1. Evolution and Natural Selection
Kelley Kuhn and Jack Pickett
CCA 2012

2. Evolution of Cartoon Fossils
You have been given a sheet showing many cartoon fossils. Cut them out. You and your partner will examine the drawings and make a list of shared characteristics that you notice vary among the fossils.
Arrange the cartoons in the order you think they may have evolved. Propose a hypothesis that explains the trend in features (such as feet, length of tail, teeth, etc.) Discuss the environment that selected for these traits.
Glue your cutouts onto a long strip of paper in the order that you selected in step 2. Write a detailed statement that summarizes your explanation on separate sheet of paper and staple this to your strip.
FOR EACH TRAIT, IDENTIFY THE ENVIRONMENTAL OR SEXUAL SELECTION THAT SELECTED FOR THAT TRAIT.

3. Natural Selection
1. More offspring are generated than the environment can support.
2. Variation exists among members of a population. (Some are faster, furrier, fatter, funnier. )
3. Those members with the best variations are most likely to survive and reproduce. (The faster bunny can escape the fox; the young comedian can joke his way out of a mortal conflict.)
4. Over time, the least beneficial traits are lost in a population of organisms and most beneficial are “selected for” so that changes slowly accumulate and new species evolve.

4. Factors that impact selection
Environment
Climate factors like rain fall and seasonal temperatures
Predators
Vegetation
Health of soil
Food source
Mating preference (aka sexual selection)

5. Types of Natural Selection
Stabilizing Selection-- The extremes are selected against.
Example: height; mostly beings tend to the average height- not too many really short ones or really tall ones.
Directional selection-- One extreme value is selected.
Example: speed; faster is always better so a population will tend to get faster over time. Also, giraffe necks…longer necks = more food.
Disruptive selection-- The extremes are both selected.
This type of selection is not as common as the first two. Example: Prey-type animal with distinctive markings which the predators know will over time move away from the norm in both directions.

6. What type of selection?

7. What type of selection?

8. What type of natural selection?

9. Argh! A Charlie Brown moment
One last time…
For your notes.

10. EVIDENCES FOR EVOLUTION
1. The fossil record (Older rock layers contain simpler fossils than younger rock layers.)
2. Homologous structures (Many structures in animals are similar in structure and arrangement but may not be used the same way.)
3. DNA/Protein sequence similarities (Organisms that are similar in appearance have sequences that are very similar.)
4. Vestigial structures (Structures that are present in an organism but are not longer used to help it survive, i.e. appendix and tail bone in humans.)

11. Analogous versus Homologous Structures Convergent Evolution versus Divergent Evolution
Analogous structures are structures that have similar functions, like the wings of a bat and the wings of a bird. They are considered a type of CONVERGENT EVOLUTION because these organisms to not share a recent common ancestor but their environments selected for a structure with a similar use.
Homologous structures are structures in related organisms that evolved over time from a common ancestor but are no longer similar in use due to differences in each organism’s environmental habitat. For example, the arrangement of bones in the human arm and the bat wing indicate a common ancestor despite the fact that their uses are now very different. This is an example of DIVERGENT EVOLUTION.

12. HOMOLOGOUS STRUCTURES

13. Analogous Structures Bat and bird

14. Classic fossils of the United States
Grand canyon fossil examples

15. Why might some of these rock layers be missing?

16. What can you assume about the fossils shown?