1. Natural Selection and Darwin’s ideas Evolution Activity Start Pre-lab
Objective:
I can determine why natural selection is a key part of Evolution.
Agenda:
Natural Selection and Darwin’s ideas
Evolution Activity
Start Pre-lab

2. How would you define POPULATION?
___________________________________________________________________________

3. How do genetic variations occur?
What is Evolution?
Change in the genetic makeup of a population over time.
Fitness – _________________________________________________________.
Populations can evolve, not individuals.
Diverse gene pool good for long-term survival of a species. ________________are important!
How do genetic variations occur?

4. Where does Variation come from?
Mutation
random changes to DNA
____________________
environmental damage
Sexual reproduction
_________________
genetic recombination
new arrangements of alleles in every offspring
__________________________________

5. “The Origin of Species”
Documented the occurrence of ____________.
Suggested that the mechanism for evolution was ______________.

6. Observations:
Observation 1 – ______________________________________________________________. .

7. Observation 2
Traits are inherited from _________________.

8. Observation 3
All species are capable of producing more _______________their environment can support.

9. Observation 4
Owing to lack of food or other resources, __________________________________.

10. Inference 1 Individuals _______________________
higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.

11. Inference 2
This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.

12. Nature Determines which characteristics are favorable.
_______________________.
Result - “Natural Selection”

13. Artificial Selection
When man determines the characteristics that survive and reproduce.
Result - the various breeds of animals and plants we’ve developed.

15. Evolution Success Measured By
______________
Whoever lives long enough and has kids is the “winner” in evolution.

16. Requirements In order for Natural Selection to work, you must have:
_____________________.
Long periods of time (according to Darwin).

17. Natural Selection 1. Populations are the units of Evolution.
2. __________________________________.

18. Comment
Acquired characteristics may allow a species to evolve "outside" of Natural Selection.
_______________

21. Essence of Darwin’s ideas
Natural selection
heritable variation exists in populations
______________________
more offspring than the environment can support
_____________
for food, mates, nesting sites, escape predators
differential survival
successful traits = _____________
differential reproduction
adaptations become more common in population

22. 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 

23. DIRECTIONAL SELECTION STABILIZING SELECTION
Effects of Selection
DIRECTIONAL SELECTION
STABILIZING SELECTION
DISRUPTIVE SELECTION
Changes in the average trait of a population
giraffe neck
horse size
human birth weight
rock pocket mice

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

25. II. GENETIC DRIFT
The smaller the population, the less genetic variety it has.
In a very small population, alleles can be lost from one generation to the next, simply by random chance.
When a population evolves only because of this type of random sampling error, _____________is taking place.

26. Genetic Drift
Chance events changing frequency of traits in a population
not adaptation to environmental conditions
not selection
____________
small group splinters off & starts a new colony
it’s random who joins the group
___________
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

27. FOUNDER EFFECT

28. BOTTLENECK EFFECT

29. 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

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

31. Human Impact on variation
How do we affect variation in other populations?
Artificial selection/Inbreeding
Animal breeds
___________________
Insecticide usage
resistant bacterial strains