Notes for Lecture #2
Darwin and evolution
Copyrighted 1996. May not be reproduced for commerical purposes
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Further reading for the interested:
- Evolution and the myth of creationism by Tim Berra
- Science on trial: the case for evolution by Doug Futuyma
Some interesting links to science and creationism discussion groups
Scientific theories and scientific facts
- Gravity as a scientific fact.
- Dropping a pencil does not "prove" gravity what about other times?
- What about gravity on other planets or stars?
- Key: all experiments designed to test for gravity has shown it occurs.
Evolution as a Scientific fact
- If evolution has occurred, there are a variety of signs we should be able to detect.
- No test that life has evolved has failed.
- However there is still considerable debate about the actual mechanisms of evolution.
Evidence for descent with modification
- Biogeography
- Functional morphology
- Paleontology
- Comparative embryology
- Animal and plant breeding
- Molecular evidence
Evidence from Biogeography
Darwin observed that organisms on isolated islands appear closest to organisms on the nearest mainland.
The Voyage of the HMS Beagle 1831-36
Armadillos and fossil Glyptodonts.
Both found in the same locations in South American.
- If these had been created separately, why would both living and extinct forms be restricted to the same area.
- Darwin thought it made more sense to assume the armadillo evolved from the glyptodon.
Variation between species on the Galapagos Islands
Each island has a slightly different species of finch, all of which appear close to a single species found on the South American mainland.
Evidence from Functional Morphology
Vestigial Organs
Humans have muscles to move their ears
Humans have a vestigial tailbone
Vestigial toes in the horse
Vestigial limbs in whales and snakes
Vestigial toes in the horse
Vestigial pelvis and femur in whales
Vestigial pelvis and femur in some snakes
Evidence from functional morphology
Fossils: The Hard Evidence for evolution
- Fossils show a succession from very simple morphological forms early in the fossil record to much more complex forms that appear much later in the fossil record.
- Fossils show multiple examples of transitional forms.
- Direct evidence for descent with modification
Classic example: Evolution of the hoof
Evidence from comparative embryology
- Early embryos of very different organisms closely resemble each other.
Evidence from animal breeding
- Darwin was greatly impressed by how much domesticated animals had been changed by artificial selection.
- Breeds of dogs, cattle, pigeons
More recent evidence
- Explosion of data in all of the above fields in the 100 years since Darwin has confirmed and expanded upon Darwin' s observations.
- Molecular data
Molecular evidence of shared ancestry
- The biochemistry of a bat is much closer to that of a whale, rather than a bird. Not expected unless bat and whale have a more recent common ancestor than bat and bird, but evolution predicts this.
- Paternity testing -- how do you tell who' s dad?
- The same approach tells us about shared ancestors
- Shared errors
- Common errors in textbooks legal evidence of plagiarism
- Common errors in different organisms --- globin pseudogenes
- pseudogenes are inactive copies of genes
- Why do human and chimps have the same errors?