Microbes influence every aspect of the environment. They are involved in every biogeochemical cycle including the water cycle
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. Studying the biogeochemical cycles from this vantage point gives students a much more comprehensive view of these processes.
At the closing of the unit an assessment that includes an essay section summarizing the cycles and a practical that has students identify various microbes at different microscope stations could be used. After assessing students on the above cycles, the natural segue would be into food webs and ecosystems. Covering the cycles first will fill in the gaps that traditional coverage of these topics generally have.
The following activities have been designed to reinforce the content and give students a first hand look at microbes in action. The first activity, Microbial Life in a Water Drop, is designed to make students aware of the lifeforms that they cannot readily see and often ignore. The second activity, Photosynthesis, gives them visual proof that microorganisms do in fact perform photosynthesis and helps them to grasp how these tiny organisms actually changed Earth's early atmosphere. The third activity, Nitrogen Fixing Bacteria, allows students to see how microbes live in a mutualistic relationship with plants to fix nitrogen. The fourth activity, Phosphate as a Limiting Factor, is designed to show students how phosphorus encourages algal growth and is a leads to eutrophication.
The equipment used in the following labs is basic lab equipment and should be available in any high school laboratory. The biological supplies can be obtained from a science supply company such as Carolina Biological Supply Company. Other supplies such as soil and dish detergent can be obtained at most local department stores.
This type of study also lends itself to outdoor explorations. Field trips to a marsh or beach can be incorporated to allow students to see bacterial activity in action. Having students collect the pond water for the first activity helps to solidify the knowledge that these organisms really come from the environment and that they were not just produced for the laboratory investigation.
