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Variation and Evolution

Variation and Evolution. Why differences among a pop’n are good!. Review of Variation. Order of DNA bases determines traits Changes can occur that can change individual Two possible ways changes occur: Mutations Genetic Shuffling (Recombination). Mutations.

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Variation and Evolution

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  1. Variation and Evolution Why differences among a pop’n are good!

  2. Review of Variation • Order of DNA bases determines traits • Changes can occur that can change individual • Two possible ways changes occur: • Mutations • Genetic Shuffling (Recombination)

  3. Mutations • Are random (cannot be predicted) • Caused by radiation and chemicals • To be passed on: • Single celled orgs (mitosis) • Sex cells of multicellular orgs

  4. Mutations con’t… • Most mutations harmful • Some are beneficial (have adaptive value) • These get passed on  • Ex: polar bears prob didn’t always have black skin; mutation caused it and it was beneficial • THIS IS MAIN SOURCE OF NEW VARIATION

  5. Genetic Shuffling • Sorting and recombination of genes = new combos of genes • Think deck of cards: deck always the same but each hand is different • Sexual reprod. uses 2 decks so even more variation • THIS IS MAIN SOURCE OF VARIATION WITHIN A SPECIES

  6. Results of Genetic Variation • Structural changes • Functional changes • Behavioral changes

  7. Structural Changes • Result of orgs entire history • Ex: polar bears vs other bears • Homologous Structures • Evolution helps explain structural similarities • Ex: (Arm structure) Humans, whales, birds and bats (RB p88) • All have 1 long bone, 2 shorter ones, and 5 digits • Tells us they all had a common ancestor • These are homologous structures!

  8. Embryology

  9. Structural Changes con’t 2. Vestigial Structures • Structures that are present but no longer in use • EX: Snakes contain tiny, non-functional leg bones which suggest it evolved from 4-legged lizards

  10. Vestigial Structures(click link) Pelvic bone in humans Hind leg limbs in whales Appendix in humans

  11. Functional Changes • Molecular change • EX: • All muscles produce tiny electric current • Eels have developed stronger current to help them find food and kill prey

  12. Behavioral Changes • Adaptive changes that increase reproductive success • EX: • Fighting among males to “win” female • Rhythms of bird calls • Rates blinking in lightning bugs

  13. Importance of Variation • Environment changes, orgs have to adapt • Without variation, species likely to become extinct • If diversity lost, difficult to recover • Endangered species have small pop’ns with little variation • If environment changes, cannot adapt

  14. $2 SUMMARY OF THE IMPORTANCE OF VARIATION in EVOLUTION • Each word is worth $.05 • Freebies: • a the as if and of in is it so by for to

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