1. Bellringer-5/11/15
What is evolution? Explain what you know.

2. EXPLORING CHANGE OVER TIME
Evolution
EXPLORING CHANGE OVER TIME

3. The Theory of Evolution
HOW DID ORGANISMS EVOLVE?

4. What is Evolution?
Evolution is the change in heritable traits through generations
CHANGE OVER TIME
Occurs in populations, not individual organisms

5. How Have Organisms Changed?
At the time life emerged on earth (about 3.8 billion years ago), the atmosphere is thought to have contained very little oxygen!
First cells were thought to be anaerobic
Recall that “anaerobic” means “without oxygen”
As the atmosphere of the Earth changed, so did the development of organisms

6. How Have Organisms Changed?
These prokaryotic (simple), anaerobic cells were able to exist in Earth’s early atmosphere
As Earth’s atmosphere and conditions changed, photosynthetic prokaryotes evolved, using sunlight to produce food
What molecule do photosynthetic organisms produce as byproduct (waste)?

7. How Have Organisms Changed?
Eventually, Earth’s atmosphere became filled with oxygen
Aerobic organisms evolved
This resulted in the evolution of eukaryotic complex multicellular organisms we have on Earth today!

8. The Endosymbiotic Theory
The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms.

9. Endosymbiotic Theory ~2 billion years ago:
Evolution of internal membranes in prokaryotes
The result was the ancestor of all eukaryotic cells.
Endosymbiotic theory: Eukaryotic cells formed from a symbiotic relationship among several different prokaryotic organisms
Prokaryotes that use oxygen to generate energy-rich molecules of ATP evolved into mitochondria.
Prokaryotes that carried out photosynthesis evolved into chloroplasts.

10. But what evidence supports the theory of evolution…?

11. Fossil Evidence
Fossils show us the similarities between organisms of the past and present
220 Million Years Ago 190 Million Years Ago Today

12. Similar Structures (Homologies)
Homologies describe similarities between the anatomical structures of species

13. Vestigial Structures
Vestigial structures are anatomical structures that still appear, but are no longer used!
Examples: Tails in humans, legs in snakes
Suggests that these structures may have existed at a previous time or in an ancestor; organisms evolved and structures not needed

14. Comparative Embryology
Insects and animals often have very similar embryonic development
Ex. All vertebrates (have a backbone) have similar development
Suggests a common ancestor

15. Biochemical (Molecular) Evidence
Comparison of DNA and macromolecules between organisms
Through gel electrophoresis
Tells us what organisms are closely related

16. NEW Evidence