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Evolutionary processes leading to speciation · Part 2 of 4
9 exam-style questions with model answers, plus 12 quick multi-choice questions — every question on this part of the standard, grouped by the 3 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Describe what is meant by a reproductive isolating mechanism, and describe three prezygotic and one postzygotic mechanism.
Two populations of a native insect are separated by a mountain range. Explain why this geographical separation alone does not mean they are separate species, and explain what would need to happen for speciation to be complete.
Discuss why prezygotic isolating mechanisms are more common than postzygotic ones in closely related species that live in the same area, and evaluate the usefulness of the biological species concept.
Describe the stages of allopatric speciation, and give one example of a geographical barrier.
Many Chatham Island species are endemic — found nowhere else — despite the islands being only about 800 km from mainland New Zealand and geologically recent. Explain why speciation has occurred so readily there.
Two populations separated for 20,000 years are reunited when the barrier between them disappears. Discuss the possible outcomes, and evaluate what determines which occurs.
Describe what polyploidy is, and describe how it can produce a new species in a single generation.
Explain why sympatric speciation is generally harder than allopatric speciation, and explain why polyploidy is an exception.
Compare allopatric and sympatric speciation, and evaluate the claim that most speciation is allopatric.