Evidence for evolution

• biogeography

• fossil record

• comparative anatomy

• homologous structures

• vestigial structures

• comparative embryology

• similar biochemistry = DNA and protein

Fossil Record

• Shows the history of life on Earth and how different groups of organisms have changed over time

Relative Dating

• Can determine a fossil’s relative age

• Performed by estimating fossil age compared with that of other fossils

• Drawbacks- provides no info about age in years

Absolute Dating

• Can determine the absolute age in numbers

• Is performed by radioactive dating- based on the amount of remaining radioactive isotope

• Drawbacks- part of the fossil is destroyed during the test

Homologous Structures

• Same/similar structure in a different species due to common ancestor

• Different function

Vestigial Structures

• Traces of homologous organs in other species; functionless in some

• Often small in size than original

• Ex. appendix, hip bones in pythons, pelvic bones in whales

Comparative Embryology

Comparative Embryology

• Comparing species in early stages of development can show evidence of common ancestry

Comparative Biochemistry

• Compare DNA and proteins of different species for level of similarities/differences

• More DNA similarities = more recent common ancestor

Comparative Biochemistry

Convergent evolution; analogous structures

• Convergent Evolution: Non-related organisms evolve to have similar traits by adapting to similar environments

• The result is analogous structures

• Structures that have similar function, but do not show relatedness

• Ex. fins in fish and dolphins

Evidence for Evolution

Why do we not find evidence of gradual change between species?

Stephen jay gould 1941-2002

punctuated equilibrium

similar to Darwin except in timing

Believed population only changes when

forces by environment

Rest of time in equilibrium