Effect of Water Movement

Why must all animals maintain balanced osmotic pressure?

To regulate water and solute levels for proper cell function.

What are the two categories of animals based on osmotic regulation?

Osmoregulators and Osmoconformers.

Define osmoregulators.

Animals that maintain constant internal solute concentrations despite external changes.

How do osmoregulators maintain osmotic balance?

Through specialized organs like kidneys and metabolic regulation.

What organ in vertebrates is essential for osmoregulation?

The kidneys.

What do kidneys do to maintain osmotic balance?

They remove excess electrolytes and wastes to regulate solute levels.

Give examples of osmoregulators.

All terrestrial and freshwater animals.

Define osmoconformers.

Animals whose internal solute concentration matches their environment.

What type of animals are typically osmoconformers?

Many marine invertebrates.

What does isosmotic mean?

Having the same solute concentration as the surrounding environment.

Define contractile vacuole.

A structure in some unicellular organisms that expels excess water to maintain osmotic balance.

What type of organisms commonly use contractile vacuoles?

Unicellular organisms like protists.

Why do protists need a contractile vacuole?

Because they live in freshwater, a hypotonic environment, where water constantly enters the cell.

How does water enter paramecia?

By osmosis through the semi-permeable membrane.

What does the contractile vacuole do with excess water?

It collects and expels water through a specialized pore.

What is the function of the contractile vacuole in osmoregulation?

To prevent the cell from bursting due to excess water accumulation.

Why do plant cells not burst in hypotonic conditions?

Because of their rigid cellulose cell wall.

What happens to plant cells in hypertonic solutions?

Water leaves the cell by osmosis, causing plasmolysis.

Define plasmolysis.

The process where the cell membrane pulls away from the cell wall due to water loss.

Why does plasmolysis occur?

Because water exits the cell in a hypertonic environment, reducing cytoplasmic volume.

What happens to turgor pressure in a plasmolysed plant cell?

It decreases significantly.