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Changes Over Time
Chapter 5 Section 1: Darwin’s Voyage
Charles Darwin
Charles Darwin was an English
naturalist on the British naval ship
HMS Beagle
A naturalist is a person who
studies the natural world
On Darwin’s journey, he made
many observations that led him to
develop the theory of Natural
Selection
Charles Darwin
Darwin’s first stop was
South America
In Brazil, Darwin saw
amazing creatures, like giant
insects and armadillos
Charles Darwin
There is a huge amount of
diversity in South America
There are many different species
of animals and plants
A species is a group of
similar organisms that can
mate with each other and
produce fertile offspring
If the offspring is not fertile, the
parents are not the same species
Horse + Donkey = Mule (not
fertile)
There are 2.5 million species of
organisms on Earth!!
The Galapagos
Islands
Darwin’s next stop was the
Galapagos Islands, off of the
west coast of South America
Here Darwin encountered
the giant tortoise
The Galapagos
Islands
Darwin observed that many
of the plants and animals on
the Galapagos were similar
to the ones on the mainland.
BUT…there were some
key differences
The Galapagos
Islands
Darwin observed that many
of the plants and animals on
the Galapagos were similar
to the ones on the mainland.
BUT…there were some
key differences
Eg The comorants on the
mainland could fly, but those on the
Galapagos couldn’t
The Galapagos
Islands
The iguanas of the
Galapagos have large claws
so they can grip slippery
rocks
The iguanas on the
mainland had smaller claws
so they can climb trees
The Galapagos
Islands
Darwin realized that some
how, these animals came
from the mainland and
eventually started to become
different from their “distant
cousins”
These organisms began to
adapt…
Adaptations
An adaptation is a trait
that helps an organism
survive and reproduce
Darwin observed birds
called finches.
There were different types
of finches that Darwin
studied, each with a different
shape beak
Adaptations
Finches have different
beaks to help them eat their
food.
Large wide beaks to crack
hard seeds
Long sharp beaks to hunt
and eat insects
Evolution
“Survival of the fittest”
Darwin believed that
species gradually change
over time…this is Evolution
Species change and adapt
so that they can survive
when their environments
change
Natural Selection
In 1859, Darwin wrote the
book The Origin of Species
In this book, Darwin explained
that evolution happens because of
natural selection
Natural Selection is the
process by which individuals
that are better adapted to
their environment are more
likely to survive.
What Affects
Natural
Selection?
Overproduction
Some species have many babies
at one time
Example: Sea turtles lay 100s of
eggs
With so many offspring
produced, there won’t be enough
resources for all of the baby sea
turtles
**Remember** All organisms
need food, water and living space
What Affects
Natural
Selection?
Competition
If there are not enough
resources, organisms will have to
compete for food, water, and a
place to live
Some times there are fights for
territory
Some times it’s a competition of
“who can run the fastest” from
predators
**Remember** The masked
booby chicks that fight to see who
will be the one to survive
What Affects
Natural
Selection?
Variations
A variation is a difference in traits
that members of the same species
may have.
Examples of variations:
Parrots with different colors
Turtles that swim faster than
others
What Affects
Natural
Selection?
Selection
Some individuals are better
adapted to their environment than
others because of their traits
They are the ones that are
“selected” to survive and
reproduce
The individuals that don’t have
these adaptations won’t survive
Geographic
Isolation
Isolation is the complete
separation.
Isolation happens when
one group of a species is “cut
off” from the rest of the
species
Geographic Isolation is
when a group is isolated
because of a river, volcano,
mountain range, etc.
Geographic
Isolation
The two separated groups
begin to adapt to their
specific environment and
develop different traits.
When this happens a new
species forms.
The Northern and Mexican
Spotted Owl is an example of
this.
Continental Drift
Many millions of years ago,
all of the continents were
Over time, the continents
drifted away from each other
This was caused by
Continental Drift
What do you think
happened to many species
after the continents
separated???