Transcript Evidence of Evolution

A.
B.
Direct Evidence
Indirect Evidence
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Visible evidence that takes us back in time
and shows organisms have changed
Ex. – Fossils
▪ Paleontologists are scientists who collect and
study fossils.
▪ The fossil record provides incomplete
information about the history of life.
▪ Over 99% of all species that have lived on Earth
have become extinct.
▪ Where are all these fossils??
Fossil Formation
Fossil Formation
Water carries small rock
particles to lakes and
seas.
Dead organisms are buried by
layers of sediment, which
forms new rock.
The preserved remains
may be later discovered
and studied.
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Lucy
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Coal Formation
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The following picture is of plant fossils found
in coal from the Minto area that are 300
million years old…..older than dinosaures!
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Relative Dating
▪ In relative dating, the age of a fossil is determined by
comparing its placement with that of fossils in other
layers of rock.
▪ Rock layers form in order by age—the oldest on the
bottom, with more recent layers on top.
▪ Grand Canyon
Relative dating allows paleontologists to estimate a fossil's age
compared with that of other fossils.
▪ Radioactive dating (Absolute Dating)
▪ Some elements are radioactive and steadily break down
into nonradioactive elements.
▪ Radioactive dating is the use of half-lives to determine
the age of a sample.
▪ A half-life is the length of time required for half of the
radioactive atoms in a sample to decay.
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C-14 breaks down into N-14 at a fixed rate.
The half life of C-14 is 5,760 years.
When an organism dies, the C-14 in the
organism starts to change into N-14.
Knowing the half-life, you can compare the
amount of C-14 to N-14 to determine the age
of the fossil
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Let’s say the fossil we are dating shows 50%
C-14 and 50% N-14…….
The fossil should be 5,760 years old.
If another 5,760 years passed, what would be
the ratio of C-14 to N-14?
Right!!.........C-14 25% to N-14 75%
Potassium 40 is an isotope with a half-life of
1.2 billion years!!
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Evidence we can look
at today that suggests
we may have a
common ancestry
with other organisms.
1.
Embryological
Similarities
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2. Comparative
Morphology
Homologous
Structures
 (Similar structure
 but different
 function!)
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Similar in function
but not in structure
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Do not show the
close evolutionary
connection
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Analogous Structures
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3. Similarities in Biochemistry (Organic
Compounds)
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DNA similarities (98% of our DNA is the same
as a chimpanzee)
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Protein in all organisms is composed of the
same 20 amino acids!!
Direct Evidence – something we can look at that
takes us back in time.
 Ex. Fossils
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Indirect Evidence – something we can look at that
show some kind of evolutionary connection
between organisms.
 Ex. Embryological similarities, Homologous
structures, Biochemistry similarities
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Darwin’s explanation of evolution is called
Natural Selection.
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What does the term Artificial Selection
mean? Discuss this with a neighbour.
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Samuri Crab
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Organisms don’t change to survive, they
survive (or die!) because they change!