Up to 32 students
45-60 minutes Introduction:
The gases in the atmosphere over geologic time have been as dynamic over millions of years as the weather is from day to day. Scientists have spent over a hundred years researching sediments, fossils and other proxies from ideas about the make up of the ancient atmosphere.
Within the Precambrian period scientists have noted that around 1.8 billion years ago there was a dramatic rise in atmospheric atmosphere. This rise in oxygen is currently attributed to cyanobacteria. Cyanobacteria is still around today and sometimes do still produce a significant of oxygen.
There are other times in Earth’s history where dramatic geologic events have released a lot of carbon dioxide and other gases into the atmosphere subsequently shifting the average global temperatures higher and turning a glacial period into an interglacial. There are fossils of palm tree related plants and cold-blooded organisms such as dinosaurs and relatives of reptiles and amphibians in the Polar Regions. There is also evidence that heat trapping gases have dropped substantially at other times and forced the Earth into deep freezes.
This lesson plan presents graphs and other evidence of the dramatic shifts in the Earth’s atmospheric content and in resulting the changes in climate. Learning Objectives:
1. Many of Earth's systems are dynamic and changed over time.
2. Oxygen was not readily available in the atmosphere until about 1.8 billion years ago.
3. Changes in atmospheric composition have helped in shifting Earth's Climate in the past along with the evolution of organisms. Guiding Questions:
Has the atmospheric composition always been the same throughout Earth's history? What would Earth be like with more carbon dioxide/ less carbon dioxide? When and how did the level of oxygen in the atmosphere rise?
Gases Gone By Worksheets
Reference Literature Activity 1: Think, Pair, Share
Have students discuss in small groups their ideas on the guiding questions. Allow them to converse for about ten minutes and have the class discuss as a group some idea that arose. Activity 2: Worksheet and Internet Investigations
Have students work on the three worksheets in class and for homework if there is not enough time available. Conclusion and Wrap Up:
Find out the consensus of the classes ideas from the guiding questions, clarify misunderstanding and misconceptions about Earth's atmospheric past.
Have students add to their LINK. New York Scope and Sequence: Intermediate and High School Science Standards: Physical Setting:
Key Idea 1.2e, 1.2h - 1.2j