Excretory Products and Their Elimination MCQs for NEET — Zoology Questions with Answers

Crustaceans like Astacus (a freshwater crayfish) have specialized excretory organs known as green glands, which help in osmoregulation by removing excess water in the form of urine. Freshwater animals need to constantly manage the influx of water due to endosmosis.

Marine animals live in a hypertonic environment where the salinity of the seawater is higher than that of their body fluids. To counteract the water loss due to exosmosis (movement of water out of their bodies), they drink sea water. This helps them maintain their hydration and osmotic balance.

Matching the organisms to their respective characteristics:

1. Astacus (a type of crayfish) is associated with the green gland (q).
2. Marine turtle has salt glands (s) to excrete excess salt.
3. Spiny lizard has hydrophilic skin (p) which helps in water absorption.
4. Uromatrix (a type of lizard) stores water in its intestine (r). Thus, the correct match is: \[(1-q), (2-s), (3-p), (4-r)\]

FACT

Urea, NH₃ (ammonia), and creatinine are metabolic wastes of nitrogenous substances. These compounds are byproducts of protein metabolism and are excreted from the body to maintain homeostasis.

Ureotelism is the process of excreting nitrogenous waste in the form of urea. It is commonly found in mammals, including humans, as well as some amphibians and cartilaginous fish. Mammals convert ammonia, which is toxic, into urea, which is less toxic and can be excreted with minimal water loss.

Uricotelic animals excrete uric acid as their primary nitrogenous waste. This is typical of animals that need to conserve water. Lizard and Crow are examples of uricotelic animals. They convert ammonia into uric acid, which is relatively non-toxic and can be excreted as a paste or solid with minimal water loss.