Evidence for Evolution Evidence from dead organisms Evidence from living organisms

Fossils – remains of dead organism Preserved remains of organisms that lived a long time ago Fossilized hard parts (most common) ex. Bones, teeth, shells, spores, seeds etc Traces of fossils (indirect evidence), footprints, leaf prints, tracks, burrows.

How does Fossilization occur? Organism becomes buried in ash or sediments Rapid burial and a lack of oxygen aid in preservation The organic remains become infused with metal and mineral ions

What Do Fossils Tell Us? Evidence for change through time Oldest fossil found – heterotrophic bacteria 3.5 BYO Older fossils in lower layers of rock Ancestor of the whale walked on land Younger fossils in higher layers

Evidence from Biogeography Continental Drift Idea that the continents were once joined and have since “drifted” apart Pangea: theoretical supercontinent: Explains the worldwide distribution of more ancient life 500-200MYA Laurasia and Gondwanaland: Explains why certain life forms exist in the northern land and some only in the southern lands 180-200MYA

Evidence from Biogeography Antarctica has fossils of plants and animals that shows that is was once a warmer land The continents in the south have unique life forms and fossils form that of the Northern continents Why are kangaroos only found in Australia Why are flightless birds only on S. America, Africa and Australia

Evidence from Living things Comparative Morphology Homologous features Analogous features Vestigial structure

Morphological Divergence or Adaptive Radiation 1 2 Morphological Divergence or Adaptive Radiation 3 PTEROSARUR 4 1 2 CHICKEN 3 Homologous structures: evolved from a common ancestor (so similar in structure) but has changed (different environmental pressures) to serve different functions STEM REPTILE 2 3 PENGUIN 1 2 3 4 1 5 2 PORPOISE 4 3 5 1 2 BAT 3 4 5 1 2 3 4 HUMAN 5

Morphological Convergence Convergent evolution Analogous structures: evolved from different ancestor (not similar in structure) but serves the same purpose (same environmental pressures)

Vestigial Structures Structures that were present in the ancestor and had a function – but is no longer functional in the modern organism Example snakes have tiny pelvic bones shows that the ancestor of the snake could walk Humans have a tail bone, appendix which were functional in the ancestors

Comparative Development During development, each animal or plant proceeds through a series of changes in form Similarities in these stages are clues to evolutionary relationships

Comparative Development

Comparative Biochemistry Kinds and numbers of biochemical traits that species share is a clue to how closely they are related All life contains DNA, makes proteins using RNA and similar biochemical processes More similarity means species are more closely related

Comparing Proteins Compare amino acid sequence of proteins produced by the same gene Human cytochrome c (a protein) Identical amino acids in chimpanzee protein Chicken protein differs by 18 amino acids Yeast protein differs by 56

Speciation & Natural Selection Natural selection can lead to speciation Speciation can also occur as a result of other microevolutionary processes Genetic drift Mutation “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” Ernst Mayr