BIOM 300 Winter 2023 Assignment 2
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BIOM 300 | Winter 2023
Assignment 2
Instructions
(1) This assignment is due on Friday February 3rd.
(2) Please submit your written solutions to crowdmark with each problem started on a separate page.
Question 1. Suppose n(t + 1) = λn(t) + C with |λ| = 1. Determine what happens to n(t) as t → ∞ .
Question 2. A alternative to the the discrete-time logistic model we studied in class is called the Beverton-Holt model, which is given by
Rn(t)
(1) n(t + 1) = .
a. Prove that if n(0) = n0 ≥ 0 and K = M(R − 1), then
Kn0
n(t) =
for all t ∈ N.
b. Prove that if R > 1 and n0 > 0, then n(t) → K as t → ∞ .
Question 3. The Ricker model is an alternative to the discrete-time logistic growth model we discussed in class. If n(t) is the population size at time t, then
(2) n(t + 1) = n(t)eR (1 − )
a. Find all the fixed points of the Ricker model.
b. For each fixed point, determine an interval of R values for which the fixed point is stable.
c. Draw a cobweb diagram for K = 1, r = 1.8 and n(0) = 0.4. Describe the long-term behaviour of n(t).
d. Draw a cobweb diagram for K = 1, r = 2.3 and n(0) = 0.4. Describe the long-term behaviour of n(t).
e. Draw a cobweb diagram for K = 1, r = 2.6 and n(0) = 0.4. Describe the long-term behaviour of n(t).
Question 4. An alternative to the continuous-time logistic growth model we discussed in class is given by
(3) = rn(t)ln ( )
where r > 0 is the per captita growth rate, and K > 0 is the carrying capacity.
a. Find an explicit solution for n(t).
b. Using the solution found in part a, show that x∗ = K is asymptotically stable.
Question 5. For many species (particularly those that reproduce sexually), the population can only grow if the population size is large enough; if the population size is too small, individuals may have trouble finding mates, or there may be a greater risk of predation. This is called an allee effect. One continuous-time model that accounts for this effect is given by
(4) = rn(t) ( − 1)( 1 − ) ,
where r > 0 is the per-capita growth rate and K > 0 is the carrying capacity.
a. Find all the equilibrium points for equation (4).
b. Assume 0 < α < K and determine the stability of each equilibrium point.
c. Under the assumptions in part b, interpret what the parameter α represents.
2023-02-10