Evidence for Evolution
1. The Fossil Record and Geology shows that the earth is very, very old
Geologists can 'read' the layers of rock to determine their ages...billions of years!!
The fossils show many extinct organisms and how they change over time. Some of them are called
Transitional Species:
For example:
* archaeoptyrx - bird-like dinosaur
* basilosaurus - a whale-like ancestor with legs and arms
* tiktaalik - a fish-like amphibian
* Lucy - a chimp-like human
Mass extinctions catastrophic events that cause most of the life on the planet to die off
mass extinctions happen because of climate changes, human activities or asteroids from space
http://exploringorigins.org/timeline.html (link for the timeline used in class)
2. Anatomical Similarities
a. Homologous structures - the same structures that have changed slightly in different animals
b. Vestigial structures - structures that have no function but worked in the ancestor species
3. DNA
* By looking at the genes of any two organisms, scientists can tell how related they are
For Example:
- Chimpanzees are 98% similar to humans
- Cats have 90% of the same genes as humans
- Cows are 80% genetically similar to humans
- 75% of mouse genes have equivalents in humans
- The fruit fly (Drosophila) shares about 60% of its DNA with humans
- About 60% of chicken genes correspond to a similar human gene
4. Biogeography
* Animals on different islands and continents are related to each other
* Their ancestors migrated to two different areas and adapted to those local environments
* All the continents used to be stuck together
* Their ancestors migrated to two different areas and adapted to those local environments
* All the continents used to be stuck together
5. Embryology
* Notice how all vertebrate embryos pass through the same stages
* We had tails and gill slits...and were all female in the beginning