Eye Dissection


Cow Eye Dissection

How do we see? The eye processes the light through photoreceptors located in the eye that send signals to the brain and tells us what we are seeing. There are two types of photoreceptors, rods and cones. These photoreceptors are sensitive to the light. Rods are the most sensitive to light and therefore provide gray vision at night. Cones are mainly active in bright light and enable you to see color. There are 100 million rods compared to the 3 million cones located in your retina. The photoreceptors help you adjust to night and day. For example, if you walk inside from the sun, you can not initially see anything. This is due to the activity of the cones and the lack of activity of the rods. The rods become activated and adapted to the dim light, resulting in gray images formed in the dark. The same thing happens when you leave a dark movie theatre during the day. The rods are mainly activated and the cones have to adjust to sunlight when you leave the theatre.

By dissecting the eye of a cow, which is similar to the eyes of all mammals including humans, you will gain an understanding of the structure and function of the parts of the eye.

Cow eye, dissecting pan, dissecting kit, safety glasses, lab apron, and gloves

Procedure (External Structure):

  1. Obtain a cow eye, place it in your dissecting pan, & rinse the eye with water.
  2. Rotate the eye until the larger bulge or tear gland is on the top of the eye. The eye is now in the position it would be in a body as you face the body.
  3. On the outside of the eye, locate the following parts:
  • fat– surrounds the eye & cushions it from shock
  • tear or lacrimal gland – forms a bulge on the top outer area of the eye & produces tears to wash the surface of the eye
  • tear ducts – tubes to carry the tears from the gland to the eye
  • optic nerve – a white cord on the back of the eye about 3mm thick just toward the nasal side; carries messages between the eye & brain
  • muscles – reddish, flat muscles found around the eye to raise, lower, & turn (right & left) the eye
  1. Turn the eye so that it is facing you & examine these structures on the front surface of the eye:
  • eyelids – two moveable covers that protect the eye from dust, bright light, and impact
  • sclera – this is the tough, white outer coat of the eye that extends completely around the back & sides of the eye
  • cornea – a clear covering over the front of the eye that allows light to come into the eye (preservative often makes this appear cloudy)
  • iris – round black tissue through the cornea that controls the amount of light that enters the inner part of the eye (may be colored in humans)
  • pupil – the round opening in the center of the eye that allows light to enter and whose size is controlled by the iris

Click here for labeled eye model

Procedure (Internal Structure):

  1. Place the eye in the dissecting pan so it is again facing you. Using your scalpel, pierce the white part of the eye or sclera just behind the edge of the cornea. Make a hole large enough for your scissors.
  2. Using your scissors, carefully cut around the eye using the edge of the cornea as a guide. Lift the eye & turn it as needed to make the cut and be careful not to squeeze the liquid out of the eye.
  3. After completing the cut, carefully remove the front of the eye and lay it in your dissecting pan.
  4. Place the back part of the eye in the pan with the inner part facing upward.
  5. Locate the following internal structures of the eye:
  • cornea – observe the tough tissue of the removed cornea; cut across the cornea with your scalpel to note its thickness
  • aqueous humor – fluid in front the eye that runs out when the eye is cut
  • iris – black tissue of the eye that contains curved muscle fibers
  • ciliary body – located on the back of the iris that has muscle fibers to change the shape of the lens
  • lens – can be seen through the pupil; use your scalpel & dissecting needle to carefully lift & work around the edges of the lens to remove it
  • vitreous humor – fluid inside the back cavity of the eye behind the lens
  • retina – tissue in the back of the eye where light is focused; connects to the optic nerve; use forceps to separate the retina from the back of the eye & see the dark layer below it

10. Answer the worksheet questions on the cow eye dissection.

Click here for eye dissection questions

  1. Dispose of the eye as your teacher advises and rinse and return all equipment to the supply cart. Wash your hands thoroughly.

Genetic Disorder Project Presentation


Genetic Disorders to PresentInternet resources to help in researchRubric for project
You have been challenged to incorporate your knowledge about cells, cell division, genetics, and DNA to research and present on a specific genetic disorder. You have already completed your basic study about the ideas of genetics and mutations. Now with the information that you have you are being asked to research a specific genetic disorder and give an oral presentation along with creating either a PowerPoint or poster to explain the genetic disorder.

Your multimedia presentation (powerpoint / poster) along with your oral presentation
should include the following points.

  • What is the name of the disorder and what is the history behind the disorder? Who discovered it or/and who have done research on the disease?
  • How is the disorder diagnosed? How does a person receive the disorder? Is it sex-linked? Is it a mutation? Is it due to heredity?
  • You will need to find out all of the signs and symptoms of the given disorder and share these with the class.
  • What types of treatment there are for the disorder?
  • Include a suggested list of readings and/or Internet sources that may be of interest to the class.
  • You are encouraged to share any other information that you feel is relevant that you feel is important for others to know about the genetic disorder.
List of possible Genetic Disorders to Present:
  • Achondroplasia (Dwarfism)
  • Albinism
  • Adrenal hyperplasia
  • Autism/ Asperger syndrome
  • Cystic Fibrosis
  • Down Syndrome (Trisomy 21)
  • Duchenne Muscular Dystrophy
  • Familial Dysautonomia
  • Gardner syndrome (intestinal polyposis)
  • Gaucher’s Disease
  • Hemophilia
  • Huntington’s Disease
  • Jacobsen Syndrome
  • Klinefelters Syndrome
  • Klippel-Feil Syndrome
  • Leukodystrophy
  • Lou Gehrig’s Disease (ALS)
  • Marfan Syndrome
  • Moebius Syndrome
  • Polycystic Kidney Disease
  • Progeria
  • Proteus Syndrome
  • Retinoblastoma
  • Rett’s Syndrome
  • Spinocerebellar Ataxia
  • Tay-Sachs Disease
  • Tourette Syndrome
  • Turner Syndrome
List of internet resources that may be helpful to you in creating your presentation:

Yahoo – Genetic Disorders http://dir.yahoo.com/Health/Diseases_and_Conditions/Genetic_Disorders/.
Site explains several different disorders and contains links to all of the different types of genetic disorders.

Genetic & Rare Conditions Sitehttp://www.kumc.edu/gec/support/.
links to different types of disorders in alphabetical order.

What can our chromosomes tell us? http://biology.about.com/science/biology/gi/dynamic/offsite.htm?site=http://gslc.genetics.utah.edu/.
A site that talks about karyotyping of genotypes.

Genetic Disorder Library
To learn more about different genetic disorders, browse through the Genetic Disorder Library.

A Genetics Glossary http://biology.about.com/science/biology/gi/dynamic/offsite.htm?site=http://helios.bto.ed.ac.uk/bto/glossary/index.html
A basic genetic glossary.

Genetics Education Center http://www.kumc.edu/gec/.
Seeks to help educate people about genetics.

The National Human Genome Research Institute http://www.nhgri.nih.gov/.
Explains about the human genome project.

Department of Energy – Human Genome Project Information http://www.ornl.gov/hgmis/.
Provides a lot of information about the human genome project.

A Gene Map of the Human Genome http://www.ncbi.nlm.nih.gov/science96/.
You can see the mapping of several different chromosomes found within the body.

Learning about the Human Genome Project and Genetics through the World Wide Web http://www.kumc.edu/gec/hgpwww.html.
Looks at the ethical issues of genetic research.

Understanding Gene Testinghttp://www.accessexcellence.org/ae/AE/AEPC/NIH/index.html.
This site talks of how genes are linked to disease and how a gene creates a genetic disorder.

Basics of DNA Fingerprintinghttp://www.biology.washington.edu/fingerprint/dnaintro.html.
Explains the basic understanding of DNA fingerprinting.

What is Genetic Testing? http://www.lbl.gov/Education/ELSI/Frames/genetic-testing-f.html.
Shows the basics of genetic testing and talks about the ethical issues of that happen due to genetic testing.


Rubric for Evaluation of Genetic Disorder Presentation.
5 points
10 Points
15 Points
20 Points
Oral Presentation Quality of Information
Bare minimums have been accomplished. Little understanding about the genetic disorder delivered in oral presentation. Could only read slides with no further understanding.Minimums plus slight extras added. Answered questions from the intro and at least one question posed to them in the process section.All information present and complete. Some problems with flow and delivery. Shows more or less some understanding of knowledge – has minor flaws.Information is well thought out, flows well, all information is completed, Appears to have been practiced, knowledge shown.

Amount of additional Information for reading and websites found and presented

no additional reading lists or websites provided or presented in bibliography.At least 2 web sites or books accessed and verified in presentation and presented in bibliography.At least 4 web sites or books accessed and verified in presentation and presented in bibliography.At least 6 web sites or books accessed and verified in presentation and presented in bibliography.
Organization of presentation
Random information is presentedDisorganized at times.OrganizedOrganized effectively with easy understanding.
Use of class time working on project
Majority of class time was wasted.Half of class time was wasted.Little class time was wasted.No class time was wasted.
Overall Multimedia
Not Completed
Missing Key Component Questions
no graphics.
Spelling errors present
presentation has some flow to it but is choppy.
Easily understood by all. Includes graphics and data tables of information retrieved.Neatly done, organized, proper spelling, allparts included,above and beyond effort.
Information that is presented is aesthetically pleasing to the eye.
Link to printable rubric in word document format

Link to Bibliography Citation Machine




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Introduction to Animals Study Guide


Introduction to Animals Study Guide

How are most animals classified?
What are the main characteristics of chordates?
How are vertebrates classified?
What are heterotrophs & give some examples.
In what ways do animals differ from plants?
What are tissues?
What determines an animal’s body plan?
In what habitat do you find most species of animals?
What is bilateral symmetry?
What does bipedal mean?
Where are the dorsal & ventral surfaces on a bipedal organism?
What is radial symmetry?
Name invertebrates that are asymmetrical, radial symmetry, & bilateral symmetry.
What does cephalization mean?
What invertebrate group was first to show cephalization?
Describe the “surfaces” of animals with radial symmetry.
Why is cephalization an advantage for animals?
What is a postanal tail & give examples of adult chordates with this characteristic?
Describe the “skeletal” support found in roundworms.
What is segmentation, & what animals exhibit this characteristic?
What is the function of kidneys, and what organisms have these organs?
How do closed & open circulatory systems differ?
How are terrestrial animals protected against water loss?
What structures show segmentation in vertebrates?
What is the advantage of having a long intestinal tract?
How are nutrients moved through a cnidarian’s body?
Describe how spiral cleavage occurs.
describe the embryo at the start of gastrulation.
What forms from endoderm in cnidarians.


Floating Leaf Disk Assay


The Floating Leaf Disk Assay for Investigating Photosynthesis

Brad Williamson




Trying to find a good, quantitative procedure that students can use for exploring photosynthesis is a challenge. The standard procedures such as counting oxygen bubbles generated by an elodea stem tend to not be “student” proof or reliable. This is a particular problem if your laboratory instruction emphasizes student-generated questions. Over the years, I’ve found that the floating leaf disk assay technique to be reliable and understandable to students. Once the students are familiar with the technique they can readily design experiments to answer their own questions about photosynthesis. I plan to add to this page as I have time to elaborate on the technique and provide suggestions for modifications.




1.                Sodium bicarbonate (Baking soda)

2.               Liquid Soap

3.               Plastic syringe (10 cc or larger)—remove any needle!

4.               Leaf material

5.               Hole punch

6.               Plastic cups

7.               Timer

8.               Light source




Buffer Solutions

Colored Cellophane or filters

Leaf material of different ages

Variegated leaf material

Clear Nail polish







  1. Prepare 300 ml of bicarbonate solution for each trial.
    1. The bicarbonate serves as an alternate dissolved source of carbon dioxide for photosynthesis. Prepare a 0.2% solution. (This is not very much—it’s about 1/8 of a teaspoon of baking soda in 300 ml of water.) Too much bicarbonate will cause small bubbles (CO2)to form on the surface of the leaf which will make it difficult to sink the leaf disk.
    2. Add 1 drop of dilute liquid soap to this solution. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn into the leaf. It’s difficult to quantify this since liquid soaps vary in concentration. Avoid suds. If your solution generates suds then dilute it with more bicarbonate solution.


  1. Cut 10 or more uniform leaf disks for each trial

    1. Single hole punches work well for this but stout plastic straws will work as well
    2. Choice of the leaf material is perhaps the most critical aspect of this procedure. The leaf surface should be smooth and not too thick. Avoid plants with hairy leaves. Ivy, fresh spinach, Wisconsin Fast Plant cotyledons—all work well. Ivy seems to provide very consistent results. Any number of plants work. My classes have found that in the spring, Pokeweed may be the best choice.
    3. Avoid major veins.


  1. Infiltrate the leaf disks with sodium bicarbonate solution.
    1. Remove the piston or plunger and place the leaf disks into the syringe barrel. Replace the plunger being careful not to crush the leaf disks. Push on the plunger until only a small volume of air and leaf disk remain in the barrel (< 10%).

    1. Pull a small volume of sodium bicarbonate solution into the syringe. Tap the syringe to suspend the leaf disks in the solution.


    1. Holding a finger over the syringe-opening, draw back on the plunger to create a vacuum. Hold this vacuum for about 10 seconds. While holding the vacuum, swirl the leaf disks to suspend them in the solution. Let off the vacuum. The bicarbonate solution will infiltrate the air spaces in the leaf causing the disks to sink. You will probably have to repeat this procedure several times in order to get the disks to sink. You may have difficulty getting the disks to sink even after applying a vacuum three or four times. Generally, this is usually an indication that you need more soap in the bicarbonate solution. Some leaf surfaces are more water repellent than others are. Adding a bit more soap usually solves the problem.


  1. Pour the disks and solution into a clear plastic cup. Add bicarbonate solution to a depth of about 3 centimeters. Use the same depth for each trial. Shallower depths work just as well.

    1. This experimental setup includes a control. The leaf disks in the cup on the right were infiltrated with a water solution with a drop of soap—no bicarbonate.


  1. Place under the light source and start the timer. At the end of each minute, record the number of floating disks. Then swirl the disks to dislodge any that are stuck against the sides of the cups. Continue until all of the disks are floating.

    1. The control is on the left in each image. In the experimental treatment, on the right, leaf disks are rising and floating on the surface.


  1. Sample results:


Time (minutes)Disk Floating


  1. The point at which 50% of the leaf disks are floating is the point of reference for this procedure. By interpolating from the graph, the 50% floating point is about 11.5 minutes. Using the 50% point provides a greater degree of reliability and repeatability for this procedure.


Only You Can Help Save Sam


Only You Can Help Save Sam!



Sam has been spending his summer boating on the great lakes.  However, he’s not too bright (after all, the brains of worms are pretty small).  He’s never learned how to swim, and he never wears his life preserver.  The worst has happened!  His boat has capsized and he’s stuck!  Fortunately, his life preserver is in the boat, but unfortunately he does not know how to reach it without falling off and drowning.

Save Sam!!




Use the Scientific Method to:



How can you and your partner save Fred using only 4 paper clips. You may not touch Fred, the boat, or the life preserver directly with your hands.



·        Gummy Worm

·        Gummy life preserver

·        1 Plastic Cup

·        4 Paper Clips



1.      Work with your partner and “Save Fred”.

2.    Follow the rules.

§        Fred, the boat, the life preserver can be touched only with the paper clips.  NO HANDS.

3.    Develop a data section that includes

§        Diagrams of how you saved Fred

§        A detailed protocol describing the diagrams.

4.    Homework:

§        Analyze and conclude the experiment.

·        This means that you must discuss (tell me what you think) about the difficulty of the task, what other strategies you and your partner worked on before you succeeded, and what you think the critical steps were for solving this problem.

§        Although this is working backwards, and not how scientists normally work, please develop a hypothesis for this lab.  (Remember that a hypothesis is an ‘if-then’ statement: if I do this, then this will happen)























Teacher Notes:

Fred sits on the inverted cup.  The cup sits covering the life preserver on the tabletop.  No real water is involved.  If the group size is 3 or 4, each person gets only 1 paper clip. Have a camera ready.

There are not any real answers – since it’s more of a team-building problem solving initiative rather than a yes/no answer.  However, what they need to figure out is that if they work together, then one person maneuvers Fred (without hooking him) and the other uses the paper clips to stretch the gummy lifesaver for him to slip on.  (The lifesaver will have a smaller inner diameter than Fred’s outer diameter by a fairly obvious amount.)

Ask them typical debriefing-type questions: what worked, what didn’t, did you plan, did you share ideas, did you just mangle poor Fred trying to make it work?, etc.

Groups of 3 and make it more of a challenge by allowing only 1 paperclip per student – that takes more thought and coordination to save Fred without drowning him.  (No mouth-to0mouth resuscitation allowed!)