Presentation on theme: "EVIDENCE FOR EVOLUTION"— Presentation transcript:
1EVIDENCE FOR EVOLUTION SBI 3UEVIDENCE FOR EVOLUTION
2Evidence 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
3Evidence for Evolution Topics To Be Discussed:Fossil recordRadiometric DatingTransitional formsBiogeographyEmbryonic developmentHomologous structuresVestigial structuresAtavismsMicro-evolution happening today
4Fossil Record Show which species were alive in the past provides evidence that living things have evolvedfossils show how different groups of organisms have changed over timeStill very incompleteArchaeopteryx
5Fossil RecordFossils in young layers of rock are more similar to today’s species than are older fossilsFossils appear in chronological order in rock layersNot all organisms appear in the fossil record at the same time
6Radiometric DatingRadioisotopes undergo radioactive decay at predictable ratesEach 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!
7Transitional Forms Incorrectly called ‘missing links’ None when Darwin wrote ‘Origin of Species’Show links between groups of organsimsHundreds found to dateEg. Dorudon was an ancient terrestrial whale (pelvis; short legs)
8Transitional FormsEg. Atrociraptor was a link between dinosaurs and birds (Archaeopteryx)Eg. Tiktaalik roseae show how amphibians may have risen from fishEyes on top like a salamander, ribs, could breathe air
9Name these critterscoelurosaurusarchaeopteryxchicken
10Biogeography Past and present distribution of species Darwin & Wallace speculated that species evolve in one location and then spread outPlants in S. Am. And Africa sameMarsupial fossils found in AntarcticaSouthern super-continent Gondwana
11BiogeographyGeographically 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
12BiogeographyMarsupials (Australia) birth undeveloped baby; matures in pouchPlacentals (N. & S. America) give birth to fully developed babiesRemarkably similar forms“Convergent evolution”
13Embryonic Development Many species look similar in early stages of developmentProvides evidence of a common ancestry
17Vestigial Organs Remnants of homologous organs in other species Eg. Pelvis and leg bones in whales when they use to live on landWhat we’d expect if nature weeded out useless traits
18Vestigial 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)
19Atavisms From Latin: ‘ancestor’ Reappearance of old traits Eg. One in 500 whales is born with protruding legsEg. Human babies born with vestigial tailsEg. Horses born with more than one toe (splint toes)Mutations ‘turn on’ dead genes
21E.Coli tested in lab over 18 year study: Micro-evolutionMicrobes 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 environmentLatest offspring grow 70% faster than originalScientists identified at least 9 DNA mutations resulting in adaptations
22Antibiotic resistance Drugs evolve to thrive in human envt.Eg. In 1941 penicillin wipes out all Staphylococcus bacteria; by % of Staph. strains are resistant to penicillinEg. AIDS treatment requires 3-drug cocktail because virus mutates at a rapid paceInsects resistant to DDTPlants adapted to herbicidesMany others!
23Lactose 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 mutationAmylase geneHighly duplicated in humans, not so much in lower apes (due to our starchy diets)
24Bad eyesight cured with glasses; bad teeth fixed by dentists Are humans evolving?Conversely, improvements in nutrition, sanitation, and medical care are curbing natural selectionBad eyesight cured with glasses; bad teeth fixed by dentistsHow many of our ancestors with bad eyes and teeth, unable to hunt, would have survived on the African savanna?De-evolution…possibly?