Natural Selection in Animals Activity Who Gives a Hoot?

Written Response #7 Evidence for evolution: what clues have scientists used to study evolution? What pieces of evidence do you think are important?

Evidence Biochemical (molecular) evidence: DNA similarities: Human Sequence: AGG CAT AAA CCA ACC GAT TAA Ape sequence: AGG CCC CCT CCA ACC GAT TAA Chimp sequence: AGG CCC CCT CCA ACC AGG CCA Chromosomal similarities (karyotypes) Humans: 46 chromosomes Chimpanzees: 48 chromosomes (Chimpanzee’s chromosome pair #2 and #3 fuse to resemble human’s pair #2

Evidence Fossil record: Relative Dating: exact age of fossil cannot be determined, only the order of appearance compared to fossils found in nearby rocks. Older fossils are found in deeper rock layers Absolute (Radioactive) Dating: gives a more exact age using natural decay of radioactive isotopes in organisms.

Evidence Embryology: similarities among developing embryos Humans for example have gills when developing

Evidence Homologous structures: structures derived from the same tissues but are used differently in different organisms Indicate: common descent The structures show morphological similarities among organisms Similar bone origins Used differently and appear differently

Evidence Analogous structures: structures that perform the same function (ex: flying) but are different anatomically (ex: bird wing versus butterfly wing) Supports evolution in similar habitats instead of from a common ancestor

Evidence Vestigial structures: may have once had a function but have evolved to be useless over time May represent a link to a previous ancestor Examples: whale’s hip bones, human appendix, human tailbone