Direct Evidence for Evolution Fossil Record Paleontologists have collected millions of fossils that make up the fossil record The fossil record is incomplete as many organisms die and vanish without leaving a trace Does give a relatively clear picture of change. Ex. Evolution of the Horse

Direct Evidence for Evolution Fossils Preserved remains or traces of an organism that lived in the past. Fossils are formed when organisms die and are buried in sediment. Eventually the sediment builds up and hardens to become sedimentary rock.

Direct Evidence for Evolution Fossil Record Shows major changes in Earth’s climate and geography i.e. Fossil shark teeth found in Arizona, indicating it was once covered by a sea Fossils can be absolute dated using radioactive decay of nearby flows They can be relative dated using nearby clues

Indirect Evidence for Evolution Homologous Structures Modified body parts with different functions that developed from the same ancestral parts Embryological Relationships Structural similarities between species during embryonic development i.e. Gill slits in humans

Indirect Evidence for Evolution Vestigial Structures Structures in the body of organisms that seem to serve no useful purpose at all May have had a function in ancestral forms Eg. human tailbones, the appendix Muscles that move our ears Whale hip bones

Indirect Evidence for Evolution Comparative biochemistry All organisms have similarities in their biochemistry All life uses DNA, ATP, Carbon The more closely two species are related, the closer the similarities between their genes Humans share: 98% of our genes with chimpanzees; 65% with chickens; 60% with bananas; 7% with bacteria

The Patterns of Evolution

Divergent Evolution Reproductive Isolation often results in Divergent evolution The process by which one species gives rise to two or more new species, whose traits become more and more different, but who share a common, structural ancestor Produces homologous structures Different function, but same origin

Convergent Evolution The process by which two or more different species evolve to become structurally similar Species must have similar niches Ex. shark and dolphin Produces analogous structures Similar function, but different origin

Parallel Evolution The process where two different species follow similar evolutionary paths Species must have similar niches Ex. Timber wolf and Tasmanian wolf Sleek, hunters, etc…

Co-evolution When two or more species influence each other's evolution. It is most often invoked to explain co-adaptations between species. Ex: Parasites and Hosts (antagonistic coevolution) can lead to evolutionary 'arms races‘ Ex: Insects and Flowering Plants (mutualistic coevolution)

Living Fossils Some organisms have changed very little over the past million years E.g. Ginko biloba (270 MYA) Hagfish (300 MYA) Red Panda (10 MYA) Pelicans (30 MYA) Crocodiles (83.5 MYA)