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From genetics…to evolution

From genetics…to evolution. What is the Theory of evolution?. Darwin’s Theory of Evolution. "the single best idea anybody ever had” (Daniel Dennet , Philosopher) “ a big idea, arguably the most powerful idea ever “ (Richard Dawkins, Philosopher)

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From genetics…to evolution

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  1. From genetics…to evolution

  2. What is the Theory of evolution?

  3. Darwin’s Theory of Evolution • "the single best idea anybody ever had” (Daniel Dennet, Philosopher) • “a big idea, arguably the most powerful idea ever “ (Richard Dawkins, Philosopher) • “Its publication (The Origin if Species) changed the world”

  4. Evolution • Synonyms: • Charles Darwin used ‘Descent with modification’ • ‘Survival of the fittest’ • ‘Theory of Natural selection’

  5. Richard Dawkins’ Theory of Evolution ‘Given sufficient time, the non –random survival of hereditary entities (which will occasionally mis-copy) will generate complexity, diversity, beauty and an illusion of design so persuasive that it is almost impossible to distinguish from deliberate intelligent design’

  6. How similar are we? • How different are we?

  7. Gene comparison slider

  8. Charles Darwin… An introduction to Charles Darwin….

  9. Opponents to The Theory of Evolution: The Blind Watchmaker oh yeah, it's David Attenborough again...

  10. The Mechanism of Evolution: Natural Selection

  11. How does natural selection work? • Too many offspring (‘over-production’) • Genetic variation (sex and mutation) • Competition: the Struggle for survival • Differential survival and reproduction (‘survival of the genetically fittest’) • Advantageous characteristics passed on to offspring • GRADUAL change over many generations

  12. Too many offspring Results in competition for available resources – food, shelter, mates, water, sunlight

  13. How are we different? Discontinuous variation Phenotype has distinct categories There are no ‘in- betweens’ • Blood types • Genetic diseases • ‘Traits’: tongue rolling, hitch-hikers thumb

  14. How are we different? Continuous variation The variation in phenotype follows a ‘normal-type’ distribution, with most individuals falling in the ‘middle of the range’

  15. Skin colour is another example of continuous variation

  16. What makes us different? Genetic variation • Meiosis • Random fertilisation • Mutation Affects BOTH continuous AND discontinuous variation Environmental effects on genotype Tends to affect continuous variation alone

  17. Environmental effects on phenotype Sequoia sempervirens tree

  18. Meiosis and genetic variation

  19. Mutation • The basis of genetics • ‘ the fuel for evolution’ • ‘the destroyer and creator of life’ • ‘Thanks to mutation, we’re not all still in the primordial soup’

  20. Gene mutation • Definition: A change in a gene or a chromosome • ‘COPYING ERRORS’ OF DNA • Mutations are the source of brand-new characteristics in the gene pool • They are the final source of all genetic variation • Mutations can occur WITHIN a chromosome • Another type of mutation affects whole chromosomes (non-disjunction) • How mutation works

  21. Causes of mutation (2) • Radiation • Chemicals • Viruses • Diet • Stress • Lifestyle • ?Gamma radiation?.... ‘Hiroshima – the most cynical Biology experiment of all time’

  22. Evolution in response to environmental change • Peppered moths in Great Britain • Antibiotic resistance in tuberculosis • Sickle Cell anaemia

  23. 1. Peppered Moths in the UK Peppered moth simulation

  24. 2. Antibiotic resistance in bacteria

  25. 3. Sickle Cell anaemia

  26. Natural selection does not always cause change • Change will only occur when there is environmental change, or when a brand new ‘advantageous’ mutation arises • Most of the time, natural selection keeps populations stable over the generations: and is considered as ‘stabilising selection’

  27. Evidence for Evolution • 1. The Fossil Record • 2. Artifical Selection – breeding of plants and domestic animals • 3. Geographical Distribution • 4. Homologous Structures

  28. Using our genome to understand human evolution By sequencing and databasing genes, we can see similarities and differences between species • The closer the genome match, the closer their evolutionary history • Human Chromosome 2 came from fusion of two great ape chromosomes • Karl Miller on human evolution • The time-tree of evolution

  29. Evidence for Evolution 1: The Fossil Record

  30. The Fossil Record • Palaeontologists uncover fossilised remains in sedimentary rock deposits and use the information to create timelines • Organic matter trapped in sand/ silt/fossils • Compressed over time • Dated by isotopic carbon (50,000 years), potassium40 (1.28 Billion years), 238 Uranium • Oldest fossils are at the bottom, youngest at the top

  31. Other methods for dating fossils • Dating Methods

  32. Fossil Evidence for Evolution http://www.pbs.org/wgbh/evolution/sex/mating/index.html

  33. Evidence for Evolution 2: Homologous structures • Homologous traits have similar embryological origins and development • Indicative of common acnestry: what Darwin called ‘Unity of Type’ • Indicative of adaptive radiation • Pentadactyl limb • Human appendix • Whale pelvic and thigh bone

  34. Homologous structures: Pentadactyl Limb

  35. Homologous structures: Whale Pelvic bone

  36. Homologous structures: Human appendix

  37. Evidence for evolution 3: Artificial Selection

  38. Evidence for evolution: Artificial selection

  39. Evidence for evolution: Geographical Distribution • Before humans arrived, Australia had > 100 types of marsupials, but no placental mammals • Hawai’I and New Zealand had unique biotic environments – plants, insects, birds but no placental mammals

  40. Evidence for Evolution: Observable Changes • Development of new species is RAPID in species with a short reproductive cycle: bacteria, viruses, parasites, moths etc etc etc

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