Question

How do unicellular organisms living in water control the entry and exit of water?

Answer 1

Unicellular organisms use osmoregulation to control water entry and exit, utilizing contractile vacuoles to expel excess water and actively managing solute concentrations inside the cell.

Step-by-step explanation:

Unicellular organisms living in water control the entry and exit of water primarily through the process of osmoregulation. Osmoregulation is vital as water constantly enters these cells due to a higher solute concentration inside the cell than in the surrounding freshwater environment. To address this, organisms like Paramecium use a contractile vacuole to collect excess water and then expel it out of the cell to maintain a proper water balance and prevent bursting.

Another method involves altering the solute concentration within the cell by pumping salts or other solutes in or out. This strategy helps manage the changes in environmental solute concentrations, thus maintaining the correct osmotic pressure within the cell. Both of these adaptations are energy-intensive but are essential for survival in environments with varying salinity levels.

Answer 2

Osmosis and vesicle transport

Step-by-step explanation:

Osmosis is the movement of water from a low concentrated solution (hypotonic) to a higher concentrated solution (hypertonic) through a semipermeable membrane. The cells regulate the movement of water by regulating the amount of osmotically active molecules in their protoplasm. This way they can influence the flow of water into or out of the cells

For larger unicellular cells such as amoeba, where osmosis alone would not be effective, they use vesicle transport. Excess water in the cell accumulates in a vessicle that transports and expels it outside the cell.