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:
Interest Grabber continued
Section 17-1
1. Using your ruler, draw a line 24 cm in length on a sheet of paper. Make
a mark at the halfway point (12 cm).
2. Then, divide this 12-cm segment in half, making a mark at 6 cm.
Continue in this way, dividing each progressively smaller segment in
half (ignoring all of the other segments) until it becomes too small to
accurately measure.
3. Now count each progressively smaller half-segment. How many
segments did you count?
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Section:
Section Outline
Section 17-1
17–1
The Fossil Record
A. Fossils and Ancient Life
B. How Fossils Form
C. Interpreting Fossil Evidence
1. Relative Dating
2. Radioactive Dating
D. Geologic Time Scale
1. Eras
2. Periods
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Section:
Compare/Contrast Table
Section 17-1
Comparing Relative and Absolute Dating of Fossils
Can determine
Is performed by
Drawbacks
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Section:
Relative Dating
Absolute Dating
Age of fossil with respect to
another rock or fossil (that is,
older or younger)
Age of a fossil in years
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
Figure 17-2 Formation of a Fossil
Section 17-1
Water carries small rock
particles to lakes and seas.
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Section:
Dead organisms are buried
by layers of sediment, which
forms new rock.
The preserved remains
may later be discovered
and studied.
Figure 17-5 Geologic Time Scale
Section 17-1
Era
Period
(millions of
Time years ago)
Quaternary
1.8–present
Tertiary
65–1.8
Cretaceous
145–65
Jurassic
208–145
Triassic
245–208
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Section:
Era
(millions of
Period
Time years ago)
Permian
290 – 245
Carboniferous
360–290
Devonian
410–360
Silurian
440–410
Ordovician
505–440
Cambrian
544–505
Era
(millions of
Period
Time years ago)
Vendian
650–544
Figure 17-5 Geologic Time Scale
Section 17-1
Era
Period
(millions of
Time years ago)
Quaternary
1.8–present
Tertiary
65–1.8
Cretaceous
145–65
Jurassic
208–145
Triassic
245–208
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Section:
Era
(millions of
Period
Time years ago)
Permian
290 – 245
Carboniferous
360–290
Devonian
410–360
Silurian
440–410
Ordovician
505–440
Cambrian
544–505
Era
(millions of
Period
Time years ago)
Vendian
650–544
Figure 17-5 Geologic Time Scale
Section 17-1
Era
Period
(millions of
Time years ago)
Quaternary
1.8–present
Tertiary
65–1.8
Cretaceous
145–65
Jurassic
208–145
Triassic
245–208
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Section:
Era
(millions of
Period
Time years ago)
Permian
290 – 245
Carboniferous
360–290
Devonian
410–360
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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Section:
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:
Section Outline
Section 17-2
17–2
Earth’s Early History
A. Formation of Earth
B. The First Organic Molecules
C. How Did Life Begin?
1. Formation of Microspheres
2. Evolution of RNA and DNA
D. Free Oxygen
E. Origin of Eukaryotic Cells
F. Sexual Reproduction and Multicellularity
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Section:
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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Section:
Figure 17-8 Miller-Urey Experiment
Section 17-2
Mixture of gases
simulating
atmospheres of
early Earth
Spark simulating
lightning storms
Condensation
chamber
Water
vapor
Cold
water
cools
chamber,
causing
droplets
to form
Liquid containing
amino acids and
other organic
compounds
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Section:
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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Section:
Primitive Aerobic
Eukaryote
Animals, fungi, and
non-plantlike protists
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:
Interest Grabber continued
Section 17-3
1. Make a list of at least six different organs in your body, and next to
each, write the main function of that organ.
2. Now, examine your list. Do any main functions overlap? Do two or more
organs do exactly the same thing?
3. Use your list to jog your memory, and write down the functions that
must be performed by a unicellular organism. For example, you may
have written that your nerves help you sense your environment.
Doesn’t a cell need to sense its environment, too?
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Section:
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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Section:
Geologic Time Scale with Key Events
Section 17-3
Era
Cenozoic
Mesozoic
Paleozoic
Precambrian
Time
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Section:
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:
Interest Grabber continued
Section 17-4
1. Choose a type of animal in your area that is represented by several
species, such as songbirds.
2. Make a list of examples of this type of animal. If you don’t know the
name of an animal, write a brief description instead.
3. Count the number of different examples you have identified. Then, write
down characteristics found in all of the examples. Do the examples in
your list seem to be more closely related to each other or to other types
of animals?
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Section:
Section Outline
Section 17-4
17–4
Patterns of Evolution
A.
B.
C.
D.
E.
F.
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Section:
Extinction
Adaptive Radiation
Convergent Evolution
Coevolution
Punctuated Equilibrium
Developmental Genes and Body Plans
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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Section:
Videos
Click a hyperlink to choose a video.
Geologic Time
Evolution of Cells
Video 1
Geologic Time
Click the image to play the video segment.
Video 2
Evolution of Cells
Click the image to play the video segment.
Go Online
Career links on fossil preparators
Interactive test
For links on the fossil record, go to www.SciLinks.org and enter the
Web Code as follows: cbn-5171.
For links on eukaryotic cells, go to www.SciLinks.org and enter the Web
Code as follows: cbn-5172.
For links on extinction, go to www.SciLinks.org and enter the Web Code
as follows: cbn-5174.
Interest Grabber Answers
1. Using your ruler, draw a line 24 cm in length on a sheet of paper. Make a
mark at the halfway point (12 cm).
2. Then, divide this 12-cm segment in half, making a mark at 6 cm. Continue
in this way, dividing each progressively smaller segment in half (ignoring all
of the other segments) until it becomes too small to accurately measure.
3. Now count each progressively smaller half-segment. How many segments
did you count?
Student answers will vary. Have students retain their paper and refer to it
when the half-life of radioactive isotopes is discussed.
Interest Grabber Answers
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?
Students’ lists will vary. Remind those having trouble that they can list
everyday events, such as finding a half-eaten pizza in their refrigerator.
Skid marks tell you that a car stopped or started very quickly.
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?
Students may say that a trained observer can see the remains of a past
event, and some may know that geology provides many clues to Earth’s
past. For example, finding a fossil of a fish in a desert would indicate that
the area had once been under water.
Interest Grabber Answers
1. Make a list of at least six different organs in your body, and next to each,
write the main function of that organ.
Students’ answers may include lung, skin, heart, stomach, kidney, and
so on.
2. Now, examine your list. Do any main functions overlap? Do two or more
organs do exactly the same thing?
To get students started, suggest an organ/function pair such as
stomach/digest food or kidneys/remove wastes from blood.
3. Use your list to jog your memory, and write down the functions that must be
performed by a unicellular organism. For example, you may have written
that your nerves help you sense your environment. Doesn’t a cell need to
sense its environment, too?
Students should be aware that unicellular organisms use food, exchange
gases, get rid of wastes, make new cell components, and for
some cells, actively move.
Interest Grabber Answers
1. Choose a type of animal in your area that is represented by several
species, such as songbirds.
2. Make a list of examples of this type of animal. If you don’t know the name
of an animal, write a brief description instead.
3. Count the number of different examples you have identified. Then, write
down characteristics found in all of the examples. Do the examples in your
list seem to be more closely related to each other or to other types of
animals?
Possible answers may include the following: Songbirds are small, perching
birds that eat seeds or insects. They seem more closely related to each
other than to other birds (and to other animals in general).
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