Caging the Blob – Student Handout
Objectives:
Through this lab experience, the student will:
1. Describe the importance of barriers in constraining the movement of organisms, particularly in the
context of pathogens and invasive species.
2. Evaluate the effect of static barriers on the movement of P. polycephalum and relate these movements
to the concept that living things sense and respond to their environment.
3. Discuss the question of when ‘sense and respond to the environment’ becomes ‘primitive intelligence’
and create a definition of intelligence.
4. Design a controlled experiment that collects quantitative data to test the effects of a new static,
invisible, or dynamic barrier on the movement of P. polycephalum.
5. Analyze data and make appropriate conclusions based on the data from each experiment.
6. Evaluate the experimental design of each lab group and make suggestions to improve control groups,
constants, and collection of data.
7. Generate a list of new questions that arise after each experiment and consider new experiments to test
these new questions.
Materials
• Assorted Lego® blocks
• Molten 2% water agar
• Petri dishes
• Sterile pipettes
• Forceps
• Lab markers
• 70% isopropyl alcohol in spray bottles
• Parafilm®
• Aluminum foil
• Oat flakes, uncooked
• Culture of P. polycephalum growing on oats
Basic sterilization tips for any day in which slime mold is being used
1. Spray/wipe lab benches down with 70% isopropyl alcohol before and after working with slime mold.
2. Use sterile forceps when transferring slime mold or food. Forceps can be sprayed with 70% isopropyl
alcohol. Never touch a surface with forceps or allow a sterilized instrument to be exposed to air longer
than necessary. Sterilize forceps after use.
3. Never remove the lid of a Petri dish and place that lid on a lab bench surface. Always open plates by
using one hand to crack and hold the lid, giving just enough space to work (with the other hand), while
allowing as little air as possible into the dish.
Procedure
Day 1:
1. Observe the growth of the cultures of P. polycephalum growing without barriers on the agar
plates with several oat flakes. These will serve as an example of uninhibited growth and will be
provided by your teacher on the projector.
• In your lab notebook, make qualitative observations about this appearance. An
accompanying picture may be helpful.
2. For each group of 4, you will construct a maze using Legos inside Petri dish. Example pictures of
properly constructed mazes will be on the board.
3. Disinfest the maze and Petri dish by spraying them down with alcohol and wiping them with a
paper towel.
4. Send a group member to pipette 2% water agar into the maze to cover the bottom of the dish. (Do
not overfill the dish; 10 ml should be more than enough for a 100 mm Petri dish.)
5. Allow agar to solidify (approximately 20 minutes).
• Tomorrow, your table will run an experiment testing the impact a variable of your choice
on slime mold growth (today’s variable was the physical barrier of Legos). Your table
will be given 2 petri dishes to run the experiment. (There is a possibility that we will be
able to have 3 Petri dishes per group depending on the availability of agar and the
growth of our slime mold. Design your experiment only having 2 groups but be prepared
adapt your experiment to 3 groups in a best case scenario). Design your investigation
with your table while being mindful of proper experimental design (variables, groups,
etc.).
i. Once finished, you must have your experiment approved by me. If I do not have
the material needed for your experiment then you are responsible for bringing it
tomorrow.
1. You will not run this part of the experiment today, but I want you to
collect the materials necessary for them now so they will be ready
tomorrow.
ii. Note: No 2 groups can test the same variable. This will allow us to test more
variables as a class. Whoever informs me of their variable first will be the group
that is allowed to test it. I will put the variables tested on the board as I learn
them so that you will know what scenarios can no longer be tested.
iii. You should list the following in your lab notebook concerning the investigation
you have designed.
1. Independent Variable
2. Dependent Variable
3. Control Variables (constants)
4. Control Group
5. Experimental Group
6. Level of Treatment (level of independent variable for each trial)
7. Replication
8. Data table to collect information
6. After the agar has solidified, use sterile forceps to place 4–6 oats colonized with P. polycephalum
(culture side down) throughout maze.
7. Seal the sides of the plate with Parafilm® and cover in aluminum foil.
8. Incubate at room temperature for about 24 hours at your lab station.
Day 2:
1. View the growth of the slime mold in your petri dish. Be sure to look at it from the bottom as well
(it is often easier to see the movement from this view). Collect qualitative data about the growth
in your lab notebook.
• Also, use a dissecting microscope to view the culture. Include any additional information
gained in your qualitative data.
2. After P. polycephalum has filled in all parts of the maze (which should have already occurred),
remove the inoculated oats with sterile forceps.
• Saved these oats with cultures of slime mold on them in an empty Petri dish. You will use
them to culture to start the culture for the dishes in the experiment you have designed.
3. Place fresh oats at the two ends of the maze.
4. Seal the sides of the plate with Parafilm® and cover in aluminum foil.
5. Incubate at room temperature in the dark for another 24 hours at your lab station.
6. Retrieve 2 petri dishes and pipette 2% water agar into them to fill the bottom of the dish. (You
may possibly retrieve 3 petri dishes here if we have enough material)
7. Allow the agar to solidify.
• While the agar solidifies, retrieve the handout for an experiment you will be beginning on
Friday called a Winogradsky column. Read through this handout until your teacher is
ready to go over this lab with.
8. Create the appropriate environment of your choice within the 2 (possibly 3) dishes keeping in
mind that we’re trying to study the impact of a barrier or external stimuli on slime mold growth.
9. Use sterile forceps to place 4–6 oats colonized with P. polycephalum (culture side down)
throughout the petri dish.
• Re-use the oats that you took out of your Lego maze earlier in the day.
10. Perform whatever steps you feel are necessary to properly maintain variables for your experiment
until class tomorrow and place them where you feel is appropriate.
Day 3:
1. Observe the growth of the P. polycephalum in the Petri dish with Legos for the next few days
considering the following questions. Remember to view the Petri dish from the bottom for a
clearer image. Collect BOTH qualitative AND quantitative data to support your claims. Consider
the following questions during your observations. These DO NOT have to be written down in
your lab book right now. You will demonstrate your knowledge through answering the analysis
questions at the end.
a. Has the plasmodium shrunk back from the dead ends?
b. Is the plasmodium connecting the two food sources?
c. If there was more than one route from one oat to the other, did the plasmodium connect
the two oats through the shortest distance?
d. What color is the plasmodium?
e. Is it the same color in all locations?
i. If it isn’t, can you explain why it would be different colors?
2. Now retrieve your 2 (3) experimental dishes.
3. Remove the inoculated oats with sterile forceps.
4. Place 2 oats at the appropriate locations in each of the dishes.
a. Depending on the success I’ve had with growing the cultures, you may have to re-use
some of the oats that were already in your dish.
5. Perform whatever steps you feel are necessary to properly maintain variables for your experiment
until class tomorrow and place them where you feel is appropriate.
Day 4 and 5:
1. Observe the growth of the P. polycephalum in the Petri dish with Legos.
2. Observe the growth of the P. polycephalum in your 3 experimental dishes. Collect BOTH
qualitative AND quantitative data to support all of your claims.
 How is the environment you expose the slime mold to affecting growth?
 Is growth affected by the level of treatment of the independent variable? (You will only be
able to answer this question if we were able to have 3 petri dishes during your personally
designed experiment).
 Are there errors you have seen in your design that you would change if given another
opportunity to run the experiment?
 Do your results lead to any other experimental questions?
Guided Inquiry Questions
1. After two days of growth, did P. polycephalum connect the oats through the shortest distance?
a. Can you provide evidence through quantitative data?
b. Does this mean the Lego® blocks acted as an effective barrier for the slime mold?
2. What other observations did you make after two or three days of growth? Provide pictures or
quantitative data.
3. Why is it important that P. polycephalum be able to sense and respond to barriers?
a. How would the behavior of limiting growth to the shortest distance between the oats be the best
behavior for survival?
b. In what situations would finding ways around the barrier be beneficial to survival?
4. Find and describe an example in which a human-imposed barrier has limited the spread of a plant,
animal, or human pathogen or an invasive species.
5. Find and describe an example in which barriers have not been effective in controlling a plant, animal,
or human pathogen or an invasive species.
6. Do you think P. polycephalum exhibits intelligence? Define intelligence and defend your answer.
Clean-Up
1. Legos®
• Soak Legos® in alcohol or 10% bleach solution.
• Wipe off any remaining slime mold with a paper towel or a small brush.
• Wash with soap and water while scrubbing with a test tube brush. Be careful not to lose the many
small pieces.
• Rinse then pour the Lego® blocks onto paper towels to dry.
2. Cultures/Petri Dish - Soak cultures and Petri dishes in a 10% bleach solution. Discard.
3. Alcohol Mister Bottles – Empty back into original alcohol bottle and rinse the alcohol mister bottles
with soap and water.