1. Some Evidence of Evolution
Geographic Locations
Anatomical Similarities
Developmental Similarities
Molecular (biochemical) Similarities

2. Some Evidence of Evolution
Geographic Locations

3. Some Evidence of Evolution
Anatomical Similarities
Homologous Structures = structural features with a common evolutionary origin. Similar in arrangement, function or both.

4. Some Evidence of Evolution
Anatomical Similarities
Homologous Structures

5. Some Evidence of Evolution
Anatomical Similarities
Homologous Structures

6. Analogous Structure = A structural or functional similarity of a body feature, but not related.
Example: Insect & bird wings are similar in function, but not structure

7. Some Evidence of Evolution
Anatomical Similarities
Vestigial Structures = a body structure that has no function in a present-day organism but was probably useful to an ancestor.

8. Some Evidence of Evolution
Anatomical Similarities
Vestigial Structures

9. Some Evidence of Evolution
Anatomical Similarities
Fossils

10. 1. Trace Fossils

11. 2. Casts

12. 3. Imprints

13. 4.Amber-Preserved & Frozen

14. 5. Petrified

15. 6. Molds

16. Some Evidence of Evolution
Developmental Similarities
Comparative embryology
Early developmental stages are compared.
Related embryos look similar.

17. Some Evidence of Evolution
Developmental Similarities
Comparative embryology

18. Some Evidence of Evolution
Molecular (biochemical) Similarities

19. Natural Selection
1. Variations exist in a population

20. Sweet! I’m better at surviving because I blend into my surroundings!
Natural Selection
2. Some variations improve the ability to survive and reproduce in the particular environment
Sweet! I’m better at surviving because I blend into my surroundings!
Boo!

21. I have more fitness than you!
Natural Selection
3. The individuals with the adaptive traits are more likely to pass on their genes to future generations
Boo!
I have more fitness than you!

22. Natural Selection
4. Over time, the frequency of adaptive alleles increases = evolution.

23. Question Break True or False? Individual organisms evolve.
Which of the following is NOT needed for natural selection to occur?
a. Heritable variation
b. Competition
c. Fossil evidence
d. Different levels of fitness

24. Speciation
One species splits into two due to isolation (geographic, reproductive, etc…)
Also known as Divergent Evolution… results in homologous structures between groups

25. Speciation
Hurricane

26. Speciation
The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Morphology, food preferences, and courtship displays change over the course of many generations of natural selection.

27. Speciation
So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. The lineage has split now that genes cannot flow between the populations.

28. Speciation

29. Speciation
The first steps of speciation have been produced in several laboratory experiments involving “geographic” isolation. For example, Diane Dodd took fruit flies from a single population and divided them into separate populations living in different cages to simulate geographic isolation. Half of the populations lived on maltose-based food, and the other populations lived on starch-based foods. After many generations, the flies were tested to see which flies they preferred to mate with. Dodd found that some reproductive isolation had occurred as a result of the geographic isolation and selection in the different environments: “maltose flies” preferred other “maltose flies,” and “starch flies” preferred other “starch flies.”

30. What is a species?
A group of interbreeding populations that cannot breed with other groups.
Giraffes and Elephants?
German Shepards and Poodles?

31. Maintaining Species Individuality
Ecological (geographic) Isolation – not around each other
Behavioral isolation – different species don’t understand each other’s mating rituals
Temporal isolation – different breeding seasons
Mechanical isolation – structural differences preventing mating

32. Speciation may lead to extreme genotype survival
What is a genotype?
Environment may favor extreme genotypes.
Over time, extremes thrive, middle genotype extinct.

33. Direction of Natural Selection and Species Formation
Stabilizing – extremes not favored (example – human birth weight)
Disruptive – extremes favored (example - short or long beaks not medium beaks)
Directional – extremes at one end favored

34. Convergent Evolution – when species become more alike
Animals live apart but in similar environments
Desirable traits are same
Example – rabbit and squirrel color