Question

3. What would happen if you placed a freshwater paramecium into ocean water? Explain the osmotic results. Why do paramecia require a contractile vacuole to survive in freshwater? Why don’t aquatic plants have a contractile vacuole?

Answer 1

The paramecium is a freshwater one and when it is placed in ocean water, the paramecium would not require the contractile vacuole since it will be present in salt water. Generally in the freshwater they require the contractile vacuole as it helps in removing the excess water from cell as the concentration of solute outside is less. When it is put in ocean water, the salt outside is higher as compared to salt inside the paramecium and hence the paramecium will expel water due to the increase in solute concentration outside and shrink. The osmotic result will be it will lead to shrinking of the paramecium due to the release of the water.

The paramecium require a contractile vacuole for its survival in freshwater because due to the hypotonic solution, the contractile vacuole helps in expelling the excess water and prevents the paramecium from bursting or swelling.

The aquatic plants don’t have contractile vacuole because they live in hypertonic condition and hence don’t need to expel out water. If the contractile vacuole will be present, it will release out the water and shrink the cell.