Evidence for Evolution (Chapter 18) The real fossil bones of the walking and swimming whale, Ambulocetus natans, are spread out in this picture with a sledgehammer for scale. The skeleton was about 12 feet long and is about 49 million years old. It was found in Pakistan.

Evidence for Evolution 1. Remains of living organisms can be trapped and preserved in… Resins that turn to amber Frozen in ice or snow In acid peat that prevents decay In sediments that produce fossils (most important)

–Date rocks and fossils using radioactive isotopes Half life is the time it takes for the radioactivity to fall to ½ of its original level 14C – half life is 5730 years so useful for dating samples 1, ,000 years old 40K – half life is 1,250 million years so use for samples >100,000 years old

–Scientists look for paleontological evidence– specifically transitional fossils example: Archaeopteryx -- transitional form between birds and reptiles microraptor Ambulocetus natans This is the "classic" picture of the archaeopteryx fossil. It was not the first found, but is the most complete. The fossil was found in a limestone quarry in southern Germany (Bavaria) in 1877 (first one was actually found in 1861)

The latest Nature reveals a new primitive mammal fossil collected in the Mesozoic strata of the Yan mountains of China. It's small and unprepossessing, but it has at least two noteworthy novelties, and first among them is that it represents another step in the transition from the reptilian to the mammalian jaw and ear.

2. Biography/Geographical Distribution The study of the distribution of living things over the earth Why are some species absent from environments that would suit them? Why are there closer relationships between species that are geographically near each other than between species that inhabit similar environments? –In Asia, find many types of placental animals and very few marsupials –In Australia, find mostly marsupials and very few placental animals

- Polar bears live in the Arctic, but not the Antarctic. For penguins, the picture is reversed.

3. Comparative Embryology/Anatomy Embryos of vertebrates look similar Useful when don’t have much of a fossil record Almost all mammals have seven cervical (neck) vertebrae and gill arches Ontogeny recapitulates phylogeny –The idea that the development of individuals is a progression through adult ancestral form

German biologist, naturalist, philosopher, physician, professor and artist who discovered, described and named thousands of new species (see below), mapped a genealogical tree relating all life forms, and coined many terms in biology, including phylum, phylogeny, ecology and the kingdom Protista (details below). Haeckel promoted Charles Darwin's work in Germany and developed the controversial "recapitulation theory" claiming that an individual organism's biological development, or ontogeny, parallels and summarizes its species' entire evolutionary development, or phylogeny: "ontogeny recapitulates phylogeny" (see below).biologistnaturalistphilosopherphysicianprofessorartist speciesgenealogicalbiologyphylum phylogenyecologyProtistaCharles Darwin'sGermanyrecapitulation theoryontogenyphylogenybelow

Homologous structures –have a common evolutionary origin, but can look quite different and have different functions –ex. Forelimbs/pentadactyl limb of birds, bat, horse, humans...

Analogous structures –have similar functions, may appear similar, yet presumed to have different evolutionary origins –ex. Wings of an insect and bird wings of bat, bird (though the BONES are homologous!), insect:

4. Biochemistry All living organisms use DNA/RNA as genetic material All use the same 20 amino acids to make their proteins –Differences of a.a. sequences accumulate (mutations) at a constant rate and therefore can be used as an evolutionary clock –The more differences in proteins, the less likely organisms are “related”

4. Selective Breeding of Domesticated Animals artificial selection When selective breeding goes too far The government has confirmed that it will use a report on the selective breeding of freak pets - including fancy goldfish - to shape the Animal Welfare Bill.

Evolving Ideas: How Do We Know Evolution Happens?