Interest Grabber
Section 17-1
Half of a Half of a Half . . .
Some forms of chemical elements are unstable—that is, they break down
into other substances. Like the decay of leftovers in your refrigerator, this
breakdown takes place over time. Unlike those leftovers, however, the
breakdown of unstable forms of an element progresses in a very orderly
way—by decaying into halves.
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Section Outline
Section 17-1
17–1 The Fossil Record
A. Fossils and Ancient Life
A. Paleontologist
B. Fossil record – provides evidence about the
history of life on Earth. It also shows how
different groups of organisms have changed
over time.
C. extinct
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B. How Fossils Form
B. Examples
C. For a fossil to form
D. Incomplete information
E. Sedimentary rock
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
later be discovered and
studied.
C.Interpreting Fossil Evidence
1. Relative Dating – the age of a fossil is determined by comparing its
placement with that of fossils in other layers of rock
2. Index fossil
3. Radioactive Dating
Compare/Contrast Table
Section 17-1
Comparing Relative and Absolute Dating of Fossils
Relative Dating
Absolute Dating
Can determine
Age of fossil with respect to
another rock or fossil (that is,
older or younger)
Age of a fossil in years
Is performed by
Comparing depth of a fossil’s
source stratum to the position
of a reference fossil or rock
Determining the relative
amounts of a radioactive
isotope and nonradioactive
isotope in a specimen
Imprecision and limitations of
age data
Difficulty of radioassay
laboratory methods
Drawbacks
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D.Geologic Time Scale
1. Eras
2. Periods
3. How are geological
times determined?
Figure 17-5 Geologic Time Scale
Section 17-1
Era
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Period
(millions of
Time years ago)
Quarternary
1.8–present
Tertiary
65–1.8
Cretaceous
145–65
Jurassic
208–145
Triassic
245–208
Era
(millions of
Period
Time years ago)
Permian
290 – 245
Carboniferous
363–290
Devonian
410–363
Silurian
440–410
Ordovician
505–440
Cambrian
544–505
Era
(millions of
Period
Time years ago)
Vendian
650–544
Interest Grabber
Section 17-2
Mystery Detective
Earth is billions of years old. There were not any witnesses to those early
years. How, then, can scientists determine the conditions on Earth long
before there were any scientists?
Think about how you draw conclusions about occurrences that you did not
witness. If you saw the charred remains of a house, for example, you could
infer that it burned down.
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Interest Grabber continued
Section 17-2
1. On a sheet of paper, list things that you can observe around you that
lead you to infer about events you did not see. For example, what do
skid marks in the roadway tell you?
2. Now, think about and list the evidence all around you that scientists
might analyze when trying to piece together a history of Earth. How
would finding the fossil of a sea animal in the middle of a desert tell a
scientist something about the past?
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Section Outline
Section 17-2
17–2
Mixture of gases
simulating
atmospheres of
early Earth
Earth’s Early History
A. Formation of Earth
B. The First Organic Molecules
B. Did organic material form before life
was present?
C. How Did Life Begin?
1. Formation of Microspheres
2. Evolution of RNA and DNA
2. Which came first?
D. Free Oxygen
D. What did Oxygen provide?
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Spark simulating lightning
storms
Cold water
cools
chamber,
causing
droplets to
form
Liquid containing
amino acids and
other organic
compounds
E. Origin of Eukaryotic Cells
E. Endosymbiotic theory – communities formed by prokaryotes
F. Sexual Reproduction and Multicellularity
Figure 17-12 Endosymbiotic
Theory
Section 17-2
Chloroplast
Aerobic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Plants and
plantlike
protists
Photosynthetic
bacteria
Mitochondrion
Primitive Photosynthetic
Eukaryote
Ancient Anaerobic
Prokaryote
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Primitive Aerobic
Eukaryote
Animals, fungi, and
non-plantlike protists
Concept Map
Section 17-2
Evolution of Life
Early Earth was hot; atmosphere contained poisonous gases.
Earth cooled and oceans condensed.
Simple organic molecules may have formed in the oceans..
Small sequences of RNA may have formed and replicated.
First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.
Later prokaryotes were photosynthetic and produced oxygen.
An oxygenated atmosphere capped by the ozone layer protected Earth.
First eukaryotes may have been communities of prokaryotes.
Multicellular eukaryotes evolved.
Sexual reproduction increased genetic variability, hastening evolution.
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Interest Grabber
Section 17-3
Team, Team, Team!
The first living things were unicellular. You, however, are multicellular. Is
there an advantage to being multicellular?
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Section Outline
Section 17-3
17–3
Evolution of Multicellular Life
A. Precambrian Time
B. Paleozoic Era
1. Cambrian Period
2. Ordovician and Silurian Periods
3. Devonian Period
4. Carboniferous and Permian Periods
C. Mesozoic Era
1. Triassic Period
2. Jurassic Period
3. Cretaceous Period
D. Cenozoic Era
1. Tertiary Period
2. Quaternary Period
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Geologic Time Scale with Key Events
Section 17-3
Era
Cenozoic
Mesozoic
Paleozoic
Precambrian
Time
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Period
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Time
(millions of
years ago)
1.8–present
65–1.8
145–65
208–145
245–208
290–245
363–290
410–363
440–410
505–440
544–505
650–544
Key Events
Glaciations; mammals increased; humans
Mammals diversified; grasses
Aquatic reptiles diversified; flowering plants; mass extinction
Dinosaurs diversified; birds
Dinosaurs; small mammals; cone-bearing plants
Reptiles diversified; seed plants; mass extinction
Reptiles; winged insects diversified; coal swamps
Fishes diversified; land vertebrates (primitive amphibians)
Land plants; land animals (arthropods)
Aquatic arthropods; mollusks; vertebrates (jawless fishes)
Marine invertebrates diversified; most animal phyla evolved
Anaerobic, then photosynthetic prokaryotes; eukaryotes,
then multicellular life
Interest Grabber
Section 17-4
Birds of a Feather
Darwin was surprised by the number of similar but not identical species
that he observed. Look around you–can you make the same observation?
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Section Outline
Section 17-4
17–4
Patterns of Evolution
A. Mass Extinctions
A. How does mass extinctions
encourage rapid evolution?
B. Adaptive Radiation
C. Convergent Evolution
D. Coevolution
E. Punctuated Equilibrium
F. Developmental Genes and Body Plans
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Flowchart
Section 17-4
Species
that are
Unrelated
form
Related
in
under
under
in
in
Interrelationshiops
Similar
environments
Intense
environmental
pressure
Small
populations
Different
environments
can undergo
can undergo
can undergo
can undergo
can undergo
Coevolution
Convergent
evolution
Extinction
Punctuated
equilibrium
Adaptive
radiation
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