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Question
Read the following statements (i - iv) and select the incorrect statements related to the abiotic factor water.
(i) For organisms living in water bodies, chemical composition and pH plays an important role.
(ii) Organisms that can tolerate only a narrow range of salinity are called stenosaline.
(iii) The salinity is < 5 ppt for inland waters and > 100 in hypersaline lagoons.
(iv) Organisms living in oceans, lakes and rivers do not face any water related problems.
Read the following statements (i - iv) and select the incorrect statements related to the abiotic factor water.
(i) For organisms living in water bodies, chemical composition and pH plays an important role.
(ii) Organisms that can tolerate only a narrow range of salinity are called stenosaline.
(iii) The salinity is < 5 ppt for inland waters and > 100 in hypersaline lagoons.
(iv) Organisms living in oceans, lakes and rivers do not face any water related problems.
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Solution
The correct option is C (ii) and (iv)
An ecosystem includes living organisms (biotic factors) along with the physical environment (abiotic factors with which they interact. For example, living (fishes, frogs) and nonliving things (soil, temperature) in a pond ecosystem.
It is a common misconception that organisms living in oceans or water bodies do not face any water related issues. For aquatic organisms the quality of water is very important for their living, along with the chemical composition, pH and the salt concentration. The salt concentration determines whether the organisms can thrive in such water or not. Therefore statement (i) is correct.
The fresh water fish produces urine in large volumes , since there is a continuous passive inflow of water to balance it’s hypertonic internal body fluid.
On the other hand, marine fishes continuously eliminate salts from the body, since it’s internal body fluid is hypotonic and produce very small volumes of urine to conserve water.
Most freshwater animals can not live in sea water for long because of imbalance in osmotic concentration. If a fish from fresh water moves to sea water, being present in hypertonic medium it will start to lose water by exosmosis and become severely dehydrated. If a marine fish moves to fresh water then being present in hypotonic medium water will enter its body by endosmosis, causing it to swell and may lead to death of the fish. Therefore statement (iv) is incorrect.
Salinity is the amount of salt dissolved in a water body. It is measured in parts per thousand (ppt), that means the number of grams of salts per kilogram of seawater.
The salt concentration is less than 5 ppt in inland water. These are freshwater bodies. The salt concentration in the sea is 30 - 35 ppt whereas it can be as high as > 100 ppt in hypersaline lagoons. Therefore statement (iii) is correct.
Figure : Inland waters, sea and hypersaline lagoon
On the basis of tolerance to salinity organisms can be categorised as follows :
Euryhaline : These organisms are able to tolerate a wide range of salinities. For example, Atlantic stingray and bull shark.
Stenohaline : These are organisms that are restricted to a narrow range of salinity. Examples include goldfish. Therefore, statement (ii) is incorrect.
An ecosystem includes living organisms (biotic factors) along with the physical environment (abiotic factors with which they interact. For example, living (fishes, frogs) and nonliving things (soil, temperature) in a pond ecosystem.
It is a common misconception that organisms living in oceans or water bodies do not face any water related issues. For aquatic organisms the quality of water is very important for their living, along with the chemical composition, pH and the salt concentration. The salt concentration determines whether the organisms can thrive in such water or not. Therefore statement (i) is correct.
The fresh water fish produces urine in large volumes , since there is a continuous passive inflow of water to balance it’s hypertonic internal body fluid.
On the other hand, marine fishes continuously eliminate salts from the body, since it’s internal body fluid is hypotonic and produce very small volumes of urine to conserve water.
Most freshwater animals can not live in sea water for long because of imbalance in osmotic concentration. If a fish from fresh water moves to sea water, being present in hypertonic medium it will start to lose water by exosmosis and become severely dehydrated. If a marine fish moves to fresh water then being present in hypotonic medium water will enter its body by endosmosis, causing it to swell and may lead to death of the fish. Therefore statement (iv) is incorrect.
Salinity is the amount of salt dissolved in a water body. It is measured in parts per thousand (ppt), that means the number of grams of salts per kilogram of seawater.
The salt concentration is less than 5 ppt in inland water. These are freshwater bodies. The salt concentration in the sea is 30 - 35 ppt whereas it can be as high as > 100 ppt in hypersaline lagoons. Therefore statement (iii) is correct.
Figure : Inland waters, sea and hypersaline lagoonOn the basis of tolerance to salinity organisms can be categorised as follows :
Euryhaline : These organisms are able to tolerate a wide range of salinities. For example, Atlantic stingray and bull shark.
Stenohaline : These are organisms that are restricted to a narrow range of salinity. Examples include goldfish. Therefore, statement (ii) is incorrect.
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