1. The Evidence for Evolution

2. 1. Evidence of an OLD Earth
Fossils - show that life on earth has changed, some life forms that were present earlier, are not present today and vice-versa
Radiometric and Carbon Dating - scientists are able to see exactly how old the earth is by using radioactive decay of specific molecules. This is how they know how old rocks and fossils are. The earth is 4.6 billion years old.

3. 2. Biochemical evidence
Biologists have also observed unity in the structures and functions of organisms that are otherwise MUCH different.
For example, plants and animals share the same GENETIC CODE that passes on traits from one generation to the next.
What is that code called?
DNA

4. 3. Structural Evidence Another unity pattern can be seen in cells.
Many organisms are made of cells with similar structure and function.
Related limb patterns - same bone structure in similar, but different appendages (HOMOLOGOUS STRUCTURES)

5. Structural Evidence continued….
Some organisms have remnants of structures that their ancestors used, but are no longer used by the new species (VESTIGiAL STRUCTURES)
Vestigial structures are structures that are reduced in size and/or function; they are traces of similar organs in other species
leg./hip bones in whales/snakes, appendix in humans, etc.

6. 4. Embryological evidence
Embryos of different animals look so similar that they are hard to tell apart.
This shows that similar genes are at work

7. In conclusion….
All of these pieces of evidence point to and support Darwin’s principle of COMMON DESCENT
Common Descent - All living organisms evolved through gradual modification of earlier forms.
Remember that evolution is a VERY SLOW process
We will look at the mechanisms of evolution (how evolution happens) next.