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EVIDENCE FOR EVOLUTION

SBI 3U. EVIDENCE FOR EVOLUTION. ‘Theory of evolution by natural selection’ called… “the greatest idea anybody has ever had…” “Today scientists have as much confidence in evolution as they do in the existence of atoms or that microorganisms cause infectious disease.” Jerry A. Coyne.

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EVIDENCE FOR EVOLUTION

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  1. SBI 3U EVIDENCE FOR EVOLUTION

  2. ‘Theory of evolution by natural selection’ called… “the greatest idea anybody has ever had…” “Today scientists have as much confidence in evolution as they do in the existence of atoms or that microorganisms cause infectious disease.” Jerry A. Coyne Evidence for Evolution

  3. Topics To Be Discussed: Fossil record Radiometric Dating Transitional forms Biogeography Embryonic development Homologous structures Vestigial structures Atavisms Micro-evolution happening today Evidence for Evolution

  4. Fossil Record • Show which species were alive in the past • provides evidence that living things have evolved • fossils show how different groups of organisms have changed over time • Still very incomplete Archaeopteryx

  5. Fossil Record • Fossils in young layers of rock are more similar to today’s species than are older fossils • Fossils appear in chronological order in rock layers • Not all organisms appear in the fossil record at the same time

  6. Radioisotopes undergo radioactive decay at predictable rates Each radioisotope decays at its own constant rate (half-life) By dating the rocks in which a fossil is found, the age of the fossil can be estimated! Radiometric Dating

  7. Transitional Forms • Incorrectly called ‘missing links’ • None when Darwin wrote ‘Origin of Species’ • Show links between groups of organsims • Hundreds found to date • Eg. Dorudonwas an ancient terrestrial whale (pelvis; short legs)

  8. Transitional Forms • Eg. Atrociraptorwas a link between dinosaurs and birds (Archaeopteryx) • Eg. Tiktaalikroseae show how amphibians may have risen from fish • Eyes on top like a salamander, ribs, could breathe air

  9. Name these critters coelurosaurus archaeopteryx chicken

  10. Biogeography • Past and present distribution of species • Darwin & Wallace speculated that species evolve in one location and then spread out • Plants in S. Am. And Africa same • Marsupial fossils found in Antarctica Southern super-continent Gondwana

  11. Biogeography • Geographically close environments are more likely to contain related species than locations that are distant locations that are environmentally similar (eg. Desert in Africa and a desert in Australia) • Animals found on islands often resemble animals from the closest continent (evolution from mainland migrants) • Fossils of same species found on the coastline of neighbouring continents (eg. Gondwana) • Related species almost never found in exactly same location or habitat

  12. Marsupials (Australia) birth undeveloped baby; matures in pouch Placentals (N. & S. America) give birth to fully developed babies Remarkably similar forms “Convergent evolution” Biogeography

  13. Embryonic Development • Many species look similar in early stages of development • Provides evidence of a common ancestry

  14. Embryonic Development

  15. Homologous Structures • Different mature forms that arose from same embryonic tissue • Eg. Wing of a bat, flipper of a whale, human arm, etc. Turtle Alligator Bird

  16. Homologous Body Structures

  17. Vestigial Organs • Remnants of homologous organs in other species • Eg. Pelvis and leg bones in whales when they use to live on land • What we’d expect if nature weeded out useless traits

  18. Vestigial Organs • Keys to our primate ancestry • Tailbone (remnants of tail) • Appendix (fermenting vessel to digest cellulose) • Arrector pili muscles (“goosebumps”) • 3 scalp muscles (ear wiggling)

  19. Atavisms • From Latin: ‘ancestor’ • Reappearance of old traits • Eg. One in 500 whales is born with protruding legs • Eg. Human babies born with vestigial tails • Eg. Horses born with more than one toe (splint toes) • Mutations ‘turn on’ dead genes

  20. Is evolution happening right now?

  21. Microbes can adapt to virtually any laboratory condition (heat, antibiotics, toxins, starvation, predators, etc.) E.Coli tested in lab over 18 year study: Created feast or famine environment Latest offspring grow 70% faster than original Scientists identified at least 9 DNA mutations resulting in adaptations Micro-evolution

  22. Drugs evolve to thrive in human envt. Eg. In 1941 penicillin wipes out all Staphylococcus bacteria; by 2009 95% of Staph. strains are resistant to penicillin Eg. AIDS treatment requires 3-drug cocktail because virus mutates at a rapid pace Insects resistant to DDT Plants adapted to herbicides Many others! Antibiotic resistance

  23. Lactose tolerance not needed after weaning in many regions (no lactase enzyme) Pastoral areas (raise cows) keep lactase turned on (3000 to 8000 years ago) Simple DNA mutation Amylase gene Highly duplicated in humans, not so much in lower apes (due to our starchy diets) Are humans evolving?

  24. Conversely, improvements in nutrition, sanitation, and medical care are curbing natural selection Bad eyesight cured with glasses; bad teeth fixed by dentists How many of our ancestors with bad eyes and teeth, unable to hunt, would have survived on the African savanna? De-evolution…possibly? Are humans evolving?

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