Students will review background information on the structure of an amoeba cell and investigate how slime mold adapts and even forms complex networks to ensure survival. The paradox between the simplicity of the cell and the complexity of what mold can do is explored.
Ask students how many single-celled organisms it takes the cross the road?
The answer to the riddle is complicated. In a way, the answer is one-at least to start. Despite having no brains or feet, one amoeba can become two, the two can divide, creating four.
- Ask students to take a moment to draw a pyramid with one amoeba at the top, two below it, then under those two, four more on the next layer. Create a layer below where each of those four split…
Time the exercise for 20 seconds (counting is fine-it does not have to be precise), and poll the class to see how many got to 8, or 12, or more. (The number does not matter as much as the exercise of seeing how quickly the numbers increase.)
- Explain to the class that in the process of asexual reproduction a cell subdivides into two identical parts. The cell has the same genetic material (DNA) so it is essentially, an exact copy. Each part contains one nucleus. An amoeba is considered a eukaryote, meaning an organism that has complex structures within a membrane.
- Review with the class a diagram of an amoeba cell. Point out to students that the amoeba has a membrane and a nucleus that contains genetic material. However, the shape of the amoeba includes pseudopods. Pseudopods are “false feet” which extend from the amoeba. As amoebas change their form, they are able to move. The pseudopods capture food by stretching out, surrounding the food, and pulling it into the amoeba’s body. This process of engulfing food is called endocytosis.
- Mention how there are many kinds of amoebas (or amoebae), and they thrive in places where their food sources are abundant. Often that means where there is vegetation, fungi, and yeast. Slime mold, of which there are over 900 different species, will survive as a unicellular organism when food is plentiful, but will adapt when and grow into a mass of amoebas when starving.
After this initial background discussion, have students read the article on PBS NewsHour: Smile Molds: No Brains, No Feet, No Problem
- Once students have read the text, be sure they have viewed the videos of slime mold solving a maze to get to food, and “Trans-Canada Slimeways” which are embedded in the article. Remind the students that these are time-lapse videos, but represent how the slime mold moves in an organized way, towards a goal. Point out how energy was not wasted by exploring the incorrect path. The mold was efficient in the quest for food.
- Discuss with students what the study of the behavior of the slime mold could mean to the scientific and mathematical community. Ask students to write a paragraph in class (or for homework), as if they were in one of the following careers, and be prepared to discuss their ideas with the group:
- Network engineer, trying to figure out how to get better coverage from cell phone towers in remote parts of North America
- An oncologist, seeking new healthy cells on which to experiment with potential cures for cancer, in a way that does not harm people or animals.
- A mathematician, seeking a formula or algorithm, replicating information repeatedly to problem-solve was to reach the broadest audiences. (Hint: Research the phrase, “Sum Ergo Computo,” meaning, “I am, therefore I compute.”)
- An environmentalist hoping to study manage the impact different kinds of slime may have on a habitats of endangered animals, or animals that need to adapt to find new sources of food.
- A geographer, tracking the migration patterns of wildlife based on food sources, using slime mold as a model.
Homework: Have students define the following vocabulary words from the lesson (see attached worksheet). Have students add an illustration to their definition, when directed to do so.
- Asexual reproduction
- Cell membrane
Summary/Wrapping Up The Lesson:
Review the images (ideally on a large screen) of different kinds of slime mold at: Slime Molds Revealed (an 11 slide photo gallery):
Discuss the diversity of the kinds of mold that can be found. What do they all have in common and how do they differ? Are any more interesting or more beautiful? Which remind you of patterns that occur in other organisms in nature or in every day life?
Outside of class, students may wish to create “slime” on their own. While many recipes can be found, these substances are not truly slime mold, they are often called “gak” they just move like slime on a much larger scale. This activity is better for extra credit than for a classroom activity in the upper grades because students may be sensitive the ingredients in a particular recipe, and the activity teaches more about the states of matter and how polymers work than how single-celled organisms move. However, the adaptability of the material and the way it changes shape to may remind students of the slime mold in the videos shown in class. Students may wish to use the substance to create hands-on models representing how microscopic substances can cover larger surfaces, as seen in the images on the photo gallery on the videos.
Recipes can be found on: