Outline the changes of distribution of the grey squirrel from 1945 to 2010.

Suggest two possible reasons for the change in distribution.

1.

2.

The niches of the red and grey squirrels overlap. Explain the concept of competitive exclusion with respect to the changes in squirrel distribution shown in the maps.

a. overall the grey squirrel distribution has increased «and the red squirrel decreased» ✔

b. in 2010 the grey squirrel was found in areas where it was previously not found ✔

c. grey squirrel has dominated/red squirrel virtually eliminated ✔

OWTTE

a. no predators ✔

b. ample food supply/habitats ✔

c. few competitors ✔

d. resistant to disease ✔

e. high reproductive rate ✔

f. no physical barrier to prevent spread of grey squirrels on mainland ✔

a. competitive exclusion states two species that occupy a similar niche in the same location cannot coexist ✔

b. one of the two competitors will always have an advantage over the other ✔

c. leads to extinction/displacement/evolution of the second competitor ✔

d. grey squirrels have replaced/occupied niches formerly occupied by red squirrels
OR
habitats favour the grey squirrel in competition for the niche ✔

e. the niche of one competitor/both competitors becomes narrower ✔

While most candidates were able to achieve a mark by noting that the grey squirrel “dominated” in the second map, students again lost marks due to an inability to communicate concepts clearly. A large number of students confused distribution with population size, an idea not addressed in the maps.

This was answered well by only a few students even though the mark scheme allowed for a wide range of answers.

This question was yet another instance where weaker students were disadvantaged by their inability to access the appropriate subject-specific vocabulary. They tended not to use the term “niche” with this question, and too frequently “niche” and “habitat” were confused.