go to section: half of a half of a half... some forms of chemical elements are unstable—that is,...
TRANSCRIPT
Go to Section:
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.
Section 17-1
Interest Grabber
Go to Section:
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?
Section 17-1
Interest Grabber continued
Go to Section:
17–1 The Fossil RecordA. 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
Section 17-1
Section Outline
Go to Section:
Relative Dating
Can determine
Is performed by
Drawbacks
Absolute Dating
Comparing Relative and Absolute Dating of Fossils
Section 17-1
Compare/Contrast Table
Imprecision and limitations of age data
Difficulty of radioassay laboratory methods
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
Age of fossil with respect to another rock or fossil (that is, older or younger)
Age of a fossil in years
Go to Section:
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.
Section 17-1
Figure 17-2 Formation of a Fossil
Go to Section:
Era Period Time
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
(millions of years ago)Era Period Time
(millions of years ago)Era Period Time(millions of
years ago)
290 – 245
360–290
410–360
440–410
505–440
544–505
1.8–present
65–1.8
145–65
208–145
245–208
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Vendian 650–544
Section 17-1
Figure 17-5 Geologic Time Scale
Go to Section:
Era Period Time
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
(millions of years ago)Era Period Time
(millions of years ago)Era Period Time(millions of
years ago)
290 – 245
360–290
410–360
440–410
505–440
544–505
1.8–present
65–1.8
145–65
208–145
245–208
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Vendian 650–544
Section 17-1
Figure 17-5 Geologic Time Scale
Go to Section:
Era Period Time
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
(millions of years ago)Era Period Time
(millions of years ago)Era Period Time(millions of
years ago)
290 – 245
360–290
410–360
440–410
505–440
544–505
1.8–present
65–1.8
145–65
208–145
245–208
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Vendian 650–544
Section 17-1
Figure 17-5 Geologic Time Scale
Go to Section:
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.
Section 17-2
Interest Grabber
Go to Section:
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?
Section 17-2
Interest Grabber continued
Go to Section:
17–2 Earth’s Early HistoryA. 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
Section 17-2
Section Outline
Go to Section:
Concept Map
Evolution of Life
Section 17-2
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.
Go to Section:
Mixture of gases simulating atmospheres of early Earth
Spark simulating lightning storms
Condensation chamber
Cold water cools chamber, causing droplets to form
Water vapor
Liquid containing amino acids and other organic compounds
Section 17-2
Figure 17-8 Miller-Urey Experiment
Go to Section:
Aerobic bacteria
Ancient Prokaryotes
Ancient Anaerobic Prokaryote
Primitive Aerobic Eukaryote
Primitive Photosynthetic Eukaryote
Chloroplast
Photosynthetic bacteria
Nuclear envelope evolving Mitochondrion
Plants and plantlike protists
Animals, fungi, and non-plantlike protists
Section 17-2
Figure 17-12 Endosymbiotic Theory
Go to Section:
Team, Team, Team!
The first living things were unicellular. You, however, are multicellular. Is there an advantage to being multicellular?
Section 17-3
Interest Grabber
Go to Section:
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?
Section 17-3
Interest Grabber continued
Go to Section:
17–3 Evolution of Multicellular LifeA. 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
Section 17-3
Section Outline
Go to Section:
Section 17-3
Geologic Time Scale with 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 evolvedAnaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life
Cenozoic
Mesozoic
Paleozoic
PrecambrianTime
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
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 EventsEra Period Time(millions of years ago)
Go to Section:
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?
Section 17-4
Interest Grabber
Go to Section:
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?
Section 17-4
Interest Grabber continued
Go to Section:
17–4 Patterns of EvolutionA. Extinction
B. Adaptive Radiation
C. Convergent Evolution
D. Coevolution
E. Punctuated Equilibrium
F. Developmental Genes and Body Plans
Section 17-4
Section Outline
Go to Section:
Section 17-4
Flowchart
that are
can undergo can undergo can undergo can undergo can undergo
in underunderform inin
Species
Unrelated Related
Inter-relationshiops
Similar environments
Intense environmental
pressure
Small populations
Different environments
Coevolution Convergent evolution
ExtinctionPunctuated equilibrium
Adaptive radiation
Videos
Click a hyperlink to choose a video.
Geologic Time
Evolution of Cells
Click the image to play the video segment.
Video 1
Geologic Time
Click the image to play the video segment.
Video 2
Evolution of Cells
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.
Go Online
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).
This slide is intentionally blank.