What is the Contract System, Anyway?
In this course, you will have the opportunity to decide what final mark you would like to work toward. You and your parents will have a chance to look over the course outline and a sample activity to help you decide what you think you can achieve. Since this is something that you are probably not used to doing, this short document has been created to help explain the concept.
You will be able to decide whether you want to work toward a mark of 60%, 70%, 80%, 90% or 100%, with the expectation that a higher mark will require you to do more work. Depending on what mark you have contracted for, most activities will have parts that you will be able to leave out. After careful consideration during the first week of the semester, you can decide up front the amount of work that you feel you can comfortably handle. Keep in mind, however, that while you can limit the amount of work you have to do, you also limit the highest mark that you can achieve in the course. The great news is that this system will help prevent students from feeling overwhelmed by the workload. You will be able to focus on the parts that you choose to do and you will also do a good job on those parts. In other words, you know your own limitations and this system will allow you to focus on the parts of assignments that you are required to complete and not worry about the rest.
Let’s look at a hypothetical situation. Imagine that you have contracted for 70% in the course. Now imagine a lab activity which has 10 questions included with it (the activity can be found on pages 3 and 4 of this document). The activity has the following contract cut-offs:
Contract Questions you must answer
60 1 - 6
70 1 - 7
80 1 - 8
90 1 - 9
100 1 - 10
Note that this activity happens to have 10 questions and that each additional question you answer takes you to the next contract level. This will not always be the case, but this activity was used as the example for the sake of simplicity. Because you have contracted for 70% in the course, you would have to complete questions 1 through 7 of this activity completely and correctly. You are always entitled and encouraged to complete work beyond your contract, which would earn you a higher mark, but it is not mandatary. Periodically completing additional questions will lead to a grade that falls within the five percentages outlined (e.g. 74%).
There are some very important requirements to keep in mind when considering the mark that you want to contract for:
1. Everything you hand in will be evaluated on an “all-or-nothing” basis. This means that everything you do, as stated earlier, must be complete and it must be correct.
2. After you submit an assignment it will be graded and handed back to you. You will have a chance to make any corrections necessary and hand it back in. For example, if you completed all 7 questions but got one of them wrong, you can correct that one answer and resubmit the assignment. Ms. Charlton and Mr. Gallant will be available every morning from 8:00 to 8:30 if you need help with any part of any assignment, even before it has been submitted. If, after making your correction and resubmitting your assignment, the question has still not been answered correctly, a mark of zero would be recorded for this activity because you did not meet your contract. That is worth saying again. If you do not answer all questions required for your contract completely and correctly, you will get a mark of zero for that assignment. Remember that incomplete and incorrect work is unacceptable when you’ve contracted to achieve a specific mark.
3. Regardless of your contract, any work attempted must be complete and correct. This means that if you have contracted for 70% but attempt 8 questions, all 8 must be complete and correct to get any credit for the assignment.
4. No assignment will be accepted after its given deadline. A mark of zero will be given for such assignments.
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I certify that I have read this Biology 11 Course Contract and I understand the expectations and conditions.
Student Signature: _____________________________________ Date:___________________
Parent/Guardian Signature: ______________________________Date: ___________________
**SAMPLE LAB ACTIVITY**
Diffusion Through Membranes
Cell membranes are selectively-permeable by nature and as such, exert some control over substances passing through them into and out of cells. In the presence of a concentration gradient, substances will diffuse from an area of high concentration to one of low concentration across a selectively permeable membrane. Water, too, will diffuse through membranes in a process called osmosis. The net movement of water is from an area of high [H2O] (i.e., low [solute]) to one of low [H2O] (i.e., high [solute]).
In this experiment you will measure diffusion of small molecules through dialysis tubing, a selectively permeable membrane. Small solute molecules and water molecules can move freely through a selectively permeable membrane, but larger molecules will pass through more slowly, or perhaps not at all. In medicine, the movement of a solute through a selectively permeable membrane is called dialysis. The size of the minute pores in the dialysis tubing determines which substances can pass through the membrane.
By detecting the presence of particular molecules on each side of the dialysis tubing, we can determine which molecules passed through the tubing and which did not. Starch molecules react with iodine to form a dark blue compound. The presence of glucose can be tested with Benedict's solution or Clinitest tablets. If glucose is present, the mixture will turn a series of shades of green. The appearance of a yellow or brown compound means the glucose is rather concentrated (check the package for concentration ranges). The presence of starch will be tested with Lugol's solution, (Iodine Potassium-Iodide or IKI). For the Lugol test, a dark blue color is a positive result.
A. Osmosis
Procedure
1. Obtain a 10 cm piece of 2.5-cm dialysis tubing that has been soaking in water. Twist one end of the tubing and fold it over, then tie off that end with string to form a bag. To open the other end of the bag, rub the end between your thumb and forefinger until the sides separate.
2. Pour molasses solution into the tube until it is about half full.
3. Twist the top of the tube and tie it securely. Be sure to leave a gap of about 1 cm between the top of the liquid and the thread. Try to squeeze out as much air as possible before tying the bag.
4. Rinse the outside of the tube with water to remove any molasses which may have contaminated it.
5. Place the tube in a 300 or 400 mL beaker and add enough water to just cover it. Label the beaker ‘A’ and make sure the names of you and your partner are on it.
6. Let stand overnight and record observations in the morning. Note that you might see a faint yellow color in the water in this beaker. This is natural pigments in the molasses and not the molasses itself.
B. Diffusion
Procedure
1. Prepare another tube as in procedure A but pour starch solution in the tube.
2. Tie and rinse the tube.
3. Place the tube in a beaker of water and label it ‘B’ and make sure the names of you and your partner are on it.
4. Add iodine solution to the water slowly until the water is a faint yellow color.
5. Let stand 20 min and record observations.
6. Prepare a similar setup except put glucose solution in the tube and do not add iodine solution. Be sure to rinse the tube before putting it in the beaker of water. Label this beaker ‘C’ and make sure the names of you and your partner are on it. Let stand 20 min.
7. Pour about 5 mL of water from beaker ‘C’ into a test tube and add half of a Clinitest tablet. Do not shake the test tube. Record the color about 15 s after the tablet stops bubbling.
Thought-provoking Questions (at least, that’s the idea)
1. a) Describe the test results which show the presence of starch.
b) Can the starch molecules pass through a dialysis membrane? Which results support this conclusion?
2. a) Describe the test result that shows the presence of glucose.
b) Can glucose molecules pass through the dialysis membrane? Which results support this conclusion?
3. Is the membrane 100% selective? Explain.
4. Describe and account for any changes that occurred in beaker ‘A.’ Be sure to specify the direction of movement for each molecule.
5. Describe and account for any changes that occurred in beaker ‘B.’ Be sure to specify the direction of movement for each molecule.
6. Describe and account for any changes that occurred in beaker ‘C.’ Be sure to specify the direction of movement for each molecule.
7. For each of the following questions, explain your answers. Base your answer on your results.
a) Which molecules pass through the membrane with ease?
b) What molecules pass through the membrane slowly?
c) What molecules were unable to pass through the membrane?
8. a) Why was the membrane rinsed off after being filled and tied?
b) Why was a 300 mL beaker with the minimum amount of water used instead of a larger beaker with, say, 500 mL of water?
9. Suppose that a tube filled with a 5% molasses solution was placed in a beaker filled with a 10% molasses solution. What would happen? Why?
10. A single starch molecule may have thousands of atoms, a glucose molecule has 24, and the ions of dissolved salt are the size of single atoms.
a) Using your knowledge of diffusion across selectively permeable membranes, explain the observations of this experiment.
b) Why is the chemical digestion of starch necessary?
c) Does this investigation show that starch molecules cannot move across living membranes? Explain.