Eyes, Eyes, Baby! Day 1

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Objective

Students will understand the function of the eye and its ability to adapt.

Big Idea

Animal eyes must adapt to their environment.

RAP - Review and Preview

3 minutes

I call students to the gathering area to start our science lesson today. I remind them that we looked at cold sensors and adaptations in our last lesson. I tell them that today we are going to learn about eye adaptations.

In order to do that we are going to look at some different eyes and discuss their similarities and differences. We will then learn about how the eye works, through a hands-on dissection activity.

Guided Investigation

10 minutes

I show students, the Eyes, Eyes, Baby! PowerPoint. I ask them to look at each eye and notice any differences and similarities they might see to their own eye structure. I offer them about a minute per eye to make observations on their observation sheet. Students may recognize some of the eyes, but I don’t name the animal that they come from.

We talk about how these eyes are all very difference, as are the animals. We talk about how these eyes are all different for a reason. However, before we can understand why eyes are so different, we have to understand how the eye works. 

Lab Safety Mini-Lesson

10 minutes

I give students a science lab safety mini-poster to put in their notebooks. We talk through this very carefully and I let them know that I take it very seriously. I tell students that any infraction of the rules, during a science lab, will be treated very seriously. Being silly in science labs is not only a bad choice, but can endanger yourself or someone you are working with. My consequence is that the students sits out and does not do the lab, but must observe others and complete the assignment anyway. 

Dissection

25 minutes

At this time, I have my guest teacher or myself begin the cow eye dissection under the document camera. Students will be seated at their desks, locating and labeling the parts of the eye on their eye diagram.

I remove the parts of the eye in the following order:

  1. I cut away the muscles and fat, while telling students what they do.
  2. I cut a slit across the cornea of the eye to release aqueous humor. This gives form to the eye.
  3. I cut through the sclera to cut the eye in half. The front of the eye is the cornea.
  4. As you open the eye from the back, you can remove the iris and show students the hole in it, that is the pupil. The pupil lets the light into the eye.
  5. Remove the cornea and with the iris out of the way, you can see the lens.
  6. Remove the lens and look through it, it shows images upside down.
  7. Place the lens on a piece of printed paper and the words are magnified.
  8. Remove the lens and the remaining goop – vitreous humor. You can now see the retina. This contains the light sensitive cells that detect light.
  9. The retina is attached in one spot. This is where the retina joins the optic nerve.

10. The optic nerve carries messages to the brain.

11. If you remove the retina, you can see a layer of blue-green. This is the tapetum, this reflects light back through the retina to increase light for night vision. We don’t have tepetum, but cats and cows do. That is why their eyes shine when light is shined on them at night.

If you are new to dissections, there are lots of wonderful resources to walk you through the process. Look at this dissection site. Don’t ever be afraid to try this for the first time in front of your students. It’s good for them to see you learn while they are learning. It shows how important it is to be a lifelong learner.

You may want to have students complete their own dissection, after you have demonstrated yours. It would be a good idea to do a second one while students do theirs in groups. I always have lots of parent helpers in the room with these kinds of activities, especially when using a razor/scalpel. 

Wrap Up

2 minutes

I wrap up the lesson before students do their dissection, otherwise this lesson will take half a day. I tell students they will complete their own dissection the following day, and we will observe and discuss each part as we do it.