Exploring the Anatomy and Physiology of the Eye!

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Objective

Students will develop models in order to identify the parts of the human eye and explain their corresponding functions.

Big Idea

Eyes are complex organs with highly specialized parts that are used by organisms to connect their brains to their physical world.

Introduction

Lesson Background & Justification:

       The Eye is an organ of vision that detects light from the environment and converts it into electro-chemical impulses in neurons. In higher organisms like humans, the eye functions as a complex optical system comprised of specialized tissues and fluids which cooperatively work together to collect and regulate light from the surrounding environment, focus it, form an image, and convert the image into a set of electrical signals that transmits the signal to the visual cortex of the brain through complex neural pathways that connect to the eye via the optic nerve. In this lesson, students learn to identify the locale and function of the eye's anatomical parts in the effort to establish both a visual and contextual foundation needed to comprehend the physiology of the eye which is explored in lesson 2 of this unit. Command of this content in this first lesson later serves as a primer for students to comprehend how the visible organs presented at the surface of our bodies can selectively process elements or stimulants from our environment and transmit this information to specific regions of the brain that are responsible for processing and remembering them.  

Essential Prior Knowledge: Prior to experiencing this lesson, students should be familiar with the following content/concepts:

             a) Structure and Function of Neurons  

            b) Organization/Hierarchy of organisms   

Lesson Preparations:

 In the effort to prepare for this lesson, I make certain that I have the following items in place: 

a) A class set of Preserved Cows Eyes (One brain for each pair of students) and dissection tools/ pans.

b) A class set of protective wear (non-latex gloves, lab coats and safety glasses).

c) A class set of rulers and scissors.

d) Student lab books.

e) Eye anatomy and physiology notes handouts. (1 per student)

Common Core and NGSS Standards:

MS-LS4-2-Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.

SP2- Developing and Using Models.

MS-LS1-8- Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. 

HS-LS1-2- Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

HS-LS4-2-Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.

Standards Rationale:

       Modeling is the process by which scientists represent ideas about the natural world to each other, and then collaboratively make changes to these representations over time in response to new evidence and understandings. It is intimately connected to other scientific processes (asking questions, communicating information, etc.) and improves students ability to recall scientific jargon through association. In the classroom, it is important that teachers engage students in modeling practices, to set the foundation of success in a lesson or instructional unit. In this lesson modeling is used in concert with other science practices in the classroom to promote students’ reasoning and understanding of core science idea presented (structure and function of the eye). 

Engage

10 minutes

Section Sequence:

       In this section of the lesson, my goal is to bring students attention to the fact that not all parts of the eye are specialized for seeing. Specifically, I utilize a clip from the popular show "Monsters Inside Me",  and encourage students to consider how and why the parasitic invasion of the eye doesn't necessarily lead to blindness. As the video draws in a great deal of interest from students, it serves as the perfect priming tool to set the stage for scientific questioning and reasoning and put the inquiry wheels in motion. This helps me to transition to the exploration activity where students take a deeper dive into the anatomy and function of the eye itself.This activity proceeds as follows:

a) Slide 1: Read the engagement questions presented on the screen. Allow for students to share their thoughts out verbally to the class. 

b) Ask: Are all parts of the eye seen here involved in the function of sight? Are there any parts that could potentially sustain damage without making the eye as a whole lose its function? Discuss briefly. Share with students that they will watch a video to see if what they articulated/hypothesized is true (if they said yes) or defies what they think (if they concluded no) and to watch for evidence in the video that either supports or refutes their thinking. Proceed to play the following video:

     

c) Post video, discuss with students any evidences that they observed which supports or refutes their articulated responses. Encourage students to utilize the vocabulary projected on the slide as they verbally share their points of views to the class.  

Standards Covered:

HS-LS1-2- Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

MS-LS1-8- Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. 

Explore

45 minutes

Section Sequence:

        In this section of the lesson, my goal is to provide students with an opportunity to explore the intricate structures that collectively create the eye. Through a guided dissection experience,  students gain an appreciation for the solid and fluid mosaic nature that the eye requires in order to adjust and manipulate light into a form that can be interpreted by the brain. This activity proceeds as follows:

a) Slide 2: Ask rhetorically: "If certain parts of the eye can be altered or fall victim to saprophytic activity and not create vision problems, then why do we have them?" Share that we will now explore the various parts of the eye and respective functions via a virtual guide. Direct students to collect their dissection materials, lab safety materials and dispense the first sheet of the Eye Anatomy and Function Students Handouts to each student pair.  

b) Launch and project Exploratorium Cow Eye Dissection on the board and select watch online. This takes students through a visual and audio eye dissection experiences. Select the preferred resolution setting and proceed to the first frame. Tell students that the virtual guide will provide us with the steps required to dissect the eye in front of them and will share the functions of each part that can be recorded on the eye diagram provided for them.

c) Play Step 1 and instruct students to summarize the content shared and record it on their handouts.

d) Play Step 2 and instruct students to record the main points/functions articulated on their handouts and to perform the actions demonstrated on the video. Provide adequate time for all students to complete each observed task. 

e) Play Steps 3-13 and repeat the steps outlined in d for each.

Note: The teacher should circulate throughout the class as the dissection video segments play to address students concerns or to clarify information.  

Standards Covered:

MS-LS4-2-Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.

HS-LS1-2- Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

SP2- Developing and Using Models.

MS-LS1-8- Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. 

Explain

15 minutes

Section Sequence:

In this section of the lesson, my goal is to provide students with a different representation of the eye that demonstrates how the individual parts that they explored through dissection work in concert to process light for the brain's interpretation. This activity proceeds as follows:

a) Slide 3: Ascertain that all students have important eye function content recorded on their individual handouts by reviewing each part via simple Q & A. For instance, ask what is the job of the lens? and what will happen to the visual perception process without it?. This assures that students not only have the information recorded but also comprehend how the identified part aid in the sum of the eye's function. 

b) Share with students that they will now watch an animation that shows how all of the eye parts work together to process light for the brain's usage. Instruct students to record new information as it appears within the video onto their handouts by supplementing their illustrations/notes from the explore activity with additional illustrations and notes to help explain functionality of the organ as a whole. Proceed to play the following video:

     

 c) Post video, solicit a student volunteer to illustrate how visual acuity is achieved using the diagram projected on the screen. Clarify any misunderstandings as the student works and invite other students to add on as the student presents his or her understanding of the process. 

Standards Covered:

HS-LS1-2- Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

SP2- Developing and Using Models.

MS-LS1-8- Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. 

Extend

15 minutes

Section Primer:

      A Photoreceptor Cell is a specialized type of neuron found in the retina that is capable of phototransduction. The great biological importance of photoreceptors is that they convert light (visible) into signals that can stimulate biological processes. More specifically, photoreceptor proteins in the cell absorb Photons or elementary particles that is one of the fundamental forces in electromagnetism and the basic unit of light, triggering a change in the cell's membrane. Over time, photoreceptor cells have evolved to accommodate diverse life forms as they further evolve. In this section of the lesson, students learn via video presentation how this specialized cell has changed over time.      

Section Sequence:

a) Slide 4: Read the question as it appears on the slide to the class. Take responses from the class and share that scientists theorize that it has taken our eyes some time to evolve into the magnificent spectacles that they are today. Tell students to use the following video to produce a simple flow chart in their lab books or on the back of their note sheets that explains how eyes have evolved from simplistic structures to those examined and explored today. Play the following video: 

      

Pause and rewind the video at students' request to ascertain that they are able to distill the vast amount of detail in the video into their flow charts (as described in in step a)

c) Allow time for class Q and A if needed beyond the video for concept edification. 

Standards Covered:

MS-LS4-2-Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.

HS-LS1-2- Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

HS-LS4-2-Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment. 

SP2- Developing and Using Models. 

MS-LS1-8- Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. 

Evaluate

10 minutes

Section Primer: 

          A cataract is a clouding of the lens in the eye that affects vision. It can occur in either or both eyes but cannot spread from one eye to the other. Most cataracts are related to aging and are therefore very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. In this section of the lesson, students are assessed on how well they comprehend  the role of the lens to visual acuity equation and also learn to infer specific loss of function of the eye based on missing components or altered components presented. 

Section Sequence:

Slide 5: Instruct students to complete the exit ticket activity as presented on the screen. Instruct for students to complete the assignment in their lab books. (See examples of student work attached to ascertain instructor expectations)

Standards Covered:

HS-LS1-2- Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

MS-LS1-8- Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories.