Which one of the following statements is correct with respect to salt water balance inside the body of living organisms?
1. When water is not available, camels do not produce urine but store urea in tissues.
2. Salmon fish excretes lots of stored salt through gill membrane when in fresh water.
3. Paramecium discharges concentrated salt solution by contractile vacuoles.
4. The body fluids of fresh water animals are generally hypotonic to surrounding water.

What is true of urea biosynthesis?
1. Uric acid is the starting point
2. Urea is synthesized in lysosomes
3. Urea cycle enzymes are located inside mitochondria
4. Urea is synthesized in the kidney

Assertion: The kidneys of camel are very efficient at reabsorbing water.
Reason: Camels' kidneys have a 1:4 cortex to medulla ratio.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

In ornithine cycle, which of the following wastes are removed from the blood?   
1. CO₂ and ammonia
2. Ammonia and urea
3. CO₂ and urea
4. Urea and urine

What will be seen in a fish living in a marine environment?
1. They do not drink the water in their surroundings.
2. They drink the water in their surroundings.
3. They move monovalent ions into their bodies through active transport across their epithelial outer tissue.
4. They move monovalent ions out of their bodies through active transport across their epithelial outer tissue.

Assertion: Euryhaline Salmon fish osmoregulate in fresh water like other freshwater fishes.
Reason: In fresh water, salmon increases cortisol secretion which increases the number and size of salt-secreting chloride cells.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Assertion: In the freshwater flatworms, protonephridia serve chiefly in osmoregulation rather than in excretion.
Reason: Most metabolic wastes in freshwater flatworms diffuse out of the animal across the body surface or are eliminated into the gastrovascular cavity.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.