TeXes Science Practice Test

What process causes the clown fish to die when placed in freshwater?

1. Evaporation

2. Diffusion

3. Osmosis

4. Filtration

The correct answer is: Osmosis

The correct choice is based on the understanding of osmosis, which is the process through which water moves across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. Clownfish are marine organisms that have adapted to life in saltwater, where the concentration of salt is much higher than that of freshwater. When placed in freshwater, the concentration of salt inside the clownfish's body is higher than that of the surrounding water. This difference in concentration creates a situation where water moves into the clownfish's cells through osmosis in an attempt to balance the solute levels on either side of the cell membrane. The influx of water can lead to the cells swelling and potentially bursting, as the fish's body is unable to expel the excess water quickly enough due to its physiological adaptations to saltwater. This process not only stresses the clownfish's cells but can also lead to severe physiological disturbances and ultimately death if the fish cannot recover. Understanding the role of osmosis in maintaining cellular homeostasis is crucial in explaining why clownfish cannot survive in freshwater environments.