To learn about a group of fungus-like organisms; the oomycetes, by baiting them from natural sources (water and soil) and observing them.
Students use a simple procedure to bait oomycetes from water and/ or soil and then examine these organisms with the microscope to see how they look. They will see large hyphae, sporangia and swimming asexual spores (zoospores), the structures involved in sexual reproduction (oogonia and antheridia), and how the shapes and sizes of these structures may vary among different kinds of oomycetes. Students may then design their own biodiversity experiments to see if the use of different natural water sources, different kinds of soils, or different baits affect the variety of oomycetes baited.
Oomycetes will be observable on the baits after 2-4 days (12 hours for pollen baits), and should remain viable for at least several days.
The oomycetes trapped on various baits will be saprophytes or the saprophytic stage of a parasitic pseudofungus. There are a number of genera and species commonly found in soils and various water sources. They can be differentiated by the structure of the sporangia, the oogonia, and the antheridia which are illustrated in many biology and mycology texts. These structures usually form in less than a week and are easily seen with a compound microscope, so they make a good observational exercise in which students can see what kinds of variation in form exist. Some factors that will affect what species may be trapped include: bait water: still pond vs. moving stream, for example time of year (although found even in water collected in mid-winter) soil: drainage, depth, soil type, pH
The oomycetes trapped on various baits will be saprophytes or the saprophytic stage of a parasitic pseudofungus. There are a number of genera and species commonly found in soils and various water sources. They can be differentiated by the structure of the sporangia, the oogonia, and the antheridia which are illustrated in many biology and mycology texts. These structures usually form in less than a week and are easily seen with a compound microscope, so they make a good observational exercise in which students can see what kinds of variation in form exist. Some factors that will affect what species may be trapped include: