Transcript CHAPTER 10.4 AND 11 NOTES

CHAPTER 14 NOTES
HOW LIFE BEGAN?
Inorganic (nonliving) matter was
transformed into simple organic
molecules
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Miller-Urey experiment (they modeled
the ancient atmosphere in a reacting
chamber, then electrodes produced
sparks to simulate lightning and after
one week they found the liquid produced
by the experiment contained amino acids
– the building blocks of proteins)
Eventually these simple organic
molecules changed into cells with DNA
and a nucleus
FOSSILS
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Paleontologists are scientists who study
fossils
The fossil record provides evidence about
the history of life on Earth and it also
shows how different groups of
organisms, including species, have
changed over time
Most fossils form in sedimentary rock
FOSSIL DATING
RELATIVE VS.
RADIOACTIVE
RELATIVE DATING
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Determines the age of a
fossil by comparing its
placement with that of
fossils in other layers of
rock
Oldest fossils are in lower
layers of the rock
Draw the picture on your
notes – which fossil is
B
older? _____
Fossil A
Fossil B
RADIOACTIVE DATING
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The use of half-lives to determine the age of a
fossil
Radioactive decay occurs at a constant rate called
a HALF-LIFE (the time it takes for half of the
atoms in a sample to undergo radioactive decay)
 EX. The half-life of Potassium-40 is 1.26 billion
years
 Ex. The half-life of Carbon-14 is 5730 years
Potassium dating is used for rocks that are
suspected to be billions of years old and carbon
dating is used for younger fossils (50,000 years)
EXAMPLE PROBLEM:
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Suppose there are 16 grams of Carbon-14 in a
living snail shell and 4 grams of Carbon-14 in a
fossilized snail shell
How many half-lives has this fossil gone through?
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2
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What is the age of the fossil if each half-life of
Carbon-14 takes 5730 years?
5730 X 2 = 11,460
How many grams of Carbon-14 will be left if the
snail shell goes through one more half-life?
2 grams
GEOLOGIC TIME SCALE
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In order to catalog the 4 billion years of life
on Earth, scientists have created the
geologic time scale to represent
evolutionary time
The scale is divided into large time spans
called ERAS, which is subdivided into
PERIODS
MOST
RECENT
GEOLOGIC
TIME
SCALE
BEGIN
END
OLDEST
MASS EXTINCTION
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When majorities of species
were eliminated during a
time period very quickly
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Ex. Dinosaurs during the
Cretaceous mass extinction
These mass extinctions can
have various causes:
volcanoes, change in
atmosphere, lands shifting,
large comet or asteroid,
weather changes