Transcript Populations

Chapter 16
Evolution
Of
Populations
16-1
I. Genetic variation is studied in populations
A. A population is a group of individuals of the same
species that interbreed
B. Gene Pool
1. All the alleles in a population
a. combined genetic info. of all the members of a
population
2. Relative Frequency = How often alleles occur in
gene pool (expressed as a
percentage)
• Gene Pool for Fur Color in Mice Page 394
3. Evolution is any change in the relative frequency
of alleles in a population.
II. Sources of Genetic Variation
A. Mutations
1. Any change in sequence of DNA
2. result of radiation or chemicals in the environment
3. does not always affect organism’s phenotype
B. Gene Shuffling
1. Responsible for heritable differences due to
crossing over
2. Sexual reproduction produces different
phenotypes = does not change relative frequency
C. Single-gene and Polygenic traits
1. Phenotypes for a given trait depends on the # of
genes controlling the trait
2. Single-gene Traits
3. Polygenic Traits
-controlled by one gene
-controlled by many genes
a. only 2 phenotypes possible
a. many phenotypes possible
b. examples: Widow’s peak,
tongue roll, freckles
b. examples: height, eye
color; weight; skin tone
Whether a trait is controlled by a single gene
or many genes, can be predicted by examining
the frequency of distribution in the population.
16-2
I. Evolution as Genetic Change
A. Natural selection affects which individuals survive
and reproduce and which do not.
B. If an individual dies without reproducing = does
NOT contribute alleles to gene pool
C. If an individual produces offspring = the alleles stay
in the gene pool
D. Populations, NOT individual organisms, evolve
over time.
II. Natural Selection on Single Gene Traits
A. Can change relative frequency  evolution
B. Example: lizard color  mutation caused red
and black color: red seen easily = eaten and
disappear / black beneficial = increase in numbers
Page 397
III. Natural Selection on Polygenic traits
A. can affect the phenotypes in 3 ways
1. Directional Selection
Page 398
a. individuals at one end of the curve have
higher fitness
2. Stabilizing Selection
Page 399
a. individuals near the center of the curve
have higher fitness
3. Disruptive Selection
Page 399
a. individuals at both the upper and lower
ends of the curve have higher fitness
IV. Genetic Drift
A. Random change in relative frequency (%)
B. May occur when small group colonizes a new habitat
C. Called Founder effect = migration (examples:
Hawaiian fruit flies or English Beetles)
English
Beetles
Population A
Population B
Page 400
V. Hardy-Weinberg Principle- p2 + 2pq + q2 = 1
A. Allele frequency will remain constant unless 1 or
more factors change
B. No evolution = Genetic Equilibrium
C. 5 conditions to maintain genetic equilibrium
1. Random mating = equal chance to pass alleles
2. Large Population= less genetic drift
3. No migration-No movement of individuals in
(immigration) or out (emigration) of population
=gene pools kept separate
4. No mutations = no new alleles introduced
5. No natural selection = no phenotypic advantage
16-3
I. Process of Speciation (formation of new species)
A. Isolating Mechanisms lead to Speciation
1. Reproductive isolation =
2. Behavioral isolation=
new species cannot interbreed
Differences in courtship or other
behaviors (page 404)
3. Geographic isolation = Separated by barriers
(rivers/mountain) (page 405)
4. Temporal
isolation =
2 or more species reproduce at different
times (different seasons/ different times of
day)
B. Speciation of Galapagos Finches (Page 409)
1. Founders arrive – finches from S.A. to Galapagos
2. Geographic Isolation– part of group A goes to
another island
3. Changes in Gene Pool – population adapt to
environment = changes
4. Reproductive Isolation – pop. B goes back to first
island  A and B cannot interbreed.
5. Ecological Competition – A and B compete for
available seeds in same habitat; continue to evolve =
species C
6. Continued Evolution – repeated over and over again
16-1
Which of the following statements is TRUE?
A. The relative frequency of an allele is not related
to whether the allele is dominant or recessive.
B. Mutations always affect an organism's
phenotype.
C. Crossing-over decreases the number of different
genotypes that appear in an offspring.
D. Evolution does not affect the frequency of
genes in a gene pool.
16-1
Most inheritable differences are a result of
A. gene shuffling during the production of
gametes.
B. frequency of alleles.
C. mutations.
D. DNA replication.
16-1
The main sources of inherited variation are
A. gene shuffling and mutations.
B. gene pools and frequencies.
C. single-gene and polygenic traits.
D. genotypes and phenotypes.
16-1
A widow's peak in humans is an example of a(an)
A. invariable trait.
B. single-gene trait.
C. polygenic trait.
D. mutation.
16-1
A graph of the length of the little finger on the
left hand versus the number of people having
fingers of a particular length is a bell-shaped
curve. This indicates that finger length is a
A. single-gene trait.
B. polygenic trait.
C. randomly inherited trait.
D. strongly selected trait.
16-2
Which of the following patterns of natural
selection on polygenic traits favors both
extremes of a bell curve?
A. stabilizing selection
B. disruptive selection
C. directional selection
D. genetic drift
16-2
Which of the following events could lead to genetic
drift?
A. A few new individuals move into a large, diverse
population.
B. A few individuals from a large, diverse
population leave and establish a new population.
C. Two large populations come back together after a
few years of separation.
D. The mutation rate in a large population increases
due to pollution.
16-2
The situation in which allele frequencies remain
constant in a population is known as
A. genetic drift.
B. the founder effect.
C. genetic equilibrium.
D. natural selection.
16-2
Which of the following conditions is required to
maintain genetic equilibrium in a population?
A. movement in or out of the population
B. random mating
C. natural selection
D. small population
16-2
According to the Hardy-Weinberg principle, no
evolution will take place if
A. all five of the Hardy-Weinberg conditions
are met.
B. any one of the Hardy-Weinberg conditions
is met.
C. at least three of the Hardy-Weinberg
conditions are met.
D. none of the Hardy-Weinberg conditions are
met.
16-3
When two species do not reproduce because of
differences in mating rituals, the situation is
referred to as
A. temporal isolation.
B. geographic isolation.
C. behavioral isolation.
D. reproductive isolation.
16-3
The most important factor involved in the
evolution of the Kaibab and Abert squirrels of
the American Southwest appears to be
A. temporal isolation.
B. geographic isolation.
C. behavioral isolation.
D. different food sources.
16-3
One finding of the Grants' research on
generations of Galápagos finches was that
A. natural selection did not occur in the finch
B. natural selection can take place often and
very rapidly.
C. beak size had no effect on survival rate of
the finches.
D. natural selection was slow and permanent.
16-3
All of the following played a role in speciation of
Galápagos finches EXCEPT
A. no changes in the gene pool.
B. separation of populations.
C. reproductive isolation.
D. natural selection.
16-3
Beak size in the various groups of Galápagos
finches changed primarily in response to
A. climate.
B. mating preference.
C. food source.
D. availability of water.
16-1
Which of the following statements is TRUE?
A. The relative frequency of an allele is not related
to whether the allele is dominant or recessive.
B. Mutations always affect an organism's
phenotype.
C. Crossing-over decreases the number of different
genotypes that appear in an offspring.
D. Evolution does not affect the frequency of
genes in a gene pool.
16-1
Most inheritable differences are a result of
A. gene shuffling due to the production of
gametes.
B. frequency of alleles.
C. mutations.
D. DNA replication.
16-1
The main sources of inherited variation are
A. gene shuffling and mutations.
B. gene pools and frequencies.
C. single-gene and polygenic traits.
D. genotypes and phenotypes.
16-1
A widow's peak in humans is an example of a(an)
A. invariable trait.
B. single-gene trait.
C. polygenic trait.
D. mutation.
16-1
A graph of the length of the little finger on the
left hand versus the number of people having
fingers of a particular length is a bell-shaped
curve. This indicates that finger length is a
A. single-gene trait.
B. polygenic trait.
C. randomly inherited trait.
D. strongly selected trait.
16-2
Which of the following patterns of natural
selection on polygenic traits favors both
extremes of a bell curve?
A. stabilizing selection
B. disruptive selection
C. directional selection
D. genetic drift
16-2
Which of the following events could lead to genetic
drift?
A. A few new individuals move into a large, diverse
population.
B. A few individuals from a large, diverse
population leave and establish a new population.
C. Two large populations come back together after a
few years of separation.
D. The mutation rate in a large population increases
due to pollution.
16-2
The situation in which allele frequencies remain
constant in a population is known as
A. genetic drift.
B. the founder effect.
C. genetic equilibrium.
D. natural selection.
16-2
Which of the following conditions is required to
maintain genetic equilibrium in a population?
A. movement in or out of the population
B. random mating
C. natural selection
D. small population
16-2
According to the Hardy-Weinberg principle, no
evolution will take place if
A. all five of the Hardy-Weinberg conditions
are met.
B. any one of the Hardy-Weinberg conditions
is met.
C. at least three of the Hardy-Weinberg
conditions are met.
D. none of the Hardy-Weinberg conditions are
met.
16-3
When two species do not reproduce because of
differences in mating rituals, the situation is
referred to as
A. temporal isolation.
B. geographic isolation.
C. behavioral isolation.
D. reproductive isolation.
16-3
The most important factor involved in the
evolution of the Kaibab and Abert squirrels of
the American Southwest appears to be
A. temporal isolation.
B. geographic isolation.
C. behavioral isolation.
D. different food sources.
16-3
One finding of the Grants' research on
generations of Galápagos finches was that
A. natural selection did not occur in the finch
B. natural selection can take place often and
very rapidly.
C. beak size had no effect on survival rate of
the finches.
D. natural selection was slow and permanent.
16-3
All of the following played a role in speciation of
Galápagos finches EXCEPT
A. no changes in the gene pool.
B. separation of populations.
C. reproductive isolation.
D. natural selection.
16-3
Beak size in the various groups of Galápagos
finches changed primarily in response to
A. climate.
B. mating preference.
C. food source.
D. availability of water.