1. EVIDENCE FOR EVOLUTION
SBI 3U
EVIDENCE FOR EVOLUTION

2. 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

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

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. Radiometric Dating
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!

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. Dorudon was an ancient terrestrial whale (pelvis; short legs)

8. Transitional Forms
Eg. Atrociraptor was a link between dinosaurs and birds (Archaeopteryx)
Eg. Tiktaalik roseae 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. Biogeography
Marsupials (Australia) birth undeveloped baby; matures in pouch
Placentals (N. & S. America) give birth to fully developed babies
Remarkably similar forms
“Convergent evolution”

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. E.Coli tested in lab over 18 year study:
Micro-evolution
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

22. Antibiotic resistance
Drugs evolve to thrive in human envt.
Eg. In 1941 penicillin wipes out all Staphylococcus bacteria; by % 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!

23. Lactose tolerance Amylase gene Are humans evolving?
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)

24. Bad eyesight cured with glasses; bad teeth fixed by dentists
Are humans evolving?
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?