Databased Question no 1 Conservationists noticed that the number of red squirrels



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Databased Question no 1
Conservationists noticed that the number of red squirrels (Sciurus vulgaris) in Wales was declining, and the number of a newly introduced species, the North American grey squirrel (Sciurus carolinensis), was increasing. In 1998, a project was started to reduce the number of grey squirrels in 244 hectares of woodland in Wales. The graph below shows the number of grey squirrels in 1998 and the number of red squirrels in 1999, 2000 and 2002. The data was collected at eight different sites (A–H).

[Source: Craig Shuttleworth, (2003), Biologist, 50, (5), page 231, © Institute of Biologists]

(a) Identify the year in which the greatest number of red squirrels was found in site E.

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(1)

(b) State the number of sites that had a greater density of red squirrels in 2002 compared with the density of grey squirrels in 1998.

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(1)

(c) Discuss the hypothesis that decreasing the density of grey squirrels after 1999 led to an

Answer Key:
(a) 2002 1

(b) 6 / A B E F G H 1

(c) hypothesis seems to be supported;

in most / five sites the red squirrel density has increased since 1999;

some sites decreased in density from 2000 to 2002;

may be other factors controlling squirrel density;

however there is no information about red squirrels in 1998 / more data
is required starting with same density of grey squirrels in 1998 and
different densities of red squirrels; 3 max

(d) (principle of) competitive exclusion;

competition occurs between them;

most successful of the two increases in numbers;



displaces the other from the population; 3 max

[8]


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