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AP Biology Evolution Unit, Chapter 15 Reading Guide CHAPTER 15 Mechanisms of Evolution __________________________________________________________________________________ OBJECTIVES Explain the mechanism for evolutionary change proposed by Charles Darwin in On the Origin of Species. Define evolution and adaptation. Explain what Darwin meant by “descent with modification.” Explain what evidence convinced Darwin that species change over time. Describe the three inferences Darwin made from his observations that led him to propose natural selection as a mechanism for evolutionary change. Explain how an essay by the Rev. Thomas Malthus influenced Charles Darwin. Distinguish between artificial selection and natural selection. Explain why an individual organism cannot evolve. Explain how evidence from biogeography, paleontology, embryology, and molecular biology supports the theory of evolution by natural selection. Explain the problem with the statement that Darwinism is “just a theory.” Distinguish between the scientific and colloquial use of the word theory. Explain how microevolutionary change can affect a gene pool. State in your own words, the Hardy-Weinberg theorem. Write the general HW equation and use it to calculate allele and genotype frequencies. Explain the consequences of HW equilibrium. Demonstrate that a population requires only one generation of random mating to establish HW equilibrium. Describe the usefulness of the HW model to population geneticists. List the conditions that must be met in order to maintain HW equilibrium. Explain how genetic drift, gene flow, mutation, and nonrandom mating and natural selection can cause microevolution. Explain the role of population size in genetic drift. Distinguish between the bottleneck effect and the founder effect. Describe how sexual selection may lead to variation of phenotypes in a population. Explain what is meant by the statement ‘natural selection is the only agent of microevolution which is adaptive’. Give the causes of genetic variation in a population. Explain how genetic variation may be preserved in a natural population. Explain the concept of relative fitness and its role in adaptive evolution. Describe what selection acts on and what factors contribute to the overall fitness of a genotype. Distinguish among stabilizing selection, directional selection, and disruptive selection. Explain how deleterious alleles may be maintained in a population. __________________________________________________________________________________ __________________________________________________________________________________________ Page 1 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide QUESTIONS 1. Define evolution. Why is evolution the unifying principle in biology? 2. Define theory as it applies to science. 3. What was the significance of Lamarck’s ideas? 4. What was the mechanism he proposed? 5. How does the present knowledge of molecular biology and genetics refute his mechanism. 6. Summarize Darwin’s theory of evolution by natural selection. 7. What was the significance of Darwin’s theory of evolution by natural selection? 8. Natural selection occurs through interaction of two factors? What are they? __________________________________________________________________________________________ Page 2 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide 9. The basis for evolution by natural selection requires inheritable variation in a population. Explain what this statement means. 10. Explain the statement: ‘Natural selection acts on individuals, but populations evolve.’ 11. Define adaptation. 12. What is the difference(s) between natural selection and adaptation? 13. What is the raw material on which mechanisms of evolution act upon? 14. What does it mean to say a population evolves? __________________________________________________________________________________________ Page 3 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide HARDY-WEINBERG THEOREM POPULATION GENE POOL ALLELE FREQUENCY GENOTYPE FREQUENCY HARDY-WEINBERG EQUATION HARDY-WEINBERG EQUILIBRIUM REQUIRED CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM __________________________________________________________________________________________ Page 4 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide 1. What is the significance of Hardy-Weinberg equilibrium? 2. If all of the above conditions hold, how many generations are required for a population to reach HW equilibrium? 3. What do deviations from HW equilibrium indicate? __________________________________________________________________________________________ Page 5 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide MECHANISMS OF EVOLUTIONARY CHANGE Summarize the effect of each of the following on allele frequencies in a population. MUTATIONS GENE FLOW GENETIC DRIFT NON-RANDOM MATING NATURAL SELECTION 4. Why is genetic drift more apparent in small populations? 5. What is the net affect of a population bottleneck? 6. Define founder’s effect. __________________________________________________________________________________________ Page 6 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide 7. Which mechanism of evolution results in adaptation to the environment? 8. Define fitness. How is fitness determined? 9. Why do phenotypic variations in a population generally resemble a bell-curve? TYPE OF NATURAL SELECTION EFFECT AND EXAMPLE STABILIZING SELECTION DIRECTIONAL SELECTION DISRUPTIVE SELECTION SEXUAL SELECTION 10. Why, do you think, Darwin devoted an entire book to sexual selection? __________________________________________________________________________________________ Page 7 of 8 AP Biology Evolution Unit, Chapter 15 Reading Guide 11. If natural selection tends to reduce variation, then how is variation preserved with the population? 12. Summarize how each of the following act to maintain genetic variation or contribute to evolutionary change in populations. NEUTRAL MUTATIONS SEXUAL RECOMBINATION GENE DUPLICATION HETEROZYGOTE ADVANTAGE 13. Explain the following statements in order to address the question: Why can’t evolution fashion perfect organisms? a) Evolution is limited by historical constraints. b) Adaptations are often compromises. c) Chance and natural selection interact d) Selection can edit only existing variations. __________________________________________________________________________________________ Page 8 of 8