Purchase a few petri plates containing prepared growth agar, and set up a demonstration with student participation. (Carolina Biological Supply or Ward's Biology are both good sources for bacteriological media at reasonable expense.)
Have students streak the plates using their fingers, material from their combs or hairbrushes, or by swabbing the tops of their soda pop cans. After a couple of days of incubation, the appearance of many and diverse bacterial colonies will impress students about the volume of bacteria surrounding them.
The purpose of this exercise is to have students appreciate the small size of bacterial cells. Set up a number of demonstration microscopes, each with a different type of organism in view. Specimens might include eukaryotic algal cells (diatoms are easily seen and have lots of surface details), a protozoan or two, and several shapes of bacterial cells. Be sure to have each microscope set on the same magnification, or indicate differences in magnification, so students can get a better idea of the comparatively small size of bacterial cells.
Freshwater algae are some of the most beautiful organisms one can view using a microscope, and they are usually large enough that students can find them easily on a microscope slide.
Obtain a few cultures of freshwater algae from a biological supply company. (Carolina Biological Supply or Ward's Biology are both good sources for algal cultures at reasonable prices.) Volvox, Pandorina, or any of the desmids make great specimens for student use. Have students make wet mounts of these cultures and view them as examples of protists.
Freshwater algae are structurally well-adapted to specific habitats. Floating algae have spines or flattened shapes to help them remain afloat. Sessile benthic algae are more streamlined and have mechanisms to attach themselves to rocks and submerged tree branches.
The specimens in the previous activity are good examples of floating algae. Other examples include Micrasterias (a desmid), Eudorina, Pediastrum, and many others. A plankton tow of a lake's surface would give other good examples of floating algae. Instruct students to look for adaptations that allow these organisms to maintain their positions in the water column.
Benthic algae include any of the Navicula or Nitzschia species that are streamlined and can also propel themselves along the substratum. Attached green algae, like Cladophora, also make good specimens for students to view.
Conduct a student taste test using a test panel and several different types of cheese. Cheese may have been developed as long ago as 8000 years. Although the enzyme rennin or a "starter culture" is used to produce curds in cheese, for some cheeses, fungal spores are added during processing to impart a particular flavor and aroma.
Penicillium roqueforti spores are added to curds to make blue cheese and Roquefort. Have students try samples of these two types of cheese, perhaps comparing major brands for taste. Another type of cheese, Camembert, is produced by adding spores of Penicillium camemberti. Limburger cheese, known for its unusual aroma, is soaked in brine that helps specific fungi and bacteria develop to add flavor to the cheese.
Add fresh bread, with the aroma of yeast, to the taste test. To make bread rise, yeast (Saccharomyces cerevisiae) is added to the batter. Yeast produces carbon dioxide during its fermentation, and bubbles are added to the bread batter, increasing the volume of the batter.
Yeasts are also used to make wines, beers, and ales, and a number of different mushrooms are eaten directly.
Bring into the classroom a variety of specimens of fungi. You will find that most students are aware of certain kinds of fungi, such as the mushrooms sold in the grocery store, but are unfamiliar with the wide variety of shapes and forms found in this interesting and diverse group.
Include such specimens as: Rhizopus stolonifer, the common black bread mold, which is also a Zygomycete; Saccharomyces cerevisiae, baker's yeast, an Ascomycete; and Coprinus lagopus, the inky-cap mushroom that is a Basidiomycete. If you do not have access to a collection of fungi, many biological supply houses (i.e., Carolina Biological Supply or Ward's Biology) have specimens for sale at a reasonable cost. Demonstration plate sets are also available from these companies. Include a number of histological slides in your demonstration, showing students the appearance of fungal hyphae.
Many students have never seen, or perhaps never noticed, lichens, especially if they are from cities where air pollution has stopped lichen growth. Be sure to include the three growth forms of lichens in your demonstration. These are also available commercially from the same suppliers mentioned in the previous paragraph.