Chapter 16: The Evolution of Populations

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Chapter 16 The Evolution of Populations
Section 16-1 Genes and Variation 1. Is the
Following sentence true or false? Mendels work
on inheritance was publish after Darwins
lifetime. False 2. Which two important factors
was Darwin unable to explain without an
understanding of heredity? The source of
variation and how genes were passed from
generation to generation 3. List the three fields
that collaborate today to explain evolution a.
Genetics b. Molecular Biology c. Theory
Gregor Mendel
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Gene Pools 4. A collection of individuals of the
same species in a given area is a
population
5. The combined genetic information of all
members of a particular population is a
gene pool
6. Is the following statement true or false? A
gene pool typically contains just one allele for
each inheritable trait False
7. The number of times that an allele occurs in a
gene pool compared to the number of times other
alleles occur is called the relative frequency
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Sources of Genetic Variation 8. Complete the
concept map
Source of Genetic variation
Include
Mutations
Gene Shuffling
9. What is a mutation? Any Change in the sequence
of DNA 10. Why do mutations occur? As a result of
mistakes in the replication of the DNA or as a
result of radiation or chemicals in the
environment
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• 11. Circle the letter that is true about
  mutations
• They can be limited to a single base of DNA
• They always affect lengthy segments of a
  chromosome
• They always affect an organisms phenotype
• They always affect an organisms fitness
• 12. Is the following statement true of false?
  Most inheritable differences are due to gene
  shuffling that occurs during the production of
  gametes

• 13. Circle the letter of each choice that is true
  of sexual reproduction
• It is a major source of variation in many
  populations
• It can produce many different phenotypes
• It can produce many different gene combinations
• It can change the relative frequencies of a
  population

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Single- Gene and Polygenetic traits 14. Is the
following sentence true or false. ?The number of
phenotypes produced for a given trait depends
upon how many genes control the trait 15. Is the
following sentence true or false? Most traits are
controlled by a single gene 16. Label the two
graphs to show which one represents a single gene
trait and which one represents a polygenetic trait
Single gene trait
Polygenetic Trait
Frequency of Phenotype ()
Frequency of Phenotype
Phenotype (height)
Widows peak
No widows peak
Phenotype
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16-2 Evolution as Genetic Change Natural
Selection on Single-Gene Traits 1. Is the
following sentence true or false? Natural
selection on single gene traits cannot lead to
changes in allele frequencies
2. If a trait made an organism less likely to
survive and reproduce, what would happen to that
trait? Fewer copies would be passed onto the next
generation and the trait could, possibly
disappear from the gene pool
3. If a trait had no effect on an organism
fitness, what would happen to the allele for that
trait? The allele and its frequency would remain
unchanged
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• 4. List three ways that natural selection can
  affect the distribution of phenotypes
• Directional Selection
• Stabilizing Selection
• Disruptive Selection

Match the type of selection with the situation in
which it occurs Type of Selection ____ 5.
Directional ____ 6. Stabilizing ____ 7.
Disruptive

• Situation
• Individuals at the upper and lower end of the
  curve have higher fitness than those in the
  middle
• B. Individuals at one end of the curve have
  higher fitness than those at the other end
• Individuals in the middle have the highest fitness

b
c
a
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8. An increase in the average size of beaks in
Galapagos finches is an example of
Directional Selection
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9. Is the following sentence true or false? The
weight of human infants at birth is under the
influence of disruptive selection
10. Draw the missing graph to show how disruptive
selection affects beak size
Disruptive Selection
Largest and smallest seeds become more common.
Key
Population splits into two subgroups specializing
in different seeds.
Low mortality, high fitness
Number of Birdsin Population
Number of Birdsin Population
Number of Birdsin Population
High mortality, low fitness
Beak Size
Beak Size
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Genetic Drift 11. Is the following sentence true
or false? Natural selection is the only source of
evolutionary change. 12. Random change in allele
frequencies in small populations is
called Genetic Drift 13. A situation in which
allele frequencies change as a result of
migration of a small subgroup of a population is
called The Founder Effect
14. What is an example of the founder effect? The
evolution of the 6th finger on the hands of the
Old Amish people of Pennsylvania
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• Evolution verses Genetic Equilibrium
• 15. What does the Hardy Weinberg Principle state?
• Allele frequency in a population will remain
  constant unless one or more factors cause them to
  change
• 16. The situation in which allele frequencies
  remain constant is called
• Genetic Equilibrium
• 17. The 5 conditions required to maintain
  genetic equilibrium
• Random mating
• Large population
• No migration
• No mutations
• No natural selection

18. Why is large population size important in
maintaining genetic equilibrium? Genetic Drift
has less effect on large populations
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• 16-3 The Process of Speciation
• What is Speciation?
• The formation of a new species
• 2. Is the following sentence true or false?
• Individuals in different species can have the
  same gene pool
• 3. What does it mean for two species to be
  reproductively isolated from each other?
• They cannot interbreed and produce offspring
• 4. What must happen in order for a new species to
  evolve?
• Populations must be reproductively isolated from
  one another

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5. List three ways that reproductive isolation
occurs 6. When does behavioral isolation
occur? Species do not interbreed because of
different courtship rituals 7. Is the following
statement true or false? Eastern and Western
meadowlarks are examples of behavioral isolation
a. Geographic Isolation
b. Temporal Isolation Nocturnal Eye Diurnal Eye
c. Behavioral Isolation
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8. When does Geographic Isolation occur? When
populations are separated by geographic barriers,
such as mountain ranges, rivers, or oceans 9.
Abert and Kaibab Squirrels in the south west are
an example of Geographic Isolation 10. Is the
following sentence true or false? Geographic
barriers guarantee the formation of new
species. 11. What is an example of temporal
isolation? Three Similar species of orchids
release pollen on different days
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• 12. Is the following sentence true or false? The
  basic mechanisms of evolutionary change cannot be
  observed in nature
• 13. Circle the letter of each hypothesis about
  the evolution of Galapagos Finches beak that was
  tested by the Grants
• The finches beak size and shape has enough
• inheritable variation to provide raw material
• for natural selection
• b. The different finch species are the
• descendants of a common ancestor
• c. Differences in the finches beak size and
• Shape produce differences in fitness and
• Cause natural selection to occur
• d. The evolution of finches is proceeding
• slowly and gradually

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• 14. Circle the letter of each
• Observation that was made by the Grants
• Differences in beak size were more important for
  survival during the wet season
• When food for finches was scarce, individuals
  with the largest beaks were less likely to
  survive
• Big beaked birds tended to mate with small beaked
  birds
• Average beak size increased dramatically

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15. Complete the flowchart to show how speciation
probably occurred in the Galapagos finches
Founders arrive
Separation of species
16. How could difference in beak size lead to
reproductive isolation? Birds with the same beak
size mated. Birds of different beak size did NOT
mate and the gene pools of the different beak
sized birds remained isolated.
Changes in gene pool
Reproductive Isolation
Ecological Competition
Continued Evolution
17. Is the following sentence true or false?
During the dry season individual birds that are
most different from each other have the highest
fitness
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Concept Map
Reproductive Isolation
results from
Isolating mechanisms
which include
produced by
produced by
produced by
which result in
Independentlyevolving populations
which result in
Formation ofnew species