Evolutionary processes leading to speciation — practice questions

Describe what a mutation is, and explain why mutation is essential for evolution to occur.

A bacterial population is exposed to an antibiotic for the first time. Within weeks, almost all bacteria present are resistant. Explain how this happened, making clear the relationship between mutation and selection.

Mutation rates are very low, and most mutations are harmful or neutral. Discuss how such a process can nonetheless be the foundation of adaptation, and evaluate the claim that evolution is 'random'.

Describe the difference between natural selection and genetic drift, and describe what is meant by the founder effect.

The kākāpō population fell to fewer than 60 birds before recovering under management. Explain how this affected the population's genetics, and why it matters for the species' future.

Two isolated populations of the same species live in identical environments, yet after many generations they have diverged genetically. Discuss how this is possible, and evaluate the relative importance of selection and drift in causing populations to diverge.

Describe what is meant by gene flow, and describe its effect on the genetic differences between two populations.

A native plant grows on two mountain ranges separated by 40 km of lowland. Its pollen is carried by insects that rarely travel more than 2 km. Explain why the two populations are likely to diverge, and why they might eventually become separate species.

Habitat fragmentation reduces gene flow, and conservation managers sometimes respond by moving individuals between fragments. Discuss the genetic consequences of fragmentation, and evaluate when such translocations are appropriate.

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.

Describe what is meant by divergent evolution and by adaptive radiation, and describe what homologous structures show.

Explain why New Zealand's fauna shows so many adaptive radiations, and why flightlessness evolved repeatedly in unrelated New Zealand bird lineages.

Discuss why adaptive radiations occur on island archipelagos more often than on continents, and evaluate what island radiations can and cannot tell us about evolution generally.

Describe the difference between homologous and analogous structures, and describe what each shows about evolution.

Explain how co-evolution occurs between a native plant and its bird pollinator, and explain why the relationship makes both species vulnerable.

Convergent and divergent evolution produce opposite patterns from the same underlying process. Discuss how this is possible, and evaluate how a scientist could determine which process explains an observed similarity between two species.

Describe the models of gradualism and punctuated equilibrium, and describe what each predicts about the fossil record.

Explain why punctuated equilibrium fits well with what is known about allopatric speciation, and why long periods of stasis occur.

Discuss whether gradualism and punctuated equilibrium should be regarded as competing theories, and evaluate what the debate shows about how science works.

Describe how fossils form, and describe two things the fossil record shows about evolution.

Explain why gaps in the fossil record are expected rather than being a problem for evolutionary theory, and explain why this matters when interpreting evidence about speciation.

Fossil evidence is often described as the most direct evidence for evolution. Discuss what fossils can and cannot establish, and evaluate why evidence from several independent sources is more convincing than any single line.

Describe how molecular biology provides evidence for evolution, and describe what vestigial structures show.

Two species look very similar but molecular analysis shows they are only distantly related. Explain how this situation arises and why the molecular evidence should be preferred.

Molecular evidence has revised many relationships previously established from anatomy. Discuss why this has happened so often, and evaluate whether molecular evidence should now be regarded as authoritative over other lines.

Describe what biogeography is, and describe two biogeographic patterns that provide evidence for evolution.

New Zealand has no native land mammals other than bats, yet has many flightless birds. Explain how biogeography accounts for this, and why it made those birds so vulnerable to human arrival.

Many southern-hemisphere distributions once attributed to Gondwanan vicariance have been reinterpreted as long-distance dispersal. Discuss how this reinterpretation was possible, and evaluate what it shows about scientific reasoning from patterns.