EVIDENCE FOR EVOLUTION SBI 3U EVIDENCE FOR EVOLUTION

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

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

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

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

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!

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)

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

Name these critters coelurosaurus archaeopteryx chicken

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

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

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

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

Embryonic Development

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

Homologous Body Structures

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

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)

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

Is evolution happening right now?

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

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!

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)

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?