1. Evidence supporting theory of evolution
Analogous structures
Structures similar in form and function.
Develop as a result of convergent evolution?

2. Evidence supporting theory of evolution
Life’s chemistry
Organisms are made of molecules and studying the molecules can help us understand possible relationships.
Example: Proteins
Made of amino acids bonded together.
Similar to a strand of pearls.
More closely related two organisms are, the more closely their proteins resemble each other.

3. Speciation Speciation: species giving rise to new species.
Some segment of original population must be isolated from the rest.
Reproductive isolation is an essential ingredient.
Occurs via two mechanisms:
Allopatric Speciation
Sympatric Speciation

4. Allopatric speciation
Definition: Speciation that occurs between isolated populations.
Originated in different fatherlands.
Must be geographically isolated.

5. Allopatric speciation
To reach and colonize new area, must realize three opportunities:
Geographic
Physiological
Ecological

6. Sympatric speciation
Definition: Speciation among populations whose ranges overlap.
Occur in same fatherland.
Can occur with species occupying different habitats, but in the same range.

7. Both types of speciation can be occurring at the same time.
Initially population is geographically isolated.
If geographic barrier is removed, populations overlap.
Could still be isolated by differences in preferred habitat, courtship displays, breeding season, preferred.

8. If not isolated by differences, then two populations will merge into one species.

9. Patterns in Evolution Convergent evolution
Unrelated species living in similar environments and facing similar environmental challenges sometimes evolve similar characteristics.

10. Patterns in Evolution Divergent evolution
Closely related species living in different environments and facing different environmental challenges sometimes evolve dissimilar characteristics.

11. Patterns in Evolution Adaptive radiation
Sometimes, several species will evolve from a single, ancestral species.

12. Patterns in Evolution Coevolution
Evolution of one species affects the evolution of another species.
As predators evolve, prey evolves. As prey evolves, predators evolve.
Example: Cheetahs feed on Thompson’s gazelles
As the speed of one population of cheetahs improves so does the speed of the Thompson’s gazelles .

13. Patterns in Evolution Gradualism
Evolution may occur as a slow, gradual process of change.
Theory favored by early evolutionists.

14. Patterns in Evolution Punctuated equilibrium
Evolution may proceed with long periods of relatively little change (stasis) punctuated with short periods of intense change.
Examples: House flies, trilobites, antibiotic-resistant bacteria.

15. Evolution does not always occur
Natural selection can only work on existing variation.
Variation cannot be created on demand.
Some species lack range of variation to support evolution.

16. Results of evolution
Everywhere we look on the Earth, you can find organisms.
Scientists have described 1.5 millions species
Still many species yet to be described.
Predictions indicate there may be times as many species as those already described.

17. Darwin’s Theory Debated
Three main criticisms:
Darwin lacked direct evidence for natural selection.
Indirect evidence was unconvincing
Darwin could not explain the source of variation in a population and inheritance of variation.
Answered by an understanding of genetics
What is the rate at which organisms evolve?
Slow and continuous or jerky and discontinuous?

18. Darwin recognizes three special cases of natural selection
Sexual selection explained flamboyant appearance amongst birds.
Sexual selection: female birds choose mates and are attracted to males with extreme features.
Females breed with them and extreme features passed to offspring.

19. Darwin recognizes three special cases of natural selection
Altruism
Individual behavior benefits a social group often at the expense of the individual.
Example: worker bees in a hive
Kin Selection
Individuals help kin raise their young.