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Lesson 1: Natural Selection
Lesson 2: Adaptation and Extinction
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5.1 Natural Selection
evolution
naturalist
natural selection
adaptation
5.1 Natural Selection
Charles Darwin
• Evolution is change over time.
• The naturalist Charles Darwin was the
first person to write a thorough collection of
evidence supporting evolution.
• Darwin’s theory serves as the basis of all
biological research today.
5.1 Natural Selection
Charles Darwin (cont.)
• Darwin explored South America and its
remote islands, such as the Galapagos,
on the HMS Beagle.
5.1 Natural Selection
Darwin’s Observations
• Darwin made observations about the
diversity and uniqueness of organisms.
– Many of the animals on the Galapagos
were similar, but not the same as
organisms in mainland South America.
– Darwin reasoned that perhaps the
organisms in the Galapagos originally
came from South America and over
time, they had evolved.
5.1 Natural Selection
Tortoises
• Darwin found giant tortoises on all the
Galapagos Islands, but nowhere else.
• He reasoned that each new population
changed slightly, or evolved, to fit its
unique environment on the island.
5.1 Natural Selection
Finches
• Darwin was impressed by the diversity of
finches on the Galapagos.
– Darwin explained that if individuals
from a species were separated, future
generations might look and behave
differently.
– The finches became different because
they became suited to the different
habitats on the islands.
5.1 Natural Selection
Selective Breeding
• Selective breeding is breeding plants
and animals to get offspring with
desired characteristics.
• This does not lead to a new species—
the organism can still breed with other
members of its species.
5.1 Natural Selection
Darwin’s Theory of Natural Selection
• Organisms with traits that allowed them to
survive under particular environmental
conditions produced more offspring.
• Eventually those traits would be common
in the species.
How can natural
selection be
modeled?
5.1 Natural Selection
Genetic Variation
• Sometimes changes occur in genes and a
new trait is created.
• If the trait is beneficial, the organism may
survive and pass the trait on to the next
generation.
• Genetic variation is necessary for evolution
to occur.
5.1 Natural Selection
Population Growth and Struggle
to Survive
• Although resources are limited, animals
often produce more offspring than could
survive.
• Darwin decided this was a natural process
that selected which organism survived, and
called it natural selection.
• Adaptation refers to traits that increase the
likelihood of surviving and reproducing in a
particular environment.
5.1 Natural Selection
Natural Selection
• Four steps or requirements of Darwin’s
theory of evolution by natural selection:
– Step 1: Overproduction
– Step 2: Relative similarity
– Step 3: Inherited variation
– Step 4: Natural selection
5.1 Natural Selection
Natural Selection (cont.)
Overproduction
Inherited Variation
Variation
Natural Selection
5.1 Natural Selection
What did Darwin observe about
the tortoises and finches in the
Galapagos?
A their large size
B their similarity to those
on the mainland
C their adaptations to
their environments
0%
0%
0%
D
0%
C
D their friendliness
B
A
B
C
D
A
1.
2.
3.
4.
5.1 Natural Selection
What is necessary for evolution
to occur?
A selective breeding
B genetic variation
C populations isolated
on islands
D none of the above
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
5.1 Natural Selection
What is not a main source of
genetic variation?
A differences in diet
B sexual reproduction
C mutations
D gamete formation
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
5.2 Adaptation and Extinction
structural adaptation
camouflage
mimicry
behavioral adaptation
extinct
5.2 Adaptation and Extinction
Adaptations
• Humans can change their environment to
meet their needs.
• Organisms have evolved adaptations to
their environment by the process of natural
selection.
5.2 Adaptation and Extinction
Understanding Adaptations
• Adaptations are inherited traits that increase
an organism’s chance of surviving and
reproducing in a particular environment.
– Adaptations are the final products of the
long process of natural selection.
– Adaptations are naturally selected for,
not intentional.
– Not all traits are adaptations.
5.2 Adaptation and Extinction
Types of Adaptations
• Structural adaptations are aspects of the
physical body that help organisms survive
and reproduce.
• Camouflage—coloring that blends with
the environment—makes organisms
difficult to see.
5.2 Adaptation and Extinction
Types of Adaptations (cont.)
• Mimicry is when one species (the mimic)
looks like another species (the model) in
order to deceive a third species.
• Behavioral adaptations are actions or
behaviors that help organisms survive
and reproduce.
5.2 Adaptation and Extinction
Extinction
• A species becomes extinct when all the
individuals of a particular species die off.
• There have been several major extinction
events in history.
5.2 Adaptation and Extinction
Causes of Extinction
• Loss of habitat
• Loss of genetic diversity
• Competition with exotic species
• Inability to adapt
5.2 Adaptation and Extinction
Causes of Extinction (cont.)
5.2 Adaptation and Extinction
What is not an example of an
adaptation?
A inbreeding
B camouflage
C mimicry
D behavior
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
5.2 Adaptation and Extinction
Why do some non-desirable traits
remain in a population?
A selective breeding
B mutation
C they are genetically
linked to more
beneficial traits
0%
0%
0%
D
0%
C
D they may be useful
in the future
B
A
B
C
D
A
1.
2.
3.
4.
5.2 Adaptation and Extinction
What cause for extinction would most
likely be involved in rapid
environmental changes such as climate
change?
A loss of habitat
B inability to adapt
C loss of genetic diversity
0%
0%
0%
D
0%
C
D competition with
exotic species
B
A
B
C
D
A
1.
2.
3.
4.
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What is evolution?
A adaptations to particular
environments
B genetic change in a
population over time
C natural selection
D differences in traits
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
What is necessary for natural selection
to occur?
A genetic variation
B constant environmental
conditions
C isolate populations
D shortage of offspring
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
Which of the following is NOT one of
the main sources of genetic variation
in a population?
A mutations
B learned abilities
C formation of gametes
D sexual reproduction
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
Which of the causes of extinction is not
influenced by human actions?
A inability to adapt
B loss of genetic diversity
C loss of habitat
D competition with exotic
species
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
Why do desert rabbits have
mottled fur?
A behavioral adaptations
B mimicry
C camouflage
D incomplete dominance
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 3.a
What causes evolution?
A genetic variation
B environmental factors
C both
D neither
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 3.e
What is one reason exotic species can
sometimes outcompete native
species?
A they have no natural
predators
B there are more of them
C the new environment
is more favorable
0%
0%
0%
D
0%
C
D the natives are
not adapted
B
A
B
C
D
A
1.
2.
3.
4.
SCI 3.e
When do we designate a species as
threatened or endangered?
A when there is one
population left
B when the number of
individuals falls below
a certain level
C when population
numbers are declining
0%
0%
D
D when genetic variation
is low
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 3.a
Which is required for natural
selection to occur?
A inherited variation
B overproduction
of offspring
C genetic variation
D all of the above
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 3.b
Which of the following did not contribute to
Darwin’s development of the theory of
natural selection?
A overproduction of offspring
B competition with exotic
species in the Galapagos
C an essay on human
population growth
0%
0%
0%
D
0%
C
D similarities and
differences of species
in the Galapagos
B
A
B
C
D
A
1.
2.
3.
4.
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