Collaboration via Slime Mold
Type of Activity:
- Inquiry activity which uses collaboration
- 9th & 10th grade general biology
This activity comes at the conclusion of a cell unit for my ninth & tenth grade general biology class. As we progress through a series of concepts related to cells, each topic also progresses through a developmental series of lab activities:
- Students develop skills related to the topic
- They practice those skills with known results to verify the technique and give them confidence
- They use their techniques to find unknowns
- They begin to ask questions and design experiments for verification
by collaboration with their classmates
Using a slime mold as a focus, students pull together the skills and concepts that they have developed to ask a simple question which can be answered on a petri plate in a limited amount of time. With the slime mold Physarum, they are introduced to an organism which does not always follow the patterns that they have noticed in others.
Physarum, easily obtained from a biological supply company, is an intriguing protist because it forms a large acellular mass which is easily studied. Students have grown masses of the protist covering a petri plate. The plasmodial stage that they study may have thousands of nuclei and is organized in channels that pulse first one direction and then another. The slime mold may change into fruiting structures if it runs out of food or if its environment dries up. The slime mold may eat a variety of foods, but typically is raised with oatmeal flakes.It can be divided into smaller masses with simple cuts, and two masses may fuse into one if they are placed close.
Students have developed the following skills or concepts while working with cells:
- Use of a monocular and dissecting microscope
- Experiences with a variety of pH indicators to demonstrate pH change, particularly with digestion using Congo Red or with carbon dioxide exhalation using Bromothymo Blue
- Making % solutions
- Experiences with the effects of osmosis and diffusion
- Experiences with the concept of surface to volume ratios in cells
- Experiences with detailed observation of cellular movement and eating behaviors of cells, particularly Paramecium
- Multiple experiences with the nature of a control in an experiment
The preparation time for this activity is minimal. Order the slime mold Physarum from a biological supply company. It will arrive in the sclerotium stage on small squares of filter paper. They can be distributed to students in that manner, or they can be subcultured on plain (not nutrient) 2% agar plates with a few flakes of oatmeal. They seem to grow best when left in the dark. With several plates of active plasmodium, the culture can be divided by cutting through and distributing agar squares.
The time devoted to this activity may vary. I allow four to five class days of lab work and one day for the slime mold symposium.
This exercise gives students the opportunity to use the skills and concepts that they have developed in a unit on cells with an unknown organism. They are asked to design and complete a controlled experiment which attempts to answer a simple question about the slime mold Physarum. Students participate in a presentation about their experiment with other students citing evidence of each others work in their final report. Students model scientific research in that their narrow area of research gives one fact of a complete picture of this organism. Students do not use a text for any portion of their work.
- Physarum culture
- Petri plates (2 or 3/student or student group)
- Agar (must be non-nutrient)
- Oatmeal (rolled flakes)
Day 1: Students (in groups of 4 to 6) learn to make their agar plates using the following recipe: 98 mLs of water and 2 grams of agar in a beaker until it boils. It should cool slightly before pouring into plastic plates. This recipe is enough for three to four plates. They must learn to make their own agar because then they will be able to custom make plates for their individual questions. After the agar is cooled, a small square of slime mold and a flake of oatmeal can be added.
Day 2: Students observe the slime mold and talk about a question that can be answered on their plate within a day or two. They begin planning plates which may place their slime mold in a different environment. Typical questions include "Does a slime mold use an acid to digest its food?", "Will a slime mold grow back into one mass if it is cut into two?", "Will a slime mold avoid a salty agar?", "Will a slime mold cross a barrier to reach food?", The questions are as individual as the students in a class. They know that the next day they will be constructing their plates that can answer a question.
Day 3: Plate construction to answer the question with moats, barriers of agar or paper, plates poured with half regular agar, half glucose or salt agar, double plates, plates with food covered with agar or plates with a pH indictor added.
Day 4 - 5: Observations, conclusions, additional plates and comparing. Students are typically very excited to see how Physarum has responded to their experiment. They then prepare for the slime mold symposium.
The symposium: Student groups or individual students explain their question and their experiment to the group. They share their results and answer to a question. They are encouraged to feel positive about a result that did not answer their question because it may be a clue for someone else. Every student must then write a summary paper about the slime mold based on the work of their colleagues. They cite evidence from each others' (by name..."Fred found that...) work as they describe the characteristics and activities of a slime mold.
The student slime mold summaries are evaluated on several levels: using the expected concepts and skills to ask and attempt to answer a question (can the student make something new out of something old?), seeing the patterns in others work, listening carefully to others, and collaboration with their classmates.
I find that this type of lab which encourages a student to develop individual interests gives them ownership in learning, and frequently leads them to additional questions. When a teacher asks the same question to everyone with similar expectations for every student, the search is over when the answer is found. Former students drop by to see what each year's group has devised in plate apparatus with slime molds...they remember the experiments because they belong to them. Students are intrigued by the notion that Physarum may be the perfect collaboration itself: thousands of nuclei working together in a functioning whole!