Light, sight, and natural selection
With the driving question “Do you see what I see?” this unit encourages students to think about how our perception of color depends on both the environment and our brain. Focusing on science research conducted in Dr. Becky Fuller’s lab, the unit addresses key science standards connected to animal behavior, natural selection, and systems biology. The curriculum is accompanied by web-based resources including virtual activities such as a virtual eye dissection and an “Ask a Scientist” interview with Becky Fuller.
Lesson 1: What do you see?
This introductory lesson serves to motivate the unit, "Do you see what I see?" by targeting individual differences in visual perception. Here, students begin to examine the driving question by probing the basics of visual perception. The lesson activities are used to foster interest in learning more about what and why students see what they do. Activities include a color sorting activity, discussions of optical illusions, eye dissections and a traditional colorblind test. These activities introduce information about how humans perceive contrast and color as well as the anatomy of the visual system. Students return to these ideas throughout the unit as they develop a response to the unit driving question.
Lesson 2: What color do you see?
In Lesson 2, students test how environmental conditions influence color perception with the simple task of sorting colored candies such as M&Ms. During this activity, students test how lighting and background color can change the speed and accuracy of M&M sorting. Students attempt to remove all the M&Ms of a certain color under varying conditions. This activity is an opportunity for teachers to address key concepts of how the eye works, how we perceive color, and how we differ in these perceptions. This lesson builds on ideas introduced in Lesson 1.
Lesson 3: Is seeing believing?
By using spectrophotometers and prisms to investigate the absorption, transmission, emission and reflection of light, students explore differences between their visual perceptions and the physical properties that contribute to these differences. This lesson builds on ideas introduced in Lesson 2 and allows students to build on physiological basis of vision introduced in Lesson 1 and extend understanding to the basic optical principles that underlie vision.
Lesson 4: Data Collection, Analysis and Experimental Design
Students have learned how their own experiences (Lesson One) and environment (Lesson Two and Three) influence their perception of color, and in this lesson, they will discuss whether the same principles apply to fish color preference. Students have already begun to think about color perception as a complicated neurological process. Part 1 of Lesson 4 begins to provide evidence for students to use to explain why this is the case.
Lesson 4 Part 1: Do fish have a favorite color?
Lesson 4 uses a "penny-pecking" experiment as an engaging central activity to examine why guppies might be used as a model for color preference. In Part 1 of Lesson 4, students examine color preferences of guppies in an experiment and discussion data to build on knowledge about human color perception gained from prior lessons. This initial experiment prepares students for discussions about the interactions between color and the environment in Part II of the lesson.
Discussions of data collection and interpretation are fundamental to this lesson. Students come to a consensus about experimental design before working in groups to run the experiment. Students work to interpret compiled class data during a whole class discussion focused on making meaning from all of the experiments.
Lesson 4 Part 2: What color do fish see?
Using the penny-pecking protocols established in Part I of Lesson 4, students examine in Part II how the environment impacts color prefererencesif fish not unlike the influence of environment in Lesson 2. Using findings from Part I of this lesson, students devise an experiment to test how the environment can change pecking behaviors in guppies. In addition to building connections between humans and other organisms, the activity encourages students to draw on what they learned about optics and sensory physiology in Lesson 3. Moreover, students investigate how variations in optical properties of the external environment can lead to variations in an animal's visual perceptions and, consequently, its mating and food preferences. In addition, the concept of variability within biological populations is addressed. Part II of this lesson emphasizes the development, testing, evaluation and revision of a hypothesis based on prior knowledge and intuition developed from related experiments.
Lesson 5: Why do guppies have favorite colors? Why do they care?
Natural and sexual selection of color preferences are the focus of Lesson 5. Students play a game that uses principles of selection to explain why guppies are attracted to certain colors. Students analyze different sensory and coloration biases that help fish to survive such as being able to find different colors of food or being camouflaged to avoid lurking predators. Students also explore how these biases can influence sexual competition; for example, brightly colored fish or those that have body coloration similar to preferred foods might be more attractive to mates. By playing the "guppy game", students observe adaptation to different environments and the evolution of sex differences and make hypotheses about the habitats that will favor certain traits. By simulating different populations of guppies under different circumstances students can observe genetic drift in populations over time. One key element of Lesson 5 is the generation of whole classroom data sets that will be analyzed as a class and individually, exposing students to various approaches for data interpretation and expression.
Lesson 6: Why can't I see what you see?
In this culminating lesson, students use the knowledge they learned in the previous lessons to make inferences about the significance of color perception in many species. Students discuss the biological advantage of color vision for humans during the synthesizing Do you see what I see? activity and make connections to other organisms and different visual systems in Find Your Niche! activity. Students learn about the evolution of color vision and how "evolution is devolution" to understand that animals evolve to have the most efficient visual system but not necessarily the most complex visual system to see what they need to see.