Chapter 9
Proterozoic World
Chapter Outline:
I.
Evolution of the Cratons and Proterozoic Supercontinents
a. Proterozoic Continents
II.
Oxygenation of the Atmosphere-Ocean System
III. Proterozoic Glaciations
a. Snowball Earth
IV. Proterozoic Life Forms
a. Proterozoic Prokaryotes
b. Early Eukaryotes
c. The Edicaran Biota and the Radiation of Animals
Key Terms:
platforms
platform phase
orogenic belt
grenville orogenic belt
piercing point
supercontinent cycle
pannotia
gondwana
redbeds
snowball earth hypothesis
edicaran biota
metazoans
microbial mats
In-Class Activities:
Not to be reprinted or redistributed © John Wiley & Sons, Inc.
Instructor Notes for In-Class Activity 1
Title:
Oxygen: Life giving gas builds up in the Proterozoic atmosphere.
Time:
5-10 minutes prep; 40– 60 minutes in class (or can assign research between class
periods)
Materials:
Internet required. Print worksheets as handouts.
Handouts:
A list of questions for students to research and discuss. Information pertaining to
oxygen in the Proterozoic atmosphere can be found in the section “Oxygenation
of the Atmosphere-Ocean System” in the textbook. Additional information
pertaining to this topic, and to the effects of oxygen on Proterozoic life can be
found at the following websites.
http://www.palaeos.org/Proterozoic
http://en.wikipedia.org/wiki/Proterozoic
http://www.absoluteastronomy.com/topics/Proterozoic
http://www.wisegeek.com/what-is-the-proterozoic-eon.htm
http://www.associatedcontent.com/article/162650/earths_proterozoic_period.html
?cat=58
http://www.geol.umd.edu/~tholtz/G102/102prot3.htm
Procedures
:
A list of questions for students to research and discuss using recommended
websites.
First, have the students read the section in their textbook titled “Oxygenation of
the Atmosphere-Ocean System” to become familiar with the evidence for
increased atmospheric oxygen concentrations in Proterozoic Eon rocks.
Using the textbook and the above listed website references, have the students
answer the following questions in groups of 3-4:
1) List four lines of evidence showing that oxygen levels were increasing
during the Proterozoic Eon.
2) Using a chemical formula, show how photosynthesis affected the
Proterozoic atmosphere.
3) What chemical sinks are thought to be responsible for removing oxygen
from the atmosphere?
4) Why are red beds not found in the Archean and the earliest part of the
Proterozoic Eon?
5) What is the “Oxygen Catastrophe” of the Proterozoic, and what does it
Not to be reprinted or redistributed © John Wiley & Sons, Inc.
6)
7)
8)
9)
Student
Instruction
s:
Specific
Suggestions
:
Objectives:
have to to do with banded iron formations?
What was the Earth’s atmosphere like prior to the Proterozoic?
What effect does photosynthesis have on the greenhouse effect?
Why are uraninite and pyrite not found in rocks younger than 2.3 billion
years ago?
Briefly, how did oxygen affect the evolution of life during the Progerozoic
Eon.
See above.
The instructor should emphasize that students should become familiar with the
effect of oxygen build-up on the evolution of life on Earth during the Proterozoic
Eon.
Students should be able to:
Clearly and concisely describe the causes and evidence for oxygen build up in the
atmosphere during the Proterozoic Eon.
Describe the concept of the oxygen sink, and cite examples.
Describe the affect of photosynthesis on biological evolution and the greenhouse
effect.
In-Class Activity 1: Handout
The Proterozoic Eon (from 2.5 billion years ago to 542 million years ago) was a time when
oxygen concentrations began to build up significantly, and when life evolved to more complex
forms. The second in-class activity pertains more to the study of the more complex life forms of
the Proterozoic Eon. This in-class exercise is designed to assist you in gaining a fundamental
understanding of the processes responsible for the increasing atmospheric oxygen content, and to
look at the geologic evidence for this.
First, individually read the section in your textbook titled “Oxygenation of the AtmosphereOcean System” to gain an understanding of the evidence for increasing oxygen content in the
Proterozoic atmosphere.
Next, in groups of 3-4, use the following references,
http://www.palaeos.org/Proterozoic
http://en.wikipedia.org/wiki/Proterozoic
http://www.absoluteastronomy.com/topics/Proterozoic
http://www.wisegeek.com/what-is-the-proterozoic-eon.htm
Not to be reprinted or redistributed © John Wiley & Sons, Inc.
http://www.associatedcontent.com/article/162650/earths_proterozoic_period.html?cat=58
http://www.geol.umd.edu/~tholtz/G102/102prot3.htm
to answer the following nine questions:
1) List four lines of evidence showing that oxygen levels were increasing during the
Proterozoic Eon.
2) Using a chemical formula, show how photosynthesis affected the Proterozoic
atmosphere.
3) What chemical sinks are thought to be responsible for removing oxygen from the
atmosphere?
4) Why are red beds not found in the Archean and the earliest part of the Proterozoic Eon?
5) What is the “Oxygen Catastrophe” of the Proterozoic, and what does it have to to do with
banded iron formations?
6) What was the Earth’s atmosphere like prior to the Proterozoic?
7) What effect does photosynthesis have on the greenhouse effect?
8) Why are uraninite and pyrite not found in rocks younger than 2.3 billion years ago?
9) Briefly, how did oxygen affect the evolution of life during the Proterozoic Eon.
Submit your answers to the nine questions to your instructor for grading. Your graded answers
will be handed back to you next week. Carefully go over your graded in-class exercise next
week to prepare for a test in the near future.
Instructor Notes for In-Class Activity 2
Title:
Edicaran Fauna: The earliest known multicellular organisms (Metazoans)
Time:
5 – 10 Minutes prep; 35 – 50 minutes in class (or can assign research
between class periods)
Materials:
Print instruction sheets as handouts.
Handouts:
A list of questions for students to answer and discuss and recommended
websites. Information pertaining the Edicaran Fauna can be found at the
following websites:
http://paleobiology.si.edu/geotime/main/htmlVersion/evidence/pro_03.html
http://y11evolution.wikispaces.com/Ediacaran+fauna
http://www.peripatus.gen.nz/paleontology/ediacara.html
http://www.ucmp.berkeley.edu/vendian/critters.html
http://www.ucmp.berkeley.edu/vendian/vendian.html
http://members.tripod.com/~Cambrian/IntrotoEdiacaran
Not to be reprinted or redistributed © John Wiley & Sons, Inc.
The section on “The Edicaran Biota and the Radiation of Animals” in the
textbook is also an excellent reference for completing the questions
contained within this in-class exercise.
Procedures:
Hand out instruction sheets to students. Using the websites listed above and
the textbook to answer the following questions.
1. From an evolutionary point of view what is important (different)
about the Edicaran fauna?
2. Which modern day life forms are thought by many to be probable
ancestors of the Edicaran fauna?
3. Why did many of the Edicaran fauna have thin bodies?
4. How old are the Edicaran fossils? Do they occur before or after the
“Cambrian explosion”?
5. What happened to the Edicaran fauna at the end of the
Precambrian?
6. During what “Period” did the Edicaran fauna exist?
7. Is there abundant evidence for predators amongst the Edicaran
fauna? Is there significant evidence that others commonly preyed
upon the Edicaran fauna?
8. What shapes (or morphologies) are common amongst Edicaran
organisms?
9. Examine the following photo:
http://www.ucmp.berkeley.edu/vendian/dickinsonia.jpg What
modern day organisms are these creatures thought to be related to?
Are these organisms common fossils outside of the Edicaran fauna?
10. How does the discovery of the Edicaran fauna confirm the
expectations of Charles Darwin?
Afterwards, have the students the evolutionary importance of the Edicaran
fauna for paleontologists.
Student
Instructions: See above
Specific
Suggestions:
Objectives:
If possible, the students should be shown examples of Edicaran fossils at a
local museum. If this is not possible, than the instructor should show
photos of Edicaran Fauna fossils from internet sources.
Students should be able to:
Describe the evolutionary significance of the “Edicaran Fauna”.
List the morphologies and relationships with modern organisms for the
“Edicaran Fauna”.
Not to be reprinted or redistributed © John Wiley & Sons, Inc.
State when Edicaran organisms lived.
Recognize that the soft-bodied Edicaran fauna suffered little from
predation.
In-Class Activity 2: Handout
The late “Edicaran Fauna” are the earliest known multicellular organisms from the Proterozoic
Eon, and thus represent a major jump in the evolution of life for the early Earth. In the past, some
thought that they represented an evolutionary dead end. However, this view has been largely
discredited, and these organisms are thought to be ancestors of many modern day organisms.
The purpose of this in-class exercise is to introduce you to these interesting fossils which have
provided paleontologists with their farthest glance back into the past world of macroscopic
(visible to the naked eye) organisms.
http://paleobiology.si.edu/geotime/main/htmlVersion/evidence/pro_03.html
http://y11evolution.wikispaces.com/Ediacaran+fauna
http://www.peripatus.gen.nz/paleontology/ediacara.html
http://www.ucmp.berkeley.edu/vendian/critters.html
http://www.ucmp.berkeley.edu/vendian/vendian.html
http://members.tripod.com/~Cambrian/IntrotoEdiacaran
Using the above references, answer the following questions.
1) From an evolutionary point of view what is important (different) about the Edicaran
fauna?
2) Which modern day life forms are thought by many to be probable ancestors of the
Edicaran fauna?
3) Why did many of the Edicaran fauna have thin bodies?
4) How old are the Edicaran fossils? Do they occur before or after the “Cambrian
explosion”?
5) What happened to the Edicaran fauna at the end of the Precambrian?
6) During what “Period” did the Edicaran fauna exist?
7) Is there abundant evidence for predators amongst the Edicaran fauna? Is there significant
evidence that others commonly preyed upon the Edicaran fauna?
8) What shapes (or morphologies) are common amongst Edicaran organisms?
9) Examine the following photo:
http://www.youtube.com/watch?v=0bjZy1tPoOYhttp://www.ucmp.berkeley.edu/vendian/
dickinsonia.jpg What modern day organisms are these creatures thought to be related to?
Are these organisms common fossils outside of the Edicaran fauna?
10) How does the discovery of the Edicaran fauna confirm the expectations of Charles
Darwin?
By answering these questions, you will be preparing for a future quiz and/or test.
Not to be reprinted or redistributed © John Wiley & Sons, Inc.