Marshmallows and “Murder”—2 Hands-On Activities for Teaching Evolution -first published Dec 7, 2015

Author: Nathasha Dias

Curriculum Connection: Grade 11 Biology, Evolution

Evolutionary biology is a captivating and continually developing field of biology. Many aspects of the evolution unit of 11U biology can be easily translated into hands-on learning opportunities for students. As a student teacher at Albert Campbell C.I, I employed two effective hands-on activities in my class: a marshmallow simulation and “murder” handshake. Both strategies require minimal prep by the teacher, but have a substantial impact on students’ visualization of evolution concepts. Handouts are available at the end of the article.

Activity #1: Marshmallow Simulation

I hoped to introduce the topics of genetic drift, genetic bottlenecks, and founder effects in a concrete and simplistic manner. Armed with a set of PowerPoint notes for students to copy and several bags of mini marshmallows, I began my lesson with the determination to promote active learning in my classroom. I noticed the students stare at the marshmallow bags with curiousity. What could marshmallows possibly have to do with evolution?

The activity was simple; after introducing these three key concepts, students would have the opportunity to perform simulations of each using marshmallows to resemble a population. This hands-on activity allowed them to solidify their understanding of new information by modelling evolutionary processes and collecting and comparing data.

The marshmallow simulation engaged all of my students. Working with marshmallows added a certain “fun factor” to the lesson that they appreciated. They loved manipulating the soft marshmallows, marking them with little spots, and pouring them from beaker-to-beaker. Student engagement was accompanied by student enjoyment; when given the chance to pull sticky marshmallows off each other, doing something as trivial as counting made my students smile and laugh. Most importantly, as they compared their data with other table groups, they understood how genetic drift, genetic bottlenecks, and founder effects decreased the variability of traits in their marshmallow populations. In turn, these realizations paved the way to improved understandings of how these mechanisms work in real life! The marshmallow simulation handout is provided at the end of the article.

Activity #2: “Murder” Handshake

Natural selection lies at the heart of Charles Darwin’s theory of evolution. I wondered about what I could use as a fun get-out-of-your-seat opener to a natural selection lesson and was inspired by my own experience of playing “murder” handshake with my colleagues at the Ontario Institute for Studies in Education. The handout for this opener is available at the end of the article.

My students were extremely excited to play the murder handshake game. Aside from having the chance to escape their seats, the mysterious aspect of an anonymous murderer peaked their interest. They hesitantly shook their peers’ hands, hoping not to be targeted by the murderer. The murderer stealthily pursued potential victims, only “murdering” those with a particular characteristic based on prior instruction. If they were finally targeted, they silently retreated to the dead zone, hoping not to reveal who the murderer was, and waited for the detective to try to solve the mystery.

Murder handshake is a fantastic lesson hook that both eases students into understanding natural selection and brings excitement to the classroom. It introduces students to the idea that a selective pressure, like the murderer in the game, can act on a population so that only organisms with certain (advantageous) traits survive. All in all, murder handshake is highly successful not only because of its clear connection to curriculum, but because it allows students to be part of the analogy that is being created.

References:

“Murder” handshake is adapted from Murder Handshake-volution created by Xin Chen, Natalia Olivares, and Jacky Wu (OISE teacher candidates, 2015).

Evolutionary Change without Selection

Marshmallow Simulation

After having learned the concept of natural selection and its ability to influence variation within populations, it can be difficult for students to wrap their heads around the idea that evolutionary change can take place even in its absence. Discussing the concepts of genetic drift, bottleneck effects, and founder effects are essential to the study of evolutionary biology. Yet, simple discussion often does not suffice. To grasp the dynamic nature of these mechanisms of change, discussion must be paired with visual demonstration. To extend further, why not have students carry out these demonstrations themselves?

The marshmallow simulation outlined below is a hands-on activity that introduces students to genetic drift, bottleneck effects, and founder effects while promoting active learning. The marked and unmarked marshmallows represent two different traits within a population of a single species living on an island.

Preparation:

Gather three 400mL beakers and one large watch glass (per table group) and place them in a row on each table.
Have students count out 50 mini-marshmallows (per table group) and place them in the first beaker.
Mark 25 marshmallows (per table group) with a marker.

Note- Preparation need not be done by the teacher. If time permits, get students to help!

Activity A: Genetic Drift

Tell students to transfer roughly half of their marshmallows into the second beaker, which represents the second generation.
Ask them to calculate the percent (%) of marked individuals in the original and second generation populations. Have them repeat steps 1 and 2 for the third beaker.
Have students compare the percent of marked and unmarked individuals in each generation. Compare data between table groups and discuss this in the context of changing allele/genotype frequencies due to genetic drift.
Tell students to return the marshmallows to the first beaker.

Activity B: Genetic Bottlenecks

Tell students to grab a small handful of marshmallows (~5 or 6) and place them in the second beaker.
Announce that the handful of marshmallows represents the survivors of a devastating earthquake (or another natural disaster—be creative!).
Ask students to calculate the percent (%) of marked individuals in the original and surviving populations.
Have students compare the percent of marked and unmarked individuals in each population. Compare data between table groups and discuss this in the context of changing allele/genotype frequencies due to bottleneck effects.
Tell students to return the marshmallows to the first beaker.

Activity C: Founder Effects

Announce that the marshmallow organisms will soon be populating a new island.
Tell students to pour several marshmallows onto the watch glass, which represents a new island.
Ask students to calculate the percent (%) of marked individuals in the original and founding populations.
Have students compare the percent of marked and unmarked individuals in each population. Compare data between table groups and discuss this in the context of changing allele/genotype frequencies due to founder effects.

“MURDER” Handshake

“Murder” handshake serves as a hook for introducing the topic of natural selection as a mechanism of evolution. It prompts students to get out of their seats and be involved in a murder mystery that serves as an analogy to how natural selection acts on populations of living organisms.

In this activity, one student acts as a murderer and targets classmates with a particular characteristic that is predetermined by the teacher. The activity resembles natural selection in that the murderer plays the role of a selective agent/pressure, the detective is an observer (like Charles Darwin himself), and the victims and survivors are members of the same species.

Preparation:

Count out one cue card per student.
Write the following messages on the cards:

“Detective”- 1 card
“Murder” and specific instruction (ex., “squeeze the hand of anyone who is not wearing glasses”)- 1 card
“Potential victim”- remaining cards

Procedure:

All students are assigned the role of either a potential victim, detective (1 per class), or murderer (1 per class) by handing out the cards.
Students are asked to keep their roles anonymous unless they are the detective.
The detective is asked to stand at the front of the class.
The teacher announces that the murderer kills by giving a handshake that ends with a firm squeeze.
The teacher instructs the students to walk around the classroom and shake hands with each other.
Students who receive a squeeze are asked to enter the dead zone (the back of the classroom).
Near the end of the game, the detective is asked to guess who the murderer is at a time determined by the teacher.

Follow Up:

The detective is asked if they see a pattern in the characteristics of “dead” individuals and survivors. The success of this step depends on how explicit the murderer’s instructions were and their success in “murdering” their classmates.
Students are asked to be seated.
The class has a discussion on the parallels between the activity and natural selection and fitness.