1. Natural Selection Videos Videos Natural selection Natural selection Speciation Population Genetics Population Genetics Evidence of evolution Evidence of evolution

2. Macroevolution Gradualism Evolution that occurs gradually over a long period of time. Punctuated Equilibrium Evolution that occurs very quickly after a long period of stability

3. Reproductive isolating mechanisms Prezygotic mechanism Factors that prevent individuals from mating Postzygotic mechanism Factors that allow an individual to reproduce but the offspring are infertile. Or Zygote forms but does not survive birth.

4. Isolating Mechanisms Geographic Isolation: Geographic Isolation: Species occur in different areas, and are often separated by terrestrial and aquatic barriers Species occur in different areas, and are often separated by terrestrial and aquatic barriers

5. Isolating Mechanisms Temporal Isolation: Temporal Isolation: Individuals do not mate because they are reproductively active and different times. Individuals do not mate because they are reproductively active and different times. Different times of day, different seasons Different times of day, different seasons

6. Isolating Mechanisms Ecological isolation: Ecological isolation: Individuals only mate within their preferred habitat. Individuals only mate within their preferred habitat.

7. Isolating Mechanisms Behavioral isolation: Behavioral isolation: Individuals of different species may meet, but one does not recognize the sexual cues that may be given. Individuals of different species may meet, but one does not recognize the sexual cues that may be given.

8. Isolating Mechanisms Mechanical isolation: Mechanical isolation: Copulation may be attempted but transfer of sperm does not take place. Copulation may be attempted but transfer of sperm does not take place.

9. Isolating Mechanisms Gametic incompatibility: Gametic incompatibility: Sperm transfer takes place, but the egg is not fertilized. Sperm transfer takes place, but the egg is not fertilized.

10. Artificial Selection

11. 3 Types of Natural Selection: Directional Selection Selects for one of the extreme phenotypes Selects for one of the extreme phenotypes - directional selection occurs in response to a change in the environment - directional selection occurs in response to a change in the environment that gives a competitive advantage to a particular phenotype that gives a competitive advantage to a particular phenotype

12. Examples of Directional Selection Bacteria developing resistance to antibiotics The beak sizes of ground finches on Daphne Island

13. 3 Types of Natural Selection: Stabilizing Selection Selects for the average phenotype and against the extreme phenotypes Selects for the average phenotype and against the extreme phenotypes Occurs when the environment is stable for long periods Occurs when the environment is stable for long periods Example birth weight of babies. Example birth weight of babies.

14. Stabilizing Selection

15. 3 Types of Natural Selection: Disruptive Selection Selects against the average and selects both extremes. Selects against the average and selects both extremes. Example: African Seed Crackers Example: African Seed Crackers

16. African Seed Crackers Birds feed on two types of seeds one large, one small. Birds with average size bills can’t eat either type efficiently And so aren’t common in the population

17. Genetic Drift: Another Force for Change Genetic Drift = Changes in a population’s gene pool that happen by chance Genetic Drift = Changes in a population’s gene pool that happen by chance - its effect is most profound in small populations populations - it reduces genetic variation in these - it reduces genetic variation in these populations populations - this could reduce a population’s ability to survive environmental change - this could reduce a population’s ability to survive environmental change

18. Genetic Drift Continued An organism can be well suited to its environment can be removed by chance An organism can be well suited to its environment can be removed by chance The result: Organisms The result: Organisms that aren’t as well that aren’t as well adapted can survive to adapted can survive to reproduce by chance reproduce by chance - this shifts the gene pool - this shifts the gene pool of the population of the population

19. Genetic Drift Once an allele is removed from a population, it is unlikely to return Once an allele is removed from a population, it is unlikely to return

20. Genetic Drift – The Bottle-neck effect Something happens to catastrophically reduce a population’s size for at least Something happens to catastrophically reduce a population’s size for at least one generation one generation Dramatically changes allele frequencies Dramatically changes allele frequencies in a small population in a small population

21. Bottle necked species Elephant seals hunted to near extinction – 20 individuals Elephant seals hunted to near extinction – 20 individuals - which 20 survived? The best adapted or the least desireable? Was their survival random luck? Was their survival random luck? -now number 30,000 but all individuals are descended from the 20 survivors -now number 30,000 but all individuals are descended from the 20 survivors -little genetic diversity this population has a reduced ability to survive an environmental challenge -little genetic diversity this population has a reduced ability to survive an environmental challenge

22. Founder Effect Occurs when a small population migrates to a new area or becomes isolated Occurs when a small population migrates to a new area or becomes isolated Limited gene pool – over time some generally rare traits become more common Limited gene pool – over time some generally rare traits become more common - Huntington’s disease in South Africa - Huntington’s disease in South Africa - Amish communities - Amish communities FE most commonly recognized in genetic disorders – occurs in other traits as well FE most commonly recognized in genetic disorders – occurs in other traits as well

23. Genetic Drift as a force for change In small isolated populations - genetic drift could allow otherwise rare alleles to become common - this could cause the isolated population to diverge from the main population and over time become a new species