1. Industrial Melanism and Microevolution

2. Microevolution of the fruit fly (Drosophila) species on the Hawaiian archipelago

3. Hierarchical Classification

4. (rat snakes) Gene Flow additions to and/or subtractions from
a population resulting in the movement
of fertile individuals or gametes
(rat snakes)

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

6. Out of Africa Likely migration paths of humans out of Africa
10-20,000ya
10-20,000ya
Migration Paths
According to the "Out of Africa" theory, modern humans appeared as a single African species nearly 100,000 years ago, then spread throughout the world (K.Wong, Is Out of Africa Going Out the Door?, Scientific American 281(2), August 1999).
50,000ya
Many patterns of human traits reflect this migration

7. Variation & Natural Selection
Variation is the raw material for natural selection
there have to be differences within population
some individuals must be more fit than others

8. Five Agents of Evolutionary Change
Mutation
Gene Flow
Non-random mating
Genetic Drift
Selection

9. Not every mutation has a visible effect.
Mutation & Variation
Mutation creates variation
new mutations are constantly appearing
Mutation changes DNA sequence
changes amino acid sequence
changes protein’s:
Structure
function
changes in protein may change phenotype & therefore change fitness
Every individual has hundreds of mutations
1 in 100,000 bases copied
3 billion bases in human genome
But most happen in introns, spacers, junk of various kind
Not every mutation has a visible effect.
Some effects on subtle.
May just affect rate of expression of a gene.

10. Gene Flow Movement of individuals & alleles in & out of populations
seed & pollen distribution by wind & insect
migration of animals
sub-populations may have different allele frequencies
causes genetic mixing across regions
reduce differences between populations

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

12. Bottleneck Effect
When large population is drastically reduced by a disaster
famine, natural disaster, loss of habitat…
loss of variation by chance event
alleles lost from gene pool
not due to fitness
narrows the gene pool

13. Cheetahs All cheetahs share a small number of alleles 2 bottlenecks
less than 1% diversity
as if all cheetahs are identical twins
2 bottlenecks
10,000 years ago
Ice Age
last 100 years
poaching & loss of habitat

14. Northern Elephant Seals
Hunted to nearly extinction in
the late 1800s for their oil.

15. Founder Effect: Polydactylism in the Amish Population migration of
a small subgroup
of the population;
a type of genetic drift

16. Amish Country:
Lancaster County, Pennsylvania

17. One Room Schoolhouse -Amish Country: Lancaster County, PA

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

21. Founder Effect
When a new population is started by only a few individuals
some rare alleles may be at high frequency; others may be missing
skew the gene pool of new population
human populations that started from small group of colonists
Small founder group, less genetic diversity than Africans
All white people around the world are descended from a small group of ancestors
100,000 years ago
(Chinese are white people!)

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

23. 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

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

25. Modes of Selection

26. Directional
Selection

27. Evolution of the Horse over 50 million yrs

28. Hyracotherium
American Museum
of Natural History

29. Orohippus
Note the
toes!

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

31. Stabilizing Selection

33. Cepaea
Snails
Disruptive Selection

34. 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

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

36. The Two-Fold Disadvantage of Sex

37. 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

38. 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.

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

40. 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.

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