Chapter Introduction
Lesson 1 How are traits
inherited?
Lesson 2 Genetics After
Mendel
Lesson 3 Adaptation and
Evolution
Chapter Wrap-Up
How do species adapt to
new environments over
time?
What do you think?
Before you begin, decide if you agree or
disagree with each of these statements.
As you view this presentation, see if you
change your mind about any of the
statements.
Do you agree or disagree?
1.
Genes are on chromosomes.
2. Only dominant genes are passed on to
offspring.
3. Modern-day genetics disprove Gregor
Mendel’s ideas about inheritance.
4. Mutations can cause disease in an
individual.
Do you agree or disagree?
5. A population that lacks variation
among its individuals might not be
able to adapt to a changing
environment.
6. Extinction occurs when the last
individual of a species dies.
How are traits inherited?
• How are traits inherited?
• Why do scientists study genetics?
• What did Gregor Mendel investigate
and discover about heredity?
How are traits inherited?
• heredity
• genotype
• genetics
• phenotype
• selective breeding
• heterozygous
• dominant trait
• homozygous
• recessive trait
From Parent to Offspring
• Heredity is the passing of traits from
parent to offspring.
• Genetics is the study of how traits
pass from parents to offspring.
• For most organisms, genes are
sections of DNA that contain
information about a specific trait of that
organism.
From Parent to Offspring (cont.)
• A gene with different
information for a trait is
called an allele.
• Each chromosome pair
has genes for the same
traits.
• A gene’s alleles are in the
same location on each
chromosome of a pair.
How are traits inherited?
• An organism passes its traits to its
offspring in one of two ways—through
asexual reproduction or through sexual
reproduction.
• In asexual reproduction, one organism
makes a copy of its genes and itself.
• In sexual reproduction, offspring receive
half of their genes from an egg cell and
the other half from a sperm cell.
How are traits inherited?
Why do scientists study genetics?
• Scientists began studying genetics to
understand how traits are inherited.
• By studying genetics, scientists have
learned that genes control how
organisms develop.
• Studying genetics can help scientists
determine how organisms are related.
Because the genes from these organisms are
similar enough to produce normal eyes when
exchanged, scientists suspect that these
species share a common, ancient ancestor.
Why do scientists study
genetics?
Heredity—the History and the Basics
• Selective breeding is the selection and
breeding of organisms for desired traits.
• In the illustration below, a farmer would
breed the rooster with the hen that
produces the most eggs per year.
Heredity—the History and the Basics
(cont.)
In 1856, Gregor Mendel
began experimenting
with pea plants to
answer the question of
how traits are inherited.
Pixtal/age Fotostock
Heredity—the History and the Basics
(cont.)
Mendel chose plants
that produced only
green pods, called
true-breeding, and
crossed them with
true-breeding plants
that produced only
yellow pods.
Heredity—the History and the Basics
• All the offspring, called hybrids,
produced only green pods.
• The yellow-pod trait
seemed to disappear,
not blend with the
green-pod trait.
• Mendel proposed that
some traits of organisms
are dominant, while
others are recessive.
(cont.)
Heredity—the History and the Basics
• When Mendel crossed
two hybrid plants with
green pods, the cross
resulted in offspring
with green pods and
offspring with yellow
pods.
• These offspring were
in a ratio of about 3:1,
green to yellow.
(cont.)
Heredity—the History and the Basics
(cont.)
• A dominant trait is a genetic
factor that blocks another genetic factor.
• A recessive trait is a genetic factor that
is blocked by the presence of a dominant
factor.
• When an individual has one dominant
allele and one recessive allele for a trait,
the dominant trait is expressed.
Heredity—the History and the Basics
(cont.)
• The alleles of all the genes on an
organism’s chromosomes make up the
organism’s genotype.
• How the traits appear, or are expressed,
is the organism’s phenotype.
Heredity—the History and the Basics
(cont.)
phenotype
from Greek phainein, means
“to show”; and typos, means
“type”
Heredity—the History and the Basics
(cont.)
• When an organism’s genotype has
two different alleles for a trait, it is called
heterozygous.
• When an organism’s genotype has two
identical alleles for a trait, it is called
homozygous.
Heredity—the History and the Basics
(cont.)
What did Mendel investigate
and discover about heredity?
• Traits are passed from parent to
offspring during asexual or sexual
reproduction.
• Through selective breeding, Mendel
showed that some traits are dominant
and some traits are recessive.
• An organism’s genotype can be
homozygous or heterozygous.
• Each gene has two types of alleles,
dominant or recessive.
• A dominant allele is expressed over a
recessive allele.
Which is a gene with different
information for a trait?
A. allele
B. chromosome
C. genotype
D. offspring
Which is a genetic factor that
blocks another genetic factor?
A. dominant trait
B. genotype
C. phenotype
D. recessive trait
Which is the process by which
one organism makes a copy of its
genes and itself?
A. asexual reproduction
B. genetics
C. selective breeding
D. sexual reproduction
Do you agree or disagree?
1. Genes are on chromosomes.
2. Only dominant genes are passed on to
offspring.
Genetics After Mendel
• How can you use models to predict
genetic outcomes?
• What are the other patterns of
inheritance?
• What role can mutations play in the
inheritance of disease?
Genetics After Mendel
• monohybrid
cross
• Punnett square
• incomplete
dominance
• codominance
• multiple alleles
• sex-linked trait
• polygenic
inheritance
• pedigree
• mutation
• genetic
engineering
Rediscovering Mendel’s Work
• In 1900, scientists realized
that genes were on
chromosomes in the nucleus.
• They confirmed that genes
were Mendel’s dominant and
recessive factors.
Predicting Genetic Outcomes
• If you flipped a coin ten
times, you might predict a
heads-to-tails ratio of 5:5.
• Probabilities are
predictions; they do
not guarantee outcomes.
Your coin flips could
result in ten heads in
a row.
Brand X Pictures
• Mendel predicted the outcome of a
monohybrid cross—a cross between
two individuals that are hybrids for one
trait.
• Mendel predicted a 3:1 ratio of the
dominant phenotype to the recessive
phenotype.
C Squared Studios/Getty Images
Predicting Genetic Outcomes (cont.)
• A Punnett square shows the probability
of all possible genotypes and
phenotypes of offspring.
• This Punnett square
predicts that 75
percent of the offspring
will express the
dominant phenotype
of green pods.
Predicting Genetic Outcomes (cont.)
How does a Punnett square
help scientists predict genetic
outcomes?
Other Patterns of Inheritance
When an offspring’s phenotype is a
combination of its parents’ phenotypes,
it is called incomplete dominance.
Other Patterns of Inheritance (cont.)
When both alleles can
be independently
observed in a
phenotype, it is called
codominance.
Nova Development
Other Patterns of Inheritance (cont.)
• Human blood type is an example of
multiple alleles, or a gene that has
more than two alleles.
• The IA and IB alleles are codominant to
each other, but both are dominant to the
i allele.
Other Patterns of Inheritance (cont.)
• When the allele for a trait is on an X or Y
chromosome, it is called a sex-linked
trait.
• In fruit flies, the allele
for eye color is on
only the X
chromosome,
not on the Y
chromosome,
Other Patterns of Inheritance (cont.)
• Some traits, such as
height, are controlled by
many genes.
• Polygenic inheritance
occurs when multiple
genes determine the
phenotype of a trait.
2007 Getty Images, Inc.
What are the other patterns of
inheritance?
Inheritance of Disease
• A pedigree shows genetic traits that
were inherited by members of a family.
• This illustration shows the pedigree for a
family in which cancer was common in
each generation.
Inheritance of Disease (cont.)
• A mutation is any permanent change
in the sequence of DNA in a gene or a
chromosome of a cell.
• If mutations occur in reproductive cells,
they can be passed from parent to
offspring.
• Cancer, diabetes, and birth defects all
result from mutations in genes.
Inheritance of Disease (cont.)
mutation
from Latin mutare, means
“to change”
Inheritance of Disease (cont.)
What role can mutations play
in the inheritance of disease?
Inheritance of Disease (cont.)
• Scientists today are using what they
have learned about genetics to help
people.
• In genetic engineering, the genetic
material of an organism is modified by
inserting DNA from another organism.
Bacteria have been genetically
engineered to produce human insulin.
• Scientists use Punnett squares and
pedigrees to predict and analyze
genetic outcomes.
• There are many patterns of
inheritance, including incomplete
dominance, codominance, and
polygenic inheritance.
• Scientists use genetic engineering to
help treat diseases and learn more
about how organisms develop.
• Scientists use models like Punnett
squares and pedigrees to predict and
show patterns in inheritance that can
be used to figure out why these
diseases are passed on.
Which refers to an offspring’s
phenotype which is a combination
of its parents’ phenotypes?
A. codominance
B. complete dominance
C. incomplete dominance
D. mutation
Which describes genes that have
more than two forms?
A. incomplete dominance
B. multiple alleles
C. mutation
D. sex-linked trait
What is any permanent change in
the sequence of DNA in a gene or
a chromosome of a cell?
A.
B.
C.
D.
pedigree
mutation
genetic engineering
codominance
Do you agree or disagree?
3. Modern-day genetics disprove Gregor
Mendel’s ideas about inheritance.
4. Mutations can cause disease in an
individual.
Adaptation and Evolution
• How does natural selection occur?
• What is an adaptation?
• Why do traits change over time?
Adaptation and Evolution
• variation
• extinction
• natural selection
• conservation
biology
• adaptation
• evolution
Mutations, Variations, and Natural
Selection
Slight differences in inherited traits among
individuals in a population are called
variations.
Creatas/PunchStock
Mutations, Variations, and Natural
Selection (cont.)
The process by which individuals with
variations that help them survive in their
environment live longer, compete better,
and reproduce more than those individuals
without these variations is called natural
selection.
Mutations, Variations, and Natural
Selection (cont.)
How does natural selection
occur?
Adaptations
• An adaptation is an inherited trait that
increases an organism’s chance of
surviving and reproducing in a particular
environment.
• Structural adaptations involve physical
characteristics, such as color or shape.
Adaptations (cont.)
• Functional adaptations involve internal
systems that affect an organism’s
physiology or biochemistry.
• Behavioral adaptations, such as
migration, involve the ways an organism
behaves or acts.
Adaptations (cont.)
Describe three types of
adaptations.
Evolution of Populations—
Why Traits Change
• Evolution is change in inherited
characteristics over time.
• Evolution by natural selection is a way
that populations change over time.
• As the environment changes, different
inherited traits might enable survival, and
the population can evolve again.
Evolution of Populations—
Why Traits Change (cont.)
Why do traits change over
time?
A population of bacteria can evolve
antibiotic resistance.
Extinction and Conservation
Biology
When the last individual of a species dies,
the species has undergone extinction.
extinction
from Latin extinctus, means
“wipe out”
Extinction and Conservation
Biology (cont.)
• Organisms called invasive species may
be introduced into a habitat, making it
difficult for some native species to
survive and reproduce.
• Conservation biology is a branch of
biology that studies why many species
are in trouble and what can be done to
save them.
Extinction and Conservation
Biology (cont.)
introduce
Science Use to bring a substance
or organism into a habitat or a
population
Common Use to make someone
known to others
• Natural selection occurs when
individuals with traits that better suit
the environment survive longer and
reproduce more successfully than
individuals without the traits.
• An adaptation is an inherited trait
that increases an organism’s chance
of surviving and reproducing in an
environment.
• Conservation biologists work to save
species from extinction.
What has a species undergone
when the last individual of that
species dies?
A. adaptation
B. evolution
C. extinction
D. variation
Migration is an example of which
kind of adaptation?
A. behavioral
B. evolutionary
C. functional
D. structural
Which term refers to change over
time?
A. adaptation
B. evolution
C. natural selection
D. variation
Do you agree or disagree?
5. A population that lacks variation among
its individuals might not be able to
adapt to a changing environment.
6. Extinction occurs when the last
individual of a species dies.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Mutations can change
the traits in individuals
that are passed from
parents to offspring,
producing variation in
a population that can
lead to greater success
and survival in new
environments.
Lesson 1: How are traits inherited?
• Traits are inherited as genes pass from parent to
offspring.
• Scientists study genetics to learn more about the
development of organisms as well as the
development of disease. Scientists also can learn
more about how organisms are related by studying
genetics.
• Mendel studied how traits are passed from parents
to offspring. He discovered that traits can be
dominant or recessive and that the outcome of
crosses between parents can
be predicted.
Lesson 2: Genetics After Mendel
• Models, such as Punnett squares,
can be used to predict the probability
of certain allele combinations given
the genotypes of the parents of a
genetic cross.
• Traits can be inherited in ways other than dominant
or recessive. Traits can be inherited as incomplete
dominance, codominance, multiple alleles, and
polygenic traits.
• Mutations are changes in genes and can cause
disease. As genes are passed from parent to
offspring, so is the disease.
Lesson 3: Adaptation and Evolution
• Natural selection is the process in which individuals
with traits that better suit the environment are more
likely to survive longer and reproduce successfully
than those individuals without these traits.
• An adaptation is an inherited trait that increases an
organism’s chance of surviving and reproducing in a
particular environment.
• Traits change over time because
individuals with adaptive traits tend
to produce more offspring than
individuals with traits that no longer
give them an advantage in a
particular environment.
Which is the selection and
breeding of organisms for desired
traits?
A. asexual reproduction
B. genetics
C. heredity
D. selective breeding
Which is blocked by the presence
of a dominant factor?
A. dominant trait
B. heredity
C. phenotype
D. recessive trait
Which occurs when multiple
genes determine the phenotype
of a trait?
A. genetic engineering
B. incomplete dominance
C. mutation
D. polygenic inheritance
Which occurs when the DNA of an
organism is modified by inserting
DNA from another organism?
A. pedigree
B. mutation
C. genetic engineering
D. codominance
Which is an inherited trait that
increases an organism’s chance
of surviving and reproducing?
A. adaptation
B. evolution
C. natural selection
D. variation
Which describes an organism’s
genotype when it has two
identical alleles for a trait?
A. phenotype
B. homozygous
C. heterozygous
D. genotype
Which is the study of how traits
pass from parents to offspring?
A. genetics
B. genotype
C. heredity
D. selective breeding
Which is used to model the
possible genotypes and
phenotypes of offspring?
A. monohybrid cross
B. multiple alleles
C. pedigree
D. Punnett square
Which shows genetic traits that
were inherited by members of a
family?
A. monohybrid cross
B. mutation
C. pedigree
D. Punnett square
Which type of adaptation involves
internal systems that affect an
organism’s physiology or
biochemistry?
A. behavioral
B. external
C. functional
D. structural