Transcript Prentice Hall Review PPT. Ch. 16

Interest Grabber
Section 16-1
Yes, No, or Maybe
Some traits, such as a widow’s peak, fall into neat categories: You either
have a widow’s peak or you don’t. Other traits, such as height, aren’t so
easy to categorize.
Go to
Section:
Interest Grabber continued
Section 16-1
1. Make a list of physical traits that you think are influenced by genes.
Then, write next to each trait whether you have the trait or not
(e.g., a widow’s peak) or whether there are many variations of the
trait (e.g., hair color).
2. Are most of the traits you listed clear-cut or are they mostly traits
that have many variations? Which traits in your list are difficult to
categorize?
3. Compare your list with that of another student. Did he or she think of
any traits that you missed? Why do you think some traits are clear-cut,
while others are not?
Go to
Section:
Section Outline
Section 16-1
16–1
Genes and Variation
A. How Common is Genetic Variation?
B. Variation and Gene Pools
C. Sources of Genetic Variation
1. Mutations
2. Gene Shuffling
D. Single-Gene and Polygenic Traits
Go to
Section:
Generic Bell Curve for Polygenic Trait
Frequency of Phenotype
Section 16-1
Phenotype (height)
Go to
Section:
Figure 16–2 Relative Frequencies of Alleles
Section 16-1
Sample Population
48%
heterozygous
black
16%
homozygous
black
36%
homozygous
brown
Go to
Section:
Frequency of Alleles
allele for
brown fur
allele for
black fur
Figure 16–3 Phenotypes for Single-Gene Trait
Section 16-1
Frequency of Phenotype
(%)
100
80
60
40
20
0
Widow’s peak
Phenotype
Go to
Section:
No widow’s peak
Interest Grabber
Section 16-2
. . . All the Help I Can Get
Natural selection operates on traits in different ways. You might be able
to predict which traits natural selection would favor if you think about the
demands of an organism’s environment.
1. Choose an animal that you know something about, such as a deer,
and write its name at the top of a sheet of paper. Then, divide your
paper into two columns, and write the heading Trait in one column and
Advantage in the other.
2. Under Trait, write in several of the animal’s traits.
3. Under Advantage, write in how you think the trait would be helpful to
the animal.
Go to
Section:
Section Outline
Section 16-2
16–2
Evolution as Genetic Change
A. Natural Selection on Single-Gene Traits
B. Natural Selection on Polygenic Traits
1. Directional Selection
2. Stabilizing Selection
3. Disruptive Selection
C. Genetic Drift
D. Evolution Versus Genetic Equilibrium
1. Random Mating
2. Large Population
3. No Movement Into or Out of the Population
4. No Mutations
5. No Natural Selection
Go to
Section:
Genetic Drift
Section 16-2
Sample of
Original Population
Descendants
Founding Population A
Founding Population B
Go to
Section:
Genetic Drift
Section 16-2
Sample of
Original Population
Descendants
Founding Population A
Founding Population B
Go to
Section:
Genetic Drift
Section 16-2
Sample of
Original Population
Descendants
Founding Population A
Founding Population B
Go to
Section:
Figure 16–6 Graph of Directional Selection
Section 16-2
Key
Go to
Section:
Directional Selection
Low mortality,
high fitness
Food becomes scarce.
High mortality,
low fitness
Figure 16–7 Graph of Stabilizing Selection
Section 16-2
Stabilizing Selection
Key
Low mortality,
high fitness
High mortality,
low fitness
Birth Weight
Go to
Section:
Selection
against both
extremes keep
curve narrow
and in same
place.
Figure 16–8 Graph of Disruptive Selection
Section 16-2
Disruptive Selection
Low mortality,
high fitness
High mortality,
low fitness
Population splits
into two subgroups
specializing in
different seeds.
Beak Size
Go to
Section:
Number of Birds
in Population
Key
Number of Birds
in Population
Largest and smallest seeds become more common.
Beak Size
Interest Grabber
Section 16-3
Country Cousin/City Cousin
What happens when a population or group of living things is divided
into two separate groups in two separate environments? To understand
what goes on, think about someone who lives in another part of the
United States or in another country.
1. Make a list of everyday things that this person encounters that you
don’t. For example, does he or she eat different kinds of food? Does he
or she live in a climate different from yours?
2. All humans are the same species. What might happen if groups of
humans were separated for millions of years in very different
environments, such as those you have just described?
Go to
Section:
Section Outline
Section 16-3
16–3
The Process of Speciation
A. Isolating Mechanisms
1. Behavioral Isolation
2. Geographic Isolation
3. Temporal Isolation
B. Testing Natural Selection in Nature
1. Variation
2. Natural Selection
3. Rapid Evolution
C. Speciation in Darwin’s Finches
1. Founders Arrive
2. Separation of Populations
3. Changes in the Gene Pool
4. Reproductive Isolation
5. Ecological Competition
6. Continued Evolution
D. Studying Evolution Since Darwin
Go to
Section:
Concept Map
Section 16-3
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
Go to
Section:
Go Online
Links from the authors on restricting use of antibiotics
Interactive test
For links on population genetics, go to www.SciLinks.org and enter the
Web Code as follows: cbn-5161.
For links on speciation, go to www.SciLinks.org and enter the Web
Code as follows: cbn-5163.
Interest Grabber Answers
1. Make a list of physical traits that you think are influenced by genes.
Then, write next to each trait whether you have the trait or not
(e.g., a widow’s peak) or whether there are many variations of the
trait (e.g., hair color).
Students’ answers will include dimples and detached earlobes.
2. Are most of the traits you listed clear-cut or are they mostly traits
that have many variations? Which traits in your list are difficult to
categorize?
Most traits listed likely have many variations.
3. Compare your list with that of another student. Did he or she think of
any traits that you missed? Why do you think some traits are clear-cut,
while others are not?
Some students may suggest that patterns of inheritance for traits with
many variations (polygenic) are more complex than for clear-cut
(single-gene) ones.
Interest Grabber Answers
1. Choose an animal that you know something about, such as a deer, and
write its name at the top of a sheet of paper. Then, divide your paper into
two columns, and write the heading Trait in one column and Advantage in
the other.
Animal choices should be sufficiently familiar that students can describe
several traits.
2. Under Trait, write in several of the animal’s traits.
Students should list traits such as size, color, and specialized behavior.
3. Under Advantage, write in how you think the trait would be helpful to the
animal.
Students should indicate that adaptive value is clearer for some traits than
for others. For example, white-tailed deer raise their tails upon sensing a
predator. This may be an alarm signal for other deer, or it may induce the
predator to chase the now-conspicuous deer.
Interest Grabber Answers
1. Make a list of everyday things that this person encounters that you don’t.
For example, does he or she eat different kinds of food? Does he or she
live in a climate different from yours?
Students’ lists should include several social/environmental factors.
2. All humans are the same species. What might happen if groups of humans
were separated for millions of years in very different environments, such as
those you have just described?
Students may understand that humans would evolve separately in
response to different environmental pressures.
This slide is intentionally blank.