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Select the true statement -...

Select the true statement -

A

In fishes kidney play a major role in ammonia excretion.

B

Ammonia is 100,000 times less toxic than urea.

C

Sharks retain a large amount of urea in the blood as a major osmolyte to balance the osmolarity of the body fluids

D

Most terrestrial reptile excrete ammonia

Text Solution

AI Generated Solution

The correct Answer is:
To determine the true statement among the options provided, we will analyze each statement step by step. ### Step-by-Step Solution: 1. **Evaluate the First Statement**: - The statement claims that in fish, kidneys play a major role in ammonia excretion. - **Analysis**: In fish, ammonia is primarily excreted through the gills rather than the kidneys. Ammonia is highly toxic and is excreted directly into the water, where it diffuses out. Therefore, this statement is **false**. 2. **Evaluate the Second Statement**: - The statement claims that ammonia is one lakh times less toxic than urea. - **Analysis**: This is incorrect. Ammonia is actually more toxic than urea. Urea is approximately 1 lakh times less toxic than ammonia. Thus, this statement is also **false**. 3. **Evaluate the Third Statement**: - The statement claims that sharks retain a large amount of urea in the blood as a major osmolite to balance the osmolarity of body fluids. - **Analysis**: This statement is true. Sharks do retain urea in their blood, which helps them maintain osmotic balance in the marine environment. This allows them to be hypertonic compared to the surrounding seawater, preventing dehydration. Therefore, this statement is **true**. 4. **Evaluate the Fourth Statement**: - The statement claims that most terrestrial reptiles excrete ammonia. - **Analysis**: This is incorrect. Most terrestrial reptiles convert ammonia into uric acid, which is less toxic and conserves water. Therefore, this statement is **false**. ### Conclusion: After evaluating all the statements, the true statement is: **"Sharks retain a large amount of urea in the blood as a major osmolite to balance the osmolarity of body fluids."**
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