module 4.5

Question 1

why do fluctuations happen?

Answer 1

-under the influence of stochastic forces, populations tend to fluctuate
-fluctuations vary
-a population’s carrying capacity rarely stays constant
-a species may thus be quite stable over its range but highly variable locally or between years

Question 2

what are examples of fluctuations?

Answer 2

for example, the population size of the red-breasted nuthatches in alberta
-species relies on conifer cone production
-lags in density-dependent processes (birth and death rates) can cause populations to overshoot or undershoot their carrying capacity

Question 3

what are oscillations?

Answer 3

-population fluctuations that are more regular than expected are called populations cycles (oscillations)

Question 4

what are the graphs of density-dependent population growth in discrete time: effect of size of r?

Answer 4

Question 5

what are extinction and allee effects?

Answer 5

populations decline when deaths exceed births
-lamda becomes less than 1.0
-r becomes negative

declining populations can result in extinction or extirpation
-extinction= total loss of a species overall
-extirpation= local extinction/loss of a species’ population

Question 6

what is the graph of the allee effect?

Answer 6

when population density of below threshold, that species is destined for extinction