Practise IB ESS HL 2.1.12 by modelling exponential and logistic curves, evaluating feedback near carrying capacity and explaining boom-and-bust population dynamics.
With reference to a named herbivore species, explain why its population growth curve follows an S-shape.
a. original colonisers are small in number;
b. unfamiliarity with local resources/habitat may hinder early growth/result in a lag phase;
c. as they reproduce there are more individuals that can reproduce/few limiting factors to constrain growth;
d. this creates a faster growth rate;
e. resulting in positive feedback/exponential increase;
f. growth rate/curve eventually slows down/flattens/plateaus out due to limiting factors;
g. limiting factors may include e.g. food/water/nesting material etc.;
h. if population increases this will reduce food availability/increase predation;
i. causing a subsequent decrease in population/minor fluctuations in growth rate;
j. maintaining a stability/equilibrium/carrying capacity/negative feedback/density dependent regulation
Note: accept marking points on an annotated diagram
Marking guidance:
Award 6 max if no herbivore is named.