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