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Water Regulation
Examples of Student Work
Contributed by: New York State Alternative Assessment in Science Project (NYSED)

Student #1

Task: At this station, you will be interpreting data presented in graphs.


Paramecia are found in stagnant pond water. Excess water is regularly removed from these organisms by the pumping action of contractile vacuoles. Paramecia were place in 3 different solutions: Pond water (containing 95% water and various dissolved minerals), Solution A, and Solution B. While observing a contractile vacuole using the high power magnification (400x) of a microscope, a student counted, in 30 second intervals, the number of times the contractile vacuole pumped water out of the cell and repeated his counts in the three solutions. The results are presented in the graphs below:

Base your answers to the following questions on the previous graphs.

  1. Using complete sentences describe your observations of the behavior of the contractile volumes in each solution:

  2. Think about the relationship between the concentration of dissolved materials in the two solutions and pond water. Use the following terms to complete the two statements below.
  3. Same as OR Greater than OR Less than

  4. What would you add to Solution A to restore the vacuole contraction to the same rate as in pond water?

  5. Using complete sentences, suggest and explanation to your answer to question 3:

  6. Using complete sentences, what would you add to Solution B to restore the vacuole contraction to the same rate as in pond water?

  7. Using complete sentences, suggest an explanation to your answer to question 5.

  8. What will happen to a paramecium if the contractile vacuole failed to remove the excess water?

  9. Using complete sentences explain how you reached your prediction in question 7.

  10. Name two (2) biological processes which take place in this investigation.


Circle the student's score for each part of the exercise. Add the points for each part and write the total score at the bottom of the scoring form.

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