Evidence for Evolution

The Fossil Record

Fossil: any preserved evidence of past life.E.g. shells, bones, teeth, artefacts, imprints / impressions- Age of the fossils indicates general trend in time / complexity- Evidence of continual change

- Extinction of certain species ( climate change, asteroid)

- Transitional forms: provide a missing link between certain evolutionary pathways.

- E.g. Archaeopteryx (flying reptile with feathers)- E.g. Crossopterygian fish (air breathing fish)

Comparative Studies in Biochemistry

DNA•All living organisms process the same four nitrogen base pairs (A, T, C, G) implies a common ancestor•More closely related species would share a greater proportion of their genome•E.g. chimpanzees share approx 98% of human genome

E.g. ERV’s•An RNA viral sequence that has become part of an organisms genome which is inherited (virus inserts itself into cells chromosome)•Offspring will therefore have a copy of the virus in the same place of the same chromosome in every cell.•Humans have 16 ERV’s which are also found in chimpanzees

Protein Sequences

•Comparing the type and sequence of amino acids in similar proteins from diff species.•Ubiquitous proteins: proteins which appear to be present in all species which are responsible for tasks required for all life. (carry out same function regardless of species)•Similarities between ubiquitous proteins indicate close ancestry common ancestor

E.g Cytochrome C•Human cytochrome C contains 104 amino acids. •Out of 104, the more which are similar the closer the species to each other. (e.g chimpanzees & gorillas are exactly the same as humans)

-Table 16.3

Comparative Studies in Anatomy

Embryology•Similarities between embryos of various species indicate a common ancestor (e.g. vertebrates)

•E.g -embryonic gill pouches/arches-presence of a well developed tail, -Similar brain development, -two chambered heart

Homologous Structures- Structures which are very similar in structure but may differ in function.- e.g forelimb of vertebrates

Vestigial Organs•structures of reduced size that appear to have no function•they are a waste of energy and resources and therefore natural selection caused their reduction in size•approx 90 in humans•E.g Humans

-Nictitating membraneoAct as a transparent third eyelid in cats, birds, frogs etc but pinkish membrane in inner corner in each eye for humans

-Muscle to move ears- Wisdom teeth

oCannot be used in mastication-Pyramididalis muscles (muscle above pubic bone)-Coccyx-Appendix-Body hair

oMuscles contract around hair to trap a layer of air around body (insulation), but doesn’t work as human hair is too fine

Vestigial Organs

E.g. other vertebrates-Wings of flightless birds (ostriches/ emus)-Wales / snakes have pelvis/femur bones although both are non-functional