Name: ______________________________
Graphing Earth’s Atmosphere
7th/8th Grade Science
Learning Targets
#7: In your graph and your conclusions, analyze and interpret data for patterns in the fossil record that document the
existence, diversity, extinction and change of life forms throughout the history of life on Earth.
#9: In your conclusions, discuss how living organisms have played many roles in the earth system such as: affecting the
chemical elements that make up the atmosphere, producing some types of rocks, and contributing to the weathering of rocks.
How Have the Atmosphere and Living Things Interacted Over Time?
The formation and evolution of the Earth’s atmosphere is a prime example of the concept of an interconnected
Earth system. While the surface features of the Earth developed, volcanic activity and other processes injected
large amounts of gaseous materials into the atmosphere. These events determined the reflectivity and the heat
absorbing properties of the early Earth. Somehow, the basic components of life (carbon, hydrogen, oxygen and
nitrogen) were synthesized into simple organic molecules from which the first life forms emerged. Scientists think
that this event occurred in the first half billion years of Earth history in an atmosphere with practically no oxygen.
The bacteria living at that time were adapted to survive in an oxygen-free environment. These primitive organisms
apparently thrived in an atmosphere that was predominately water vapor and carbon dioxide, with small amounts
of methane, ammonia and other gases.
Over time, organisms contributed to the development and evolution of the environment. In the same way, the
changing environment determines the formation and ability of organisms to survive. For instance, green plants
use carbon dioxide to create their tissue and in doing so, release oxygen. Most biologists and atmospheric chemists
who study the evolution of the atmosphere think that the amount of oxygen in our atmosphere today is the result
of the two processes: photosynthesis and the oxidation of iron in the crust which forms “red bed” deposits. It is
generally safe to say that the Earth’s atmosphere and the biosphere coevolved through these interactions.
How Can We Study Earth’s Ancient Atmosphere?
Scientists know that the Earth’s present atmosphere is quite different from the way it was 4.5 billion years ago.
Scientists have analyzed oxygen isotopes from gases trapped in ice cores to collect data on Earth’s ancient climate.
We can use these data to illustrated changes in the concentration of gases in the atmosphere over time. Although
the data seem to suggest that some gases decreased to 0%, there are actually tiny amounts of these gases still
present in our modern atmosphere. Also, there were probably small amounts of oxygen present in the air long
before oxygen appears in the climate record. In this activity, you will be a scientist attempting to illustrate changes
in Earths’ atmosphere over time. You will use data from 4.6 billion years ago to the present for 4 important gases:
oxygen, nitrogen, hydrogen and carbon dioxide. Then, you will correlate this data to events in the history of life on
Earth.
Make a Prediction
1. Write down what you already know about early Earth’s atmosphere.
% oxygen in the atmosphere
2. Based on this prior knowledge, what do you predict a graph of Earth’s oxygen concentration will look like
over time? Sketch the shape of your predicted curve in the graph provided below.
Time
Analyze and Interpret Data
Part I.
1. Read the data table below.
GAS
Carbon dioxide
Nitrogen
Hydrogen
Oxygen
Other gases
Table 1. % Composition of Earth’s Atmosphere from Its Formation to the Present Day
Billions of Years Before the Present
4.5
4
3.5
3
2.5
2
1.5
1
0.5
Present
80
20
10
8
5
3
1
0.07
0.04
0.025
10
35
55
65
72
75
76
77
78
78
5
3
1
0.5
0
0
0
0
0
0
0
0
0
0
0
1
5
10
15
21
5
42
34
26
23
21
18
13
7
1
2. In the space below, write a one-sentence summary of what this data table shows.
3. Create a line graph to illustrate the % of carbon dioxide present in Earth’s atmosphere over time. To do
this, use a colored pencil to plot a point for each % amount during each time period. Connect your plot
points with a smooth line.
4. Using a different colored pencil, graph the data for nitrogen (on the same graph).
5. Continue graphing the data for each of the other gases. Don’t forget to use a different colored pencil for
each gas.
6. For each gas, lightly shade the entire area below the line you drew. Use the same color that you used to
draw the line. This area represents the proportion of each gas present in the atmosphere throughout
Earth’s history.
7. Think, pair, share with someone who has completed their graph. Ask for detailed feedback and make any
changes before moving on.
Part II.
1. Read the data table below.
Table 2. Major Events in the History of Life on Earth
Geological Event
Earth forms
Earliest known bedrock forms
Evidence of first organic matter in rocks
Photosynthesis evolves in plants
Limestone deposits become common
Many fossils of marine invertebrates
Earliest land plants evolve
Earliest land animals evolve
Dinosaurs dominate
Earliest human fossils
Billions of Years Ago
4.5
3.9
3.7
3
1.8
0.55
0.44
0.4
0.17
0.006
2. In the space below, write a one-sentence summary of what this data table shows.
3. Plot the major events in the history of life on Earth on the same graph as your gas data. To do this, you
might write the name of the event beneath the graph next to the time it occurred.
4. Create a small picture next to each event to represent what happened at that time. Stretch it to show
creativity and synthesis in your pictures. I will not assess how well you draw, but I will assess any
evidence of higher order thinking you attempt to show in your drawings.
Name: ______________________
Graphing Earth’s History
7th/8th Grade Science
Learning Targets
#7: In your graph and your conclusions, analyze and interpret data for patterns in the fossil record that document the
existence, diversity, extinction and change of life forms throughout the history of life on Earth.
#9: In your conclusions, discuss how living organisms have played many roles in the earth system such as: affecting the
chemical elements that make up the atmosphere, producing some types of rocks, and contributing to the weathering of rocks.
Draw Conclusions
To show proficiency (a 4), answer the following questions.
1. Look back at the predicted graph you drew. Compare it to the graph of actual data.

What differences do you notice? What knowledge do you have that accounts for these differences?

What similarities do you notice? What knowledge do you have that accounts for these similarities?
2. What gas has made up the largest portion of the Earth’s atmosphere for most of Earth’s history?
3. What gas increased dramatically over the history of the Earth?
4. What gas did not appear in any measureable amount until about 2.0 billion years ago?
5. What gas has been almost nonexistent in the atmosphere since about 3.0 billion years ago?
6. Which gas appeared in the atmosphere about the time that limestone deposits became common?
7. What event is correlated with the increase in atmospheric oxygen (and the decrease in carbon dioxide)?
Why might these events be correlated?
8. If the natural trend that you see in the graph continues, how might Earth’s atmosphere change in the next
500 years?
9. If human activity continues at its present rate, what will probably happen to the levels of carbon dioxide
and other gases?
To show evidence of mastery (above a 4), respond to the following questions.
1. What event in Earth’s history probably had the most effect on the composition of the atmosphere? Why?
2. The atmosphere of Venus and Mars are mostly carbon dioxide, while the atmosphere of Earth is mostly
nitrogen and oxygen. Why is Earth’s atmosphere different?
3. Hydrogen gas is practically nonexistent in the atmosphere today. Looking at the physical and chemical
properties of hydrogen can help explain why. What do you think was the cause of the elimination of
hydrogen from Earth’s atmosphere by about 2.5 billion years ago?
4. How do the changes in the atmosphere’s composition throughout Earth’s history illustrate the Gaia
Hypothesis? Read about the Gaia Hypothesis in the handout provide before responding to this question.
Submit your graph and your responses to the “Draw Conclusions” questions for summative
assessment by ____Monday Nov. 4th______________________________________.