Do You See What I See?

March 2015

Do you see what I see?

Light, sight, and natural selection

Lesson 2: How does biology affect perception? I. Overview Students begin their investigations of individual difference in perception beginning with a colorblindness test and reading of an interview with a person with colorblindness. In order to further understand how the structures of the eye affect perception, students dissect a cow eye and make connections between the parts and their functions in contributing to sight. Students will use this evidence in Lesson 5 to revise their model of perception.

Connection to the driving question In the first lesson, students were introduced to the idea that individuals perceive color differently, and they built a model of color perception. In this lesson, they explore the mammalian eye and colorblindness to learn how biological factors and genetics can affect color perception, knowledge which they will use in subsequent lessons to revise their model.

II. Standards

National Science Education Standards  Science as inquiry. Identify questions and concepts that guide scientific investigation (9-12 A: 1/1).  The Behavior of Organisms. …In sense organs, specialized cells detect light, sound, and specific chemicals and enable animals to monitor what is going on in the world around them (9-12 C: 6/1).

Benchmarks  Something can be "seen" when light waves emitted or reflected by it enter the eye—just as something can be "heard" when sound waves from it enter the ear. 4F/M2

III. Learning Objectives

Learning Objective Assessment Criteria Location in Lesson Know the causes for Students provide an explanation including Colorblindness Test colorblindness genetics and genetic mutation Activity, “Interview with a Colorblind Person” Reading

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Understand the structures and Students correctly identify structures “The Biology of How functions of the parts of the within the eye and describe how the We See” Reading, mammalian eye physical characteristics of the structure “Eye Construction contribute to its function in enabling sight Game” Know the cells involved in color Students correctly differentiate the “The Biology of How perception functions of rods and cones and can We See” Reading describe how cone(s) are involved in colorblindness Understand the role of the brain Students are able to distinguish the eye as “The Biology of How in color perception a sensory organ and the brain as an We See” Reading, information processing organ which “sees” “Interview with a Colorblind Person” Acquire appropriate laboratory Students demonstrate care and attention Eye Dissection Activity skills to proper safety procedures during eye dissection Practice collecting evidence Students collect and describe several Throughout lesson pieces of evidence related to the perception of color

IV. Adaptations/Accommodations If, for whatever reason, it is not possible to do the eye dissection, a digital activity called the Eye Construction Game can be used instead. It is available on the Project NEURON website at http://neuron.illinois.edu/games/eye-construction-game. Alternatively, the Eye Construction Game can also be used as an assessment tool. If a student is not comfortable with the dissection, there are also a series of videos available (as a YouTube playlist) of a detailed, narrated eye dissection of a fresh and preserved cow eye. This can be found on the Project NEURON website at http://neuron.illinois.edu/videos/eye-dissection-videos.

Safety Students need to wear appropriate eye goggles and gloves when handling eyes for dissections. Caution students about the proper use of sharp instruments like scalpels and scissors. Dispose of dissected eyes properly.

V. Timeframe for lesson

Opening of Lesson  Revisit student models from Lesson 1 – 2 minutes

Main part of lesson  Activity 1: Colorblindness test – 5 minutes  Activity 2: Pair and share reading – 10 minutes  Activity 3: Eye dissection – 30 minutes

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Conclusion of Lesson  Wrap-Up Discussion – 10 minutes

VI. Advance prep and materials

Activity 1: Colorblindness Test

Materials  Use Ishihara color test plates. If possible, have enough plates (or copies of the plates) to hand out to students so that they can look at the images. o All 38 of the Ishihara Plates can be found online at the address listed here. (Note: All color vision plates are copyrighted but can be used under the Fair Use Policy for education). However, the scanned (and reprinted) colors will not be nearly as accurate as the official Ishihara plates: http://www.color-blindness.com/2012/10/22/ishiharas- test-for-colour-deficiency38-plates-edition/ o Official Ishihara printed plates can be found on Amazon.com, although they can cost between $100 and $200 per set.

Preparation  Order or print the Ishihara images ahead of time, if necessary.  Print copies of “Interview of a Colorblind Person”

Activity 2: Pair and Share Reading

Materials  “Interview of a Colorblind Person” (U1_L2_Reading_ColorblindInterview.docx) or the extended version (U1_L2_Reading_ColorblindInterview_Extended.docx)  “The Biology of How We See” (U1_L2_Reading_BiologyOfHowWeSee.docx)

Preparation  Print enough copies of the readings for each pair of students in the class.

Activity 3: Eye Dissection

Materials For the activity, each student group will need:

 One cow eye per group  Gloves  Safety goggles  Lab aprons (optional)  Dissection materials including: scalpels, forceps, blunt probes, and scissors  Exploratorium dissection manuals

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Preparation  Print student dissection manuals from the Exploratorium found at http://exploratorium.info/learning_studio/cow_eye/doit.html.  Order eyes in advance. One supplier of preserved sheep and/or cow eyes is Carolina Biological Supply: http://www.carolina.com/. Local butcher shops may also be able to supply fresh eyes if notified ahead of time.  Carolina Comparative Mammalian Eye Dissection Kit can be ordered from: http://www.carolina.com/product/221492.do Homework and Assessments  Homework can include the Language and color (BBC Horizon) video clip in Lesson 3  Assessments include evidence from student discussions and student artifacts (see Assessment section in Implementation)

VII. Resources and references

Resources  The materials for this lesson can be downloaded for free from the Project NEURON website: http://neuron.illinois.edu/do-you-see-what-i-see/lesson-2  The National Eye Institute (NEI) at the National Institutes of Health (NIH), https://nei.nih.gov/  Colour Blind Awareness website. http://www.colourblindawareness.org/  Colblindor website. http://www.color-blindness.com/  We Are Colorblind website. http://wearecolorblind.com/ References “The Biology of How We See” Reading  “Drawing of the Eye” by the National Institutes of Health – National Eye Institute. Retrieved from https://www.flickr.com/photos/nationaleyeinstitute/7544457228. Public Domain.

Eye Dissection  Cow’s Eye Dissection. Exploratorium. http://exploratorium.info/learning_studio/cow_eye/doit.html  Vision and Art: The Biology of Seeing  Gregory, R.L. (1997) Eye and Brain: the psychology of seeing (5th ed.). Princeton, NJ: Princeton University Press

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VIII. Lesson Implementation

Opening Begin the lesson by referring to students’ models of perception that they developed in the previous lesson, especially any parts of their models that referred to biological structures like eyes. Remind them that they will be investigating the human eye and how it affects color perception.

If students read “Interview with a Colorblind Person” for homework, students can share their thoughts as an opening to the colorblind test. Otherwise, the reading can be integrated into the colorblind test activity.

Main Part of Lesson

Activity 1: Colorblindness Test Show the entire class the Ishihara color test plates one at a time, or pass them around for closer inspection. It is important to realize that individual differences and students who have color-blindness may be identified so take care throughout this activity. Also mention that only an eye doctor or physician (ophthalmologist or optometrist) can accurately diagnose color-blindness.

The official Ishihara plates come with a description of each plate, including the number(s) that will be seen by a person with normal color vision and/or different types of color-blindness. Some plates are used as a control (can be seen by anyone), and some plates have numbers that can ONLY be seen by individuals with normal color vision or color-blindness.

Ask students:

 What do you see when you look at the plates? o Students may state numbers, but also encourage them to examine the dots, which are made of varying hues of color.  What causes people to see something different? o Because the hues of the dots in the numbers are slightly different than the background dots, some people may not be able to distinguish the colors, or they may distinguish hues that people with normal color vision cannot see.  What about their eye might be different?  How do you think the daily life experiences of people with color-blindness would be different from those of people with normal color perception?

This last two questions can be used to transition into the Pair and Share Reading Activity. If students are not expected to know the answer, but ask them to keep their questions in mind as the investigation continues.

Activity 2: Pair and Share Reading This last question can be used to transition into the readings “Interview with a Colorblind Person” (U1_L2_Reading_ColorblindInterview.docx) and “The Biology of How We See”

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(U1_L2_Reading_BiologyOfHowWeSee.docx). If students have previously learned (or will learn) about inheritance probability, Punnett squares, and/or sex-linked traits, they can read the extended version of the interview (U1_L2_Reading_ColorblindInterview_Extended.docx), which includes these additional topics.

Ask students to get into pairs (or assign them based on reading level, if possible) and hand out one set of copy to each pair. Ask that each student take a moment to read their articles, then discuss what they learned with their partner. Write or project the following questions for each pair to discuss:

 What did you already know before you started the reading?  What was something interesting and new you learned from the reading?  What causes colorblindness? o Genetic mutations that affect the function of cones.  Where is this component in the eye? o Cones and rods are contained within the retina, at the back of the eye.  Where in the body does “seeing” occur? o This is a tricky question but important to point out that the eye is a sensory organ that detects information from the environment. The processing and interpretation of sight actually occurs in the brain (and to a little extent the neurons at the back of the eye).  What other questions do you have, or what is not clear?

Once students have had an opportunity to discuss what they’ve read with each other, be sure to clarify any additional questions that students have, or redirect them to resources where they can find the answers. Other questions may lead into the next activity of a cow eye dissection.

Activity 3: Eye Dissection A possible introduction to the activity can also include a discussion on model organisms.

 Why do you think we are going to dissect a cow’s eye? o While students will probably identify reasons such as the cow eye being from a mammal, the same class of organisms as humans, and that cow eyes are easy to obtain, they might not mention the ethical issues. Make certain to have a short conversation about the use of animal models in science (as opposed to human eyes).

Tell students that they are going to dissect a cow’s eye and emphasize the safety rules when using sharps and the proper dissection protocol before distributing the eyes to the students. If students are unable to perform the eye dissection, for whatever reason, see alternative activities in Section IV Adaptations/Accommodations.

Ask students to identify the structures that they are going to look for when dissecting the eye based on the readings that they did.

 Distribute the Student Dissection Manual (see Advance Prep and Materials) to the students.  Distribute the specimens and dissection supplies.

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Ask students to record observations, data, or drawings in their lab journals or notebooks. Students can write down their reflections and interesting findings made during the dissections. Provide assistance and guidance as needed while students carry out the dissections.

After students finish the dissection, they clean up the dissection work area and dispose of the dissected specimen safely and in accordance with the regulations in the school or local guidelines.

At the end of the eye dissection activity, have a discussion by asking students the following questions:

 Which structure in the eye did you find most interesting?  What parts of the cow eye are different than a human eye? o Cows (and many other animals, like sheep and cats) have a tapetum, a reflective layer at the back of the eye which aids in vision at night.  Can you name the structures of eye? (cornea, lens, retina, optic nerve, etc.)  How does the structure of each eye relate to its function when it comes to sight? Some important examples are o Cornea – external, transparent part of the eye that allows light to enter o Iris – ring of muscles that control the amount of light to enter the eye o Lens – changes shape to focus light on the retina o Retina – has rods and cones that detect light and sends signals to the optic nerve o Optic nerve – sends nerve impulses of information to the brain for further processing  What part of the eye does one use when perceiving different colors? o The retina, or more specifically, specialized cells called cones within the retina.

Conclusion Conclude the lesson by revisiting what students did to investigate the eye and how biology can affect color perception. Ask them to suggest pieces of evidence they will include when they revise their models, or give students time to record these pieces of evidence in their lab notebooks.

Tell students that they will continue their investigations in the next lesson by looking at factors in the environment that may affect color perception.

The BBC Horizons video of scientists investigating language and color perception (link available in Lesson 3) can be assigned as homework or viewed in class as the opening of Lesson 3.

Assessments Summative assessment throughout the lesson include student’s responses to discussion questions. Assessment criteria are included in Section III. Learning Objectives.

A comprehensive summative assessment occurs in Lesson 5 when students revise their model of color perception. If students are recording their pieces of evidence in lab notebooks, these can be artifacts of student learning.

Test bank assessment questions are available on the Project NEURON website.