Enliven Your Class with Simulations and Analogies
Judy Jones

Many years ago, I figured out that my students were not always as excited about the amazing biological discoveries and concepts as I was! I also realized that they are at a very concrete level of understanding. Many of the concepts in biology are difficult to understand and require the ability to conceptualize things that are not visible even with microscopy. So I began to collect some interesting activities and analogies to help them learn some of these difficult ideas more thoroughly and to engage them with fun learning activities.

Here are some of my favorites. I've included links to the full projects of three activities (MSWord files). Feel free to download them.

Nerve impulse transmission down a neuron: Have the students stand up in the classroom holding hands so that they form one long continuous line (that is the neuron). You squeeze the first student’s hand. When that person feels the squeeze in one hand, he or she quickly squeezes the hands of the person on the other side. And the squeezing continues sequentially down the line as quickly as possible. This simulates the depolarization of the neuron during a nervous impulse. Students can try to speed this up but it will never equal the speed of transmission along a real neuron. In larger diameter neurons, the speed of transmission can be 100-1000 meters per second.

Hedge model of electrophoresis: So many concepts we teach are rather abstract. I find that concrete models really help my 9th grade biology students visualize what is happening at a molecular level. For example, when I try to explain why DNA fragments of different sizes move at different speeds in an electrophoresis gel apparatus, I use this model: Imagine an elephant and a mouse standing before a big hedge of brambles. When the bell rings, they have to race through the brambles to the other side. Who gets through first? This is a “no-brainer” for my students. The mouse always wins! Then I can explain that agarose gels are sort of like the hedge. The elephant is a large piece of DNA and the mouse is a small piece of DNA. When the electricity is turned on (the bell), the DNA starts to travel – large pieces move through the gel more slowly than small.

Park Bench model of enzyme action: Have the students imagine a city park with 100 people randomly walking around in a grassy area. In this section of the park is one magical park bench built for two. Occasionally, two people bump into the bench simultaneously. This causes them to sit down. When they stand up, they are holding hands and have become a couple. (So far, we have the people who are the substrate molecules; the bench which is the enzyme; and the couple which is the product.) Now, have the students imagine that this process continues until all 100 people have formed couples. You can ask many questions at this point.

• How could we speed up this reaction? We could provide more benches (enzymes)? The enzyme in this case is the limiting factor.
• Was the bench (enzyme) changed by the reaction? Enzymes are reusable and are not changed by the reaction that they catalyze.
• What happens to the speed of the reaction as it continues? It slows because as the concentration of people (substrate) goes down, there is less probability of them bumping simultaneously into the bench (enzyme).
• Would this bench work on ants or elephants? The answer is probably not. Enzymes work by shape and are specific to a particular substrate. (You could have the students create a “bench” for the ants and the elephants – something that is the right shape.)
• What if we burned the bench? It would not work – the shape has been changed.
• What if we froze the bench? It might work but very slowly. The substrate molecules move more slowly and the frozen bench would slow down the reaction. (Temperature affects enzyme function. High temperature can permanently denature enzymes; very cold temperature can slow enzyme function considerably.)
• Would 12 M H2SO4 (sulfuric acid) destroy the bench? Would lye (a base) destroy the bench? Yes, these substances could burn holes in the bench. So acids and bases can definitely affect enzyme function.

As you can see, I get a lot of mileage out of this analogy. And my students report back that when they take a test, they remember the model well!

MODELS USING PROPS

Atoms and Molecules: I love to use lego bricks when I teach about atoms and molecules – my “baby biochemistry” unit. When I teach about subunits, I can put together a string of small legos into a long chain and then break off each piece – representing, for example, the glucose subunits of a starch molecule. If I use legos of different colors, I can use the model for the 20 possible amino acid subunits of proteins. I also use legos to explain how we can eat “cow protein”, digest it into subunits, absorb the subunits, and then reconstruct it in a different arrangement to make “human protein.” The subunits have not changed, just their arrangement. Legos are fun for the students and I can even make up kits for groups of students to use at lab tables. So find your owns kids old legos or ask your students to donate them and you will have a treasure trove of atoms and molecules for years to come!

Protein Structure and Function: Another great model to use when teaching about proteins involves those large loops segments (tangle toys) that you can find in toy stores. I once bought up every one I found at a local store. They usually come in different colors and four segments will make a circle when jointed together. The sets I found were not just different colors, some of them also had differently colors little bumps and shapes. So I form a long wavy chain with these and use it to represent an amino acid sequence of a protein (polypeptide) which is the primary structure. Then I can spiral a part of it into a helix to show the secondary structure. Finally, I can form a big handful globular shape to show the tertiary structure – and then connect that shape to enzyme function. I can use the little bumps to represent possible di-sulfide bonding and bumps of other colors to represent hydrogen bonding sites. This visual model really helps my students with understanding the structure of proteins at a basic level. Click here to see the tangle toy website with pictures of the loops that I am talking about.

PROJECTS
My high school students have learned a lot about cell organelles in middle school, but they do not have a good understanding of how those organelles function and interact in a living cell. The first activity I assign them is the Cell Simile Project (see attachment). The students research the functions of the organelles and then envision a human-built system and compare the cell organelles to features of this human-built system. They write analogy statements for each organelle. For example, if their “built” system is a factory, they might say: “The main office of the factory where all the information for running the factory is kept is like the nucleus of the cell where all the information for the functioning of the cell is stored. Over the years, my students have used a wonderful array of human-built systems for their comparisons – football franchises, supermarkets, schools, cruise ships, farms, circuses, and even night clubs! They create a poster of the human-built system with their analogies labeling each part. The posters are colorful and fun and are displayed for several weeks in the hallway outside of the classroom.

ACTIVITIES
Meiosis dance
Years ago, I attended a teacher workshop where we were taught how to do a “Meiosis Square Dance.” We got into groups of about 10 (8 of us were chromatids – representing 4 chromosomes and the other two played other roles in the process, including the dance caller). The music was played and we performed our dances – including crossing over – where we traded hats or scarves! This was great fun for us. But I knew that my students would probably not necessarily respond to the square dance music so I adapted the project and have them use any music they want and even produce dramas as an alternative. I divide the class into two large groups and they go to work. They choose a director and a team of design folks. They plan the dance or drama, select music, and assign roles. Then they practice and finally perform. Here is a rubric that they are given to make sure they include all the parts of the process. This rubric is used for my senior honors class (Biology 2) but it could be adapted for beginning biology students.

Owl Families Simulation – Who Gives a Hoot?
This is an adaptation of an activity developed by some teachers at the North Carolina School of Science and Math. It is so popular that most of the biology teachers at our school do it. Basically, the class is divided into 4 or 5 owl families of different configurations (see attachment), and then the parent owls feed their fledglings and themselves for a period of time. They are preying on rodents (M and M’s) and the “parents” are feeding their fledglings, (you can see why this is popular!). After the preying time, they count all of their food by color. As we process the results, I inform the class that if they didn’t eat a certain number of rodents, they will die of starvation. (I choose this number as I circulate around during data collection to ensure that the small family survives.) Then I inform them that one of the rodent species is contaminated with a pesticide and if they ate more than a certain number of this species (color) they will die of pesticide poisoning from biological accumulation.

Fishy Frequencies
Teaching about the Hardy-Weinberg equilibrium is not easy. I developed this activity from a germ of an idea I got from one of the science teacher journals. My students all pretend that they are fish eating sharks and they prey upon gold fish and pretzel fish crackers during the simulation. There are clear rules to the predation. The first round, the students randomly “eat” any of the fish and during the second round they “select” for the gold fish avoiding the pretzel fish. See the attached activity for the specifics. The data chart is set up so that the students can easily follow the math of the Hardy-Weinberg equation. Some students don’t really understand the concept behind the math, but they do clearly see that allele frequencies change when selection is introduced and do not change when there is no selection. And some of my more math sophisticated students are delighted to see a connection to the quadratic equations they have learned in their math classes.

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There is a lot of research supporting the idea that students learn best when you use models, simulations, and analogies. I encourage you to begin your own collection of ideas to help improve learning! Please let me know if you have questions or ideas that you would like to share.

E-mail Judy.