QUESTION 8 (3 marks)
Over time, the South African cheetah population has suffered drastic reduction due to periodic droughts, disease and hunting. Currently, only small, isolated populations of cheetahs exist in the wild. Explain, in terms of genetic diversity, why cheetah populations are now on the verge of extinction.
QCAA guide · typeset solution
QCAA sample response and mark allocation
8 | The cheetah population has suffered a severe bottleneck. This means that (by chance) certain alleles may be over- or under-represented in the surviving population, and some (potentially ‘fitter’) alleles may have been lost altogether. This reduces genetic variability and means that the small surviving population’s gene pool is not representative of the original population. If the environment suddenly changes, the selection pressures on the cheetahs will also change. Having a limited gene pool may mean the population cannot adapt to the changing conditions and are therefore at increased risk of extinction. | • explains that - the reduction in population has reduced genetic variability [1 mark] - some alleles may have been eliminated from the gene pool [1 mark] - a population with limited genetic variability may not be able to evolve in response to changing conditions [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
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