Chapter 8
Archean World
Chapter Outline:
I.
Overview of Archean Time
II.
Origin of Earth and the Solar System
a. Using Meteorites and Moon Rocks to Decipher Early Earth
History
b. Birth of the Universe and Solar System
c. Early Evolution of Earth and the Moon
III. Origin of the Atmosphere and Ocean
IV. Earth’s Oldest Rocks
a. Early Continental Crust
V.
Archean Life Forms
a. The Earliest Evidence of Life
b. Adiobotic Synthesis of Amino Acides and the Earliest Life
Forms
c. Does Life Exist Beyond Earth?
Key Terms:
Archean Eon
Proterozoic Eon
cratons
canadian shield
meteorites
asteroids
magma ocean
outgassing
greenstone belts
mobile crust phase
banded iron formations
cyanobacteria
photosynthesis
autotrophic
heterotrophic
stromatolites
photochemical dissociation
hydrothermal vents
archaebacteria
In-Class Activities:
Instructor Notes for In-Class Activity 1
Title:
The Big Bang and Solar Nebular Theories: The formation of the
Universe and our Solar System
Time:
5-10 minutes prep; 40 – 50 minutes in class (or can assign research
between class periods)
Materials:
Internet required. Print instruction sheets as handouts.
Handouts:
A list of questions for students to research and discuss using
recommended websites. The textbook section called “Birth of the
Universe and Solar System” is a useful reference for answering the
handout questions.
Students will watch the following four video clips and answer the
following 10 questions on their handouts.
http://www.youtube.com/watch?v=hVApTLE7Csc&feature=related
http://www.youtube.com/watch?v=AVlB9tOWTU4&feature=related
http://www.youtube.com/watch?v=hSZqhqR5XKM&feature=related
http://www.youtube.com/watch?v=B1AXbpYndGc&feature=related
Procedures:
First, have each individual student review the section “Birth of the
Universe and Solar System”” in the textbook.
Next have the students in groups of 3-4 watch the first film clip:
http://www.youtube.com/watch?v=hVApTLE7Csc&feature=related
After watching the 1st film clip, have the students discuss the following
questions and answer them as a group.
1) Did Edwin Hubble discover that the universe is larger or
smaller than what was previously thought? Briefly, how did he
do this?
2) Briefly, what does the redshift increase in stars that are farther
from the Earth tell us about the universe?
Next have your students watch the second video:
http://www.youtube.com/watch?v=AVlB9tOWTU4&feature=related
The students can now answer questions 3-6.
3) Explain how geologist can look back in time by looking
through telescopes. How did this convince scientists that a “
Big Bang occurred”?
4) How are “Cepheids” useful for estimating distances in the
universe?
5) About how old is the universe?
6) According to this video, is the expansion of the universe
slowing down? What role does anti-gravity play in this? What
might this mean for the fate of our universe?
The students will now watch the third video:
http://www.youtube.com/watch?v=hSZqhqR5XKM&feature=related
The students can now answer questions 7-8.
7) Which element formed first, which formed second? How are
the heavier elements such as Nitrogen and Carbon formed?
8) Where did the debris that formed the planets, the moons, the
asteroids, and comets come from? Briefly explain.
Now have your students watch the 4th and last film pertaining to the
formation of our solar system and answer questions 9 and 10.
http://www.youtube.com/watch?v=B1AXbpYndGc&feature=related
9) When did our sun form, where does the light from the Sun come
from?
10) What is a “supernova”, and what might this have to do with the
formation of our solar system according to the Solar Nebular
theory.
Each member of the group should become familiar with the answers to
the above questions. Knowledge of this information will be useful in
preparing for both a future quiz and test.
Student
Instructions: See above.
Specific
Suggestions:
The instructor should emphasize the importance and interesting nature
of the subject material. For example, the instructor might state that the
“Big Bang” theory and “Solar Nebular” theories are probably the most
important stories that science has ever told. They basically explain the
nature and existence of time, energy, mass and space in our physical
universe.
Objectives:
Students should be able to summarize the evidence provided in the four
video clips for the “Big Bang” and “Solar Nebular” theories.
Students should be able to list the discoveries of Edwin Hubble as they
pertain to the formation of the “Big Bang” theory.
Students should be familiar with the events that led to the formation of
the elements.
Students should become familiar with the predicted fate of our universe
if the anti-gravity force becomes more powerful.
Students should know how old the universe is according to the “Big
Bang” theory, and how old the solar system is according to the “Solar
Nebular” theory.
In-Class Activity 1: Handout
In 1929, Edwin Hubble made several important discoveries that you will learn about
today, and that led to the “Big Bang” theory. The “Big Bang” theory is the best
explanation for the formation of our physical universe, which consists of time, mass,
energy and space. Since Hubble’s time, cosmologists have continued to find more
evidence for this “Big Bang” that occurred in our distant past. Today, you will also learn
about the “Solar Nebular” theory, which is the best explanation for the formation of our
solar system and Earth according to the overwhelming majority of scientists. These
theories are important because they are scientist’s best explanation for why matter, time,
space, energy, life, humans and you as an individual exist.
First, have each member of your group individually read “Birth of the Universe and Solar
System”” in the textbook.
Next, with your group members, watch the first film clip:
http://www.youtube.com/watch?v=hVApTLE7Csc&feature=related
After watching the 1st film clip, discuss the following 2 questions and answer them as a
group.
1) Did Edwin Hubble discover that the universe is larger or smaller than what was
previously thought? Briefly, how did he do this?
2) Briefly, what does the Redshift increase in stars that are farther from the Earth tell
us about the universe?
Watch the second video as a group:
http://www.youtube.com/watch?v=AVlB9tOWTU4&feature=related
Discuss questions 3-6, and write down your consensus answer for your group.
3) Explain how geologists can look back in time by looking through telescopes.
How did this convince scientists that a “ Big Bang occurred”?
4) How are “Cepheids” useful for estimating distances in the universe?
5) About how old is the universe?
6) According to this video, is the expansion of the universe slowing down? What
role does anti-gravity play in this? What might this mean for the fate of our
universe?
Now, watch the third video as a group:
http://www.youtube.com/watch?v=hSZqhqR5XKM&feature=related
Discuss questions 7-8, and write down your consensus answer for your group.
7) Which element formed first, which formed second? How are the heavier elements
such as Nitrogen and Carbon formed?
8) Where did the debris that formed the planets, the moons, the asteroids, and comets
come from? Briefly explain.
Now, watch the fourth and last video:
http://www.youtube.com/watch?v=B1AXbpYndGc&feature=related
Discuss questions 9-10, and write down your consensus answer for your group.
9) When did our sun form, where does the light from the Sun come from?
10) What is a “supernova”, and what might this have to do with the formation of our
solar system according to the Solar Nebular theory?
Submit your answers for the above 10 questions for your group to your instructor for
grading.
Each member of the group should become familiar with the answers to the above
questions. Knowledge of this information will be useful in preparing for both a future
quiz and test.
Instructor Notes for In-Class Activity 2
Title:
Stromatolites: Earth’s oldest fossils
Time:
5 – 10 Minutes prep; 35 – 50 minutes in class (or can assign research
between class periods)
Materials:
Internet required. Print instruction sheets as handouts.
Handouts:
A list of websites and questions to be answered. Students will find Ch.
8 “The Earliest Evidence of Life” to be useful in answering some of the
questions. Also, students will find the following websites particularly
useful:
http://www.youtube.com/watch?v=Qt9butyran8
http://www.fossilmuseum.net/Tree_of_Life/Stromatolites.htm
http://www.lpi.usra.edu/education/timeline/gallery/slide_27.html
http://www.baylor.edu/Geology/index.php?id=26727
http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html
http://www.fossilmall.com/Science/About_Stromatolite.htm
Procedures:
Hand out instruction sheets. Instruct the students to use the websites
listed above and Ch. 8 “The Earliest Evidence of Life” in their
textbook as references to answer the following questions:
1) Briefly, what are stromatolites? When did they first appear on
the Earth?
2) Billions of years ago, were stromatolites diverse?
3) Were Precambrian stromatolites primarily formed by
eukaryotic or prokaryotic organisms? Explain.
4) Are stromatolites still forming today? Where is this occurring?
5) What types of sedimentary rock types are most likely to
preserve stromatolites?
6) What effect did stromatolites have on the Precambrian
atmosphere?
7) What is the relationship between banded iron formation and
stromatolites during the Precambrian?
8) What type of environmental conditions did stromatolitic
building organisms prefer?
9) Are stromatolites always formed by organisms?
10) Which domains of life are thought to be involved in the
formation of stromatolites?
Students should discuss their findings with their group members, come
to a consensus, and write their answers neatly down on sheets of paper
to hand in for grading.
If time remains students should discuss why stromatolites are
important when scientists study the origin of life on Earth.
Student
Instructions: See above
Specific
Suggestions:
Students should be encouraged to learn more about stromatolites online
or from books on their own time (in addition to this in-class activity).
If available, the instructor should pass around samples of actual
stromatolite samples.
Objectives:
Students should be able to:
Clearly define the term “Stromatolite”.
Become familiar with the types of organisms typically involved in
forming Precambrian stromatolites.
State the effect of stromatolite building on the Precambrian
atmosphere.
Recognize the relationship between the formation of stromatolites and
banded iron formations.
Recognize the importance of studying the relationship between
stromatolites and the origin of life on Earth.
State where stromatolites are forming today, and what types of
environmental conditions are most favorable for their growth.
In-Class Activity 2: Handout
Stromatolites are the Earth’s oldest fossils. The study of these structures is important for
researchers interested in the origin of life on our planet. The purpose of this in-class
exercise is to learn more about what these creatures looked like, when they lived, what
environmental conditions did they prefer, their geological/biological significance, their
effect on atmospheric content during the Precambrian, and their relationship with banded
iron formations.
Use Ch. 8 “The Earliest Evidence of Life” in your textbook as a reference, and the
following websites to answer the below questions.
http://www.youtube.com/watch?v=Qt9butyran8
http://www.fossilmuseum.net/Tree_of_Life/Stromatolites.htm
http://www.lpi.usra.edu/education/timeline/gallery/slide_27.html
http://www.baylor.edu/Geology/index.php?id=26727
http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html
http://www.fossilmall.com/Science/About_Stromatolite.htm
1) Briefly, what are stromatolites? When did they first appear on the Earth?
2) Billions of years ago, were stromatolites diverse?
3) Were Precambrian stromatolites primarily formed by eukaryotic or
prokaryotic organisms? Explain.
4) Are stromatolites still forming today? Where is this occurring?
5) What types of sedimentary rock types are most likely to preserve
stromatolites?
6) What effect did stromatolites have on the Precambrian atmosphere?
7) What is the relationship between banded iron formation and stromatolites
during the Precambrian?
8) What type of environmental conditions did stromatolitic building organisms
prefer?
9) Are stromatolites always formed by organisms?
10) Which domains of life are thought to be involved in the formation of
stromatolites?
Discuss the answers to the above questions as a group, come to a consensus, and write the
answers down neatly on paper. Use complete sentences. Your graded in class exercise
will be handed back to you next week. Completing this exercise will help prepare you for
a future quiz and test.
If time permits, discuss the question, “What can scientists learn about the origin of life by
studying early stromatolites?”
1.