Evidence for Evolution Evidence Fossil Record Geographic Distribution

Evidence for Evolution

Evidence • • • Fossil Record Geographic Distribution of Living Species Body Structures Similarities in Embryology Biochemical Evidence

Fossil Record • shows evidence of how organisms have evolved over time • Transitional fossils have been found which show intermediate stages of evolution of modern species from species now extinct

Evolution of the Horse

• The fossil record is an “incomplete record” because: • Not all fossils have been found • Some fossils have decomposed • Not all organisms left fossils

Geographic Distribution of Living Species • Species living in different places with similar environments have similar anatomies and behaviors, even though they are unrelated

• They are exposed to similar pressures of natural selection so they evolve similar characteristics

Homologous Body Structures • Homologous: Structures that share the same origin and basic structure but have different functions • Ex. Bat wing, whale fin, human arm

Analogous Structures • Analogous: structures that are not of common origin but have the same function • Ex. Bird wings and insect wings

Homologous versus Analogous Structures http: //evolution. berkeley. edu/evolibrary/home. php

Vestigial Structures • Structures that have no function in their present-day organism but resemble functional structures of other organisms.

- This suggests that the structures are inherited from a common ancestor. - Human coccyx is at the end of the spine and seems to the remnants of a tail. - Human appendix seems to have no apparent function (may have needed it in the past to digest food). - Whales & snakes contain pelvic bones just as humans do, but they serve no function.

Embryology • The early stages, or embryos, of many animals with backbones are very similar.

• During development, organisms may exhibit characteristics of other organisms. • The human embryo exhibits characteristics of the embryos of its ancestors. • Early in their development, embryos posses gill slits like those of fish. • Later in development, the embryos develop a tail. • Human fetuses have a fine fur (lanugo) during the fifth month of development

Biochemical Evidence • All organisms use DNA and RNA to transmit genetic information • ATP is an energy carrier in all organisms.

• Organisms with similar amino acid sequences or similar DNA fingerprints are believed to have a more recent common ancestor. • Ex: • The amino acid sequence for the protein hemoglobin in humans is very similar to the sequence in the Rhesus monkey. They differ by only eight amino acids.

# of amino acid differences between human hemoglobin and other organisms.

• The DNA fingerprint pattern will be very similar for organisms that share a more recent common ancestor.