QUESTION 8 (3 marks)
Australia has many bird species that have evolved to be largely dependent on mangroves. These species are patchy in their distribution because of:
• the island-like distribution of their habitat
• exclusion by possible competitors
• geographical barriers. Identify and describe the mode of speciation that may have caused diversity in mangrove bird species.
QCAA guide · typeset solution
QCAA sample response and mark allocation
8 | This is allopatric speciation, where populations of the same species are separated by barriers (island-like distribution, exclusion by competitors, geographical barriers) meaning that no exchange of genetic material is possible and gene flow is halted. Over many generations, mutation, natural selection and genetic drift result in genetic and phenotypic divergence until a new species is formed. | • identifies the mode as allopatric speciation [1 mark] • describes two elements of allopatric speciation - cessation of gene flow due to a barrier between population groups [1 mark] - genetic drift over time until divergence [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
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