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EVOLUTION BY WAY OF
NATURAL SELECTION
VOCABULARY
Species – a type of organism.
Reproduction within a species creates
the same species.
Extinction – the end of a species
What Is Evolution?
• The gradual change in living things over
long periods of time.
• Evolution is a scientific theory, meaning it
is a well-tested explanation for the
observations made on the Earth.
NATURAL SELECTION
• The process that causes evolution.
• Also called Survival of the Fittest
HERE’S HOW IT WORKS
1. MUTATION OCCURS or
2. SEXUAL REPRODUCTION CAUSES
VARIANCE
3. NATURAL SELECTION weeds out the
weak and allows the strong to survive
and reproduce
An Example of Natural
Selection?
The Peppered Moth
What is the Peppered Moth?
• In England there lives a moth called the
Peppered Moth.
• It is called the Peppered Moth because it
is mainly white with speckles of black on it.
The Peppered Moth
• In England, the Industrial Revolution
began in 1750.
• Before 1750 the Peppered Moth looked
like this:
The Peppered Moth
• Before 1750, the Peppered Moth blended
in with the trees it liked to live on.
• It was CAMOUFLAGED.
Tree
A Variety of the Peppered Moth
• Before 1750 some Peppered Moths had babies
that were darker than their parents because of a
mutation. All the other Peppered Moths called
them freaks because they stood out on the
trees.
Tree
Variety
• Both the dark moths and the light moths
were called Peppered Moths.
• There’s just 2 varieties.
A Question for You
• Which variety of Peppered Moth was
easier to spot by birds who love to eat
moths?
What Does That Mean?
• Because the dark variety is easier to spot,
they died often before they could have
babies.
What Does That Mean?
• More of the light variety were able to
reproduce.
• Less of the dark variety were able to
reproduce.
• This is called NATURAL SELECTION or
Survival of the Fittest.
Natural Selection
• Since the dark one’s are not as FIT to
survive, they will not survive much longer.
That’s why Natural Selection is called
Survival of the Fittest.
The Industrial Revolution
• With the coming of the Industrial
Revolution, things were about to change
for the Peppered Moth.
• The Industrial Revolution created factories
with chimneys that pumped out dark
smoke called soot.
• The soot covered everything: buildings,
roads, and trees.
The Trees Changed colors
• Gradually, as the Industrial Revolution
kept increasing, more and more soot
covered everything.
• The bark on trees became darker and
darker until they were almost black.
The Trees Changed Colors
Trees before the Industrial
Revolution
Trees after the Industrial
Revolution
A Question for You
• Now after the Industrial Revolution, which
variety of Peppered Moth was easier to
spot by birds who love to eat moths?
What Does That Mean?
• Because the light variety is easier to spot,
more of them died before having babies.
What Does That Mean?
• Now, more of the dark variety were able to
reproduce.
• Less of the light variety were able to
reproduce.
• The light variety was now headed towards
EXTINCTION, where no more would be
around ever again.
What Does All of this Mean?
• The more fit organism survives and
reproduces (NATURAL SELECTION).
• This allows for a change in the species or
a entirely new species over long periods of
time (EVOLUTION)
EVOLUTION
• EVOLUTION CAN CHANGE SPECIES
• EVOLUTION CAN CREATE NEW
SPECIES
EVIDENCE OF EVOLUTION
FROM COMMON ANCESTOR
1. COMPARATIVE ANATOMY – similar structures
in different organisms
2. VESTIGIAL ORGANS – no longer have a
function; point to earlier times
3. STRUCTURE OF CELLS & MOLECULES –
same in different organisms
4. MOLECULAR PHYLOGENY – shared genetic
code (DNA)
5. FOSSIL RECORD – evidence in rock