1. Mechanisms of Evolution

2. Gene Pool
Combined genetic information of all the members of a particular population

3. Directional Selection
Form of natural selection in which the entire curve moves. Favors an extreme trait
one extreme of the trait experiences selection against it so trait shifts toward the other extreme
Example: there was a selection pressure against short giraffe necks, since giraffes with short necks could not reach as many leaves to feed. As a result, the distribution of neck length shifted to favor individuals with long necks
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4. Stabilizing Selection
Form of natural selection by which the center of the curve remains in its current position. selects against the two extremes of a trait
EX. A plant that is too short may not be able to compete with other plants for sunlight. However, extremely tall plants may be more susceptible to wind damage. Combined, these maintain plants of medium height. The number of plants of medium height will increase while the numbers of short and tall plants will decrease.

5. Disruptive Selection
Form of natural selection in which a single curve splits into two
Select against individuals in the middle
Example: imagine a plant that is pollinated by three different pollinators, one that was attracted to short plants, another that preferred plants of medium height and a third that visited only the tallest plants. If the pollinator that preferred plants of medium height disappeared from an area, medium height plants would be selected against and the population would lean toward both short and tall, but not medium height plants

6. Genetic Drift
A random event that results in part of a population being removed, regardless of their adaptations.
Resulting population is successful because they are lucky not necessarily better adapted.

7. True or False
A gene pool is all of the genetic information for a population.

8. True!

9. True or False
Disruptive Selection means that the medium trait is going to be favored.

10. False
Both ends of the graph are favored (extremes)

11. True or False
Genetic Drift is a random event that removes genes from the gene pool.

12. True!

13. Bottleneck Effect
Caused by genetic drift: populations size is reduced; can reduce genetic variation.
Example of a bottleneck: Northern elephant seals have reduced genetic variation because of a population bottleneck humans inflicted on them by hunting them. Hunters reduced population to 20 individuals.Their population has since rebounded to over 30,000—but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.

14. Founder’s Effect
Caused by genetic drift: Occurs when a new colony is started by a few members of the original population. Can reduce genetic variation.
Example, the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington’s disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency.
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15. Gene Flow
Transfer of genes from one population to another; causes genetic variation
Ex. Immigration

16. Speciation Formation of a new species
When 2 populations of species become so drastic they can no longer interbreed, they are considered 2 different species .
Ex. Salamanders in California

17. True or False
The founder’s effect means that only a few genes are being passed to each generation because they come from one group of settlers

18. True

19. True or False
Gene flow means that it is a random event and does not introduce new traits.

20. False

21. Reproductive Isolation
Separation of a species or population so that they cannot interbreed and produce fertile offspring
Ex. Horse + Donkey=Mule
What’s special about a mule? What sex is a mule?
Can they reproduce? Why?

22. Behavioral Isolation
Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding
Ex. Birds dance/pose/sing to attract a mate

23. Geographical Isolation
Form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

24. Temporal Isolation
Form of reproductive isolation in which two populations reproduce at different times
Closely related species fireflies mate at different times of night
Frog species live and breed same pond reproduce different times of year
Plants frequently have differing flowering seasons
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25. True or False
Behavioral isolation means that organisms do not recognize the other one hitting on them.

26. True or False
Geographical isolation does not result in new species

27. False

28. Mimicry
An organism that evolves to look like another organism in order to survive
Ex. King cobra and coral snake

29. Camouflage
Organism that evolves to look like the environment in order to survive
Ex. Iguana and walking stick

30. Resistance The capacity of a species or strain of
microorganism to survive exposure to a
toxic agent (as a drug) formerly effective
against it
Ex. Bacteria and penicillin
A population is treated with a chemical Individuals with a mutation are immune to chemical and don’t die. Next generation is not susceptible to chemical because most offspring had immune(resistant) parents who were able to survive and reproduce

31. True or False
Mimicry and camouflage mean the same thing.

32. False