Lecture 17
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All living things evolved from a common ancestor
Evidence for evolution: Lecture Outline 17

A. The Geological Record - Presented by Dr. Dunn

1) The antiquity of the earth.
2) The occurrence and dating of fossils.

B. The Anatomy of Living Organisms.

1) Comparative Anatomy:

(a) Even-toed foot of Artiodactyla
(b) Mammalian forelimbs.
(c) Horse Evolution
(d) Skulls and jawbones: reptile to mammalian

2) Vestigial Structures.

3) Comparative Embryology.

C. Biogeography: Geographic distribution of organisms.

"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).

(1) Galápagos Islands and Adaptive Radiation
        Darwin’s Finches

(2) Isolation into separate land masses from a once-connected landmass.

a) Ratite birds. The living families of flightless, ratite (i.e. raft-like, keel) birds from different parts of the world; separated before Mesozoic break-up of Gondwanaland. Their monophyletic relationship has been established by DNA hybridization (see below). Ostrich from Africa; Cassowary from Australia and New Guinea; Kiwi from New Zealand; Tinamou from tropical America

b) Marsupials in South America and Australia.

D. Biochemistry and molecular biology

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.

(1) Restriction "mapping" (see Lecture Outline 15: Uses of RFLP’s)

(2) DNA hybridization ("annealing").

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.

(3) Protein sequence.

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.

Chimpanzee 0
Rhesus monkey 1
Rabbit 9
Duck 11
Rattlesnake 14
Tuna 21
Moth 31
Yeast 45

(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.

Man versus Man: 100%
Man versus Chimpanzee: 97%
Man versus Baboon: 50%
Man versus the dog: 0%