Evidence for Evolution

1. Evidence for Evolution Fossil record Comparative Anatomy Similarities in body structures Comparative EmbryologySimilarities in early development Comparative Molecular BiologySimilarities in DNA BiogeographyGeographic distribution of living species

2. Fossil Record • A relic or impression of an organism from the past, usually preserved in rock • Usually found in sedimentary rock (sandstone, mudstone, shale, and limestone) • Hard parts of animals: teeth and bones • Thin tissues such as leaves can leave imprints • Plant tissue can also be petrified • Imprints such as footprints are rare.

3. Fossil Record • Stratification • The study of rock layers • Sedimentary rocks form in layers • Dating • Relative = comparing fossils in a strata (can not give age in term of years) • Radioisotopic = using isotopes of elements to determine age in years • Carbon-14 used for dating recent fossils up to 50,000 yrs • Potassium-40 used to date rocks up to hundreds of millions of yrs

4. Fossil Record • Layers on the bottom are the oldest, find prokaryotes and eukaryotes • Above them are multicellular organisms • Then trilobites and other invertebrates • Then vertebrates and fish • Amphibians and reptiles • Dinosaurs, crocodiles, birds, mammals…

5. Comparative anatomy Convergent Evolution analagous (similar) structures in unrelated organisms that evolve independently when adapting to similar environments Ex. Wings (Birds, bats, insects)

6. Comparative Anatomy Homologous structures = structures that have different mature forms in different organisms but develop from the same embryonic tissues

7. Comparative anatomy Homologous structures can be tricky Does this suggest a lack of homology, or is there some other explanation?

8. Some helpful terms for lab • Niche = the full range of environmental conditions (physical and biological) under which an organism can exist • How a population responds to abundances of resources and enemies • Grows when resources are present and predators are scarce • Adaptive radiation = species coming from a common ancestor have over time successfully adapted to their environment

9. Comparative anatomy Archaeopteryx 150-million-year-old fossil bird Evolutionary link between reptiles and birds Discovered 1862 Size of a crow Bird similarities: Wings Feathers Skeletal structures Reptile similarities: Reptilian teeth Long jointed tail

10. Comparative anatomy Vestigial Structures Structure that serves no useful function in an organism Suggest a common ancestor Do not affect an organism’s ability to survive Whale skeleton—why does it have pelvic bones?

11. Comparative embryology Similarities in early development (embryos) Indicates same groups of embryonic cells develop in the same order and patterns to produce the tissues and organs of all vertebrates Produce the homologous structures discussed earlier

12. Comparative molecular biology Similarities in DNA/genes Information used to construct genealogical trees Organisms ranging from yeast to humans use an enzyme known as cytochrome C to produce high-energy molecules as part of their metabolism. The gene that codes for cytochrome C gradually has changed over the course of evolution.

13. Biogeography geographic distribution of living species Darwin’s finches came from mainland S. America, evolved differently on different islands in Galapagos