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Unit 4: Heredity and continuity of life
Quick questions on Natural selection, fitness and the modern synthesis (QCE Biology Unit 4)
13short 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 the four preconditions for natural selection?Show answer
Natural selection acts whenever all four of the following are true.
What is worked examples?Show answer
Peppered moths in industrial Britain. Before industrial revolution: pale moths (peppered) camouflaged on lichen-covered tree bark; dark (melanic) form rare. As soot killed lichens and darkened bark, pale moths became visible to bird predators. By 1900, dark form was over 95 per cent in industrial areas. After clean air legislation, lichens recovered and the pale form recovered.
What is darwinian versus neo-Darwinian theory?Show answer
Darwin's original theory (1859).
What is peppered moths in industrial Britain?Show answer
Before industrial revolution: pale moths (peppered) camouflaged on lichen-covered tree bark; dark (melanic) form rare. As soot killed lichens and darkened bark, pale moths became visible to bird predators. By 1900, dark form was over 95 per cent in industrial areas.
What is antibiotic resistance in bacteria?Show answer
Mutations conferring resistance occur spontaneously at low frequency. Antibiotic application kills sensitive cells. Resistant survivors reproduce and pass the resistance alleles on.
What is cane toads in northern Australia?Show answer
Released in 1935 to control sugarcane pests, they have expanded across northern Australia. The invasion front is moving faster than the rear, because the toads with the longest legs disperse fastest, reach new ground first, and have higher reproductive success there. Leg length at the invasion front has increased by about a third in 70 years.
What is galapagos ground finches?Show answer
Beak depth in Geospiza fortis tracks rainfall. In dry years only large hard seeds remain; large-beaked birds survive and breed. In wet years small soft seeds dominate and beak depth declines.
What is neo-Darwinian modern synthesis?Show answer
Fisher, Haldane, Wright, Mayr, Dobzhansky, Simpson and others integrated:
What is defining fitness as physical strength?Show answer
Fitness is reproductive success.
What is saying organisms "evolve" in their lifetime?Show answer
Individuals do not evolve; populations do, across generations.
What is treating mutation as directed by the environment?Show answer
Mutations are random with respect to need. The environment selects among the variants already present.
What is confusing acclimation with adaptation?Show answer
A single individual acclimatises to heat (physiology). A population adapts to heat through changes in allele frequency over generations.
What is forgetting that natural selection is just one mechanism?Show answer
Genetic drift (especially in small populations), gene flow and mutation also change allele frequencies.