Environmental Impact and Natural Selection: A Simulation
Want to introduce your students to the impact that an environment can have on natural selection? The story of the peppered moth during Industrial-era London provides a great example of the interaction between environmental changes and the selection of traits within that environment.
This simulation will explore the environmental impact on selected traits within a changing environment, and the ways that changing environments can alter a phenotype within a population.
The Peppered Moth: A Background
In order to avoid detection from predators, the peppered moth is dotted with spots in order to blend in with the surrounding trees. These spotted moths are more likely to survive since they can avoid being seen by birds and other predators. However, the changing world of the Industrial Revolution brought with it some unintended consequences for these moths.
Coal factories produced an unprecedented amount of smog that drastically impacted nearby forests. Trees became layered in black soot which meant that these white peppered moths could no longer blend in with the trees. However, the small subset of black peppered moths suddenly had an environmental advantage: they could blend in with the new soot-covered trees. White peppered moths began to decline in numbers while black peppered moths had higher survival rates in their new environment. These genes passed to the next generations, and the peppered moth population saw a transformation in phenotype.
Source: Ask a Biologist
Biology Corner provides a great simulation that demonstrates the impact that the Industrial Revolution had on the peppered moth population. This simulation can be done with individuals at their desks or with larger groups working together to complete the activity. It can supplement classroom instruction and provide students with a fun way to experience natural selection that results from environmental changes.
In this simulation, students will use forceps in order to catch “prey” made with small circles made with a hole punch. Holes made with white paper will simulate the white moths, and the newspaper circles will represent the darker moths. This simulation will demonstrate what happens when a predator tries to catch prey in different environments.
Here’s what you’ll need to complete the simulation:
- Sheet of white paper and newspaper
- Hole punch
- 30 small newspaper circles
- 30 small white circles
- Place a sheet of white paper on the table and have one person spread 30 white circles and 30 newspaper circles over the surface while the other person isn’t looking.
- The “predator” will then use forceps to pick up as many of the circles as he can in 15 seconds.
- The number that are left are doubled to represent the next generation
- This trial will be repeated with white circles on a newspaper background, newspaper circles on a white background, and newspaper circles on a newspaper background. Record the data in chart below.
In my own teaching experiences, I find that activities like these work best when done in groups. I believe that encouraging students to work with others allows them to share what they know about a topic and learn from each other. Plus, it’s a great opportunity to build teamwork skills.
This activity can be really successful if done as an ABC (activity before content). Before introducing the concepts you decide to attach to this activity, perform the simulation before you provide any formal explanation of the concepts. That way, they can associate what they learned in the activity with the formal explanation provided by the teacher. I also find that it makes it more enjoyable not to spoil the purpose of an activity like this.
Introducing a bit of competition can also really engage students. Setting a challenge or goal can make it a fun and enjoyable experience, and I always find that students learn more when they enjoy what they are doing. Make it a race to see which group can collect the most circles, or set a goal to collect at least a certain number of circles before the time is up.
It is also important to emphasize the practice of collecting and analyzing data. The data table can reinforce science practices outlined by the Next Generation Science Standards. This data collection should be reinforced as a way to observe the phenomenon being explored in the simulation.
Connecting Concepts (NGSS)
Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.
- DCI: LS2.C: Ecosystem Dynamics, Functioning, and Resilience
- Ecosystems are dynamic in nature; their characteristics can vary over time. Disruptions to any physical or biological component of an ecosystem can lead to shifts in all its populations.