An osmoregulator would maintain its internal fluids at a concentration that is __ relative to its surroundings. a. isotonic b. hypertonic c. hypotonic d. hypertonic, hypotonic, or isotonic
The Correct Answer and Explanation is:
Correct Answer: d. hypertonic, hypotonic, or isotonic
An osmoregulator is an organism that actively maintains the concentration of its internal body fluids at a constant level regardless of changes in the surrounding environment. This ability is crucial for survival, especially in environments where salinity levels can vary widely, such as freshwater and marine ecosystems.
Osmoregulators can maintain their internal fluid concentration as hypertonic, hypotonic, or isotonic relative to their environment depending on the species and its habitat:
- In freshwater environments, the surrounding water has a lower concentration of solutes compared to the organism’s body fluids. Freshwater osmoregulators, such as many fish and amphibians, maintain their internal fluids in a hypertonic state relative to the environment. They face a constant influx of water and loss of salts, so they excrete large volumes of dilute urine and actively absorb salts through their gills.
- In marine environments, the surrounding water has a higher solute concentration than the internal fluids of many marine animals. Marine osmoregulators, such as bony fish, maintain a hypotonic internal environment. These organisms lose water to their surroundings and gain salts, so they drink seawater and actively excrete excess salts through specialized cells.
- Some marine animals, such as sharks and rays, maintain an isotonic internal environment by balancing urea and other solutes in their blood to match the osmolarity of seawater. This strategy reduces the need for active osmoregulation while still protecting internal tissues from damage.
In conclusion, osmoregulators do not maintain a fixed relationship with their environment in terms of tonicity. Instead, they adjust their internal mechanisms to keep fluid balance and support cellular function, whether the external environment is fresh, salty, or variable. Therefore, the correct answer is d. hypertonic, hypotonic, or isotonic.
