Change over Time - Fort Thomas Independent Schools
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Transcript Change over Time - Fort Thomas Independent Schools
Change over Time
©2008 Susan Anderson
Darwin
British Naturalist
Journey to Galapagos / South America
Saw:
New/different SPECIES
Fossils similar to living organisms
(where had these organisms gone?)
He asked why were those organisms on
the islands different from those on the
mainland?
Adaptations
Example for Darwin:
Finches
Different beaks
Different foods
Less competition
Evolution
Gradual change over time to become
better adapted to their environment.
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
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.
“Geographic Isolation”
Continental Drift
Large scale geographic isolation.
Members were separated when the
continents split.
Example:
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?
Fossil Record
Sedimentary Rock
Petrified
Minerals dissolved in the water around remains soaks in
and replaces the remains, changing them to rocks
Molds/Casts
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
Relative Dating
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
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
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?