Important questions based on NCERT syllabus for Chapter 19 - Excretory Products and their Elimination:
Question-1: What is the role played by Renin-Angiotensin in the regulation of kidney function?
Solution: Renin is released from JGA on activation due to fall in the glomerular blood pressure/flow. Renin converts angiotensinogen in blood to angiotensin-I and further to angiotensin-II. Angiotensin-II being a powerful vasoconstrictor, increase the glomerular blood pressure and thereby GFR. Angiotensin-II also activates the adrenal cortex to release aldosterone. Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule. This also leads to.an increase in blood pressure and thereby GFR. This is generally known as the Renin-Angiotensin mechanism.
Question-2: What is the procedure advised for the correction of extreme renal failure? Give a brief account of it.
Solution: Kidney transplantation is the ultimate method in the correction of acute renal failures (kidney failure). A functioning kidney is used in transplantation from a donor, preferably a close relative, to minimise its chances of rejection by the immune system of the host. Modem clinical procedures have increased the success rate of such a complicated technique.
Question-3: How have the terrestrial organisms adapted themselves for conservation of water?
Solution: Terrestrial adaptation necessitated the production of lesser toxic nitrogenous wastes like urea and uric acid for conservation of water. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals. Ammonia produced by metabolism is converted into urea in the liver of these animals and released into the blood which is filtered and excreted out by the kidneys. Some amount of urea may be retained in the kidney matrix of some of these animals to maintain a desired osmolarity. Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid ‘ in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.