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Evidence for Evolution

Evidence for Evolution. The Fossil Record Fossil : any preserved evidence of past life. E.g. shells, bones, teeth, artefacts, imprints / impressions Age of the fossils indicates general trend in time / complexity Evidence of continual change

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Evidence for Evolution

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  1. Evidence for Evolution

  2. The Fossil Record Fossil: any preserved evidence of past life. E.g. shells, bones, teeth, artefacts, imprints / impressions • Age of the fossils indicates general trend in time / complexity • Evidence of continual change • Extinction of certain species ( climate change, asteroid) • Transitional forms: provide a missing link between certain evolutionary pathways. • E.g. Archaeopteryx (flying reptile with feathers) • E.g. Crossopterygian fish (air breathing fish)

  3. Comparative Studies in Biochemistry DNA • All living organisms process the same four nitrogen base pairs (A, T, C, G)  implies a common ancestor • More closely related species would share a greater proportion of their genome • E.g. chimpanzees share approx 98% of human genome E.g. ERV’s • An RNA viral sequence that has become part of an organisms genome which is inherited (virus inserts itself into cells chromosome) • Offspring will therefore have a copy of the virus in the same place of the same chromosome in every cell. • Humans have 16 ERV’s which are also found in chimpanzees

  4. Protein Sequences • Comparing the type and sequence of amino acids in similar proteins from diff species. • Ubiquitous proteins: proteins which appear to be present in all species which are responsible for tasks required for all life. (carry out same function regardless of species) • Similarities between ubiquitous proteins indicate close ancestry  common ancestor E.gCytochrome C • Human cytochrome C contains 104 amino acids. • Out of 104, the more which are similar the closer the species to each other. (e.g chimpanzees & gorillas are exactly the same as humans) • Table 16.3

  5. Comparative Studies in Anatomy Embryology • Similarities between embryos of various species indicate a common ancestor (e.g. vertebrates) • E.g • embryonic gill pouches/arches • presence of a well developed tail, • Similar brain development, • two chambered heart

  6. Homologous Structures - Structures which are very similar in structure but may differ in function. - e.g forelimb of vertebrates

  7. Vestigial Organs • structures of reduced size that appear to have no function • they are a waste of energy and resources and therefore natural selection caused their reduction in size • approx 90 in humans • E.g Humans • Nictitating membrane • Act as a transparent third eyelid in cats, birds, frogs etc but pinkish membrane in inner corner in each eye for humans • Muscle to move ears • Wisdom teeth • Cannot be used in mastication • Pyramididalis muscles (muscle above pubic bone) • Coccyx • Appendix • Body hair • Muscles contract around hair to trap a layer of air around body (insulation), but doesn’t work as human hair is too fine

  8. Vestigial Organs • E.g. other vertebrates • Wings of flightless birds (ostriches/ emus) • Wales / snakes have pelvis/femur bones although both are non-functional

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