1. Evidence of Evolution
Organism DNA
1a. Some of the strongest evidence for evolutionary relationships comes from studying the DNA of different organisms.
1b. The fact that all organisms use the same DNA molecule to code for genetic information suggests that these organisms share a distant ancestor.

2. Evidence of Evolution 2. Embryonic Development
2a. Among vertebrates, the early stages of embryonic development share many similarities.
2b. Embryos of humans, chickens, and turtles aren’t identical but their embryonic cells have the same order of development, shape, and tissue structure.

3. Evidence of Evolution
3. Homologous Structures
3a. Eventually, these similarities give rise to what are known as homologous structures.
Example: The forelimbs of many animals (dolphins, bats, alligators, and humans) share many of the same type of bones.

4. Evidence of Evolution
3. Homologous Structures
3b. They may have different functions, but the similar pattern of bones provides strong evidence that vertebrates all descended from a common ancestor.

5. Checkpoint 1
Although human, whale, and bird forelimbs have different functions, their parts and basic structure are similar. What does this suggest about the ancestry of humans, whales, and birds?

6. Evidence of Evolution
4. Vestigial Structures
4a. Many organisms also have vestigial structures, features that don’t serve a purpose in an organisms body but are homologous structures possessed by other organisms.
The human tailbone and appendix.
Remnants of hind limbs in some species of whales and snakes.

7. Evidence of Evolution
5. Fossils
5a. Fossils are the mineralized remains of organisms that died thousands, millions, or even billions of years ago.

8. Evidence of Evolution
5. Fossils
5b. The fossils and their relative locations leave behind clues to:
What the region’s climate was like.
How habitats changed.
When a new species appeared in the region.

9. Evidence of Evolution
5. Fossils
5c. When we find fossils of related animas across a long span of geologic time, we’re sometimes able to understand how modern animals developed.
5d. This collection of fossils and the information that scientists have gathered from them is known as the fossil record.

10. Evidence of Evolution 5e. One such animal is the horse.
5. Fossils
5e. One such animal is the horse.
Eohippus, or “dawn horse”, lived about 55 million years ago.
It stood less than 1m high and had 3 soft toes instead of a hoof.

11. Evidence of Evolution
5. Fossils
5f. Scientists can trace a very clear line of relationship between Eohippus and the modern horse, because each step in the family tree represents a very small but very noticeable change.

12. Evidence of Evolution
5. Fossils
5g. Miohippus is undeniably related to Epihippus.
But there are clear differences found in rock layers of different ages.

13. Evidence of Evolution 5h. Although the modern horse has:
5. Fossils
5h. Although the modern horse has:
A much more complex brain
A larger size
Different toe structure (hoof)
It still shows the forelimb structure (and many other structures) of Eohippus.

14. Checkpoint 2
On the diagram, find the horse called Merychippus. Then look at the 20 million years following it. Describe the importance of Merychippus to horse evolution.

15. Checkpoint 3
If the line from Eohippus that eventually led to the modern horse was the only one that was eventually “successful,” why do you think that so many other types of prehistoric horses lived and then went extinct?

16. EXAM FRIDAY!!! Agenda 3/5/13 Assignment: Homework:
Evidence of Evolution
Homework:
Fossils and the Fossil Record Reading Questions