Evolution and Population Notes
Name:
Chapter 17
Date:
Period:
Evolution of Populations
Evolution
(In Genetic Terms)
 Natural selection acts directly on

, not
a group of ______________________ of the


__________________________________ in which evolution occurs
Combined _____________________ information of _______________________
__________________________________________________________________

Relative
Frequency
species that mate and
produce __________________________.
Population
Gene Pool
.
The number of times a particular
occurs in a gene pool,
compared with the
.
Example:
Allele
Frequency
(Equation)
Phenotype
Frequency
(Equation)
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Determining Phenotype and Allele Frequencies Using Japanese Four o’ Clock Flowers:
RR
RR
RW
Phenotype Frequency
RW
White =
RR
RW
RW
Allele Frequency
RR
R=
Pink =
W=
Red =
Predicting Genotypes and Phenotypes of Second Generation:
According to the laws of probability, the chance of an R gamete meeting with another R gamete is the
product of the allele frequencies in the gene pool.
Red (RR) = R
x
White (WW) =
W
R
x
=
W
RR
=
WW
The frequency of all types expected in the second generation must add up to 1.0
1.0 - RR - WW = RW
Single-Gene Trait

Controlled by only _________ gene.

Single-gene traits may have just _______ or
_______ distinct phenotypes.

Dominance of an allele for a single-gene trait does
not necessarily mean that the ________________
_________________________________________
Polygenic Trait
 Traits controlled by ______ or __________ genes.
 Each gene of a polygenic trait often has
________________________________________.
 A single polygenic trait often has many possible
________________________________________.
_________________________________________
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Evolution as Genetic Change in a Population
Natural Selection on Polygenic Traits
Type of
Selection
Description

Example
Individuals at one __________ of the curve
have higher _____________________ than
Directional
Selection
individuals in the ________________ or at
the other __________

Individuals near the _______________ of
the curve have higher
Stabilizing
Selection
______________________ than
individuals at either end.

___________________________________

Individuals at the _______________
and ___________________ ends of the
curve have higher fitness than
Disruptive
Selection
individuals near the middle.

Can create ________ distinct
_______________________.
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
Occurs in _________________ populations
when an ____________________________
Genetic
Drift
___________________________________.

Genetic drift is a ________________ change
in _________________________________.
What conditions are necessary to maintain genetic equilibrium? (Hardy-Weinberg Principle of Genetic
Equilibrium) Based on a set of assumptions about an ideal hypothetical population that is not evolving.
1. The population must
.
2. There can be
.
3. There must be
.
4. There can be
.
5. No
.
A population is in
if allele frequencies in the population
. If allele frequencies
not
, the population will
.
The Process of Speciation
Speciation
Species
Occurs when a population _________________________________________ and the
Reproductive
Isolation
two populations _______________________________________. When populations
become reproductively isolated, they can _____________________________________
______________________________.
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Types of Reproductive Isolation:
Behavioral
Isolation
Geographic
Isolation
Temporal
Isolation
Occurs when
develop
that are capable of interbreeding
in courtship rituals or other behaviors
Occurs when
are separated by
______________________________ such as rivers, mountains, or bodies of water.
Happens when two or more species ___________________________ at different times
Patterns and Processes of Evolution
Gradualism
Punctuated Equilibrium
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Biology Keystone Exam Preparation
Natural Selection and Evolution
1. The frequency of an allele in a fly population changes from 89% to 20% after three generations. Which
other events most likely occurred during the same time period?
A. an environmental change and a fly population increase
B. an environmental change and a fly population decrease
C. interbreeding of flies with an invasive species and fly population speciation
D. interbreeding of flies with an established local species and fly population speciation
Use the graph below to answer question 2.
2. Tail length in mice varies within a population. Scientists observed change in the distribution of tail lengths
in a mouse population over time. At the genetic level, what has most likely happened to the allele for the
shortest tail lengths?
A. The allele changed from being dominant to being recessive.
B. The allele changed from being autosomal to being sex-linked.
C. The allele became less frequent than the alleles for longer tail lengths.
D. The allele began to code for long tail lengths instead of the shortest ones.
Use the circle graphs below to answer question 3.
3. The graphs illustrate change in a lizard population over time. Which process most likely led to the change
in the lizard population?
A. natural selection acting on a harmful trait
B. natural selection acting on a beneficial trait
C. natural selection acting on a dominant trait
D. natural selection acting on a recessive trait
4. In North America, the eastern spotted skunk mates in late winter, and the western spotted skunk mates in
late summer. Even though their geographic ranges overlap, the species do not mate with each other. What
most likely prevents these two species from interbreeding?
A. habitat isolation
C. geographic isolation
B. gametic isolation
D. reproductive isolation
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5. A mutation occurs in the genes that code for coat color in deer. Which change will most likely result from
this mutation?
A. a change in the selection pressures acting on coat color
B. a change in the coat-color genes of deer predator species
C. an increase in coat-color diversity in the population
D. an increase in the number of genes for coat color in the population
Use the illustrations below to answer question 6.
6. The skeletons of mammalian forelimbs represent variations of a structure that was present in their common
ancestor. What has most likely caused the variation in forelimbs?
A. changes in muscle structure
C. trait formation due to behaviors
B. changes in the genetic codes
D. development of vestigial structures
7. A population of animals is permanently split by a natural barrier into two separate populations in different
environments. What will likely result after a long period of time?
A. The evolution of the two populations will be identical.
B. The production of variations will stop in the two populations.
C. The two populations will evolve into separate species.
D. Autotrophic nutrition will replace heterotrophic nutrition in the two populations.
8. When changes occur in the genes of sex cells, these changes
A. lead to mutations in the parent organism
B. are always harmful to the offspring
C. can be the basis for evolutionary change
D. only affect sexually reproducing organisms
9. When a species includes organisms with a wide variety of traits, it is most likely that this species will have
A. a high proportion of individuals immune to genetic diseases
B. a greater chance to survive if environmental conditions suddenly change
C. less success competing for resources
D. limitless supplies of important resources, such as food and water
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10. The sorting and recombination of genes during reproduction is important to evolution because these
processes
A. decrease variation and help maintain a stable population
B. increase variation that enables species to adapt to change
C. decrease the chances of producing offspring that are adapted to the environment
D. increase the ability of all the offspring to adapt to the environment
11. In the early stages of development, the embryos of dogs, pigs, and humans resemble one another. This
observation suggests that these animals may have
A. a similar number of chromosomes
C. the same blood components
B. similar habitat requirements
D. a common ancestry
12. The idea that evolution takes place at a continuous but very slow rate is known as
A. succession
C. punctuated equilibrium
B. artificial selection
D. gradualism
13. Which statement is best supported by the theory of evolution?
A. Genetic alterations occur every time cell reproduction occurs.
B. The fossil record provides samples of every organism that ever lived.
C. Populations that have advantageous characteristics will increase in number.
D. Few organisms survive when the environment remains the same.
14. Differences between the members of a population will most likely be passed to future generations if they are
A. due to genetic changes and result in unfavorable variations
B. due to genetic changes and result in favorable variations
C. not due to genetic changes and result in unfavorable variations
D. not due to genetic changes and result in favorable variations
15. A gene pool consists of
A. all the genes that mutate in a single generation
B. all the heritable genes for traits in a population
C. all the gametes produced by a population
D. the mutated alleles for a particular trait
16. A characteristic that an organism exhibits during its lifetime will only affect the evolution of its species if
the characteristic
A. results from isolation of the organism from the rest of the population
B. is due to a genetic code that is present in the gametes of the organism
C. decreases the number of genes in the body cells of the organism
D. causes a change in the environment surrounding the organism
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17. A researcher recently discovered a new species of bacteria in the body of a tubeworm living near a
hydrothermal vent. He compared the DNA of this new bacterial species to the DNA of four other species of
bacteria. The DNA sequences came from the same part of the bacterial chromosome of all four species.
According to these data, the unknown bacterial species is most closely related to
A. species I
B. species II
C. species III
D. species IV
18. Which species in the chart below is most likely to have the fastest rate of
evolution?
A. A
B. B
C. C
D. D
19. The gene COII is in the genome of many organisms. A comparison of the
number of base differences between the COII gene in a rat and that of two
other animals is shown.
A. Based on the data, describe a possible evolutionary relationship
between rats, mice, and cows.
_______________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
B. Describe how different organisms having a common gene such as COII supports the theory of evolution.
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
C. The COII gene of a monkey has 203 base differences from the same gene in a rat and 201 base
differences from the same gene in a mouse. Compare the evolutionary relationships between the
monkey, the rat, and the mouse.
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
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