Notes: Evidence of Evolution Objective: What are the different evidence for evolution?
Page 1 Evidence for Evolution. Page 2 Evidence for Evolution ‘Theory of evolution by natural...
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Transcript of Page 1 Evidence for Evolution. Page 2 Evidence for Evolution ‘Theory of evolution by natural...
Page 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
Page 3
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
Page 4
Fossil Record
• Fossils in young layers of rock are more similar to today’s species than do older fossils
• Fossils appear in chronological order in rock layers
• Not all organisms appear in the fossil record at the same time
Page 5
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)
Page 6
• Eg. Atrociraptor was a link between dinosaurs and birds (Archaeopteryx)
• Eg. Tiktaalik roseae show how amphibians may have rose from fish
• Eyes on top like a salamander, ribs, could breathe air
Transitional Forms
Page 9
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
Page 10
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
Page 11
• Marsupials (Australia) birth undeveloped baby; matures in pouch
• Placentals (N. & S. America) give birth to fully developed babies
• Remarkably similar forms
• “Convergent evolution”
Biogeography
Page 12
Primate fossils
• Recent finds have closed the gaps on the link between apes and humans
• Eg. Raccoon-sized primate with opposable thumbs and nails instead of claws found in Germany (2009)
Page 13
Primate fossils
• Darwin proposed that all hominids (human-like) originated from primates in Africa
• That’s where most fossils are found!
• DNA can confirm relationships found in fossils
• We have enough to see our evolution but the record is very incomplete!
Page 14
Primate Brain Development
• Human brain size has tripled compared to our earliest hominid ancestors
Page 18
Primate Bone structure
• Bone sizes and shapes gradually become similar to modern humans’ over time
• Pelvis, femur, digits, etc.
• Changes overlay changes in environment (from trees to land)
Page 19
Ardipithecus
• “Ardi”• Oldest human
ancestor (4.4 myo)• Unearthed in
Ethiopia (2008)• Bipedal due to hip
and toe modifications
Page 25
Embryonic Development
• Many species look similar in early stages of development
• Provides evidence of a common ancestry
Page 27
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
Page 29
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
Page 30
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)
Page 31
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
Page 33
“In vitro” 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
Page 34
Antibiotic resistance
• 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!
Page 35
Are humans evolving?
• 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)
Page 36
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?