Transcript Evolution

Evolution
The process in which species
change over time.
Charles Darwin
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Was a British
naturalist.
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He was hired to
travel on the HMS
Beagle to learn as
much as he could
about the living
things he saw on
the voyage.
The HMS Beagle
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Traveling with the ship, Darwin observed
many different plants and animals.
He was very curious about why these living
things were so different from the ones he
studied in England.
This curiosity led to develop: The theory of
_______________ by natural selection.
The Galapagos Islands
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The Beagle traveled to the Galapagos
Islands of South America.
Here, Darwin made some of his most
important observations!
The Galapagos Islands
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Darwin observed that the __________
of the Galapagos were very different
from one island to the next.
The beaks of the birds varied in shape
and size.
Darwin’s Finches
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As Darwin studied his finches, he
noticed that each species was well
suited to the life it led.
Insect eaters: sharp, needlelike beaks
Seed eaters: strong, wide beaks
The Galapagos Islands
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Darwin also noticed that the iguanas
that lived on the island were different
from the iguanas on the mainland.
Island Iguanas had large claws.
Mainland Iguanas had small claws.
The Galapagos Iguanas
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Darwin realized that the claws of the
iguana were also beneficial to the life
it led.
The large claws of the island iguanas
kept them from slipping off of the
rocks.
The small claws of the mainland
iguanas allowed them to climb trees
where they ate leaves.
Galapagos Iguanas
Life After the Beagle
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________________ are traits that help
organisms survive and reproduce.
Beak shape and claw length are
examples of this.
When Darwin returned home from life
on the Beagle, he tried to understand
how these specific traits arose.
Darwin’s Conclusion
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Darwin reasoned that arrived on one
of the Galapagos Islands faced
conditions that were different from the
mainland.
He came up with the conclusion that
species must gradually change over
many generations to become better
adapted to their environment.
This change over time is called
_____________.
The Theory of Evolution
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What is a scientific theory?
A well-tested concept that explains a
wide range of observations.
The theory of evolution is what
scientists have determined to be true
based on significant amounts of
research, observations, and evidence
to back this up.
How does evolution happen?
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Darwin still didn’t know one thing: how does
evolution happen?
Darwin bred pigeons. He allowed only
pigeons with many tail feathers to mate.
This produced pigeons with two or three
times the usual number of feathers.
This process is called ___________
______________.
Maybe, he thought, something happens like
this in nature!
Selective Breeding in Nature
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Why are certain traits selected for
(and how) in nature?
____________ _____________ is the
process by which individuals that are
better adapted to their environment
are more likely to survive and
reproduce than other members of the
same species.
The Origin of Species
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Charles Darwin, along with biologist
Alfred Russel Wallace, published his
explanation in a book called The Origin
of Species.
Natural Selection
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Factors that affect the process of
natural selection:
1. Overproduction
2. Competition
3. Variations
Overproduction
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Most species produce far more
offspring that can possibly survive.
Sea turtles lay more than 100 eggs.
If all of the young turtles survived, the
sea would be full of turtles!
But this is not the case… not all of the
offspring will survive.
Overproduction
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Sea Turtles are
organisms that
overproduce
Natural Selection
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Factors that affect the process of
natural selection:
1. Overproduction
2. Competition
3. Variations
Competition
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Offspring must compete with each
other to survive.
Offspring compete for resources- food,
water, living space, etc.
Only some will escape from predators.
Only a few offspring will survive long
enough to reproduce.
Competition
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Sea Turtle hatchlings compete for
space.
Natural Selection
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Factors that affect the process of
natural selection:
1. Overproduction
2. Competition
3. Variations
Variations
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Any difference between individuals in
the same species is called a
variation.
We know that this is a result of
genetics.
Some variations make certain
individuals better adapted to their
environment.
Variations
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Some newly hatched turtles are able
to swim faster than others.
Natural Selection
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Individuals that are better adapted to
their environment are more likely to
survive and reproduce.
When these well-adapted individuals
reproduce, their offspring inherit the
alleles for these adaptations.
Thus…
Natural Selection
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The environment has “selected” these welladapted organisms to be the parents of the
next generation.
Nature… has selected… natural selection
Over a long period of time, natural selection
can lead to evolution (the changing of a
species).
Helpful variations gradually accumulate in a
species, while unfavorable ones disappear.