets larger

logistic modifies from exponential by making per capita growth rate and function of density

Question 4

What are the assumptions of the logistic growth model [r=f(N)]

Answer 4

1. assume sufficient resources to sustain a stable population of k individuals (carrying capacity is constant)
2. the maximum growth rate per capita equals rm when there are no effects of density (growth rate decreases as N increases, is 0 at K, and negative when N>K)
3. assume decrease in r is linear function of N

Question 5

what can oscillation around K be due to

Answer 5

time lag
fluctuating K

Question 6

in logistic model, where does the maximum instantaneous rate of change occur

Answer 6

N = K/2

Question 7

Explain where fish are harvested, in terms of population size, on the logistic growth model to get maximum sustainable yield

Answer 7

harvest population to K/2 and then harvest the yield
BUT very sensitive, and should take precautionary principle and under harvest or fishery could collapse