evolution and natural selection powerpoint
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Evolution and Natural Selection
How species change over time
Evolution and Natural Selection
Genetic variations are passed on through reproduction
Evidence for evolution illustrates how organisms are related
Natural selection leads to evolution
Our understanding of evolution has changed over time
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.
EvolutionPre-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.
EvolutionPre-Darwin Beliefs
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.
Lamark was wrong
Charles Darwin1809 - 1882
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 BeagleWhat did Darwin find?
The finches on each island in the Galapagos had different types of beaks.
Voyage of the BeagleWhat did Darwin find?
The tortoises on each island in the Galapagos had different types of shells.
What was Darwin’s hypothesis?
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 SelectionFor natural selection to
occur, there must be at least two varieties of a species.
For example: the peppered moth
Peppered MothsAt 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
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: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!
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
Evidence for EvolutionEmbryo Development
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.
Examples of Vestigial Organs
Kiwi (flightless bird)
Whales (hind leg bones)
Humans (tailbone, appendix)
Evidence for EvolutionFossils
Fossils provide a look
into the pastScientists can
trace how a species has
evolved by studying
fossils
Wrap Up the Evidence
Common AncestryHomologous StructuresVestigial OrgansEmbryonic DevelopmentFossils
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