Download Chpt. 15.1- Darwin`s Theory of Evolution by Natural Selection

Darwin’s Theory of Evolution by
Natural Selection
Galapagos Islands
Darwin arrived at the
Galapagos Islands in
1835.
 Collected birds and
other animals on the
4 islands. He noticed
that different islands
had their own slightly
different varieties of
animals.
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Charles Darwin
Darwin was a naturalist
(collected biological and geological
specimens for study)
 Developed a widely accepted theory of evolution
through the process of natural selection.
 Other theories were in place
before Darwin developed his theory

What two ways did people think change
occurred? (think back to our Earth unit)

Years later, Darwin
determined that the
finches didn’t live
anywhere else. He
suspected that
populations of the birds
from the mainland
changed after reaching
the Galapagos.
Darwin thought that perhaps artificial selection
(process of breeding to produce desired traits
in offspring) could work in nature.
Natural Selection

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Natural selection- The process whereby
organisms better adapted to their
environment tend to survive and produce
more offspring. If you don’t adapt, you’ll die.
Nature “selects” traits for organisms to aid in
survival.
What is natural selection
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This explains Darwin’s observations of
different finch birds and their beaks.
Darwin thought the different species of
finches evolved from the same original
species in response to adaptation to their
environment.
The overall goal for natural selection and
evolution is so that animals will be more likely
to survive and reproduce in the future.
More about natural selection and
adaptation

Variation is a difference in a physical trait.

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Galápagos tortoises that live in areas with tall
plants have long necks and legs. Why would that
be an advantage?
Galápagos finches that live in areas with hardshelled seeds have strong beaks. Why would that
be an advantage?
Types of adaptations
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Structural adaptation
Protective coloration (Camoflauge)
Mimicry
Behavior adaptations (Herds)
Hibernation
Structural adaptation

A structural adaptation involves some part
of an animal's body.

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Teeth
Body coverings
Movement
Protective Coloration

Also called camouflage

Their camouflage makes it hard for
enemies to single out individuals.
Mimicry

Mimicry allows one animal to look, sound,
or act like another animal to fool predators
into thinking it is poisonous or dangerous.
Behavior Adaptations

Behavior adaptations include activities that
help an animal survive.

Behaviour adaptations can be learned or
instinctive.
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Social behaviour
Behavior for protection
Hibernation
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This is deep sleep in which animal’s body
temp droops, body activities are slowed to
conserve energy.

E.g. Bats, woodchucks & bears.
Origin of Species
In 1859, Darwin published
On the Origin of Species
by Means of Natural
Selection.
 Used the term evolution
only on the last page.
Evolution- Cumulative
changes in groups of
organisms through time.
 Natural Selection is the
mechanism evolution can
occur.
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