1. Chapters 22, 23, 24, (25 and 26?) Test on Friday, March 13, 2015
Evolution Unit
Chapters 22, 23, 24, (25 and 26?)
Test on Friday, March 13, 2015

2. Charles Darwin (1809-1882) Born in England
Attended medical school, HATED IT, and dropped out to become a priest
Liked to stuff birds instead of dissect humans
Didn’t like grave robbing for bodies
Boarded the H.M.S. Beagle for a 5 year UNPAID journey as a naturalist

3. Charles Darwin “Descent with modification” from an ancestral species
November 24th 1859

4. What is Evolution? GENE POOL!
Change in the genetic makeup of a population over time.
Fitness – those with favorable variations will survive and reproduce.
Populations can evolve, not individuals.
Diverse gene pool good for long-term survival of a species. Genetic variations are important!
GENE POOL!

5. Alfred Russel Wallace (1823-1913)
Presented a paper with identical ideas as Darwin on July 1, 1858 at the Linnaean Society meeting
Was a botanist who came up with virtually the same concept of natural selection more or less independently through his studies on the Malay archipelago. Darwin panicked because he was not ready with his book yet!

6. Lamarckian vs. Darwinian view
in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring
Darwin
giraffes born with longer necks survive better & leave more offspring who inherit their long necks 

7. Where does Variation come from?
Mutation
random changes to DNA
errors in mitosis & meiosis
environmental damage
Sexual reproduction
mixing of alleles
genetic recombination
new arrangements of alleles in every offspring
new combinations = new phenotypes

8. Genetic variation in a population

9. Evolution Things to remember:
a.  Individuals cannot evolve.  Populations evolve.
b.  Natural selection is the mechanism of evolution.
c.  Evolution occurs by chance (NOT GOAL ORIENTED).

10. SO WHAT IS THIS THEORY OF NATURAL SELECTION?
It can be broken down into four basic tenets, or ideas

11. Theory of Natural Selection
1. Organisms are capable of producing huge numbers of offspring.
2. Those offspring are variable in appearance and function, and some of those variations are heritable.

12. Theory of Natural Selection
3. Environmental resources are limited, and those varied offspring must compete for their share.
4. Survival and reproduction of the varied offspring is not random. Those individuals whose inherited characteristics make them better able to compete for resources will live longer and leave more offspring than those not as able to compete for those limited resources.

13. Natural Selection
Adaptation = a genetic variation favored by natural selection. When allele frequencies shift, speciation occurs
ie…. Heterozygote Advantage
(Keeps the recessive allele in the
population)
Ex: Sickle Cell Anemia
aa – dies of sickle cell anemia
Aa – some side affects
BUT resistant to malaria!
AA – no disease present
BUT prone to malaria

14. Natural Selection in Action
Camouflage
(Cryptic coloration)

15. Natural Selection in Action
Industrial melanism

16. Natural Selection in Action
Mullerian Mimicry – Unpalatable mimics unpalatable
Monarch or Viceroy Butterfly

17. Natural Selection in Action
Batesian Mimicry – Palatable mimics unpalatable
Coral vs. King Snakes: Red on yellow, kill a fellow, red on black won’t hurt Jack

18. Natural Selection in Action
Warning Coloration (Aposematic coloration)

19. Natural Selection in Action
Disruptive Coloration

20. Natural Selection in Action
Counter Shading

21. Natural Selection in Action
Eye spots

22. Effects of Selection
Stabilizing Selection - average phenotypes have a selective advantage over the extreme phenotypes
Directional Selection - phenotype at one extreme has a selective advantage over those at the other extreme
Disruptive Selection - both extreme phenotypes are favored over the intermediate phenotypes

23. Modes of Selection Original population Frequency of individuals
In this case, darker mice are favored
because they live among dark
rocks and a darker fur color conceals
Them from predators.
These mice have colonized a
patchy habitat made up of light
and dark rocks, with the result
that mice of an intermediate
color are at a disadvantage.
If the environment consists of
rocks of an intermediate color,
both light and dark mice will
be selected against.
Phenotypes (fur color)
Original population
Original
population
Evolved
Frequency of individuals

24. In addition to natural selection, evolutionary change is also driven by random processes…

25. Genetic Drift
Chance events changing frequency of traits in a population
not adaptation to environmental conditions
not selection
founder effect
small group splinters off & starts a new colony
it’s random who joins the group
bottleneck
a disaster reduces population to small number & then population recovers & expands again but from a limited gene pool
who survives disaster may be random
Founders: When a new population is started by only a small group of individuals. Just by chance some rare alleles may be at high frequency; others may be missing; skew the gene pool of new population. Ex: human populations that started from small group of colonists
example: colonization of New World
Bottleneck: 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

26. Ex: Cheetahs All cheetahs share a small number of alleles
less than 1% diversity
2 bottlenecks
10,000 years ago
Ice Age
last 100 years
poaching & loss of habitat

27. Peregrine Falcon
Conservation issues
Bottlenecking is an important concept in conservation biology of endangered species
loss of alleles from gene pool
reduces variation
reduces adaptability
Breeding programs must consciously outcross
Golden Lion Tamarin

28. Human Impact on variation
How do we affect variation in other populations?
Artificial selection/Inbreeding
Animal breeds
Loss of genetic diversity
Insecticide usage
Overuse of antibiotics
resistant bacterial strains

29. Hidden variations can be exposed through selection!
Terminal
bud
Lateral
buds
Brussels sprouts
Cabbage
Flower cluster
Leaves
Cauliflower
Flower
and
stems
Broccoli
Wild mustard
Kohlrabi
Stem
Kale
Artificial selection

30. Note the Difference Macroevolution
-Evolutionary change above the species level e.g. the appearance of feathers on dinosaurs
Macroevolutionary change
Is the cumulative change during thousands of small speciation episodes
Microevolution
Is change in the genetic makeup of a population from generation to generation