bio final ch23.txt
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How can you define evolution on its smallest scale?
What is genetic variation?
Differences amoung individuals in the composition of their genes or other DNA segements.
Explain geographic variation.
Differences in the genetic composition of separate populations. Remember the house mice that have diferent number of chromosomes because they are separated by mountains on an Atlantic island.
A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring?
A population's genetic makeup is decribed as a gene pool, which is?
A gene pool consists of all copies of every type of allele at every locus in all members of the population.
+ 2pq + q2
- 1. No mutations
- 2. Random mating
- 3.No natural selection
- 4. Extremely large population size
- 5. No gene flow
What is Natural Selection?
The type of selective force that determines whether or not a population will evolve.
A difference, on average, between the survival and capacity for reproduction between individual with certain phenotypes compared to individuals with other phenotypes.
What process can cause chance events that fluctuate allele frequencies unpredictably from one generation to the next, especially in small populations?
Genetic drift. Remember the flower graphic.
What is Founder Effect?
When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population.
A sudden change in the environment, such as a fire or flood, may drastically reduce the size of a population.
Four Key Points of Genetic Drift
- 1. Genetic drift is significant in small populations.
- 2. Genetic drift can cause allele frequencies to change at random.
- 3. Genetic drift can lead to a loss of genetic variation within populations. Remember flower graphic.
- 4. Genetic drift can cause harmful alleles to become fixed.
What is gene flow?
The transfer of alleles into or out of a population due to movement of fertile individuals or their gametes.
What is relative fitness?
The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.
Types of Natural Selection
- Directional selection - when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a population's frequency curve for the phenotypic character in one direction or the other.
- Disruptive (Diversifying) selection - when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediat phenotypes.
- Stabilizing selection - acts against both extreme phenotypes and favors intermediate variants.
What is sexual selection?
A form of selection in which individuals with certain inheirted characteristics are more likely than other individuals to obtain mates.
What is sexual dimorphism?
A difference between the two sexes in secondary sexual characteristics.
Selection within the same sex, individuals of one sex compete directly for mates of the opposite sex.
individuals of one sex (ususally the females) are choosy in selecting their mates from the other sex.
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