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| The Case: |
Snake Bite |
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 Tom and Kathy Brown live in a farm in rural Missouri with their two sons, Kyle, 3, and Rick, 8. Tom takes care of the farm while his wife works as a secretary at a local law firm. One Saturday, while cleaning the house, Kathy notices that the food supplies are low. She goes into town to buy groceries and leaves Tom to take care of the kids.
Tom, hot and sweaty after mowing the lawn, decides to take a quick shower. The boys, eager to play, sneak outside. Only later does Tom hear the children screaming from the back yard. He quickly rushes outside and finds a horrifying scene: Kyle is bleeding from the chin, while Rick is holding his left forearm. The snake that bit the children is slithering off into the nearby woods. Tom fetches a hoe and cuts off the snake's head. He quickly wraps a tourniquet around Rick's arm and bundles the kids into the car. Knowing that he will need the snake, he tosses the head and body into a sack and races toward the hospital.
Sadly, Kyle dies at the hospital, and Rick is placed in critical condition. The patient chart beside his bed reads, "Diagnosis: Venomous snake bite. Symptoms: low blood pressure, swelling, hemorrhaging and initial tissue necrosis in left forearm. Urine discolored.
In the meantime, the snake was sent to the local university. There, a herpetologist examined the snake and made the following notes.
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Case Analysis
1) Evolution concerning the development of new snake venoms
2) Characteristics used to classify snakes (external and venom/protein based)
3) Fear of snakes being a learned behavior (one that the children had not learned).
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Option: Include a know / need to know chart like the one below:
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What do you know?
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What do you need to know?
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Learning Goals
Goal(s)
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Identify external morphology of snakes for taxonomic purposes
- Explore venom types and their physiological effects.
- Elaborate on the adaptations occurring in the snake to help it survive in its environment
- Identify the relevance of snakes for humankind and human beliefs about snakes
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Standards
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Investigations and Activities
Lab activity classifying snakes using a taxonomic key and dead specimens
Research:
- Relevance of snakes and beliefs about snakes. Find information to dispel misconceptions.
- Snake venom types and affects of various venoms on the body.
- Adaptations found in snakes to enable them to survive in their environment.
- Optional Activity: Create a phylogenetic (family) tree of poisonous snakes and other organisms based on shared proteins. See Biology Student Workbench site.
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Resources
Resources
Books:
Amphibians and Reptiles of Missouri, Tom R. Johnson, 1987.
Internet Resources:
"Is Rattlesnake Venom Evolving?"
http://www.amnh.org/naturalhistory/features/0700_feature.html
"Is Rattlesnake Venom Evolving?" The Cold Blooded News: The Newsletter of the Colorado Herpetological Society.
http://coloherp.org/cb-news/cbn-0009/Venom.html
"Safety Information: Rattlesnake Bites"
http://wellness.ucdavis.edu/safety_info/poison_prevention/
poison_book/rattlesnake_bites.html
"Snakes of North America"
http://www.pitt.edu/~mcs2/herp/SoNA.html
"Herps of Texas-Snakes"
http://www.zo.utexas.edu/research/txherps/snakes/
"Georgia Museum of Natural History"
http://museum.nhm.uga.edu/index.html
Students will usually obtain additional references or resources
to help answer or explore their questions. |
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Special Data Items
Lab Activity Instructions and Worksheets
Using Biology Workbench
1. Open Netscape Navigator application.
2. Type the following URL into the Location box into the navigator window.
http://workbench.sdsc.edu
SETTING UP AN ACCOUNT
3. Click on the hotlink "Set up a free account," which is in blue and is underlined. This will bring you to a new screen.
4. Supply the information requested. Use your full name without spaces (for example: venomproject) and for a password, use "biology."
5. Click on the button "REGISTER."
6. At the next screen, click on "Biology Workbench," which should be blue and underlined.
STARTING A NEW SESSION
Scroll down and click on the button called "Session Tools."
1. At the next screen, click on the title screen where it says "Click here to toggle between menus and buttons." This will make all the tools show up as buttons.
2. Click on the button labeled "NEW."
3. At the next screen, name the session "Snake Bite Investigation" in the white box to the right of the words "Session Description."
4. Click on the button "Start New Session". If you have done this correctly, you will see the name of your session under the column starting with "Default Session".
FINDING VENOM PROTEIN SEQUENCES FOR THESE CASES
5. Click on the button "NDJINN Search"
6. Enter "Crotalus Venom" and select SwissProt and GenBank Vertebrates from THE database list
7. Click on the "RUN" button.
8. Import Protein Sequencem from Crotalus viridus viridus (Prairie Rattlesnake).
9. Click on Protein box for this myotoxin protein sequence.
10. Select "BLASTP."
11. Scroll down and change the number of hits to 30.
12. Click on Submit.
13. Select several sequences from the list. Note: Do not select same genus and species more than once.
14. Run "CLUSTALW."
15. Click the "RUN" button.
16. On the next screen, click the "SUBMIT" button.
17. Scroll down to view the tree you have made.
18. Print the tree and label with the genus, species names.
1. snake.jpg
2. tree.gif
3. snakes.jpg
4. rattlesnakes.gif
5. notebook_snake.jpg
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Student Products
Pamphlet describing how to differentiate between venomous and non-venomous snakes.
Newspaper article describing misconceptions involving snakes as well as the different ways that snakes are viewed by distinct cultures.
A report detailing the physiological effects of snake venom on the human body.
A poster demonstrating snake adaptations to the environment (predatory behavior, venom, physiology, anatomy, etc.)
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Assessment and Evaluation Plan
Exam questions based on student presentations 20%
Large group discussion (sharing conclusions from small group discussions) 20%
Peer evaluation 20%
Presentation and evaluation of student products 40%
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Implementation
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Course name:
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General Zoology
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Likely sequence in
syllabus:
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As part of the Chordates, following the Amphibians
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Time during term:
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End of semester, during Chordate unit
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Duration:
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two weeks with products to be turned in during finals
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Setting:
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Lecture/Lab room and computer lab
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Students in course:
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Freshmen and Sophomore majors and
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Collaborative elements:
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Work in groups, Share access to resources, Likely to discuss cases outside of class
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Additional notes:
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Optional activities can be added.
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Credits
Special thanks to Alan Oliviera for translation and collaboration
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