How do aquatic animals regulate osmosis for survival?

Aquatic animals regulate osmosis through various mechanisms such as active transport, selective permeability, and excretion.

Aquatic animals, both freshwater and marine, face unique challenges in maintaining their internal osmotic balance due to the nature of their environment. The process of osmosis, the passive movement of water molecules from an area of lower solute concentration to an area of higher solute concentration, can lead to either dehydration or overhydration if not properly regulated.

Freshwater animals live in an environment where the concentration of solutes is lower than in their body fluids. This means that water tends to move into their bodies by osmosis, while salts tend to diffuse out. To counteract this, freshwater animals have developed mechanisms to excrete excess water and reabsorb salts. For example, fish have specialised cells in their gills, known as chloride cells, which actively transport salts back into their bodies. They also produce large amounts of dilute urine to get rid of the excess water.

Marine animals, on the other hand, live in an environment where the concentration of solutes is higher than in their body fluids. This means that water tends to move out of their bodies by osmosis, while salts tend to diffuse in. To counteract this, marine animals have developed mechanisms to excrete excess salts and reabsorb water. For example, fish have specialised cells in their gills that actively transport salts out of their bodies. They also produce small amounts of concentrated urine to conserve water.

In both cases, the animals' cell membranes also play a crucial role in regulating osmosis. They are selectively permeable, allowing certain substances to pass through while blocking others. This helps to maintain the balance of water and solutes within the cells.

In conclusion, the regulation of osmosis in aquatic animals is a complex process involving multiple mechanisms. It is crucial for their survival, allowing them to maintain their internal osmotic balance despite the challenges posed by their environment.