Evidence for Evolution Biology I

Fossil Record SIMPLE to COMPLEX Of course, the fossil record is not complete – not every organism gets fossilized Still, there are LOTS of fossils and a simple to complex trend is clearly shown. Also, transition organisms…

Fossil Record – Transition Organism Tiktaliik Rosea Transition fossil - from fish to amphibian… Click here for more…

Comparative Anatomy Comparing the anatomical structures of different organisms to determine their relatedness Homologous structures structures in different spcecies May look different superficially Similarities indicate a COMMON ORIGIN / COMMON ANCESTOR

Example – Homologous Structures Bones of mammals below show common ancestry

Embryology Embryology – the study of embryos Organisms that are more closely related share similar developmental patterns in their embryos. Structures that may be absent in adults are found in embryos Gill slits Tail

Vestigial Organs Organs that have no function in the organism in which they are found, but DID have a function in an ANCESTOR Why would an organism waste energy maintaining a useless organ? They wouldn’t, except that it must be a left over from an ancestor who DID use the organ Supports the idea of evolutionary change…

Example – Vestigial Structure Human Tailbone

Vestigial Organ – Whale hindlimb

…also in snakes…

Molecular Biology Analysis of DNA shows us exactly who is closely reltaed to whom by seeing how similar the “letters” of the DNA molecules are between species

Molecular Biology Example Humans and Chimps share 98% of DNA

Biogeographical Evidence Galapagos animals similar to those on mainland S. America rather than those on other tropical islands – Why? Suggests organisms from S. America came to the islands and changed to fit their new environment Otherwise, why wouldn’t they be totally different from organisms from mainland– the environment is certainly totally different and much more like other tropical islands.