Teacher Feedback Drives Adaptation of Mi-STAR’s Natural Selection Unit

Adaptation by natural selection is a simple concept that can be remarkably difficult to grasp. Even after teaching the original Mi-STAR unit on natural selection, teachers reported that some students still hang on to their prior conceptions about how populations change over time. So when Mi-STAR began revising Unit 8.1: Bugs in the Bed!?, it used teachers’ feedback to make sure to clarify a handful of important key concepts. In addition, curriculum developers added materials to deepen student learning and changed the Unit Challenge to boost student engagement.

“The topic is still bedbugs, so the students still get to enjoy those creepy critters,” said Lindsey Watch, Mi-STAR curriculum development associate. “But we streamlined the unit, so students can really explore the phenomenon of natural selection and how it drives evolution of a species. We also tried to focus on areas with lingering student misconceptions.”

Once people have internalized their own explanations for phenomena like natural selection, it can be hard to change their viewpoint, even in the face of compelling evidence. “When students think about organisms that are better adapted, they tend to think those organisms are choosing to make changes, when really the environment has been selecting the most successful individuals over time,” said Watch. “It’s not just middle school students who struggle with this,” she added. “It's a hard concept to get your head around.”

To drive that point home, developers revamped the lessons to provide students many opportunities to clarify their understanding of these phenomena.

In the new Lesson 2, students use a variety of tools (a fork, a spoon with a piece of yarn tied to the handle, and an origami “cootie catcher”) as model “beaks” to pick up two different kinds of food, marshmallows and dried beans, and compare how well those beaks can collect the food pieces. Fork beaks got the most food when marshmallows were on the menu but starved when beans were served. Conversely, spoons thrived on beans, while the cootie catchers ate well on both kinds of food. And having a sporty yarn accessory made no difference at all.

“With the yarn, they get that not all traits are related to survival,” said Jen Pera, a science teacher at Jeffers High School, in Painesdale, who piloted the lesson in her class. And students also realized that survival is not actually determined by the kind of beak you have. “Your chances of survival depend on how well your traits are suited to that environment, in this case, your food source,” she said.

Lesson 2 highlights the key idea that an organism’s traits affect how likely it is to survive in a given environment.

Mutations are addressed separately in Lesson 3. Previously, the lesson revolved around a telephone game, with students whispering messages to each other to see how information can change over time. The message always morphed into something completely different. “That gave students the impression that mutations were relatively common,” said Pera. “Sometimes in a class we would end up with seven mutations, and we should have one.”

Now they roll dice to see if DNA mutates. This new version illustrates how unusual mutations are and, then in Lesson 4, students investigate how the rare beneficial mutations become dominant. Using a similar model with forks and spoons, students simulate multiple generations to see how the distribution of traits change over time. “The class started out with half forks, half spoons,” said Pera. “Then they go through rounds collecting food, and at the end of the lesson one type ‘dies’ and is replaced by the other utensil. Then the food changes.”

This exercise comes on the heels of a lesson that addresses how traits arise and clarifies an important evolutionary concept. “Just like a utensil, an organism can’t just mutate to be better at getting the food that’s available,” Pera said. “The one that already has the right trait has the best chance of surviving and reproducing.”

Mi-STAR staff and teachers have also made additional improvements to Unit 8.1 in response to teacher feedback.

A more-engaging Unit Challenge

The original unit revolved around the problems of Terry, an exterminator who was debating whether to continue using heat to kill bedbugs or switch to an insecticide that killed 99.9 percent of the pests. Most students had no experience with that scenario, said Pera. Now, a hotel has a bedbug infestation, and the owner has to figure out how to address the problem. “Most of our students have stayed in hotels, so they can relate to that,” said Pera.

Pre/post assessments

Mi-STAR also used teacher feedback to redesign the unit’s embedded and pre/post assessments to make them shorter and easier to score and grade.

Literacy resources

“The teachers said their kids need more experience reading about science content,” said Watch. So Mi-STAR has incorporated a variety of reading resources into enhanced units. First, the team has partnered with Reading Apprenticeship to incorporate sense-making through text into Unit 8.1 (v2) and Unit 7.1 (v2). The additions support students to reinforce their understanding of the unit’s ideas by making sense of a variety of short scientific texts. Second, Mi-STAR has integrated optional opportunities for individual reading into Share phases throughout the unit. These can be used for homework, as a sub plan, or for individual work. All of these are made available in addition to the reading assignments for substitute lessons made available last year.

Accessing the updated units

Mi-STAR teachers now have access to this enhanced unit and others by default in their unit list in the curriculum portal. The original version of the unit will still be available this year by request for teachers who have been using it.