Transcript Reproductive Isolation

Chapter 16: The Evolution of Populations
Section 16-1 Genes and Variation
1. Is the Following sentence true or false?
Mendel’s work on inheritance was publish after
Darwin’s 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
Gregor Mendel
3. List the three fields that collaborate today to
explain evolution
a. Genetics b. Molecular Biology c. Theory
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
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
11. Circle the letter that is true about
mutations
a. They can be limited to a single base of DNA
b. They always affect lengthy segments of a
chromosome
c. They always affect an organism’s phenotype
d. They always affect an organism’s 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
a. It is a major source of variation in many populations
b. It can produce many different phenotypes
c. It can produce many different gene combinations
d. It can change the relative frequencies of a population
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
Phenotype (height)
Frequency of Phenotype
(%)
Frequency of Phenotype
Polygenetic Trait
Widow’s peak
No widow’s peak
Phenotype
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
4. List three ways
that natural
selection can
affect the
distribution of
phenotypes
a. Directional
Selection
b. Stabilizing
Selection
Match the type of selection
with the situation in which it
occurs
Type of Selection
b 5. Directional
____
c 6. Stabilizing
____
a 7. Disruptive
____
Situation
c. Disruptive
Selection
a. Individuals at the upper and lower
end of the curve have higher fitness
than those in the middle
b. B. Individuals at one end of the
curve have higher fitness than those
at the other end
c. Individuals in the middle have the
highest fitness
8. An increase in the average size of beaks in Galapagos finches is
an example of Directional Selection
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
Low mortality,
high fitness
High mortality,
low fitness
Beak Size
Population splits
into two subgroups
specializing in
different seeds.
Number of Birds
in Population
Key
Number of Birds
of Birds
Number
in Population
in Population
Largest and smallest seeds become more common.
Beak Size
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
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
18. Why is large population size
a. Random mating
important in maintaining genetic
b. Large population
equilibrium?
c. No migration
d. No mutations
e. No natural selection
Genetic Drift has less effect on
large populations
16-3 The Process of Speciation
What is Speciation?
The formation of a new species
If two species are reproductively
isolated from each other
They cannot interbreed and produce
offspring
What must happen in order for a new
species to evolve?
Populations must be reproductively
isolated from one another
Three ways that reproductive
isolation occurs
a. Behavioral isolation
Species do not interbreed because
of different courtship rituals
b. Temporal Isolation- organisms
interbreed at different times of
the day or season
Three Similar species of orchids
release pollen on different days
Behavioral Isolation
Eastern and western meadowlark
Sing different songs to attract mates
C. Geographic Isolation
When populations are separated by
geographic barriers, such as mountain
ranges, rivers, or oceans Abert and
Kaibab Squirrels in the south west are an
example of geographic isolation
14. Circle the letter of each
Observation that was made
by the Grants
a. Differences in beak size
were more important for
survival during the wet
season
b. When food for finches was
scarce, individuals with the
largest beaks were less
likely to survive
c. Big beaked birds tended to
mate with small beaked
birds
d. Average beak size
increased dramatically
15. Complete the
flowchart to show how
speciation probably
occurred in the
Galapagos finches
Founders arrive
Separation of species
Changes in gene pool
Reproductive Isolation
Ecological Competition
Continued Evolution
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.
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
Concept Map
Reproductive Isolation
results from
Isolating mechanisms
which include
Behavioral isolation
Geographic isolation
Temporal isolation
produced by
produced by
produced by
Behavioral differences
Physical separation
Different mating times
which result in
Independently
evolving populations
which result in
Formation of
new species