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Evolution
a change in a species over time
There are many types of evidence that
support the theory of evolution
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1. Anatomical Evidence:
2. Fossil Evidence:
3. Radioactive dating:
4. Relative Dating:
5. The Fossil Record
6. Embryological Evidence:
7. Chemical Evidence:
8. The Molecular Clock:
1. Anatomical Evidence:
• In the early 1800's, The French biologist
Lamarck began to look at similar structures
in different species.
• These homologous structures are body parts
and organs that are similar.
• EX: bat’s wing, dolphin’s
• flipper,
Theory of Use and Disuse
• Lamarck
• that individuals would acquire or lose structures
through their use or disuse.
EX: A giraffe got its
long neck by stretching
for the highest leaves.
It then passed this trait
on to its offspring.
Problems
• tailbone
• Appendix
• Neither one is still used but we still have
them.
• Ex: Another scientist tested this by cutting
the tails off mice.
2. Fossil Evidence:
• Fossils- the imprints or remains of plants or
animals that existed in the past
• Fossils allow scientists to follow changes in
organisms over time.
3. Radioactive dating:
• elements that give off radiation as they
decay
• not all elements decay at the same rate
• half-life- measuring the decay rate
• non-radioactive element- the time it takes
for ½ of the element to break down
•
Carbon-14 is the radioactive form
of carbon
• half-life of 5,770 years
• All living things have
carbon-14
• when the organism
dies its C-14 starts to
decay.
• By measuring how
much C-14 is left
• tell how old the fossil
is.
Example:
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•
Carbon-14 is the radioactive form of carbon
half-life of 5,770 years.
when the organism dies, it decay.
By measuring how much C-14 is left in a
fossil, you can tell how old the fossil is.
A sample had 100 grams of C-14
• 50 grams after 5770 years
Relative Dating:
• compares the rock
layers above and
below the fossil
• Layers of sedimentary
rock toward the
bottom are older
• those toward the top
are younger.
Which layer is older?
C
B
A
Which layer is older?
Which Layer is younger?
Relative time is recorded in rocks.
Each of these rock
layers represents a
period of time in
Earth's history, so the
entire sequence of layers
is another timeline.
As more and more
layers are deposited,
the older rock layers
end up at the bottom
of the sequence and
the newer ones toward
the top.
The arrow shows the
relative order of the
rock layers from
earliest to most recent.
Evidence of the events in
Earth's history is found within
the rocks.
a.) Brachiopod
b.) Eurypterid
c.) Trilobite
d.) Ammonite
5. The Fossil Record
• This includes ALL of the fossil evidence
scientists have collected
Steno’s drawing of a shark head helped him see that
“tongue stones” were actually fossil shark teeth (right).
Example
• Some fossil bones of a leg and a foot were found in
sedimentary rock in the Mississippi River valley.
• Could tell from the
bones:
• 4 toes on each front
foot
• toes were spread apart.
Fossils found in the
same layers helped them
figure out it was
probably the size of a
cat, but had other traits of
a horse.
They named it
Eohippus = early horse.
They used radioactive dating
• To determine the age to be about 50 million
years.
spread-apart toes would
help it to walk on mud
Other fossils in those layers :
•climate was warm and wet
•possibly a tropical climate
surrounded by swamps and
mud
Theory of evolution so far
• 1. Anatomical
Evidence:
• 2. Fossil Evidence:
• 3. Radioactive dating:
• 4. Relative Dating:
• 5. The Fossil Record
Scientists put all of this
information together to help form
a better idea
of what an organism looked like,
how it lived and how it changed
over time
mutations
• Changes of what organism looked like
ADAPTATION.
• a change that makes it easier for an
organism to survive
One of the
most difficult
• animals that could not adapt became extinct.
6. Embryological Evidence:
• Embryos are developing organisms.
• Scientists compare the embryos of different
species to see how closely related they are.
7. Chemical Evidence:
• Chemical similarities in the DNA
of different species = shows
us how they might be related.
• Ex: The DNA of a zebra
• and a quagga
8. The Molecular Clock:
• The more similar the structure of protein
molecules between 2 organisms, the more recent
their common ancestor.
• Scientists developed a time scale
• how long it takes proteins to change over time
• They use this to figure out how long ago a protein
changed.
http://www.ucmp.berkeley.edu/education/explorations/tours/geotime/gtpage5.html
http://www.ucmp.berkeley.edu/education/explorations/tours/geo
time/clonus/transparent.gif
Now let's make a
similar timeline for
some of the major
events during the
history of life on
Earth.
Here are pictures of
some fossils. Your
goal is to put them
into the correct order
of when they first
appeared on Earth.
http://www.ucmp.berkeley.edu/education/explorations/tours/geot
ime/clonus/transparent.gif
Theory of evolution
• 1. Anatomical
Evidence:
• 2. Fossil Evidence:
• 3. Radioactive dating:
• 4. Relative Dating:
• 5. The Fossil Record
• 6. Embryological
Evidence:
• 7. Chemical
Evidence:
• 8. The Molecular
Clock: