Transcript Evolution and Natural Selection

Evolution and Natural
Selection
How species change over
time
Evolution and Natural
Selection
GSE’s
Genetic variations are passed on through
reproduction LS3-9a
Evidence for evolution illustrates how
organisms are related LS3 -9b
Natural selection leads to evolution LS3 – 9d
Our understanding of evolution has changed
over time LS3 - 9e
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Evolution
 The
theory that organisms
today developed from more
simple life forms and have
changed (evolved) over time
Natural Selection
 The
theory that states that
those organisms best adapted
to their environment have a
better chance of surviving
and reproducing
Evolution
Pre-Darwin Beliefs
Earth was only a few thousand years old.
 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.
 We now know the planet has changed and,
through fossils, discovered organisms have
changed, as well.
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Evolution
Pre-Darwin Beliefs
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Jean Pierre Lamark believed that organisms could
change their traits during their lifetime by use or
disuse.
He thought that these traits could be passed on to
offspring. Over time this would cause change in a
species.
Lamark was
wrong
Charles Darwin
1809 - 1882
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Scientist credited with the
Theory of Evolution & Natural Selection
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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
Darwin’s Voyage
Voyage of the Beagle
What did Darwin find?
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The finches on each island in the
Galapagos had different types of beaks.
Voyage of the Beagle
What did Darwin find?
The
tortoises on each island in the
Galapagos had different types of shells.
What was 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.
Darwin published his
research in 1859
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?
Before
After
Before
After
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.
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Over time, the black moths
have become more common.
Evidence for Evolution:
Common Ancestry
Common Ancestry: If species evolved from a common
ancestor, then they should share common anatomical
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!
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Evidence for Evolution:
Homologous Structures
If animals evolved from a common
ancestor, then they should share
common structures – and they do!
 These are called
homologous structures
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Evidence for Evolution
Embryo Development
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What do you notice? List 2 observations
Evidence for Evolution:
Vestigial Organs
Some organisms have structures or
organs that no longer have a useful
function.
 These structures or organs may have
been useful to the ancestors of a species,
but over time have evolved into what we
term vestigial organs.
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Examples of Vestigial Organs
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Kiwi (flightless bird)
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Whales (hind leg bones)
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Humans (tailbone, appendix)
Evidence for Evolution
Fossils
Fossils provide a look
into the past
 Scientists can trace how
a species has evolved
by studying fossils
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Wrap Up the Evidence
Common Ancestry
 Homologous Structures
 Embryonic Development
 Vestigial Organs
 Fossils
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Any Questions?