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WAHuman BiologyQuick questions
Unit 4: Human Variation and Evolution
Quick questions on Speciation and isolating mechanisms: WACE Year 12 Human Biology Unit 4
3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is allopatric speciation?Show answer
Allopatric speciation involves geographic isolation. A physical barrier, such as a mountain range, river, sea or distance, splits a population into two that can no longer interbreed. With gene flow now blocked, the two gene pools change independently: they experience different selection pressures, accumulate different mutations, and are subject to genetic drift. Over many generations they diverge so much that, even if reunited, they can no longer interbreed to produce fertile offspring.
What is sympatric speciation?Show answer
Sympatric speciation occurs without geographic separation: populations living in the same area diverge into separate species. This can happen through behavioural differences, exploiting different niches or food sources, or chromosomal changes that prevent interbreeding with the original population. Disruptive selection, which favours both extremes of a trait, can contribute by pulling a population toward two distinct forms.
What are reproductive isolating mechanisms?Show answer
Once populations have diverged, isolating mechanisms keep them from interbreeding and so keep the species separate. They fall into two groups:
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