1. Industrial Melanism and Microevolution

2. Hierarchical Classification

3. Gene Flow additions to and/or subtractions from
a population resulting in the movement
of fertile individuals or gametes

4. Gene Flow and Human Evolution
Increasing migra-
tion of people
throughout the
world has contributed
to an increase in
gene flow

5. Mutation and Sexual Recombination
produce the variation that makes
evolution possible

6. Genetic Drift occurs by chance when only
certain members of a population reproduce
and pass on their genes

7. Genetic Drift

8. Bottleneck Effect: a sudden change in the
environment drastically reduces the size of the population

9. Cheetah

10. Northern Elephant Seals

11. Founder Effect: Polydactylism in the Amish Population migration of
a small subgroup
of the population

12. Founder Effect in Amish
Ellis-van Creveld Syndrome
Causes dwarfism and polydactyly

13. The evolution of fruit fly (Drosophila) species on the Hawaiian archipelago (Founder Effect)

14. Natural Selection is the primary mechanism of adaptive evolution
Out of all the factors that can affect a gene pool only natural selection is likely to adapt a population to its environment

15. Mapping Malaria and the Sickle-Cell Allele
This is a good example of
heterozygote
advantage.

16. Modes of Selection

17. Types of Selection
Most traits are polygenic - variations in the trait result in a bell-shaped curve
Three types of selection occur:
Directional Selection – the curve shifts in one direction ex: resistance to antibiotics by bacteria

18. Directional Selection

19. Evolution of the Horse over 50 million yrs

20. Hyracotherium
American Museum
of Natural History

21. Orohippus
Note the
toes!

22. Directional selection for beak size in a Galápagos population of the medium ground finch

23. Types of Selection (2) Stabilizing Selection
Ex - when human babies with low or high birth weight are less likely to survive

24. Stabilizing Selection

26. Cepaea
Snails
Disruptive Selection

27. (3) Disruptive Selection
The curve has two peaks; dark shells
appear in most forested areas whereas
light-banded shells appear in areas of low lying vegetation
Ex – When Cepaea snails vary because a wide geographic range causes selection to vary

28. Disruptive or Diversifying Selection
Small-billed birds feed on soft seeds; large-
billed birds feed on hard seeds (Black-
bellied Seed Crackers – Cameroon, Africa)

29. The Two-Fold Disadvantage of Sex

30. Why Natural Selection Cannot Fashion
Perfect Organisms
Evolution is limited by historical constraints.
2) Adaptations are often compromises.
3) Chance and natural selection interact.
4) Selection can only edit existing variations.

31. Natural selection can affect the
distribution of phenotypes in
three ways. They are:
_______________ selection
and
_______________ selection.

32. A small population of organisms is
suddenly cut off from the others
in the population. This is known as
the _____________ effect.
A small group of organisms migrates from
one area to another. There is not a wide
variation in the gene pool. This is known
as the ___________ effect.