Transcript Lecture V: Natural Selection & Adaptations

Today’ Agenda:
Journal Question:
a. What is an adaptation?
*1. Lecture V: Natural Selection &
Adaptations (slide 37)
2. Biome Presentations
3. Homework: Study Guide
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Lecture V: Natural
Selection & Adaptations
By Dr. Rick Woodward
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What you should know for Exam I
(That is not on the study guide)
A. Geographic Isolation
B. Adaptive Radiation
C. Gene mutation has
adaptive value….
D. Today’s lecture on natural
selection and adaptations
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Geographic Isolation
A. Geography separates a
species from reproducing.
(1) Example: The Grand
Canyon separating squirrel
populations
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Adaptive Radiation
A. Diversity of finch species
found on the Galapagos
Islands. (Adaptations)
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An Adaptation…
A. Big Mamma …Blending in….
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Darwin’s Theory of
Natural Selection
(1) In nature there is a
tendency toward
overproduction.
a. Examples: mice,
watermelons, ants, fish,
and mosquitoes are all
well-known
overproducers.
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Darwin’s Theory of
Natural Selection
(2) Not all offspring that are
produced survive.
a. Example: many bacteria that
are treated with antibiotics will
die.
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How antibiotics destroy bacteria:
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Darwin’s Theory of
Natural Selection
(3) Variations exist in any
population.
(4) Variations are inherited.
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Darwin’s Theory of
Natural Selection
(5) Those individuals with
variations that are
suitable for their
environment will live
longer and leave more
offspring on average.
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Natural selection
Microevolution: change in allele frequency in a population
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In the Galapagos
A. Based on Darwin’s observations in
the Galapagos:
1. Darwin’s described evolution as
descent with modification.
-structural or functional changes
occur from one group of
descendants to the next, and so on.
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In the Galapagos
2. Darwin performed extensive
research on the island’s
finch population.
a. Studied finches
structural modification
(bird’s beaks) to environment
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Natural Selection
& Adaptations

The leaf bug
A. An adaptation is a
characteristic that helps
an organism survive in
its environment or
reproduce.
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The Evolution of
Complex Adaptations
A. Adaptations in organisms
you see today are the result
of chance variations that
arose at a particular time
in the evolutionary history
of that type of organism.
B. Example: The eye
(next slide)
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A Series of
Changes During
the Evolution of
the Eye
A. Simple animals such as flatworms
have groups of light-sensitive cells
to detect light.
B. More complex animals have visual
systems that form images.
C. In mollusks the images are blurry.
D. The images are focused for a turtle.
E. The images are focused and
enhanced by color in the eagle and
many other vertebrates.
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Explaining the
Complexities of the Eye
A. Biologist know that the eye
began only as a group of lightsensitive cells.
B. The ability to distinguish
between light and dark was an
advantage because it enabled
organisms to avoid danger
and exploit new food
resources more efficiently
than organisms without this
adaptation.
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Explaining the
Complexities of the Eye
C. Later, over time, new variations
arose that resulted in the
formation of a simple lens
providing a blurry image.
D. Seeing even a blurred image
is an advantage over seeing
no image at all.
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Explaining the
Complexities of the Eye
E. Later changes led to a sharpening
of focus, and, probably at the same
time, still other changes permitted
color vision.
F. The structure becomes more
adaptive and improves an
animal’s chances of survival, and,
therefore, the passing of its genes
to offspring. (natural selection)
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Types of Adaptations
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A. Structural Adaptations
1. The most obvious adaptations
are those involving structure or
anatomy.
2. Traits such as the structure
of a bird’s beak, the hoof of a
horse, or the shape of a tooth
are called structural
adaptations.
3. Many obvious structural
adaptations in animals are for
obtaining food.
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Structural Adaptations
A. The neck of the
Giraffe
B. The slow hypothetical
evolution: Response to
Acacia Trees
C. Neck increased in
length to reach food
in trees.
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Structural Adaptations that
mimic the environment
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Structural Adaptations that
Mimic the Environment
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Structural Adaptation in the Angler Fish
A. Protruding from the top of the
angler fish’s skull is a long
filament that is broad and flat at
its tip.
B. It hangs in front of the fish’s
mouth and attracts prey, much
like a fishing lure.
C. When the prey bites at the lure,
the angler fish sucks the prey
into its mouth.
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Deep Sea Hairy Angler Fish
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Physiological Adaptations
A. The enzymes needed for digestion,
clotting of blood, or muscular
contractions in animals fall into the
category of Physiological
Adaptations.
B. Such adaptations have a chemical
basis.
C. Other examples include the poison
venom of a snake, the proteins used
in a spider’s web, and the ink of an
octopus.
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Behavioral
Adaptations
A. Organisms are also adapted in
their responses to the
environment.
B. Birds migrate in search of
food, squirrels hunt and store
nuts, wolves track their prey,
C. Such responses are examples
of behavioral adaptations.
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In-Class Assignment for
next class session
1. Create an organism with:
(1) At least three structural
adaptations.
(2) At least two physiological
adaptations.
(3) At least two behavioral
adaptations.
2. Draw this organism and
explain how these adaptations
benefit this being and allow it
to compete and survive.
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