2nd Year NotesBiology class 12th

2nd Year Biology Chapter 15 Homeostasis

2nd Year Biology Chapter 15 Homeostasis Question and answer

Short and Simple Question and Answer

Q 1. What is homeostasis?

Ans. Homeostasis is the process of maintaining a stable internal environment in an organism, protecting it from the negative effects of external environmental fluctuations.

Q 2. Define osmoregulation.

Ans. Osmoregulation is the mechanism by which organisms regulate the balance of solutes and the gain and loss of water between their bodies and the external environment.

Q 3. How are plants distributed based on osmoregulation?

Ans. Plants are distributed in various habitats, such as aquatic, moderate, and severely dry terrestrial environments. These categories are referred to as hydrophytes, mesophytes, and xerophytes, respectively.

Q 4. What are osmoregulators?

Ans. Osmoregulators are animals that actively regulate their body fluid concentration to discharge excess water in hypotonic conditions and excrete salts in hypertonic conditions.

Q 5. What is ebony?

Ans. Ebony is a tree that deposits unique chemicals in its branches and trunk, especially in the old xylem, which is no longer used for water transport. It produces very dark, black wood in the center.

Q 6. What is a protonephridium?

Ans. A protonephridium is a network of closed tubules without internal openings found in Planaria.

Q 7. What is the difference between the excretory system of insects and other animals?

Ans. Insects are the only group of animals that eliminate excretory waste with feces. In all other animals, there is no structural and functional relationship between the nutritive and excretory systems.

Q 8. What technique is used for the removal of kidney stones?

Ans. Kidney stones can be removed through kidney surgery or by using lithotripsy, a non-surgical technique to break up kidney stones.

Q 9. What is hemodialysis?

Ans. Hemodialysis is a medical procedure in which blood is circulated through an artificial kidney (dialyzer) to remove waste products and excess water from the blood.

Q 10. What are heterotherms?

Ans. Heterotherms are animals capable of varying degrees of endothermic heat production but do not regulate their body temperature within a narrow range, such as bats and hummingbirds.

Q 11. What are pyrogens?

Ans. Pyrogens are chemicals produced by pathogens like bacteria and viruses and by blood cells in response to infections. They displace the hypothalamic set point, causing a fever.

Q 12. Name the excretory structures in the animal kingdom associated with the digestive tract.

Ans. Malpighian tubules.

Q 13. Define excretion.

Ans. Excretion is the process of eliminating nitrogenous waste from an organism’s body.

Q 14. Define thermoregulation.

Ans. Thermoregulation is the maintenance of an organism’s internal temperature within a tolerable range.

Q 15. What is a hypotonic environment?

Ans. A hypotonic environment has more water or a more diluted solution compared to the cell’s concentration.

Q 16. What is a hypertonic environment?

Ans. A hypertonic environment has a higher concentration than the cell’s internal solution.

Q 17. What is an isotonic environment?

Ans. An isotonic environment closely resembles the internal solution of the cell.

Q 18. What are hydrophytes?

Ans. Hydrophytes are plants adapted to survive in aquatic environments. They have extensive surface areas on their leaves, numerous stomata on the upper leaf surface, and are adapted to excessive water loss.

Q 19. What are mesophytes?

Ans. Mesophytes are plants adapted to environments with moderate water availability. They can adjust the opening and closing of stomata to control water loss.

Q 20. What are xerophytes?

Ans. Xerophytes are plants adapted to environments with limited water availability. They have small, thick leaves, a thick and waxy cuticle, and stomata located on the lower leaf surface in depressions to reduce water loss.

Q 21. What are osmoconformers?

Ans. Osmoconformers are animals that maintain their body fluids isotonic to the external environment, even in marine saltwater conditions, without actively adjusting their osmotic state.

Q 22. Define anhydrobiosis?

Ans. Anhydrobiosis is the ability of terrestrial animals to tolerate dehydration, and this capacity varies among different species.

Q 23. What is excretion?

Ans. Excretion is the process of eliminating nitrogenous waste and other wasteful metabolites from the body.

Q 24. What are excretophores?

Ans. Excretophores refer to the seasonal shedding of yellow leaves in plants, which helps them get rid of accumulated waste.

Q 25. In what form is nitrogen excreted by animals?

Ans. Excess nitrogen is primarily excreted by animals in the form of ammonia, urea, or uric acid. Smaller amounts of nitrogen are excreted as creatinine, creatine, trimethylamine oxide, amino acids, purine, and pyrimidine.

Q 26. What are ammonotelic, ureotelic, and uricotelic animals?

Ans. Ammonotelic animals excrete ammonia, ureotelic animals excrete urea, and uricotelic animals excrete uric acid.

Q 27. What are flame cells?

Ans. Flame cells are part of the tubular excretory system found in some animals. These cells have cilia that beat to propel interstitial fluid into the tubular system

Q 28. What are nephridiopores?

Ans. Nephridiopores are openings through which the tubular excretory system drains into the external environment.

Q 29. What are metanephridia?

Ans. Metanephridia are a type of tubular excretory system found in earthworms. They have an internal ciliated opening called a nephrostome, which collects coelomic fluid.

Q 30. What are Malpighian tubules?

Ans. Malpighian tubules are suspended tubular structures found in terrestrial arthropods, particularly insects. They collect excretory products from the hemolymph.

Q 31. What is a nephron?

Ans. A nephron is the basic functional unit in the kidneys responsible for filtering and processing blood.

Q 32. What are metabolic wastes?

Ans. Metabolic wastes are the byproducts generated at the metabolic level, including urea, creatinine, uric acid, bilirubin, and toxins.

Q 33. What is bilirubin?

Ans. Bilirubin is a product of hemoglobin breakdown and the metabolism of various hormones.

Q 34. What is the urea cycle?

Ans. The urea cycle is a metabolic pathway involved in the production of urea. It converts two ammonia molecules and one carbon dioxide molecule into one molecule of urea.

Q 35. What is the ureter?

Ans. The ureter is a duct that carries urine from the kidney to the urinary bladder.

Q 36. What is the urethra?

Ans. The urethra is a tube that carries urine from the urinary bladder out of the body during urination.

Q 37. What are cortical nephrons?

Ans. Cortical nephrons are nephrons located along the cortex of the kidney.

Q 38. What are juxtamedullary nephrons?

Ans. Juxtamedullary nephrons are nephrons found at the border of the cortex and medulla, with their tubular system looping deep into the inner medulla. They play a significant role in the production of concentrated urine.

Q 39. What is Bowman’s capsule?

Ans. Bowman’s capsule is a cup-shaped swelling at the inner end of a nephron that surrounds the glomerulus.

Q 40. What is the glomerulus?

Ans. The glomerulus is a ball of capillaries found within Bowman’s capsule. It filters blood as it enters through the afferent arteriole and exits through the efferent arteriole.

Q 41. What are peritubular capillaries?

Ans. Peritubular capillaries are a network of capillaries arising from the glomerulus and surround the nephron’s tubules.

Q 42. What are vasa recta?

Ans. Vasa recta are a loop of blood vessels extending from juxtamedullary nephrons to maintain the osmotic balance of the medulla.

Q 43. What is glomerular filtrate?

Ans. Glomerular filtrate is the filtrate produced in the glomerulus, containing various useful substances such as glucose, amino acids, and salts in an aqueous solution.

Q 44. What is a counter current multiplier?

Ans. The counter current multiplier mechanism causes a gradual osmotic outflow of water from the filtrate in the descending loop of Henle. The ascending loop of Henle actively transports sodium into the kidney interstitium to maintain its high concentration.

Q 45. What is the role of aldosterone and antidiuretic hormones in the kidney?

Ans. Aldosterone promotes the active uptake of sodium in the ascending limb of the loop of Henle. Antidiuretic hormone (ADH) actively transports water from the filtrate to the kidney’s interstitium.

Q 46. What are hypercalcemia and hyperoxaluria?

Ans. Hypercalcemia is the condition of having high levels of calcium in the bloodstream, while hyperoxaluria is the presence of high blood levels of oxalates. Both conditions contribute to the formation of kidney stones.

Q 47. What is the percentage of incidence of different types of stones?

Ans. The incidence of calcium oxalate stones is approximately 70% of all kidney stones. The incidence of other types, such as calcium phosphate and uric acid stones, is around 15% and 10%, respectively. These salts precipitate during urine formation and accumulate to form stones.

Q 48. What is the most common way of lithotripsy?

Ans. The most common method of lithotripsy is extra-corporeal shock wave lithotripsy, where high concentrations of X-rays or ultrasound are directed from a machine outside the body to break kidney stones into small pieces that can be passed out in urine.

Q 49. What is dialysis?

Ans. Dialysis is a medical procedure used in cases of chronic renal failure to clean the blood by passing it through an artificial kidney or by filtering it within the abdomen. This helps remove waste products and excess water from the blood, performing a function similar to healthy kidneys.

Q 50. Name different types of dialysis.

Ans. There are two main types of dialysis:

  • Hemodialysis
  • Peritoneal Dialysis

Q 51. How is peritoneal dialysis done?

Ans. Peritoneal dialysis involves filling the peritoneal cavity of the abdomen with dialysis fluid through a catheter. This fluid absorbs excess water and waste products from the body, which are then drained out. The process is repeated several times a day.

Q 52. What is a dialyzer?

Ans. A dialyzer is a machine used for hemodialysis, functioning similarly to a natural kidney. It helps remove nitrogenous waste and excess water from the blood and is used when the kidneys have failed. Dialysis is performed until a matching kidney transplant is available.

Q 53. What is uremia?

Ans. Uremia, also known as end-stage renal disease, refers to the advanced stage of kidney failure. It requires ongoing dialysis treatment until a suitable kidney donor can be found for transplant.

Q 54. What are heat-shock proteins?

Ans. Heat-shock proteins are special proteins synthesized by plant cells to survive heat stress. These proteins include enzymes and other proteins that help protect cellular structures and prevent denaturation under high-temperature conditions.

Q 55. How do plants respond to cold stress?

Ans. Plants respond to cold stress by increasing the proportion of unsaturated fatty acids in their cell membranes. This adaptation helps maintain membrane structure at lower temperatures by preventing the formation of ice crystals.

Q 56. What are poikilotherms (cold-blooded)?

Ans. Poikilotherms are animals whose body temperature fluctuates in response to changes in the external environment. This group includes invertebrates, amphibians, and reptiles.

Q 57. What are homeotherms (warm-blooded)?

Ans. Homeotherms are animals that can maintain a constant body temperature regardless of changes in the external environment. This category includes birds and mammals.

Q 58. What are endotherms?

Ans. Endotherms are animals that generate their own body heat through metabolic processes. They can regulate their body temperature independently, such as mammals, birds, some fishes, and flying insects.

Q 59. What are ectotherms?

Ans. Ectotherms are animals that produce heat at a low metabolic rate and primarily rely on external heat sources to regulate their body temperature. Most invertebrates, fish, amphibians, and reptiles fall into this category.

Q 60. What are structural adaptations for temperature regulation in animals?

Ans. Structural adaptations for temperature regulation may include long-term changes in subdermal fatty layers for insulation, fur or pelage, the presence of sweat glands, and modifications in lung structure to aid in heat regulation.

Q 61. What is shivering thermogenesis?

Ans. Shivering thermogenesis refers to the process where the body increases heat production by increasing muscle contraction through movements or shivering.

Q 62. What is non-shivering thermogenesis?

Ans. Non-shivering thermogenesis involves the production of heat triggered by hormones, such as thyroid hormones, which do not rely on muscle contractions like shivering.

Q 63. What is brown fat?

Ans. Brown fat is a type of adipose tissue found in some mammals, including humans, specialized for rapid heat production. It is located between the shoulder blades in humans and is involved in warming blood.

Q 64. What is evaporative cooling?

Ans. Evaporative cooling is the process of cooling the body by allowing sweat or water to evaporate from exposed body surfaces, which helps dissipate excess heat.

Q 65. What is vasodilation and vasoconstriction?

Ans. Vasodilation is the widening of blood vessels, often occurring in hot conditions, to help regulate body temperature by increasing blood flow near the skin’s surface, promoting heat loss. Vasoconstriction is the narrowing of blood vessels, typically in cold conditions, to reduce blood flow to the skin’s surface and conserve heat.

Q 66. How do land mammals respond to cold weather?

Ans. Land mammals respond to cold weather by raising their fur, which creates a thicker layer of still air that acts as insulation between their skin and the surroundings.

Q 67. What is blubber?

Ans. Blubber is a thick layer of insulating fat found just under the skin of marine mammals, such as whales and seals, which helps them regulate their body temperature, especially in cold water.

Q 68. How do marine mammals regulate their temperature in warm seasons?

Ans. Marine mammals release excess heat into warm seas by increasing blood flow in the outer layer of their skin. This helps dissipate heat from the skin surface.

Q 69. What regulatory mechanisms do terrestrial mammals use to cope with warm temperatures?

Ans. Terrestrial mammals use several mechanisms to regulate their body temperature in warm conditions. These include sweat gland activation for evaporative cooling, panting (especially in dogs), and the use of saliva and urine for evaporative cooling in animals like bats.

Q 70. How do thermoreceptors play a role in high-temperature regulation?

Ans. When temperatures rise above the set point, warm-temperature thermoreceptors located in the skin, hypothalamus, and other parts of the nervous system send signals to increase blood flow to the skin, activate sweat glands, and promote the evaporation of sweat for cooling.

Q 71. What is the role of cold receptors in response to cold temperatures?

Ans. Cold receptors send signals to the hypothalamus when temperatures drop, inhibiting heat loss mechanisms and activating heat conservation mechanisms. This includes constricting superficial blood vessels and stimulating shivering and non-shivering mechanisms.

Q 72. Why does filtration occur only in the glomerular part of the nephron and nowhere else?

Ans. Filtration occurs in the glomerular part of the nephron due to two main reasons: the porous nature of the glomerular walls, allowing substances to pass through, and the development of high blood pressure at the glomerulus, known as filtration pressure.

Q 73. Name two metabolic altered states that commonly lead to kidney stone formation?

Ans. Two common metabolic altered states that lead to kidney stone formation are hyperoxaluria, caused by high blood oxalate levels due to increased intake or production of oxalate, and hyperoxaluria, characterized by higher blood oxalate levels from increased oxalate production.

Q 74. What is renal failure?

Ans. Renal failure refers to the failure of the kidneys to effectively filter urea from the blood. Common causes include the destruction of glomeruli due to various factors.

Q 75. Provide one key adaptation in plants to high and low temperatures?

Ans. To cope with high temperatures, plants have evolved evaporative cooling mechanisms. To deal with low temperatures, they adjust the solute concentration within their cells to prevent ice crystal formation, supercooling the cytosol.

Q 76. How do the ascending and descending loops of Henle differ in their physiology while contributing to sustaining a high concentration in the kidney interstitium?

Ans. The descending loop of Henle allows a gradual outflow of water from the filtrate back into the kidney, while the ascending loop of Henle prevents water outflow and actively transports sodium ions into the kidney interstitium. Together, they help maintain a high concentration in the interstitium.

Q 78. How do bony fishes regulate osmoregulation?

Ans. Bony fishes regulate osmoregulation by:

  • Taking in a large amount of seawater
  • Excreting concentrated urine with maximum salt excretion and minimal water loss
  • Actively removing salts from the body through gills and rectal glands

Q 79. Describe the position and function of sphincter muscles in the excretory system?

Ans. Sphincter muscles are located near the junction of the urethra and the urinary bladder.

Function: Sphincter muscles control the release of urine from the bladder.

Q 81. The skin excretes water, salts, and sebum, yet it is not considered an excretory organ. Why?

Ans. While the skin does excrete water, salts, and sebum, it primarily does so for thermoregulation and protection against microorganisms, not for excretion of waste products. Therefore, it is not classified as an excretory organ.

Q 82. List some substances synthesized by the liver?

Ans. The liver synthesizes various substances, including nitrogenous wastes like ammonia (NH3), urea, uric acid, albumin, bile, lipids, cholesterol, and lipoproteins.

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