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D.3.1-D.3.10
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D.3.1: Outline the method for dating rocks and fossils using radioisotopes,
with reference to 14C and 40K.
D.3.2: Define half-life.
D.3.3: Deduce the approximate age of materials based on a simple decay
curve for a radioisotope.
D.3.4: Describe the major anatomical features that define humans as
primates.
D.3.5: Outline the trends illustrated by the fossils of Ardipithecus ramidus,
Australopithecus including A. afarensis and A. africanus, and Homo
including H. habilis, H. erectus, H. neanderthalensis and H. sapiens.
D.3.6: State that, at various stages in hominid evolution, several species
may have coexisted.
D.3.7: Discuss the incompleteness of the fossil record and the resulting
uncertainties about human evolution.
D.3.8: Discuss the correlation between the change in diet and increase in
brain size during hominid evolution.
D.3.9: Distinguish between genetic and cultural evolution.
D.3.10: Discuss the relative importance of genetic and cultural evolution in
the recent evolution of humans
 D.3.1: Outline
the method for dating
rocks and fossils using radioisotopes,
with reference to 14C and 40K.
 D.3.2: Define half-life.
 D.3.3: Deduce the approximate age of
materials based on a simple decay curve
for a radioisotope.
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Isotopes:
• Version of an element with a different number of
neutrons from the usual version of the same element.
• Example: carbon-14 or carbon-13
Radioisotopes:
• Isotopes that release some of their subatomic
particles to reach stability.
• Radiation is not harmful to us but can be measured in
the lab.
• Examples: Carbon-14 and Potassium-40
 Half-life
is the amount of time it takes for
half of the radioactive isotopes in a
substance to decay. (example below is
carbon-14)
Number of
Half-Lives
Number of
years which
have passed
% of original
remaining
1
5730
50
2
11460
25
3
17190
12.5
4
22920
6.25
Etc.
Etc.
Etc.
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Curve decreases exponentially.
Theoretically the curve will never reach zero but in
reality their will eventually be no more radioactive
isotopes in a
sample.
 7.5
g of this sample
remain as C-14.
What is the
approximate age?
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D.3.1:
• 1) Get a sample of the material.
• 2) Measure the percentage of radioactive isotope left.
• 3) Use this percentage to calculate the age of the sample
using the radioisotope’s halflife.
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D.3.2: Half-life is the amount of time it takes for
half of the radioactive isotopes in a substance to
decay. (carbon-14=5730 years)
D.3.3: Deduce the approximate age of materials
based on a simple decay curve for a
radioisotope.
 D.3.4: Describe
the major anatomical
features that define humans as primates.
 Primates!
 Trends
in primate evolution show increased
hand and shoulder mobility, less hair,
shortened face, increased brain to body ratio.
Trends
move
Prosimians
(least related
to us)
Gibbon
New World
Monkeys
Old World Monkeys
Orangutan
Gorilla
We share a most
recent common
ancestor with
chimps and
bonobos.
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Opposable Thumbs:
• Grasp objects (very important for climbing)
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Long thin straight fingers:
• Fine motor skills to manipulate objects
Paw
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Fingernails:
• Primates lack claws making climbing easier.
Some prosimians have
modified nails that serve
as a “grooming claw”
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Shoulder socket:
• Increased range of motion
• Freedom of movement is impossible in other animals
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Forward facing eyes:
• Allows for stereoscopic vision (3D)
 D.3.4: The
major anatomical features that
define humans as primates include:
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Opposable Thumbs (Grasp objects)
Long thin straight fingers (allows fine motor skills)
Fingernails (allow for easier gripping)
Shoulder socket with increased range of motion (important for
climbing)
Forward facing eyes (Allows for stereoscopic vision (3D) and
depth perception)