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Charles Darwin and
Natural Selection
(Control yourselves, ladies)
History
Darwin sailed on the HMS Beagle for a 5year round the world trip at the age of 22.
Darwin was a naturalist-a person who
studies the natural world.
In the Galapagos, Darwin observed the
diverse organisms and fossils, leading to
his theory of EVOLUTION by NATURAL
SELECTION.
The Beagle’s voyage
Diversity and fossils
Darwin saw great diversity (variety) in the life
he saw.
insects that look like flowers
armies of ants
Giant marine iguanas that ate algae in cold
water
He saw fossils that were similar to living
creatures.
What happened to these ancient creatures?
Giant Sloth: similar to living sloths, but
where did they go?
Darwin’s Finches
Darwin saw similarities in the finches of
South America and the Galapagos.
Finches differed most in their Beak shapes.
Adaptation- a trait that helps an organism
survive and reproduce.
Different beaks helped finches
find different foods and survive
to reproduce.
Darwin’s Theory of
Evolution
Darwin hypothesized that plants and
animals gradually change over
generations to become better adapted
to their environment.
This does not mean that they change
while the organism is alive. It happens
over generations.
Natural Selection
This is what Darwin proposed as the
driving force behind evolution.
“INDIVIDUALS THAT ARE BETTER
ADAPTED TO THEIR
ENVIRONMENT ARE MORE LIKELY
TO SURVIVE AND REPRODUCE
THAN MEMBERS OF THE SAME
SPECIES.”
5 points of natural
selection
1.Populations have variation
2. Some variations are favorable
3. More offspring are produced than will survive
4. Organisms compete, and those with more
favorable traits will survive.
5. Populations change over time.
Example:
1. Green and Brown
Bugs
2. Brown are
camouflaged
3. Some bugs will be
eaten
4. Bugs hide, and
fewer brown ones are
eaten
More brown ones
reproduce
Example:
Kids, this is
why we try to
educate you.
Don’t be
“selected”.
NOTE:
The favorability of a trait depends entirely on
the environment.
If the environment changes, a trait could be
harmful to an organism
Example: A white mouse can hide well in the
arctic, but would stick out to predators in a
green field.