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evolution and natural selection power point
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Evolution and Natural Selection
How species change over time
Evolution and Natural Selection
GSE’sGenetic variations are passed on
through reproductionEvidence for evolution illustrates
how organisms are relatedNatural selection leads to evolutionOur 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.
Larmark 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 Selection
For natural selection to occur, there must be at least two varieties of a species.
For example: the peppered moth
Peppered Moths
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
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
Any Questions?