Lesson: Fungal Symbioses
Target Groups: High School Biology and Ecology, average and advanced levels, adaptable to more basic levels and middle school.
Note: Structured effectively, the following lesson can be used as an entire unit on fungi with periods of independent research, lecture and discussion enrichment and the included inquiry based labs and authentic assessments. Alternatively, it could be an independent unit on Symbiosis and ecological methods. Content from the Teaching the Fungal Tree of Life Website can be a useful starting and reference point for the exploration.
1. Students collect symbiotic fungi from the environment.
2. Students record data from fungal collections.
3. Students analyze data and construct hypotheses
4. Students report formally on findings and hypotheses
Parasitism vs. Mutualism
Scientific Method and formal presentation
Forest ecosystems, even those in human-developed locations, are influenced by fungi living in symbiosis (intimate association) with other organisms. Lichens are associations between fungi and algae and/or cyanobacteria. Mycorrhizae are associations between fungi and the roots of plants. Many plants harbor fungal parasites, most often visible as brown spots on leaves.
Teacher should be familiar with Content in Fungal symbiosis presented in Teaching the
Fungal Tree of Life Website
Paper bags (lunch size)
Coffee cans with both ends cut, extra plastic lids
Microscopes, rulers, handlenses, colored pencils, dissection supplies Internet access, Plant identification guides
Methods (3days to 2 weeks)
Day 1: Field work
Students from a class are assigned a plot of wooded land for which to assess fungal involvement in the ecosystem. Subgroups of students are assigned one of the following to research and report upon.
Students collect and label in paper bags small samples of all different types of
lichens in the local ecosystem. Students should note on each bag where each lichen was collected, objects with which it was associated (tree, rock, etc.) location specifics, etc.
Students should bring to the field 3 small coffee cans with both top and bottom
removed, but with 2 plastic caps for each can. Students press coffee can into ground in 3 locations in order to remove 3 “cores” the depth of a coffee can. A trowel may be necessary to ensure the removal of the entire core. Students should mark orientation and location of cores (up/down) where found, associations (collect leaves of trees for identification, etc.)
Students collect and label in paper bags any and all possible parasites on leaves, stems, blades of grass. Students should note on each bag pertinent information regarding location, prevalence of supposed infection, other possible causes of discoloration patches. Enough plant material should be collected in order to identify the plant species affected.
Day 2: Lab observation and identification
Students generate a data table of characters of lichens found. Microscopic observations of moistened lichen carefully crushed between two slides can provide means of distinguishing between different “species”.
Lichen Lichen 2 Lichen 3 Lichen4 Lichen 5
Students should divide cores into regions of depth (ex: 0-4cm, 4-8cm, etc.), then search each region for mycorrhizal root tips. Tips can then be sorted and number and
types of potential “species” can be tallied for each horizon and each core. Root tips can be examined and drawn under the microscope for detailed description of representatives of each mycorrhizal type.
Students should take detailed observations of specimens macroscopically and microscopically. Students can determine if each specimen is truly a fungal parasite by identifying hyphae and/or sporangia in the affected region under the microscope. Students build data table that includes all data collected for each specimen, including but not limited to host species, macroscopic and microscopic observations, measurements of reproductive structures, etc.
Day 3: Background Research
Students improve understanding of their topic by doing online and/or library research of their assigned topic. Roles of each symbiont in symbiosis, potential fungal names (based on plant host), importance of diversity of each type of symbiosis, etc.
Day 4/5: Presentation
Students present formal poster of investigation including
Introduction to the symbiosis
Brief description of methods
Table of results, graphs of certain measurements
Discussion of results: How diverse are participants in the symbioses in this ecosystem? What are the fungal partners and why do you hypothesize this? Is there a correlation between location and species, type/# of mycorrhiza and soil horizon, and what is a hypothetical explanation for this? Etc.
Posters can be presented as though in a symposium where questions are encouraged and the entire class is exposed to all types of symbiosis studied.
Students can be given a Rubric for poster at beginning of unit. Clear expectations of specific content and skills should be built in ahead of time. Suggested points for rubric:
Background addresses importance of this symbiosis to forest ecology.
Methods are concise and take up no more than 20% of presentation.
Results include both picture (photo or drawn) and graphical presentations of data.
Discussion puts forth at least 1 plausible hypothesis regarding data collected and 1 plausible hypothesis regarding the importance of the diversity of these fungi to forest ecology.