Notes - Biology-12 Short Questions Chapter 15: Homeostasis

Short Question Answer Biology-12 students. Study Preparation notes of short Question Answers are compile by Sir KhanZada Faisal from Superior College Sialkot.

`Short questions

Homeostasis:

Q1. Define Homeostasis. Give its importance.

Ans. “The protection of internal environment from the harms and fluctuations of external environment is called homeostasis” (Greek- Homeo=Same, Stasis=Standing)

Importance:

1. Homeostasis is the central requirement of an organism and is necessary for normal body functions.
2. Due to homeostasis organisms are able to live in the changing conditions they have better homeostatic system to survive and adapt in the changing conditions.
3. Homeostasis contributes in the evolutionary process.

Q2. Define excretion; Differentiate between Osmoregulation and thermoregulation.

Ans. “The mechanism which eliminates or removes metabolic wastes especially nitrogenous wastes is called excretion”

• In it urinary system is involved.
• Its wastes are always in liquid forms.

Osmoregulation;	Thermoregulation;
The mechanism in which living organisms maintain salt and water concentration in within the body with respect to external environment. Due to which animals and plants are able to live in wide range of habitats.	The mechanism in which living organisms maintain their internal body temperature within a tolerable range with respect to external environment. Due to which animals and plants are able to live in different temperature zones.

Q3. What is feedback mechanism; Give an example.

Ans. “the detection of changes by the receptors and sending signals by control system to the effectors for a response is called feedback mechanism”

Negative feedback mechanism;	Positive feedback mechanism;
In this effectors’response is opposite to the change in external environment. It tends to stabilize a system. E.g.Temperatureregulation.	If the effectors’ response is similar or towards the change in external environment. Destabilize a system. Blood clotting, Milk production.

Q4. Compare physical control system with living control system.

Physical control system;	Living control system;
Temperature control system in Iron, fridges, oven etc. This system have three components Sensor, control centre, and on/off switch. The sensor detects temperature change from set point. Sensor sends signals to control centre. The control centre takes action by switching on/off heating or cooling units in response to drop or rise in the temperature compared to set point respectively.	It is control system in living organisms. This system also has three components Receptors, Control centre, and effectors. Receptors detect temperature changes from a set point. Receptors send signals to control centre for action of cooling and heating system. Control system sends message to effectors for response.

Osmoregulation:

Q5. Distinguish between hypotonic and hypertonic environment and isotonic environment.

Ans.

Hypotonic environment:	Hypertonic environment:	Isotonic environment
If the extracellular environment has more diluted solution as compare to the cell concentration. More salt concentration inside the cell. Water enters into the cell. Cell solution becomes dilute. Cell become turgid and may be burst.	If the extracellular environment is more concentrated as compare to the cell concentration. More salt concentration present outside the cell. Water will remove from cell. Outer solution becomes dilute. Cell becomes shrinked.	If the concentration of extracellularenvironment resembles to internal solution of the cell. No effect on cell solution. No turgidity or shrinkage. Normal saline solution.

Q6. Define and compare hydrophytes, mesophytes and xerophytes.

Ans.

Hydrophytes:	Xerophytes:	Mesophytes:
The plants growing in aquatic or abundant water supply habitats are called hydrophytes. Adaptations: They have large surface area for excessive transpiration. Cuticle absent on root, stem and leaves. Large amount of stomata present on upper surface of leaf and stem. Short root system. E.g. Hydrilla, Vallisnaria and nelumbium etc.	The plants growing in severely dry habitats or in very less/no supply of water are called xerophytes. Adaptations: They have small; thick leaves to protect water from lose by reducing surface area. Their cuticle is thick waxy and leathery. Stomata are present on lower surface of leaves located in depressions. Root system and root hairs are well developed. Opuntia, Cactus, and Calatropis etc.	the plants growing in moderate water available habitats are called mesophytes. Adaptations: Leaves and branches have cuticle on it. Stomata are kept open to promote loss of excess water and close in restricted supply of water to prevent the loss of water. Rot system and root hairs are well developed. Brassica, rose and mango etc.

Q7. Compare osmoconformers and osmoregulator.

Ans.  

Osmoconformer:	Osmoregulator:
The animals which do not need to adjust their internal osmotic state with respect to external osmotic state. These animals keep their body fluid isotonic to the external environment. E.g. most of marine invertebrates, Hag fishes.	The animals which need to adjust their internal osmotic state with respect to external osmotic state. Their body fluid concentration is different from outside environment. E.g. Al chordates, protists.

Q8. How do bony fishes osmoregulate in marine water?

Ans. Bony fishes are descendants of fresh water ancestors but later became marine.

• Theses fishes constantly lose water from their hypotonic body fluid to hypertonic environments.
• They drink large amount of sea water.
• They excrete concentrated urine.
• As a result maximum salt and minimum water is lose from body.

Q9. Explain the role of contractile vacuole.

Ans. fresh water animals are constantly facing the osmotic flooding of body fluids and loss of salt. i.e. they need to avoid salt loss and endosmosis so amoeba, paramecium use contractile vacuoles to pumps out excess water and prevent salt from loss.

Q10. Explain Anhydrobiosis with an example.

Ans.                             “Ability to tolerate dehydration is called anhydrobiosis”

Terrestrial animals can tolerate dehydration and it differs in various animals. This character is called as Anhydrobiosis.

1. Kangaroo rat,survive without drinking water. It feeds on seeds of desert plants containing more carbohydrates, which produce metabolic water.
2. Human beingcan tolerate short supply of water due to help of role of ADH.

Excretion

Q11. Why leaves are called as excretophores?

Ans. the falling of yellow leaves in autumn. This is because that the autumn season is the time for the plants to get rid of from the accumulated waste products in leaves. So leaves are used to excrete waste products by falling off from plants so these yellow leaves are called as excrtophores.

Q12. Write down the formula of urea and uric acid.

Ans.

Urea;	Uric acid;
It has no ring structure. It is more soluble in water. It is more toxic if retain in large amounts. It is released by mammals, amphibians, sharks, some bony fishes etc.	It is double ringed structure. It is very less soluble in water. It is less toxic if retained in large amounts. It is released by reptile, birds, some amphibians, some bony fishes etc.

Q13. Differentiate between Ammonotaly,  ureotely and  uricotely. Give example

Ans.

Ammonotely:	Ureotely:	Uricotely:
Phenomena of removing NH3 by cell or organisms as nitrogenous waste are called ammonotely. Animals excrete ammonia are called as ammonotelic animals Ammonia is very toxic and dissolves quickly in body fluids. So it must be kept in low concentration in the body. About 500ml water is required to eliminate 1g nitrogen in the form of ammonia. E.g. Most aquatic animals and many fishes.	The plants growing in severely dry habitats or in very less/no supply of water are called xerophytes. Adaptations: They have small, thick leaves to protect water from lose by reducing surface area. Their cuticle is thick waxy and leathery. Stomata are present on lower surface of leaves located in depressions. Root system and root hairs are well developed. Opuntia, Cactus, and Calatropis etc.	The plants growing in moderate water available habitats are called mesophytes. Adaptations: Leaves and branches have cuticle on it. Stomata are kept open to promote loss of excess water and close in restricted supply of water to prevent the loss of water. Rot system and root hairs are well developed. Brassica, rose and mango etc.

Q14. Write excretory organs of    A. Planaria B. Earthworm C.  Cockroach

Ans.                                                 Excretion in planaria:-

• These animals have simple tubular excretory system with network of closed tubules without internal openings are called protonephridium.
• This spread throughout the body. Each branch ends in a cellular setup called as Flame cell.
• Each flame cell has a tuft of cilia.
• The beating of cilia looks like a flickering flame; therefore these cells are called as flame cells.
• No blood is involved.
• This is also present in rotifers, some annelids, larvae of molluscs and lancelets.

Mechanism of excretion:-

• The beating of cilia propels interstitial fluid into a the tubular system.
• The tubular system is drained into excretory ducts, which opens to the exterior through several nephridiopores.

                                 Excretion in earthworm:-

• They have tubular excretory system called as metanephridium.
• They have a pair of metanephridia in each segment.
• They have internal ciliated openings called as nephrostome.
• From the nephrostome, the nephridia become a tube. This tube ends in a bladder.
• The bladder opens to the exterior by a pore called nephridiopore

Mechanism of excretion:-

• The nephrostome is immersed in coelomic fluid and enveloped by a network of blood capillaries.
• The nephrostome collects coelomic fluid.
• Fluid moves along the tubule, epithelium reabsorbs the salt from lumen and send to blood vessels surrounding the nephridium.
• The remaining material is urine containing nitrogenous waste. Which expel out by nephridiopore.

                                                   Excretion in cockroach:-

• Arthropods and insects have excretory structure called malpighian tubules.
• The proximal end of these tubes opens into the beginning of hind gut while distal end is blind.

Mechanism of excretion:-

• The suspended tubular structure collects waste from the haemolymph.
• The epithelium lining of tubules transport solutes including salts and nitrogeneous wastes from haemolymph into the lumen of the tubules. Here uric acid is formed.
• Fluids then enter into hind gut and reach the rectum.
• Rectum reabsorbs most of the salt and water.
• Wastes are excreting as solid excreta (in the form uric acid crystals) along with the faeces.

Q15. Name the waste products produced during metabolism of proteins, purines and pyrimidines.

Ans. Waste products of proteins:- During metabolisms proteins are converted into amino acids and then amino acid is converted into urea, uric acid and ammonia which is then release from body as a nitrogenous waste through excretion.

Purines and pyrimidines: - These are converted into hypoxanthine, Xanthine, uric acid, allontoin, urea and uric acid during metabolism.

Q16. Skin does not come within the definition of excretory organ comment.

Ans.

1. Sweat glands (sudorific glands) in the skin secrete a fluid waste called sweat or perspiration; however, its primary functions are

• temperature control and
• Pheromone release.

2. It also remove sebum (oily secretions) by sebaceous glands seems to be excretory in nature. But its primary functions

• Protection against microorganisms.
• Lubricant for hair and skin.

Therefore, its role as a part of the excretory system is minimal. Sweating also maintains the level of salt in the body. Therefore skin may not be considered as an excretory organ.

Q17. Write two important functions of liver.

Ans.  These are the important functions of the liver.

1. Synthysis:-

• It can synthesize nitrogenous wastes like ammonia, urea and uric acid.
• It also produces some plasma proteins like prothrombin, fibrinogen and albumin etc.

2. Storage:-

• It stores iron and many metals.
• It also stores glycogen as energy reserve material.

Q18. What is bile; give its factions.

Figure 1; Urea cycle

Ans. Bile: -A bitter greenish-brown alkaline fluid which aids digestion and is secreted by the liver and stored in the gall bladder. Itemulsifies fats in small intestine.

Q19. Draw metabolic pathway of urea cycle.

Ans. Drawn in the image.

Q20. Differentiate between ureter and urethra.

Ans. Ureter:-

• Urine leaves the kidney through a duct called as ureter.
• This takes the urine from kidney to urinary bladder.

Urethera:-

• Urine leaves the body during urination from the bladder through a tube called the urethra.
• Urethra empties in vagina in females or through penis in males.

Q21. Compare the cortical nephron with juxtamedullary nephron.

Ans. 

Cortical Nephron;	Juxtamedullary Nephron;
Nephron located in renal cortex region is called cortical nephron. These nephrons have small U-shaped tubules. They work in dilute environment as compared to juxtamedullary nephron. They have only peritubular capillaries They produce dilute urine.	Nephron located in renal medulla region are called juxtamedullary nephron These nephrons have long U-shaped tubules. They work in concentrated environment as compare to cortical nephron. They have peritubular capillaries and Vasa Recta. They produce concentrated urin.

Q22. What is glomerular filtrate?

Ans. Glomerular filtrate

• The blood passing through the glomerulus is filtered into bowman’s capsule called as glomerular filtrate.
• It contains numerous useful substances such as glucose, amino acids, salts etc in aqueous solutions.

Q23. Define mechanism of counter current multiplier. Give its functions.

Ans. The descending and ascending loop of Henle of long juxtamedullary nephron and the overlying vasa recta forms counter current multiplier.

• The descending limb has selective permeability for water while the ascending limb actively secretes salts.
• The interstitial fluid of the kidney is gradually concentrated from cortical to medullary part.
• The inner medulla is highly concentrated with the presence of urea and through a mechanism of counter current multiplier.
• This mechanism cause osmotic outflow of water from its filtrate, instead actively transport Na⁺  into kidney environment to maintain its high concentration.
• Increasing osmotic concentration from cortex to inner medulla is a main factor for the production of hypertonic urine in mammals including human.

Q24. What are vasa recta? Give its functions.

Ans. In juxtamedullary nephrons additional capillaries extends down and form a loop of vessels called vasa recta. Vasa recta areinvolved in the production of concentrated urine and conserve water.

Q25. What is role of aldosterone and antidiuretic hormones in kidney?

Ans. The absorption of the filtrate is done by the hormonal mechanisms. Following hormones are involved.

1. Aldosterone:

• The active uptake of sodium in the ascending limb or thick loop of henle is promoted by the action of aldosterone.
• This hormone is secreted from adrenal cortex.

2. Antidiuretic hormone:

• The other site in the nephron, where reabsorption of water takes place in collecting tubules.
• ADH released from posterior pituitary actively transports water from filtrate in collecting tubules back to kidney.
• In sufficient or excess supply of water, reabsorption of water from the filtrate is reduced. This is especially due to inhibition of release of ADH in the presence of hypo-osmotic body fluids. The reduction in reabsorption causes large volumes of diluted urine.

Q26. Compare the metabolic states of kidney stones; also give their %age.

Ans.  Kidney stones are formed in the following metabolic diseases.

1. Hypercalcemia:

It is the high level of circulatingcalcium in blood because of the diseases and diet.

2. Hyperoxaluria:

• It is the higher level of oxalate in the blood. This is the major cause of the formation of calcium oxalate stones.
• Oxalates are present in green vegetables and tomatoes.
• Phosphate stones formed in pelvis by accumulation of phosphate in it.

Q27. What is lithotripsy?

Ans. It is the technique used to break up stones without surgery that form in the kidney, ureter or gall bladder. In this extracorporeal shock wave lithotripsy is used.

Extracorporeal shock wave lithotripsy:-

• In this technique high concentrations of X-rays or ultra sound are directed from a machine outside the body to the stone inside.
• The shock waves break the stone in tiny pieces or turn it into sand, which are passed out of the body through urine.

Q28. Explain about dialysis.

Ans. In chronic renal failure, the kidney function is lost completely and it can never remove nitrogenous wastes. To remove nitrogenous wastes particularly the urea, the blood of the patient is treated through dialysis. There are two types of dialysis.

1. Haemodialysis:

Haemodialysis means “cleaning the blood”

• In this procedure blood is circulated through a machine which contains a dialyzer also called an artificial kidney.
• Dialyzer is a kidney machine that works on the same principles as in the kidney for the removal of nitrogenous wastes and excess water from the blood.
• It is used after kidney failure and dialysis is done again and again until a matching donor’s kidney is transplanted.
• Dialyzer has two spaces separated by thin membrane. Blood passes from one side of the membrane and dialysis fluid on the other side.
• The wastes and excess water pass from the blood through the membrane into dialysis fluid.

2. Peritoneal dialysis:

Peritoneal dialysis works on the same principles except that abdomen has a peritoneal cavity, lined by a thin epithelium called peritoneum.

• Peritoneal cavity is filled dialysis fluid that enters the body through a catheter.
• Excess water and wastes pass through the peritoneum into the dialysis fluid.

Q29. What is renal failure?

Ans. A process in which kidney is fail to perform its normal functions is called as renal failure.

Causes:

• Various factors of pathological and chemical nature may progressively destroy the nephron, particularly its glomerular part.
• As a result level of urea and other nitrogenous wastes increases in the blood plasma.
• Rise in urea causes increase in blood pressure and anaemia etc.

Q30. What is uremia? Give its permanent treatment.

Ans. High degree renal failure is also called as uremia or end stage of renal disease.

• In this case the dialysis is done continuously.
• The only Permanent treatment is  the surgical transplantation of a matching donor’s kidney.

Thermoregulations

Q31. How most plants have adapted to survive in heat stress? (Heat shock proteins)

Ans.

1. Heat shock proteins. Most plants survive in heat stress. The cells of these plants synthesize large quantities of special proteins called heat-shock proteins.

These proteins embrace enzymes and other proteins and help to prevent denaturation.

2. Plants use evaporative cooling. As a result they can lower down the high temperature. So plants of temperate regions face the stress of 40^oC and above temperature.

Q32. Write structural/ physical adaptations for heat exchange between animals and environment.

Ans. Animals use different mechanisms for heat regulation.

1. Structural adaptations.

• Long term changes in sub dermal fatty layer insulation or pelage.
• The presence of sweat glands.
• Lungs modified for painting (control of body temperature through respiratory tract).

2. Physical adaptations.

• Regulation of blood flow to the skin specifically greater blood flow in hot surrounding to disperse heat (by vasodilatation) and lower in colds to save heat loss(vasoconstriction).
• The activation of certain muscles causes plumage fluffing.
• Activation of sweat gland is done for evaporative cooling.

Q33. Differentiate between endotherm and ectotherm and hetrotherms.

Ans.

Ectotherm:	Endotherm:	Hetrotherm:
These are the animals which are produce metabolic heat at low level and that is also exchanged quickly with the environment, absorb heat from their surroundings. Most invertebrates, fishes, amphibians and reptiles are in this category.	These are the animals that generate their heat through heat production as by product during metabolism. These include birds, some fishes, flying insects and mammals.	These are animals which produce their endothermic heat but generally do not regulate their body temperature within a narrow range. The examples are bats and humming birds.

Q34. Differentiate between poikiliotherms and homeotherms with examples.

Ans.

Poikiliotherms;	Homeotherms;
These are the animals in which body temperature fluctuates more or less with the changing air or water temperature. Mostly invertebrates, fishes, amphibians and reptiles.	These are the animals in which body temperature is maintained in the changing air or water temperature. All birds and mammals Are present in this group.

Q35. Compare shivering and non-shivering thermogenesis.

Ans.

Shivering thermogenesis;	Non shivering thermogenesis;
The increase in rate of heat production by increased muscle contraction by movement or shivering is called shivering thermogenesis.	The hormones trigger fine heat production as do thyroid hormones and are called as non-shivering thermogenesis.

Q36. Explain the process of panting with an example.

Ans. It is the process in animals control their body temperature through respiratory tract. E.g. it can be observed in the dogs and many carnivores.

Q37. Differentiate between vasodilation and vasoconstriction.

Ans.