1. Theory of Natural Selection
10.3 pg. 304

2. Artificial Selection
Where humans change a species by breeding it for certain traits.
Ex. Humans select traits that are favorable in plants and animals, then breed only those with the trait, producing more of that trait.

3. Heritability
The ability of a trait to be passed down from one generation to the next.

4. Struggle for survival
Resources are limited in a population, limiting population growth.
Food, water, shelter, disease limit population growth
Population – individuals of the same species that live in an area

5. Natural Selection
Mechanism where individuals that have inherited beneficial adaptations produce more offspring than other individuals.
Nature is the selecting agent

6. Four main principles of natural selection
1. Variation
2. Overproduction
3. Adaptation
4. Descent with modification

7. Variation
Heritable differences result from differences in the genetic material of an organism
Could be inherited from parent or the result of a mutation

8. Overproduction
Having more offspring raises the chance that some will survive, but it also results in more competition for resources

9. Adaptation
A certain variation may allow an individual to survive better than other individuals.
More successful individuals are
“naturally selected” to live longer
and produce more offspring.

10. Decent with modification
Over time, more individuals will have the favorable trait in every following generation, as long as environmental conditions stay the same.

11. Fitness
Fitness - The measure of the ability to survive and produce more offspring relative to other members of that population.

12. Genetic Variation within Populations
11.1 pg. 329

13. Genetic Variation Why its beneficial…
A population with a lot of genetic variation has a wide range of phenotypes.
A wide range of phenotypes means some individuals can adapt with a changing environment and survive.

14. Genetic Variation How its stored in a population…
Stored in a gene pool
The combined alleles of all individuals in a population

15. Genetic Variation How it’s measured… Measured by allele frequency
How common an allele is in a population

16. Mutations Random change in DNA of a gene
This can form a new allele, which can be passed to offspring if in a reproductive cell, increasing the variation in a gene pool

17. Recombination Happens when new allele combinations form in offspring.
Happens during meiosis

18. Natural Selection in Populations
11.2

19. Normal Distribution
Frequency is highest in the middle (mean) and decreases towards the extreme ends.
A population follows a normal distribution when: all phenotypes provide an equal chance of survival

20. Microevolution
Microevolution - a change observed in allele frequency in a population over time.
Microevolution occurs on a small scale.

21. Directional Selection
Selection that favors phenotypes at one extreme
Example:
Drug
resistant
bacteria

22. Stabilizing Selection
Selection that favors the intermediate phenotype, it is most common
Example:
Wasps

23. Disruptive Selection Selection that favors both extremes Example:
Buntings (species
of bird)

24. Other Mechanisms of Evolution
11.3 pg. 335

25. Gene Flow Definition: movement of alleles from one
population to another
How it works: occurs when
individuals move between
populations

26. Gene Flow Lots of gene flow between populations 
Increases genetic variation of receiving population & keeps gene pools similar
Limited gene flow between populations 
Two populations become more genetically different.
Species could possibly evolve into two different species.

27. Genetic Drift Definition: Change in allele frequencies due to chance.
How it works: causes loss of genetic diversity in a population.

28. Genetic Drift Key Terms Bottleneck Effect: occurs
after an event greatly
reduces the size of a
population

29. Genetic Drift Key Terms
Founder Effect: occurs after a small number of individuals colonize a new area.

30. Genetic Drift Negative Effects… Population losses genetic variation
Population is less likely to have individuals that can adapt to survive in changing environment
Lethal alleles carried by heterozygous individuals will become more common due to chance.

31. Sexual Selection
Definition: occurs when certain traits increase mating success.
How it works: Females are choosy about mates, forcing mates to have certain traits that will increase their mating success.

32. Sexual Selection Types
Intrasexual: involves competition among males; whoever wins, wins the female.
Bighorn sheep butting heads
Intersexual: males display certain
traits that will attract the female
Peacocks fanning tails
Frigate Birds

33. Speciation Through Isolation
11.5

34. Reproductive Isolation
Occurs when members of a population can no longer mate with each other
This is the final step in speciation…

35. speciation
The rise of 2 or more species from 1 species. (splitting of species into different species).
There are 3 reasons for speciation…

36. 1. Behavioral Isolation
Behavioral Isolation is caused by differences in…
Mating rituals
Chemical signals
Courtship songs/dances

37. 2. Geographic Isolation Geographic Isolation is caused by…
Physical separation
Distance between populations

38. 3. Temporal Isolation Temporal Isolation exists when…
Timing of mating rituals is off
Timing can change because of seasons, weather, time of day, etc.

39. Patterns in Evolution
11.6 pg. 347

40. Convergent Evolution
Evolution towards similar characteristics in unrelated species
Ex. Birds and insects with wings
Ex. Fins of sharks and dolphins

41. Divergent Evolution When closely related species evolve in different
directions and become
increasingly different.
Due to different
environments
Ex. Kit Fox and Red Fox

42. Coevolution
Process in which two or more species evolve in response to changes in each other.

43. Coevolution
Beneficial Relationships: Acacia plant and ants. Ants will hide in plants hollow holes and sting potential predators.

44. Coevolution
Evolutionary Arms Races: species respond to pressure from the other through better adaptations over generations.

45. Extinction Elimination of a whole species from Earth.
Ex - Tasmanian tiger—known as a thylacine

46. Extinction
Background Extinction: Occur continuously at a slow rate; part of the cycle of life.
Mass Extinction: Rare; operate at a global level, occurring suddenly due to a catastrophic event.

48. Patterns in Speciation
Punctuated Equilibrium: speciation occurs suddenly, not gradually and are followed by long periods of little evolutionary change.

49. Patterns in Speciation
Adaptive Radiation: diversification of one ancestral species in to many descent species (usually over a wide range of environments)