Zoology MCQs for NEET — Practice Questions with Answers

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.

Uric acid in humans is formed from the breakdown of purines, which are nitrogen-containing compounds found in DNA and RNA. The liver converts purines into uric acid, which is then excreted by the kidneys.

Green glands, also known as antennal glands, are excretory organs found in crustaceans such as prawns. They play a role in osmoregulation and waste removal. These glands are located near the base of the antennae.

In earthworms, the excretory structures are nephridia. Nephridia are tubular structures that help in the excretion of waste materials from the body. They function similarly to kidneys in higher organisms and are distributed throughout the segments of the earthworm's body.

The 'Columns of Bertini' are extensions of the renal cortex into the medulla of the kidney. These columns are made up of cortical tissue and help support the functional units of the kidney, the nephrons, by providing a pathway for blood vessels and nerves.

Each human kidney contains approximately 1 million nephrons. Nephrons are the functional units responsible for filtering blood and forming urine. This large number of nephrons ensures efficient filtration and waste removal from the body.

The adrenal cortex regulates urinary excretion of $Na^+$ through the secretion of aldosterone. Aldosterone increases the reabsorption of sodium ions in the kidneys, which helps in maintaining electrolyte balance and blood pressure.