Download Change over Time - Fort Thomas Independent Schools

Change over Time
©2008 Susan Anderson
Darwin
British Naturalist
 Journey to Galapagos / South America
 Saw:
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New/different SPECIES
Fossils similar to living organisms
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(where had these organisms gone?)
He asked why were those organisms on
the islands different from those on the
mainland?
Adaptations
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Example for Darwin:
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Finches
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Different beaks
Different foods
Less competition
Evolution
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Gradual change over time to become
better adapted to their environment.
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Gradualism
Punctuated Equilibria
Natural Selection
“Survival of the Fittest”
 Extinction
 Overproduction – not all offspring survive
 Competition- usually indirect (food, space)
 Variations – genetic
 Selection- helpful variations accumulate,
unfavorable ones disappear
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Formation of New Species
Sometimes a group is separated from the
rest of its species. (river, mountain range,
weather carries them)
 If a group is separated long enough, they
may evolve different traits.
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“Geographic Isolation”
Continental Drift
Large scale geographic isolation.
 Members were separated when the
continents split.
 Example:
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Animals isolated on Australia are unlike other
mammals.
Review
What is evolution?
 Name something Darwin observed that he
thought was the result of evolution
 Some insects look just like sticks. How
could this be an advantage to the insects?
 How could the “stick trait” have evolved
through natural selection?
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Fossil Record
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Sedimentary Rock
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Petrified
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Minerals dissolved in the water around remains soaks in
and replaces the remains, changing them to rocks
Molds/Casts
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Most fossils are found in this type of rock
Why?
Remains get dissolved and leave behind a hollow space
(mold), then it’s filled with minerals (cast)
Preserved

Can be found in tar or amber
Dating Fossils
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Relative Dating
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Only be used when the rock layers have been
preserved in their original sequence
Doesn’t tell actual age, only which fossils are
older or younger
Absolute Dating
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Uses radioactive elements to determine exact
age of fossils
HALF LIFE – the time it takes for half the
atoms of a sample to decay
Review
Describe how fossils form in sedimentary
rock.
 Explain the process of absolute dating.
 How are gradualism and punctuated
equilibrium similar?
 How are gradualism and punctuated
equilibrium different?

Other Evidence
Homologous Structures
 Embryology
 DNA similarities
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Branching Tree Diagrams

A diagram the shows how scientists think
different groups of organisms are related.
Review
Name three types of evidence from
modern day organisms that scientists use
to determine evolutionary relationships.
 What are homologous structures?
 Most scientists today consider similarities
in DNA to be the best indicator of how
closely two species are related. Why do
you think this is the case?
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Homework