Evolution

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Evolution
.the process by which the earliest forms on
Earth have been transformed into the vast
diversity of life forms seen today (Raven,
Evert, and Eichhorn 1999).
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Natural selection
.the process by which certain favorable
mutations become more and more common from one
generation to the next (Raven, Evert, and
Eichhorn 1999). and unfavorable mutations
become less common.
3
Species
a group of populations that have the potential
to interbreed in nature (Raven, Evert, and
Eichhorn 1999).
4
Allele
The different forms of a gene are called
alleles (Raven, Evert, and Eichhorn 1999).
5
Gene pool
all the alleles of all the genes of all the
individuals in the population. (Raven, Evert,
and Eichhorn 1999). The pool is imaginary
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Population genetics
Population geneticists are interested in gene
pools, the changes in their composition over
time, and the forces causing these changes
(Raven, Evert, and Eichhorn 1999).
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Fitness
The extent to which the alleles in an
individuals genotype are present in succeeding
generations (Raven, Evert, and Eichhorn 1999).
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Fitness
What factors contribute to an individuals
fitness?
9
Hardy-Weinberg equilibrium
The null hypothesis against which evolutionary
change is measured.
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Hardy-Weinberg equilibrium
The frequencies of alleles in a populations gene
pool remain constant from generation to
generation. ASSUMING 1. No mutations. 2.
Isolation from other populations. 3. Large
population size. 4. Random mating. 5. No
natural or artificial selection.
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1. Mutation
mutations are inheritable changes in the
genotype (Raven, Evert, and Eichhorn
1999). changes in individual alleles.
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Mutation
Mutation generates the differences on which other
evolutionary forces act.
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2. Gene flow
Gene flow is the immigration or emigration of
individuals (or pollen) between populations.
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Gene flow
Gene flow tends to decrease the differences
between populations. For plants, gene flow tends
to decrease as the distance between populations
increases.
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3. Genetic drift
A change in population gene frequencies that is
the result of chance sampling of individuals from
one generation to the next.
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Genetic drift
A change in population gene frequencies that is
the result of chance sampling of individuals from
one generation to the next. Two situations that
can have important consequences Founder
effect Bottleneck effect
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4. Nonrandom mating
Mating by individuals that are more similar or
different genetically, on average, than two
individuals drawn at random from the population.
Inbreeding Self-pollination Outcrossing
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Locus
The location of a gene on a chromosome.
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Homozygote vs. Heterozygote
Homozygote an individual with two copies of the
same allele at a locus. Heterozygote an
individual with two different alleles at a locus.
20
Nonrandom mating
Inbreeding and self-pollination tend to increase
the number of homozygotes (individuals with two
copies of the same allele) in a
population. Outcrossing tends to increase the
number of heterozygotes in a population.
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5. Selection
.the process by which certain favorable
mutations become more and more common from one
generation to the next (Raven, Evert, and
Eichhorn 1999). or unfavorable genes become
less common.
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Causes of evolution
The frequency of alleles in a populations gene
pool can change from generation to generation,
due to 1. Mutations. 2. Gene flow from other
populations. 3. Small population size. 4.
Non-random mating. 5. Selection.
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Hardy-Weinberg equilibrium
The frequencies of alleles in a populations gene
pool remain constant from generation to
generation. ASSUMING 1. No mutations. 2.
Isolation from other populations. 3. Large
population size. 4. Random mating. 5. No
natural or artificial selection.
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Maintenance of variability
Genetic variability is preserved and promoted
by Sexual recombination Outbreeding
promotion Diploidy Heterozygote advantage
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Phenotype vs. genotype
Genotype is the genetic makeup, or alleles
possessed by an individual. Phenotype is the
physical expression of the genotype.
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Adaptation
Developmental plasticity the tendency for
individuals phenotypes to vary in response to
environmental conditions.
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Species
a species is a group of natural populations
whose members can interbreed with one another but
cannot (or usually do not) interbreed with
members of other such groups (Raven, Evert, and
Eichhorn 1999). This is the biological species
concept.
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Speciation
Allopatric vs. sympatric speciation
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Reproductive isolation
Prezygotic mechanisms Postzygotic mechanisms
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Next Systematics
Assignment Choose any 5 boldface terms from
chapter 13 and define them in your own words.