Color Variation over Time in Rock Pocket Mouse Populations

Contributor
Mary Colvard Howard Hughes Medical Institute (HHMI)
Type Category
Instructional Materials
Types
Lesson/Lesson Plan , Student Guide , Instructor Guide/Manual , Activity
Note
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.

Description

This activity provides an introduction to natural selection and the role of genetic variation by asking students to analyze illustrations of rock pocket mouse populations (dark/light fur) on different color substrates in the Sonoran Desert (light/dark) over time. Based on this evidence, and what they learn about variation and natural selection in the accompanying short film, students use this evidence to explain the change in the rock pocket mouse populations on the lava flow (dark substrate) over time. This is one of several classroom activities, focusing on related topics and varying in complexity, built around the short film. This ten minute film shows adaptive changes in rock pocket mouse populations, demonstrating the process of natural selection and can be accessed at http://www.hhmi.org/biointeractive/making-fittest-natural-selection-and-adaptation. The film is also available as an interactive video with embedded questions, which test students’ understanding as they watch the film. That version can be accessed at http://www.hhmi.org/biointeractive/pocket-mouse-film-quiz. The series also has two animations which will help to reinforce the concept. They can be accessed at http://www.hhmi.org/biointeractive/pocket-mouse-and-predation and http://www.hhmi.org/biointeractive/pocket-mouse-evolution.

Intended Audience

Educator and learner
Educational Level
  • High School
Language
English
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

HS-LS4-4 Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Clarification Statement: Emphasis is on using data to provide evidence for how specific biotic and abiotic differences in ecosystems (such as ranges of seasonal temperature, long-term climate change, acidity, light, geographic barriers, or evolution of other organisms) contribute to a change in gene frequency over time, leading to adaptation of populations.

Assessment Boundary: none

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
At the beginning of the lesson, students place four illustrations showing different numbers of light and dark colored rock pocket mice at two locations (light/dark substrate) in sequence from oldest to most recent. Watching the short film, students learn about the changes of rock pocket mouse populations, and that the environment contributes towards determining whether or not randomly arising mutations in fur color are advantageous, neutral, or deleterious. As students return to the four illustrations after watching the video, they analyze the illustrations by counting and graphing the color distribution of rock pocket mice at the two locations (light/dark). Based on this evidence, students arrange the four illustrations in a sequence from oldest to most recent, and make an argument for how natural selection leads to a change in fur color in the populations of rock pocket mice over time. Before starting the activity, it is helpful if the teacher familiarizes students with the rock pocket mouse and its habitat. To engage student interest in the lesson, teachers should raise the question of how there came to be two different populations of pocket mice (light/dark). To get a sense of their initial thinking, students should not skip the step of an initial ordering the rock pocket mice illustrations before they watch the short film. Throughout the activity, students should work with a partner or in small groups and be encouraged to share their thinking as they make decisions about re-ordering their illustrations, graphing the data, and answering the questions.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students are applying the theoretical framework of evolution by natural selection to explain the patterns observed in the rock pocket mouse populations through answering four open-ended questions. The teacher should make sure that students construct their explanations based on their evidence collected by analyzing the four illustrations showing light and dark colored rock pocket mice at two locations, as well as the information from the short film and the animations. Teachers can use probing questions, such as “What story about the change in coat color at location A and B does your graph tell you? How does that connect to what you learned from the short film? What about the animation helps you explain why the proportion of light and dark colored mice changed over time in location B?” Different ways to help students monitor their own learning include encouraging students to explain their thinking to each other when working in small groups, defending their answers to the large group, which naturally leads into peer review of their work.

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Part of the activity asks students to write a scientific summary that describes changes in the rock pocket mouse populations at the location that changed from light to dark substrate due to a dark lava flow (location B). The teacher can use probing questions about the data students collected and analyzed from the illustrations and the information from the short film, to make sure that students construct their argument based on evidence from their data table and graph, and the information from the short film. Such probing questions could include: “What is your data table and graph telling you about the number of light colored and dark colored rock pocket mice over time at location B? What do you remember from the short film about what caused the changes in the coat color of the rock pocket mice? Why would coat color influence the chance of a rock pocket mouse to survive and reproduce on a dark or light substrate?” Different ways to help students monitor their own learning include encouraging students to explain their thinking to each other when working in small groups, defending their answers to the large group, writing and sharing their answers on white boards, large post-it notes, or using an Elmo. This can naturally lead from students constructing written arguments to presenting oral arguments which in turn can lead to counter-arguments. It is the teacher’s responsibility to make sure that students cite evidence from the illustrations, the short film, and the animation when making their arguments and counter- arguments.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Teachers should remind students to use evidence from the rock pocket mouse population illustrations and the short film and animation as they work through four open-ended questions about the change of rock pocket mouse populations over time. Students are being asked to identify the change in the number of light and dark rock pocket mice as the color of the substrate changes from light to dark due to dark lava flow at location B. The illustrations and short film show that there is natural variation of coat color in the population of rock pocket mice living on the lava flow. The short film explains that mutations can cause a change in coat color, and that these genetic changes are being passed on to offspring. The animation and the short film also show the competitive advantage of a coat color allowing an individual mouse to blend into the background to avoid predators. As students work through the questions, teachers should monitor and use questioning as needed to make sure that students use reasoning to synthesize the evidence from the illustrations and short film to construct an explanation about how natural selection provides a mechanism for the rock pocket mouse populations to adapt to the change in their environment due to dark lava flow. Through skillful questioning teachers can make sure that students realize that mutations are random, that variations of traits (fur color in this case) occur normally in populations, and that a change in environmental conditions (the color of the ground) provides a selective advantage to those individuals already possessing these traits. It is also important that students understand that individuals are selected, but only populations evolve.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
This activity instructs students to create mathematical representations of the evidence they collected by counting the number of light and dark mice in the four illustrations at two locations, A and B. Based on what they learned from the short film, students order the four illustrations from oldest to most recent. Students are asked to complete a data table with the number of dark and light mice at each of the four illustrations at each of the two locations. Students then are provided with a section of grid paper and instructed to create a graph based on the data that shows the distribution of the mice at location A and B. While there is a reminder that students should label the axes and give the graph an appropriate title, students are encouraged to decide how to graph the data, and the teacher should encourage students to come up with their own way on how to graph the data. The activity is a paper and pencil activity, and students can create the graphs using colored pencils. The teacher can include the use of technology and ask students to create the graphs in Excel or a different graphing program. After having completed the graphs, students use the mathematical representations they created to identify patterns of light/dark fur color in the rock pocket mouse populations on the light and dark background over time. They cite it as empirical evidence to support their explanation of how natural selection provides a mechanism for the rock pocket mouse populations to adapt to the change in their environment.

Resource Quality

  • Alignment to the Dimensions of the NGSS: Through organizing, analyzing and explaining the illustrations of rock pocket mice populations in a changing environment, students are actively engaged in all three dimensions of the NGSS. As students answer a series of four open-ended questions, they construct an explanation/make an argument about how natural selection provides a mechanism for the rock pocket mouse populations to adapt to the change in their environment due to dark lava flow, making sense of the disciplinary core idea of how natural selection leads to adaptation, by engaging in the practices of constructing explanations and engaging in argument from evidence. The short film, with many vivid visuals, reinforces the disciplinary core idea and adds the lens of the nature of science. As they are completing the data table and create a graph, students use the mathematical representations they created to identity patterns of light/dark fur color in the rock pocket mouse populations on the light and dark background over time, which they cite as empirical evidence to support their explanation, making the crosscutting concept of patterns an integral part of the learning experience.

  • Instructional Supports: The activity provides students with a phenomenon by asking them to organize four illustrations of dark and light colored rock pocket mice at two locations from oldest to most recent. A ten minute short film, narrated by scientists, showing footage of rock pocket mice in their habitat, their predators, as well explanations of mutations and several short animations, further engages students in the phenomenon. While the short film is engaging, teachers may need to create some interest by talking about rock pocket mice at the beginning of the lesson, as the illustrations by themselves may not motivate students sufficiently to engage in the task of ordering them prior to watching the short film, without being familiar with rock pocket mice. Teacher materials with teaching tips and answers to the student questions are provided, which helps the teacher support all students. The tips include a reminder that students should place the four illustrations of dark/light rock pocket mice at two locations in order, before they watch the short film. This is an important tip, as it provides an opportunity to reveal students’ prior knowledge. Teachers can build on the teacher material suggestion that students work in pairs and ask students to share their thinking and defend their answers in their small groups and to the large group. A public display of the students’ work and feedback from peers (e.g. via a gallery walk or large group discussion) can help all students solidify their understanding. As part of this series, HHMI has two animations which will help to reinforce the concept. There are several helpful tips on how to use the animations to address individual learner needs. http://www.hhmi.org/biointeractive/pocket-mouse-and-predation shows a light and a dark colored rock pocket mouse in two different environments (light sandy desert and dark lava flow) as an owl sweeps down to capture the mouse that stands out from the background. http://www.hhmi.org/biointeractive/pocket-mouse-evolution shows the spread of a favorable mutation (in this instance dark fur) through the population of rock pocket mice. The simulation makes the abstract scientific idea that even a small selective advantage can lead to a rapid change of the rock pocket mouse population visible and concrete. There are no suggestions on how to connect instruction to students’ home, neighborhood, community, and/or culture. Teachers could find examples of similar phenomena in local ecosystems on their own.

  • Monitoring Student Progress: The ordering and graphing task as well as the open ended nature of the questions afford the teacher ongoing opportunities to monitor their students’ progress. No rubrics or scoring guidelines are included in the materials. The teacher guide contains detailed information of what should be included in the student answers to the four questions. The teacher can use that information to provide on-going feedback to students as they are working on the activity. The interactive video format of the short film provides the teacher with additional opportunities to monitor students’ understanding as they watch the film. A total of six multiple choice questions are embedded at three points during the film. After selecting a correct response, students immediately receive feedback that the answer is correct, followed by a brief explanation and the instruction to continue to the next question or the film. An incorrect response results in an explanation of why the answer is not correct and the invitation to try again. At the end of the video, the cumulative results for the quiz are shown (answers selected, and attempts) and can be printed.

  • Quality of Technological Interactivity: The activity itself is a paper and pencil resource. The animations and short film can be streamed or ordered for free as a DVD.