All living things evolved from a common ancestor
Evidence for evolution: Lecture Outline 17
1) The antiquity of the earth.
"An important revelation of the early descriptive work was that although a particular type of habitat might occur in several widely scattered places in the world, the species in that habitat are typically more closely related to nearby species than to species in that habitat in other parts of the [world]." (Futuyma, 1986).
The longer the period since the two species have diverged from a common ancestor, the greater the number of substitutions that are found in corresponding genes (DNA) and proteins between the two species.
The DNA double helix can be "denatured" (i.e. separated into two separate single strands) by heating in solution and rapidly cooling. DNA from one organism is denatured and the single strands and adsorbed on a filter. Radiolabeled DNA from a second organism is similarly denatured but left in solution. The filter with the DNA from the first organism is dipped in the solution with the radiolabeled DNA. Hybridization between the two species of DNA is a function of how closely similar their sequences are. The relatedness of the organisms is measured by the amount of radioactivity that sticks to the filter.
Cytochrome c is a component of the electron transport chain in all five Kingdoms. Its 3-D structure and function has been conserved for over 3.5 billion years. Differences between human cytochrome c (with 141 amino acids) and other species are shown below.
(4) Immunological testing
Injecting human blood serum into rabbits forms antibodies against human blood serum. When rabbit antibodies are mixed with human blood a precipitate is formed. By comparing the amount of precipitate formed when the antihuman antibodies react with a foreign blood serum hints at biological relatedness - the greater the reaction, the closer the supposed relationship.