Chapter 48, Problem 1TYK

Which of the following statements about osmoregulation is true?

a. In freshwater invertebrates, salts move out of the body into the water because the animal is hypoosmotic to the water.

b. A marine teleost has to fight gaining water because it is isoosmotic to the sea.

c. Most land animals are osmoconformers.

d. Vertebrates are usually osmoregulators.

e. Terrestrial animals can regulate their osmolarity withoutexpending energy.

Summary Introduction

Introduction:

Maintenance of the organism’s body fluid through passive regulation of water content is known as osmoregulation. It also helps in maintaining the ion balance while getting rid of metabolic wastes from the body. It can be regulated by osmosis and passive diffusion.

The movement of molecules from high concentrated region to low concentration region through a semipermeable membrane is called osmosis. Osmosis is also a form of passive diffusion. On the basis of osmolarity, the solution can be divided into three types. The hyperosmotic solution has a higher osmolarity, a solution with lower osmolarity is called hypoosmotic solution, and the solution with the same osmolarity on either side of the membrane is called an isosmotic solution.

Answer to Problem 1TYK

Correct answer:

Vertebrates are usually osmoregulators.

Explanation of Solution

Justification/explanation for the correct answer:

Option (d) states that the vertebrates are usually osmoregulators. All the vertebrates have a mechanism in their body to maintain the composition of extracellular fluids. It constitutes of fluids such as blood, lymph, and interstitial fluid. The concentration of this fluid must be regularly monitored so as to control the concentration as well as the volume of fluid. Hence, option (d) is correct.

Explanation for the incorrect answer:

Option (a) states that in freshwater invertebrates, salts move out of the body into the water because the animal is hypoosmotic to the water. Freshwater vertebrates are hypoosmotic to the water, due to which, the salts move out of the body into the water. Osmoregulation occurs inside a closed body system that occurs usually in vertebrates. Most of the freshwater invertebrates are hyper or isoosmotic regulator. So, it is incorrect.

Option (b) states that marine teleost has to fight to gain water because it is isosmotic to the sea. Marine teleost maintain their body osmolarity with the environment and are called osmoconformers. So, it is incorrect.

Option (c) states that most land animals are osmoconformers. Most of the marine invertebrates are osmoconformers. Land animals maintain a constant and stable internal environment through a process called homeostasis. So, it is incorrect.

Option (e) states that terrestrial animals can regulate their osmoregulatory without expending energy. Terrestrial animals have to spend energy in order to regulate their internal environment. Osmoregulation such as osmosis, diffusion, needs energy when flow is against the concentration gradient. So, it is incorrect.

Hence, options (a), (b), (c), and (e) are incorrect.

Conclusion

Therefore, it can be concluded that vertebrates can maintain the composition of extracellular fluid such as blood, lymph, and interstitial fluid through osmoregulation. The concentration of this fluid must be kept under regulation.