Question

Which of the following is/are incorrect?

I. Organisms living in oceans, lakes, and rivers do not face any water-related problems.

II. Euryhaline can tolerate a wide range of salinities.

III. Stenohaline is restricted to a narrow range of salinities.

IV. No freshwater animals cannot live for long in seawater but sea animals can live in freshwater for a long time because of osmotic balance.

V. The salt concentration is less than 5% in inland water, 30-50% in the sea, and >100% in some hypersaline lagoons.

A. All are correct except I.
B. None of the above.
C. Only IV
D. I, III, and IV

Answer 1

Hint: Euryhaline life forms have a distinctive osmoregulation feature that allows them to survive in salinity-varying environments. Stenohaline refers to an organism, usually a fish, that cannot withstand large changes in water salinity. Salinities in hypersaline environments are higher than in normal seawater.

Complete step-by-step answer:
Many might believe that organisms living in oceans, lakes, and rivers are immune to water-related problems, but this is not the case. Water quality (chemical composition, pH) becomes important for aquatic organisms. Therefore, the statement I is incorrect.
Euryhaline organisms can withstand a wide range of salt concentrations (or salinities). Poecilia sphenops, for example, is a fish that can reside in fresh, brackish, or salt water. Thus, statement II is correct.
Stenohaline life forms are species that can only withstand certain salinity ranges. They cannot withstand large changes in salt content in water, and the organism's tolerance for salt content varies depending on the species. Due to the high salt content, freshwater fish such as goldfish cannot survive in seawater. The same is true for fish that live in saltwater, except that they cannot survive in freshwater. So, III is correct.
Freshwater fish are hypertonic to their surroundings, which means they are saltier and water constantly moves into their bodies via Osmosis. When freshwater fish are placed in salt water, they become hypotonic, or less salty, in comparison to the environment. This means that water is constantly escaping from the fish's body, eventually killing it. Hence many freshwater animals cannot survive in seawater and vice versa due to Osmotic problems. Thus, statement IV is correct.
The concentration of salt is expressed as salinity in parts per thousand. It is less than 5% in inland waters, 30-35% in the sea, and greater than 100% in certain hypersaline lagoons. So, statement V is correct.

Hence, option A is the correct one.

Note: Most stenohaline life forms are osmoconformers, which means that their osmolarity does not change based on the salt content of their surroundings. A stenohaline organism's internal environment is isosmotic to its external environment.