Which of the following organisms would lose the most water by osmosis across its gills when placed in a hypertonic environment?

• A. Marine fish
• B. Reptile
• C. Amphibian
• D. Freshwater fish

Answer: (D)

Verified step by step guidance

1. Understand the concept of osmosis: Osmosis is the movement of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.
2. Define a hypertonic environment: In a hypertonic environment, the concentration of solutes outside the organism is higher than inside, causing water to move out of the organism to balance the solute concentrations.
3. Consider the environment of each organism: Marine fish are adapted to salty (hypertonic) environments, reptiles and amphibians are generally adapted to land or freshwater environments, and freshwater fish are adapted to environments with lower solute concentrations.
4. Analyze the freshwater fish: When placed in a hypertonic environment, freshwater fish, which are adapted to low solute concentrations, will lose water rapidly through osmosis as water moves out to the higher solute concentration outside.
5. Conclude that freshwater fish will lose the most water by osmosis in a hypertonic environment, as they are not adapted to such conditions, unlike marine fish which have mechanisms to cope with high salinity.