Question

1. **a single - celled organism has star - shaped organelles called contractile vacuoles that move water from the inside of the cell to the outside of the cell. the data presented in the table above were obtained in an experiment in which the organism was placed in water with different salt concentrations. the rate at which the contractile vacuole contracted to pump out excess water was recorded.

salt concentration	rate of contractile vacuole contractions per minute
high	8
medium	15
low	22
very low	30

how could you explain the relationship between the rate of contractile vacuole contractions and the salt concentration?
a. when the salt concentration outside the cell is very high, the contractile vacuole has to contract more rapidly.
b. when the salt concentration outside the cell is very low, it has no impact on the contractile vacuole contractions.
c. when the salt concentration outside the cell is very high, the contractile vacuole does not need to contract as rapidly.
d. when the salt concentration outside the cell is very low, the contractile vacuole does not need to contract as rapidly.

1. *explain your answer to #5 using evidence from the table.

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Explanation:

Question 5 (Multiple Choice)

To solve this, we analyze the table: as salt concentration decreases (from very high to very low), the rate of contractile vacuole contractions increases. Let's evaluate each option:

• Option a: When salt concentration is very high, the rate is 2 (low), so this is incorrect.
• Option b: At very low salt concentration, the rate is 30 (high), so it does impact, making this incorrect.
• Option c: At very high salt concentration, the rate is 2 (low), meaning it doesn't need to contract rapidly. This matches the data.
• Option d: At very low salt concentration, the rate is 30 (high), so it needs to contract rapidly, making this incorrect.

We use the table data. The rate of contractions is 2 at very high salt concentration, 8 at high, 15 at medium, 22 at low, and 30 at very low. As salt concentration decreases (from very high to very low), the contraction rate increases. This shows that when the external salt concentration is very high, the contractile vacuole contracts at a low rate (2 per minute), so it does not need to contract rapidly. Conversely, at very low salt concentration, the rate is high (30 per minute), meaning it needs to contract rapidly to pump out excess water. This supports option c from question 5.

Answer:

c. When the salt concentration outside the cell is very high, the contractile vacuole does not need to contract as rapidly.

Question 6 (Explanation)