Evolution

Evolutionary biology studies the history of life forms on Earth and the processes that change them over time. In this chapter you will begin with theories of the origin of life, from the idea of chemical evolution proposed by Oparin and Haldane to Stanley Miller's 1953 experiment, in which electric discharges in a closed flask containing CH4, H2, NH3 and water vapour at 800 degrees C produced amino acids. You will then examine the evidence for evolution from fossils, homologous organs such as the forelimbs of whales, bats, cheetahs and humans, analogous organs such as the wings of butterflies and birds, industrial melanism in peppered moths in England, and the rapid rise of antibiotic-resistant bacteria. The chapter explains adaptive radiation in Darwin's finches and Australian marsupials, Darwin's theory of natural selection, Hugo de Vries's mutation theory, and the Hardy-Weinberg principle, p^2 + 2pq + q^2 = 1, along with the factors that disturb it: gene migration, genetic drift, mutation, recombination and natural selection. It ends with a brief account of human evolution, from Dryopithecus and Australopithecus to Homo sapiens.

Detailed Worksheet: Evolution Section A - Definitions (10 marks) 1. What is chemical evolution? Name the two scientists who proposed that the first form of life came from pre-existing non-living organic molecules. (2 marks) 2. Distinguish between homologous and analogous organs with one plant example of each. (2 marks) 3. Define adaptive radiation. Give one example from Darwin's observations and one from Australia. (2 marks) 4. State the Hardy-Weinberg principle and write its equation. (2 marks) 5. What is genetic drift? Explain the founder effect. (2 marks) Section B - Calculations and Applications (15 marks) 6. In a population of 500 individuals in Hardy-Weinberg equilibrium, the frequency of the recessive phenotype (aa) is 0.16. Calculate the frequencies of alleles A and a, and the number of individuals expected to be AA, Aa and aa. (3 marks) 7. In a population, the frequency of the dominant allele B is 0.7. Calculate the expected genotype frequencies of BB, Bb and bb at equilibrium, and verify that they add up to 1. (3 marks) 8. In a sample of 1,000 people, 910 can roll their tongue (dominant trait) and 90 cannot. Assuming equilibrium, calculate the frequency of the recessive allele and the percentage of heterozygous carriers. (3 marks) 9. Using the timeline of human evolution, arrange the following in order and state the brain capacity where known: Homo erectus, Australopithecus, Homo habilis, Neanderthal man, Dryopithecus. (3 marks) 10. Classify each pair as homologous or analogous and give the type of evolution it shows: (i) thorn of Bougainvillea and tendril of Cucurbita (ii) flippers of penguins and dolphins (iii) sweet potato and potato (iv) heart of vertebrates. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of Miller's experiment showing the electrodes, the spark discharge, the flask with gases (CH4, H2, NH3, water vapour), the condenser, the boiling water and the trap for collecting organic compounds. (4 marks) 12. Draw graphs showing the three types of natural selection: stabilising, directional and disruptive, with the original and the resulting population curves. (3 marks) 13. Draw a labelled diagram of the adaptive radiation of Darwin's finches showing different beak types and their diets. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Before industrialisation set in, more white-winged moths than dark-winged moths were found on trees near Manchester. After industrialisation, the dark-winged moths became more common. Explain this observation using natural selection, and analyse why this is regarded as evidence of evolution. (5 marks) 15. Compare Darwin's theory of natural selection with de Vries's mutation theory, including the concepts of fitness, branching descent, saltation and the role of variation. Evaluate which ideas are accepted in the modern synthetic theory. (5 marks) 16. Antibiotic-resistant bacteria and herbicide-resistant weeds now appear within decades rather than millions of years. Explain how this happens, why it is described as evolution by anthropogenic action, and suggest two steps to slow it. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw all diagrams neatly in pencil and label every part. Show working for Hardy-Weinberg calculations.