Transcript Evolution and Natural Selection

Evolution and Natural
Selection
How species change
over time
Evolution
 The
theory that
organisms today
developed from more
simple life forms and
have changed (evolved)
over time
Natural Selection
 Organisms
that are best
adapted to their
environment have a
better chance of
surviving and reproducing
Early Beliefs
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Earth was only a few thousand years old.
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We now know it is billions of years old.
Neither the planet nor the species that
inhabited it had changed since the
beginning of time.
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We now know the planet has changed and,
through fossils, discovered organisms have
changed, as well.
Evolution
Pre-Darwin Beliefs
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Jean Pierre Lamark believed that organisms
can change their traits during their lifetime
by use or disuse.
He thought that these traits are passed on
to offspring. Over time this would cause
change in a species.
Larmark was
wrong
Charles Darwin
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Scientist credited with the
Theory of Evolution & Natural Selection
Voyage of the HMS Beagle – a 5 year
voyage to South America and the South
Pacific, collecting specimens, making
observations and keeping a scientific journal
of his findings
Voyage of the Beagle
What did Darwin find?
1.
The finches on each island in the
Galapagos had different types of
beaks.
2. The tortoises on each island in the
Galapagos had different types of
shells.
Darwin’s Hypothesis?
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Darwin hypothesized that organisms had
a common ancestor, but had adapted to
their particular environments and
changed over time.
He further proposed that only members
if a species best suited for their
environment will survive and reproduce.
He called this Natural
Selection
Darwin published his
research in 1859
Key Ideas that led to Darwin’s
Theory
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Overproduction-plants and animals will more
offspring than can possibly survive
Variation-within a species there will be natural
differences that are passed on through
mutations
Adaptation-inheritance of traits that give an
organism an advantage in a particular environment
Selection –adaptations allow organisms to survive
long enough to reproduce
Speciation-new species arises with enough
accumulated differences usually because a
species is isolated
Natural Selection
For natural selection to occur,
there must be at least two
varieties of a species.
 For example: the peppered moth
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Peppered Moths
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At the beginning of the Industrial
Revolution in England, coal burning
produced soot that covered the
countryside in many areas
What do you think
happened?
Evolution/Natural
Selection
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White moths became easier
to see, while the black
moths became harder to
see. The black moths were
more likely to survive and
pass on the gene for dark
color to their offspring.
Over time, the black moths
have become more common.
Evidence for Evolution
1.
Common Ancestry: If species evolved from a
common ancestor, then they should share
common anatomical (physical) traits
Hawaiian Honeycreeper: family of
birds in Hawaii that have similar
skeletons and muscles, indicating they
are closely related. Over time, their
common ancestor evolved into several
species, each with a specialized bill
for eating certain foods. Just like
Darwin’s finches on the Galapagos!
2. Homologous Structures
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If animals evolved from a common ancestor,
then they should share common structures –
and they do!
These are called
homologous structures
They look similar but are
adapted for different
uses.
3. Embryo Development
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Similarities early
in development in
many organisms.
4. Vestigial Organs-
structures or organs that may have been
useful to ancestors but, over time no
longer have a useful function
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Kiwi (flightless bird)
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Whales (hind leg bones)
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Humans (tailbone, appendix)
5. Fossils-similar fossils were found in
several different geographic locations and
layers
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Any Questions?