Cow Eye Dissection

Essential Question:
How does the eye view and transfer an image to the brain?

Teacher Prep:
Prior to class, all scalpels are checked to ensure there are no loose blades. Goggles, dissecting trays, and dissecting gloves are placed on tables prior to students entering the class. Giant Post-It Notes are posted around the room with one of the following words listed: Iris, Pupil, Sclera, Retina, Optic Nerve, Vitreous Humor. The document camera is also plugged into the computer to allow students to watch me as I model how to dissect the eye.

Engage:
At the beginning of class, students will watch a video segment of a young woman dissecting a cow eye. (While watching the segment, the scalpels and dissecting scissors are placed on the tray). After watching the segment, students are asked to describe the parts of the eye in which light travels through to reach the brain.

Explore:
Before beginning the actual demonstration, students are able to view the cow eye as I model how to trim the excess fat and position it for the first incision. The image from the document camera transfers to the Smartboard allowing for students to have a close up view of the eye.
Working with their lab partner, students first check to make sure they have all the supplies necessary to begin and exchange any which may be defective. Each lab partner takes turns trimming the excess muscle from the eye. After setting the eye back on the lab tray, one student is responsible for cutting vertically (either with a scalpel or dissecting scissors) down the eye. Once the eye has been cut, students locate and identify the: iris, pupil, retina, sclera, and optic nerve. Another student records the answers to the Guided Questions (listed below) in his or her scientific journal.
1. What is first part of the eye light travels? How does the surrounding muscle adjust it's size?
2. What is the vitreous humor and what is the purpose of it?
3. How would images appear to our brain if it had difficulty interpreting the signal from the optic nerve?
4. Describe the functions of each part of the eye.
5. Illustrate the path light travels to reach the brain.

Explain:
Once students have answered the Guided Questions and cleaned their work area, students use post-it notes to summarize each part of the eye or describe how it feels. Students are given 5-8 minutes to place their notes on the giant Post-It Notes around the room and to read the responses left by their classmates.

Elaborate:
Students will generate a list of 5 activities they do before coming to school. Using their list students will describe how the activities would be completed if they could not rely on their brain to correctly interpret images.

Evaluate:
Formative: As I observe each lab group, I will ask students for their answers to the Guided Questions.
Summative: Students will be given a test at the end of the unit focusing on the identification and functions of the parts of the eye.