AAC+-+07+-+Concept+2+Notes+-+Natural+Selection+PPT (1) Flashcards
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The process of biological change in populations over
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Evolution can occur on a small scale affecting a
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Evolution on a large scale affecting changes in
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Creationism
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Catastrophism (Cuvier)
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Gradualism (Hutton)
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Struggle for Existence
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Uniformitarianism (Lyell)
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Inheritance of Acquired
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Intelligent Design
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English Naturalist
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Went on a voyage to the
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Saw that different species of
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Developed his theory of
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Natural Selection: organisms with the “best”
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Lots of offspring and limited resources causes
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Variation: differences in the physical traits of
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Sources of Variation:
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Adaptation: a feature that allows an
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A change in gene frequency
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Beneficial traits should
1
Directional Selection:
had light-colored
wings, but dark
moths started to appear.
Because
survived, adding
more genes for
2
Disruptive Selection: a
disadvantaged
because
3
Stabilizing Selection:
For example: Human babies
born
with below-normal
and above-
1
Two different colorations of a species of beetles
2
Brightly colored fish mate more frequently than
3
The average baby chick weighs ~45 grams when
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Fossil evidence reveals that over time, the size of
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Each allele has a frequency in a population’s
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All frequencies can be calculated.
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In a given population with only 2 versions of
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In a population of wildflowers, the red allele is
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Of the 500 total plants in the population, 20 are
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1000 total (500 plants with 2 alleles each = 1000 total)
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r = 20 + 20 + 160 = 200 alleles
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R = 320 + 320 + 160 = 800 alleles
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In a population
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Of the 500 total
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800/1000 = p = frequency of dominant “R” allele = 0.8
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200/1000 = q = frequency of recessive “r” allele = 0.2
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Check: p + q = 1 and 0.8 + 0.2 = 1
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In a population of pea plants, the tall allele is
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Of the 400 total plants in the population, 50 are
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In a population of pea plants, the tall allele is
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Of the 400 total plants in the population, 50 are
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In a population of pea plants, the tall allele is
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Of the 400 total plants in the population, 50 are
Mechanisms
of Microevolution
1
Mutations
2
Natural Selection
3
Genetic Drift
4
Gene Flow
5
Non-random Mating (Sexual
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Mutation = any change in a DNA sequence.
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Natural selection = organisms more fit for their
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Genetic drift = random change in the frequency of
Mechanisms
of Microevolution
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Gene flow = movement of genes into/out of a
Mechanisms
of Microevolution
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The selection of traits that aren’t necessarily good
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Genetic equilibrium (Hardy-Weinberg
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Evolution
1
Population is large.
2
Must be random mating.
3
No migration.
4
No mutations.
5
No natural selection.
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We already know that in all populations with only
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When a population is in HWE, we can use an
Hardy-Weinberg
Equilibrium
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p2 = genotypic frequency of homozygous
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2pq = genotypic frequency of
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q2 = genotypic frequency of homozygous
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Round heads are dominant to cone heads and 51%
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51% = 0.51 of the population
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This means the other 49% of the population
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0.49
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p2 is the frequency
Hardy-Weinberg
Equilibrium
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 34 are yellow.
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Assume the population is in Hardy-Weinberg
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 34 are yellow.
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Assume the population is in Hardy-Weinberg
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R = Red
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34/241= 0.14 = yellow phenotype
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√0.14=√q2
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q = 0.37
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p + q = 1, so 1 - .37 = 0.63
Hardy-Weinberg
Equilibrium
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 34 are yellow.
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Assume the population is in Hardy-Weinberg
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RR = p2 = (0.63)2 = 0.3969 = 39.69%
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Rr = 2pq = 2(0.63)(0.37) = 0.4662=
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rr = q2 = (0.37)2 = 0.1369 = 13.69%
Hardy-Weinberg
Equilibrium
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 85 are red.
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Assume the population is in Hardy-Weinberg
Hardy-Weinberg
Equilibrium
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 85 are red.
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Assume the population is in Hardy-Weinberg
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 14 are rr, 200 are Rr,
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Note: Actual population
Hardy-Weinberg
Equilibrium
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 14 are rr, 200 are
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RR = 27/241 = 0.11 = 11% RR
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Rr = 200/241 = 0.83= 83% Rr
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rr = 14/241 = 0.06= 6% rr
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 14 are rr, 200 are
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R= red, r = yellow
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Gene pool = 482 total alleles (241 turtles
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R allele = 27 + 27 + 200 = 254
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r allele = 14 + 14 + 200 = 228
Hardy-Weinberg
Equilibrium
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In turtles, red color is dominant to yellow color.
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In a population of 241 turtles, 14 are rr, 200 are Rr, and 27 are
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RR = p2 = .532 = .2809
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Rr = 2pq = 2(.53)(.47) = .4982
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rr = q2 = .472 = .2209
frequencies.
Therefore, the population is evolving and the Rr genotype is
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If the population is in HWE and you
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Find frequency of homozygous recessive
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Take the square root to find q.
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Find p using p
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Use p2 + 2pq + q2 = 1 to find other
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If you are trying to figure out if a population is
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First use the actual
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Once you have p and q, use p2 + 2pq + q2 = 1 to
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If these genotype
