Evolution - Chapters 22, 23, 24, 25 and 26 (Unit Exam-Tuesday March 24) The theory of evolution is the unifying theory of biology. It explains how all organisms are related and the mechanisms that have given rise to the diversity of life that has existed in Earth’s history. It can be studied at the macro and micro levels. The inferred origin of life is 3.9 billion years ago. How the first cell arose is a matter of some debate in the discipline. Fossil evidence suggests that evolution has progressed from simple organisms to the more complex. Nearly all of the organisms that have ever existed on the planet are now extinct. Phylogenies are used to show evolutionary relatedness between organisms. Relatedness is established using morphology, physiology, behavior, and molecular evidence. Cladistics is often used to construct phylogenies. Learning Goals - Students will be able to… distinguish between Lamarckian and Darwinian evolution identify the observations Darwinian evolution attempts to explain describe the evidence for Darwinian evolution summarize the sources of variation in populations explain how microevolution can be monitored using Hardy-Weinberg equilibrium describe the three mechanisms that drive the evolution of populations summarize pre and post-zygotic reproductive barriers distinguish between allopatric and sympatric speciation describe the evidence that suggest speciation rates have varied over Earth’s history summarize the key events in Earth’s evolutionary history describe the evidence for the endosymbiont theory distinguish between monophyletic, paraphyletic, and polyphyletic groups explain how to develop parsimonious phylogenies Vocabulary Lamarckian evolution Darwinian evolution adaptations natural selection artificial selection homology analogy homologous structures analogous structures vestigial structures convergent evolution fossil record biogeography macroevolution microevolution genetic variation average heterozygosity geographic variation cline population gene pool Hardy-Weinberg principle genetic drift founder effect relative fitness directional selection stabilizing selection disruptive selection sexual selection sexual dimorphism intrasexual selection intersexual selection neutral variation balancing selection heterozygote advantage frequency-dependent selection speciation biological species concept species reproductive isolation hybrids pre-zygotic barriers post-zygotic barriers morphological species concept ecological species concept phylogenetic species concept allopatric speciation sympatric speciation allopolyploid hybrid zone punctuated equilibrium macroevolution protocells radiometric dating geologic record endosymbiont theory Cambrian explosion Pangaea mass extinction adaptive radiation homeotic genes phylogeny systematics taxonomy taxon cladistics clade monophyletic paraphyletic shared ancestral character shared derived character outgroup bottleneck effect gene flow polyploidy autopolyploid ingroup parsimony orthologous genes paralogous genes molecular clock Analysis Questions 1. How are Miller-Urey type experiments used as evidence for the origin of life? 2. Why are proto-cells key to the development of life on Earth? 3. The first appearance of free oxygen in the atmosphere likely triggered a massive wave of extinctions among the prokaryotes of the time. Why? 4. What evidence supports the hypothesis that mitochondria preceded plastids in the evolution of eukaryotic cells? 5. What factors promote adaptive radiations? 6. How does Larmarkian evolution differ from Darwinian evolution? 7. Explain how Darwinian evolution is supported by homology, analogy, the fossil record, and biogeography. 8. The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. What is the most likely explanation for these observations? 9. State the Hardy-Weinberg principle and identify the conditions that must be met to equilibrium. 10. In a population, 16 people have the genotype AA, 92 have the genotype Aa, and 12 have the genotype aa. Determine p and q for this population. 11. Describe the three mechanisms that drive the evolution of populations. 12. If evolution has gone on for so long, why haven’t perfect organisms evolved? 13. What is the biological species concept? 14. What factors can impede reproductive compatibility? 15. What is the biological basis for assigning all human populations to a single species? 16. How is allopatric speciation different from sympatric speciation? satisfy 17. According to the phylogenetic tree pictured below, whales, deer, and cows represent a _____________ (monophyletic, paraphyletic, or polyphyletic) group. Explain your choice. 18. To distinguish a particular clade of mammals within the larger clade that corresponds to Mammalia, would hair be a useful character? Why or why not? 19. If you were using cladistics to build a phylogenetic tree of cats, which of the following would be the best outgroup? Explain your choice. a. b. c. d. e. lion domestic cat wolf leopard tiger 20. The most parsimonious tree of evolutionary relationships can be inaccurate. Why is this possible? 21. What is a molecular clock? What assumption underlies the use of a molecular clock?