Half of a Half of a Half ' ' '

1
Half of a Half of a Half . . .
Interest Grabber
Section 17-1

• Some forms of chemical elements are unstablethat
  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
  wayby decaying into halves.

2
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?

3
Section Outline
Section 17-1

• 171 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

4
Compare/Contrast Table
Section 17-1
Comparing Relative and Absolute Dating of Fossils
Relative Dating
Absolute Dating
Can determine Is performed by Drawbacks
5
Figure 17-2 Formation of a Fossil
Section 17-1
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.
6
Figure 17-5 Geologic Time Scale
Section 17-1
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
Permian Carboniferous Devonian Silurian Ordovi
cian Cambrian
290  245 360290 410360 440410 505440 544
505
1.8present 651.8 14565 208145 245208
Quaternary Tertiary Cretaceous Jurassic Triass
ic
Vendian
650544
7
Figure 17-5 Geologic Time Scale
Section 17-1
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
Permian Carboniferous Devonian Silurian Ordovi
cian Cambrian
290  245 360290 410360 440410 505440 544
505
1.8present 651.8 14565 208145 245208
Quaternary Tertiary Cretaceous Jurassic Triass
ic
Vendian
650544
8
Figure 17-5 Geologic Time Scale
Section 17-1
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
(millions of years ago)
Era
Period
Time
Permian Carboniferous Devonian Silurian Ordovi
cian Cambrian
290  245 360290 410360 440410 505440 544
505
1.8present 651.8 14565 208145 245208
Quaternary Tertiary Cretaceous Jurassic Triass
ic
Vendian
650544
9
Mystery Detective
Interest Grabber
Section 17-2

• 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.

10
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?

11
Section Outline
Section 17-2

• 172 Earths 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

12
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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Figure 17-8 Miller-Urey Experiment
Section 17-2
Mixture of gases simulating atmospheres of early
Earth
Spark simulating lightning storms
Cold water cools chamber, causing droplets to form
Condensation chamber
Water vapor
Liquid containing amino acids and other organic
compounds
14
Figure 17-12 Endosymbiotic Theory
Section 17-2
Chloroplast
Plants and plantlike protists
Aerobic bacteria
Ancient Prokaryotes
Photosynthetic bacteria
Nuclear envelope evolving
Mitochondrion
Primitive Photosynthetic Eukaryote
Animals, fungi, and non-plantlike protists
Primitive Aerobic Eukaryote
Ancient Anaerobic Prokaryote
15
Team, Team, Team!
Interest Grabber
Section 17-3

• The first living things were unicellular. You,
  however, are multicellular. Is there an advantage
  to being multicellular?

16
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. Doesnt a cell need to sense its
  environment, too?

17
Section Outline
Section 17-3

• 173 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

18
Geologic Time Scale with Key Events
Section 17-3
(millions of years ago)
Key Events
Era
Period
Time
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
Cenozoic Mesozoic Paleozoic Precambrian Ti
me
Quaternary Tertiary Cretaceous Jurassic Triassic P
ermian Carboniferous Devonian Silurian Ordovician
Cambrian
1.8present 651.8 14565 208145 245208 290245
363290 410363 440410 505440 544505 650544
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Birds of a Feather
Interest Grabber
Section 17-4

• Darwin was surprised by the number of similar but
  not identical species that he observed. Look
  around youcan you make the same observation?

20
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 dont 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 Outline
Section 17-4

• 174 Patterns of Evolution
• A. Extinction
• 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
in
under
under
form
in
in
can undergo
can undergo
can undergo
can undergo
can undergo
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Video Contents
Videos

• Click a hyperlink to choose a video.
• Geologic Time
• Evolution of Cells

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Video 1
Video 1
Geologic Time

• Click the image to play the video segment.

25
Video 2
Video 2
Evolution of Cells
Click the image to play the video segment.
26
Internet
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.

27
Section 1 Answers
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.

28
Section 2 Answers
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 Earths past.
  For example, finding a fossil of a fish in a
  desert would indicate that the area had once been
  under water.

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Section 3 Answers
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. Doesnt 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.

30
Section 4 Answers
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 dont 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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End of Custom Shows

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