chapter 15 Homeostasis Solved Exercise
Excretion and osmoregulation are vital processes in living organisms, ensuring removal of nitrogenous wastes and regulation of water-salt balance. Below are solved fill-in-the-blanks and short questions, perfect for FSc Biology and MDCAT entry test preparation.
✅ Q.2 Fill in the Blanks (Solved)
(i) Osmoregulation is the ability of an organism to regulate its fluid contents.
(ii) The detoxification of ammonia to urea requires the precursor of ornithine.
(iii) In kidney, nephron is closely associated with network of capillaries (peritubular capillaries / vasa recta).
(iv) In insects, salt and water reabsorption takes place in the Malpighian tubules.
(v) The antidiuretic hormone acts on collecting ducts to promote reabsorption of water in vertebrate nephron.
(vi) The nephrons arranged along the border of cortex and medulla, with tubular system looping deep in the inner medulla, are called juxtamedullary nephrons.
(vii) The non-surgical procedure of removing kidney stone is termed as lithotripsy.
(viii) Hypothalamus is the homeostatic thermostat in human.
✅ Q.3 Short Questions (Solved)
(i) Differentiate between osmoconformers and osmoregulators.
👉 Osmoconformers: Organisms whose internal osmotic concentration changes with the external environment (e.g., most marine invertebrates).
👉 Osmoregulators: Organisms that maintain constant internal osmotic concentration regardless of environment (e.g., humans, freshwater fish).
(ii) Define anhydrobiosis with an example.
👉 Anhydrobiosis is a dormant state in which organisms survive extreme desiccation (loss of water).
Example: Tardigrades (water bears) can survive without water for years.
(iii) Why does filtration take place only at glomeruli part of nephron and nowhere else?
👉 Because glomerulus has high blood pressure (afferent arteriole wider than efferent arteriole) and filtration slits in Bowman’s capsule, which facilitate ultrafiltration.
(iv) Mention two metabolic altered states that generally (70%) cause kidney stone formation.
👉 1. Hypercalciuria (excess calcium in urine)
👉 2. Hyperoxaluria (excess oxalate in urine)
(v) What is a renal failure?
👉 Renal failure is the inability of kidneys to remove metabolic wastes and maintain water-salt balance. It leads to accumulation of toxic substances in blood (uremia).
(vi) Account one each main adaptation in plants to high and low temperatures.
👉 High temperature: Plants develop thick cuticle and sunken stomata to reduce water loss.
👉 Low temperature: Plants produce antifreeze proteins and accumulate solutes to resist freezing.
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