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Mechanisms of Evolution Rachel Fisher PhD Candidate, Science Education, University of Arizona June 18, 2014 Objectives: • Describe the term ‘evolution’ • Define and provide examples of the four mechanisms of evolution • Take home several teaching resources that will help in your teaching of evolution at all levels What is ‘evolution’ anyways??? • When your students hear the term ‘evolution,’ what is their response? What words/phrases do they use? • What words and/or phrases do you associate with this word (evolution)? • Which words/phrases do you use when teaching this concept – if you don’t use this word when teaching, explain why Evolution • The Accidental Species: The Misunderstandings of Human Evolution (Gee, 2013) • One of the most ‘abused’ words in any argument over science • Darwin did not use the term ‘evolution’ in the Origin until the 6th edition (1873), although he did use the word ‘evolved’ Evolution • Descent with modification • Change in gene frequency in a population from one generation to the next • Descent of different species from common ancestor Source: ‘Understanding Evolution What ‘drives’ evolution? • Mechanisms • • • • Natural selection Mutation Genetic drift Gene flow Source: ‘Understanding Evolution’ How Does Natural Selection Work? • Individuals within species are variable • Some variation is passed on to offspring (heritable variation) • Differential reproduction • Variability of the environment • Environment = any circumstance that affects chances of organism surviving long enough to pass down traits (e.g. climate, relationship one organism has with another, such as predation, mating, etc.) • Individuals best adapted to survive in their environment pass on their traits to the next generation • How does this image show: • Variation? • Heritable variation? • Differential reproduction? • Variability of the environment? Source: ‘Understanding Evolution’ Natural Selection at Work! • Genetics of Coat Color Adaptation in Old Field Mice (Peromyscus polionotus) • Dr. Hopi Hoekstra, Harvard University A. Mainland Mice B. Santa Rosa Island Beach Mice Source: Hoekstra et al. (2006), Science Peromyscus polionotus MC1R (melanocortin 1 receptor) gene • Gene that affects pigmentation • Single DNA base pair mutation – presence or absence accounts for much of coat color variation of inland and beach mice Simulations of Natural Selection • Mouse color simulations: • http://www.evo-ed.com/pages/sims_page.html Natural Selection Teaching Resources • Clipbirds http://evolution.berkeley.edu/evolibrary/search/lessonsummary.ph p?&thisaudience=9-12&resource_id=35 • Breeding bunnies http://evolution.berkeley.edu/evolibrary/search/lessonsummary.ph p?&thisaudience=9-12&resource_id=58 • Dr. Hoekstra discusses genetic basis of coat color adaptation (39 minute video): • http://www.nescent.org/media/NABTSymposium2010.php Mutation • Random changes in DNA that can be beneficial, harmful, or neutral • Not all mutations matter – only those passed via reproductive cells matter to evolution • What causes mutations? • DNA does not copy accurately • External causes (chemicals/radiation) Mutation Teaching Resources • Evolution at a crime scene – ‘Evo in the news’ http://evolution.berkeley.edu/evolibrary/news/060301_crime • Solving the history of the Neanderthals (interactive activity) http://evolution.berkeley.edu/evolibrary/search/lessonsummary.ph p?&thisaudience=9-12&resource_id=76 • Other Mutation lessons (evo in the news, labs, etc….) http://evolution.berkeley.edu/evolibrary/search/search_lessons.ph p?topic_id=&keywords=teach+about+mutation&type_id=&sort_by= audience_rank&Submit=Search Genetic Drift • Change in gene pool due to chance • Takes place in all populations Source: ‘Understanding Evolution’ Genetic Drift • Jar of Marbles Example Source: ‘Understanding Evolution’ Genetic Drift Source: ‘Understanding Evolution’ Effects of Genetic Drift • Genetic drift can cause small populations to lose genetic variation – reduced variation means populations may not be able to adapt to new selective pressures (e.g. climate change, etc.) • Bottleneck effects - population size reduced for at least one generation Source: ‘Understanding Evolution’ Genetic Drift Teaching Resources • Cheating Cheetahs Prosper: http://evolution.berkeley.edu/evolibrary/search/lessonsummary.ph p?audience_level[3]=912&topic_id=&keywords=bottleneck%20&type_id=&sort_by=resour ce_title&Submit=Search&thisaudience=9-12&resource_id=180 Source: ‘Understanding Evolution’ Genetic Drift Teaching Resources • Huntington’s Disease in Humans http://evolution.berkeley.edu/evolibrary/article/side_0_0/medicine _05 • Genetic Drift Online Simulation http://www.biology.arizona.edu/evolution/act/drift/manual.html Gene Flow • Movement of genes between populations – ‘migration’ Source: ‘Understanding Evolution’ Sources for Content/Pedagogical Tools • Understanding Evolution – UC Berkeley: • http://evolution.berkeley.edu/ • University of Montana – Evolution Teaching Resources: • http://evoled.dbs.umt.edu/default.htm • Molecular Insights in Classic Examples of Evolution (Dr. Hopi Hoekstra) • http://www.nescent.org/media/NABT2010/hoekstra.html • From Mice to Molecules: The Genetic Basis of Color Adaptation (Dr. Hopi Hoekstra) • http://www.nescent.org/media/NABTSymposium2010.php • Evo-Ed – Cases for Evolution Education: • http://www.evo-ed.com/Pages/Mice/index.html • Rap Guide to Evolution: • http://music.bababrinkman.com/; http://rapguidetoevolution.co.uk/videos What About Assessment? • Many lessons discussed today from Understanding Evolution have assessments built in • E.g. Formative or summative writings on ‘Evo in the news’ or labs • Evolution misconception diagnostic (multiple choice) • http://evolution.berkeley.edu/evolibrary/search/lessonsummary.php?type _id=14&thisaudience=13-16&resource_id=426 • Other assessments via Understanding Evolution: • Minute papers/exit tickets (e.g. ‘What is evolution?’) • Problem-based discussions Understanding Evolution: Problem-based discussion Natural selection in Darwin’s finches 1) What characteristics of the graphs show that there was variation in the population? How much variation was in the population in 1976? How much variation was in the population in 1978? 2) What happened to the population size between 1976 and 1978? What other changes occurred in the population? 3) Based on the data, what is the approximate average beak depth of the population in each year? Graffiti Feedback? Questions? Comments? Other Resources to Share? Contact Information: [email protected]
