Eye Dissection

 

Cow Eye Dissection

Introduction:
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.

Objective:
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.

Materials:
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.
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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.

 

Bacteria Virus Worksheet Bl

 

Bacteria Worksheet    

 

 

 

Bacterial Cell Evolution

1. Bacteria are microscopic _____________.

2. Fossils evidence shows bacteria are about __________ years old, while eukaryotes are about __________ years old.

3. Discuss where bacteria can be found.

 

4. Ribosomal differences have put bacteria into what two kingdoms? Which is the older group?

 

5. What is absent in the cell wall of Archaebacteria? Describe this substance.

 

 

6. Describe the environments in which you would find Archaebacteria.

 

 

7. Compare & contrast these tree groups of Archaebacteria — methanogens, extreme halophiles, and thermoacidophiles.

 

 

 

 

8. Most bacteria are found in what kingdom?

9. Name & describe the three shapes of Eubacteria.

 

 

10. Are Eubacteria aerobic or anaerobic? Explain.

 

11. Eubacteria may be heterotrophic or photosynthetic. Explain what this means & give an example of each type.

 

 

12. What type of staining is used to group Eubacteria?

13. Describe the appearance of gram-positive and gram-negative bacteria under a microscope.

 

14. Explain why Eubacteria do not all stain the same color during Gram staining.

 

15. Describe, in detail, cyanobacteria.

 

 

16. Cyanobacteria, also known as ______________ bacteria lack a membrane bound __________ & _____________.

17. How are heterocysts helpful to cyanobacteria?

 

18. What is eutrophication?

 

19. Explain the role of cyanobacteria in eutrophication.

 

 

20. What bacterium causes syphilis? Describe this bacteria.

 

21. Streptococci bacteria causing strep throat are in what group?

22. Why are actinomycete bacteria important?

 

23. Compare & contrast these three groups of Proteobacteria — enteric bacteria, chemoautotrophs, and nitrogen-fixing bacteria.

 

 

 

 

24.Name a genus of nitrogen-fixing bacteria found on the roots of soybeans in our area.

 

Characteristics of Bacteria

25. Name the three main parts of all bacteria.

 

26. Describe the cell wall of bacteria. How does this differ from a plant cell wall?

 

 

27. Compare & contrast the cell membrane of Eubacteria with that of other eukaryotes.

 

 

28.Are Gram positive or negative bacteria more protected against antibiotics & why?

 

29. Where does cell respiration take place in eukaryotes? in bacteria?

30. Describe how the cell membrane of photosynthetic bacteria are adapted for this process. Where does this process take place in plants?

 

 

31. Compare & contrast the cytoplasm of bacteria with that of eukaryotes.

 

 

32. Describe the DNA (hereditary material) found in bacteria. Make a sketch of what you think this would look like.

 

 

 

33. Where is the capsule of a bacteria, what is it made of, and give two ways it helps a bacterium?

 

 

34. Where is the glycoclayx of a bacteria, what is it made of, and how does it help a bacterium?

 

35. How do pili help the bacteria that have them?

 

36. How do Gram positive bacteria protect themselves against harsh environments?

 

37. Describe two methods of locomotion in bacteria.

 

 

38. Compare & contrast saprophytic and photoautotrophic bacterial nutrition.

 

 

39. Distinguish among these three bacteria & give an example of each — obligate anaerobes, facultative anaerobes, & obligate aerobes.

 

 

 

 

40. Compare & contrast these three methods of bacterial reproduction — transformation, conjugation, and transduction.

 

 

 

Bacteria and Humans

41. What does a pathologist do for a living?

 

42. Compare & contrast the two types of toxins bacteria produce.

 

 

43. Besides injuring the body by releasing toxins, how else do bacteria hurt the body?

 

44. Describe four antibiotics against bacteria.

 

 

 

45. Explain how antibiotic resistance occurs.

 

 

46. Name two  bacterial diseases carried by ticks.

47. name two bacterial diseases caused by eating contaminated food.

48. Name a sexually transmitted bacterial disease.

49. Name a bacterium that can cause disease whenever it gets into deep wounds.

50. Name a bacterium that is transmitted by coughing & infects the lungs.

51. Describe, in detail, how bacteria can be useful to humans.

 


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Evaluation Webquest Classification

Evaluation

Students will be evaluated as a group in the areas listed in the rubric.

Beginning

1

Developing

2

Accomplished

3

Exemplary

4

Score
Classify plants and animals according to internal and external features using a developed classification systems, organized using a flow chart. Classification of a total of 6 out of 10 living organisms (that includes the created living things) correctly with 6 flow charts. Classification of a total of 7 out of 10 living organisms (that includes the created living organisms) correctly with 6 legible and easy to follow flow charts. Classification of a total of 8 out of 10 living organisms (that includes the created living organisms) correctly with 6 legible and easy to follow flow charts and 1 flow chart that combines all 6 flow charts. Classification of a total of 9 or 10 living organisms correctly with 6 flow charts that are easy to follow  and 1 flowchart that combines all 6 flow charts and is easy to follow.
Poster of new living thing that communicates what the new living thing looks like.
Poster that includes:  

1)a picture of an original living thing
2)a description of five characteristics listed

A poster that includes:  

1) a picture of an original living thing

2)a  description of six  characteristics listed in an organized fashion

3)few spelling errors

A poster that includes

1)a picture of an original living thing

2) a  description of six or more characteristics listed in an organized fashion

3) no spelling errors.

4)easy to read
A poster that includes:

1) a picture of an original living thing2) a description of six or more characteristics listed in an organized fashion

3) no spelling errors.

4) good artistic design.

Presentation of classification findings and new living thing

 1)Information presented relevant and in a logical order

2)One media used for presentation effectively

1)Information presented relevant and in a logical order

2)Two media forms used for presentation excluding video effectively.

1)Information presented relevant and in a logical order

2)Video used for presentation media effectively.

 

1)Information presented relevant and in a logical order

2)Two media forms used for presentation including video effectively.
Work
co-operatively
in a group

 

1)Work
co-operatively using information technology skillsOR

2)Demonstrate ability to collaborate to develop a group display.

1)Work co-operatively using information technology skills

AND

2)Demonstrate ability to collaborate to develop a group display with satisfactory results

1)Work co-operatively using information technology skills

AND

2)Demonstrate ability to collaborate to develop a group display
with average results

1)Work co-operatively using information technology skills

AND

2)Demonstrate ability to collaborate to develop a group display with  above average results

Group
self-evaluation

 

Worked together though some problems
(had disagreements)
Worked together with a few problems
(only minor disagreements)
Worked together and every one had input into decisions though a few problems Worked well together, no problems and everyone had input into decisions.

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Floating Leaf Disk Assay

 

The Floating Leaf Disk Assay for Investigating Photosynthesis

Brad Williamson

 

Introduction:

 

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.

 

Materials:

 

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

 

Optional:

 

Buffer Solutions

Colored Cellophane or filters

Leaf material of different ages

Variegated leaf material

Clear Nail polish

 

 

 

Procedure:

 

 

  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 0
2 0
3 0
4 0
5 0
6 0
7 1
8 1
9 1
10 1
11 4
12 7
13 8
14 10

 

  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.