Role of Lungs, Liver & Skin in Excretion — NEET Biology

Correct answer: C — S1, S2, S3, and S4

The question assesses the understanding of various excretory functions performed by organs other than kidneys, as well as general principles of nitrogenous waste excretion. S1: Lungs do remove large amounts of CO2 (approximately 200 mL/minute) and significant quantities of water every day. This statement is correct. S2: The liver secretes bile-containing substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins, and drugs, which are ultimately eliminated with digestive wastes. This statement is correct. S3: Sweat glands produce a watery fluid containing NaCl, small amounts of urea, and lactic acid, facilitating both cooling and waste removal. This statement is correct. S4: Sebaceous glands eliminate sterols, hydrocarbons, and waxes through sebum, which also provides a protective oily covering for the skin. This statement is correct. S5: In ammonotelic animals, kidneys do not play any significant role in the removal of ammonia; instead, it is generally excreted by diffusion across body surfaces or through gill surfaces. This statement is incorrect. S6: Uric acid is the least toxic nitrogenous waste and can be removed with a minimum loss of water, whereas ammonia is the most toxic and requires a large amount of water for its elimination. This statement is incorrect. Therefore, statements S1, S2, S3, and S4 are correct.