Destruction of the Rainforest and Atmospheric Oxygen

• To provide conceptual understandings in Earth System science and to develop student understanding and application of these science concepts in a variety of real-life situations.
• To develop student understanding and application of science process, problem-solving, and critical analysis skills.
• To strengthen student mathematical skills and understanding through integration of mathematics with science activities.
• To develop student abilities to utilize multiple representations while organizing and solving problems.
• To develop student understanding of national and state science standards and scientific literacy.
• To develop student understanding of the impact of attitudes about science and science learning.

The Earth Systems course is a second Earth/Space science course designed expressly for pre-service teachers. The Earth Systems course has similar inquiry based courses in Earth/Space, Physics, Chemistry and Life Science as prerequisites. Students are asked to put their learning in these other courses to use in the Earth Systems course in order to connect concrete and abstract learning activities. The course is a combined lab/research/lecture format with a limit of 24 pre-service teachers. Students are expected to provide a list of the equipment needed for the lab activities and to provide those that are commonly available (e.g. two liter pop bottles) Activities are targeted to last a total of one class period (three hours) but some activities such as the one here lasted a total of three class periods spread over two weeks. The activity was devised by students as a result of being challenged about their assertion that destruction of the flora of the Brazilian Rainforest would lead to a serious decrease in atmospheric oxygen.

Be prepared for consternation, exasperation and cognitive dissonance as pre-service teachers take their first steps towards being leaders and not followers in building scientific knowledge. The total time taken by this activity was nine hours but easily could have been shortened or extended by exploring other avenues of questions students had. They did report more confidence in engaging in scientific inquiry and in saying "I don't know" when they didn't know. In the end students again researched the question and learned that most atmospheric oxygen was produced by oceanic phytoplankton, not rainforests.

The students studying the impact of the destruction of the Brazilian Rainforest on the Atmosphere had completed their group research and had finalized the writing of their interactions. One of their interactions was that the destruction of the rainforest flora would lead to a decrease of atmospheric oxygen. When pressed to further explain their position they stated that it was self-evident. Plants produced oxygen- less plants, less oxygen. This led to a lively debate between those students who thought that the loss would be so small it would be imperceptible, and those that thought the impact would lead to a serious decrease in atmospheric oxygen. The students decided that they would develop a laboratory exercise to settle the issue. The first attempt was to create small pop-bottle terraria with a few plants and others with many plants, then test the concentration of oxygen in each terrarium. After the experiment had begun the students decided that it would be impossible to test for the concentration of oxygen in the atmosphere in each bottle, because they didn't have the equipment needed to do so.

Then they decided that they could easily test the concentration of oxygen in water so they devised a more elaborate experiment. Each group would fill three Mason jars with water and place a few sprigs of Elodea (an aquarium plant) in one of the jars and triple the amount of Elodea in another jar. The third jar contained no Elodea at all and was to be used as a control. They would wait a week and then use a Hach Water Oxygen Test kit to determine the oxygen levels in the water in each of the Mason jars. When they opened the jars a week later, much to their surprise, all the plants were dead and there was no discernable oxygen in any of the jars, even the control. The lids of the jars had rusted. The experiment was an abject failure on one level but taught them volumes about how rusting occurs, if plants use oxygen in photosynthesis, and that sometimes more learning comes from failure than from success.

Teaching materials-Pop bottles, Mason jars, Elodea plants, Hach Water Oxygen Test Kits

Rubrics for the development of the laboratory activity and for the evaluation of it are aligned, that is, the same rubric is used by both students and instructor. Since the students taking the Earth Systems course have no classroom experience there is no component of classroom teaching assessed but instead the assessment includes how well the student groups were able to explain to their peers on if/how the laboratory activity met the stated goal of answering the question it was designed to answer, how well they explained the scientific concepts involved and what problems they had in performing the activity. In this case although the activity was not able to show that the assertion that less rainforest flora would result in a serious drop in atmospheric oxygen it did lead to a rich conversation among the class groups on what other avenues of learning opened up as a result of the failure and what the meaning of the words "serious drop" are in the context of the atmospheric subsystem.

Slattery, W., R. Teed, T. Cole (2007). Earth Systems: A Multi-Disciplinary Course Designed for Pre-Service Middle School Teachers. Journal of Geoscience Education 55(3), 218-221.