Which of the following statements regarding freshwater fish and saltwater fish is true?

• A. Freshwater fish tend to gain water by osmosis and excrete large amounts of dilute urine.
• B. Saltwater fish do not drink water and excrete large amounts of dilute urine.
• C. Saltwater fish tend to gain water by osmosis and excrete large amounts of dilute urine.
• D. Freshwater fish lose water by osmosis and excrete small amounts of concentrated urine.

Answer: (A)

Verified step by step guidance

1. Understand the concept of osmoregulation: Osmoregulation is the process by which organisms maintain the balance of water and solutes in their bodies. Freshwater and saltwater fish face different challenges due to the differing salinity of their environments.
2. Analyze the environment of freshwater fish: Freshwater fish live in a hypotonic environment (lower solute concentration outside their bodies). Water tends to enter their bodies by osmosis, and they must excrete excess water to maintain balance. They produce large amounts of dilute urine to remove this excess water.
3. Analyze the environment of saltwater fish: Saltwater fish live in a hypertonic environment (higher solute concentration outside their bodies). Water tends to leave their bodies by osmosis, so they drink seawater to compensate for water loss. They excrete small amounts of concentrated urine to conserve water and eliminate excess salts.
4. Evaluate the given statements: Compare the provided statements to the biological processes of freshwater and saltwater fish. Identify which statement aligns with the correct osmoregulatory strategies of each type of fish.
5. Select the correct answer: Based on the analysis, the correct statement is that freshwater fish gain water by osmosis and excrete large amounts of dilute urine, while saltwater fish drink water and excrete small amounts of concentrated urine.