12th Class Biology Chapter 1 Homeostasis Short Question Answers

biology short QA

12th Class Biology Chapter 1 Homeostasis Short Question Answers Below

What do you know about homeostasis?
The protection of internal environment from the harms of fluctuations in external environment is termed as homeostasis.
Define osmoregulation?
The mechanism of regulation generally between organism and its environment of solute and the gain and the loss of water is osmoregulation,OR It is the regulation of water and solutes between organisms and their environment.
How plants are distributed on the basis of osmoregulation?
Plants are distributed in different habitats of aquatic moderate and severely dry terrestrial nature thus termed as hydrophones mesophytes and xerophytes respectively.
Who are osmoregulators?
In the animals whose body fluid concentrations differs noticeably with outside environment actively regulate to discharge excess water hypotonic and excrete salts in hypertonic conditions therefore are called as osmoregulators. Examples:freshwater,invertebrates,frogs,fishes etc.
What is ebony?
It is a tree that deposit strange chemicals in branches and trunk,especially in old xylem,which is no longer used for water transport.Ebony produces very black wood in the center.
What is protonephridium?
A protonephridium is a network of closed tubules without internal openings in Planaria.
What is the difference between the excretory system of insects and other animals?
Insects are the only group of the animals who eliminate excretory wastes with faces otherwise in all others there is no structural and functional relationship between nutritive and excretory systems.
Which technique is used for the removal of kidney stones?
The kidney stones have been removed by kidney surgery. Presently lithosphere is used for the non-surgical removal of kidney stone. It is a technique used to break up stones that form in the kidney ureter or gall bladder.
What is haemodialysis?
In haemodialysis blood is circulated through a dialyzer called an artificial kidney.Dialyzer has two spaces separated by thin membrane.Blood passes from one side of the membrane and dialysis fluid in the in the other.The wastes and excess water pass from the blood through then membrane into the dialysis fluid.
What are heterotherms?
Heterotherms is of those animals that are capable of varying degrees of endothermic heat production but generally do not regulate their body temperature within the narrow range e,g.bats humming bird etc.
What are pyrogens?Or what is pyrexia?
In bacteria and viral infections mainly leukocytes increase in number.These pathogens and the blood cells produce chemicals called as pyrogens. Pyrogens displace the set point of hypothalamus above normal point of 37ᵒC.
Name the excretory structures in animal kingdom that are associated with digestive tract?
Malpighian tubules.
Define Excretion?
The mechanism which eliminates nitrogenous waste is referred to as excretion.
Define Thermoregulation?
The thermoregulation of internal temperature within a tolerable range is designated as thermoregulation.
What is Hypotonic environment?
When external environment has more water or diluted solution compared to the cell concentration,it is designated as hypotonic environment.
.What is Hypertonic environment?
When there is more concentrated external environment or solution than cell concentration it is termed as hypertonic environment.
What is Isotonic environment?
When external solution resembles to internal solution it is known as isotonic environment.
What are Hydrophytes?
Hydrophytes have the adaptations to remove the flooding of its cells in fresh water.In this type the surface area of leaves is very large to transpire water excessively.Extensive stomata are present on the upper surface facing the atomosphere to promote loss of water.
What are Mesophytes?
Mesophytes have moderate water availability.In sufficient supply of water stomata are kept open to promote loss of excess water,however,in restricted supply stomata close to prevent the loss.
What are Xerophytes?
Xerophytes have the adaptations for reduced rate of transpiration.Many possess small thick leaves.Their cuticle is thick waxy and leathery.Stomata are on lower surface of leaves and located in depression.In rainy season stores water for use in dry conditions.e.g cactus.
What are Osmoconformers?
Animal body fluids are kept isotonic to the external environment even for marine saltwater environment.These animals thus do not require actively to adjust their internal osmotic state.so are known as osmoconformers.Examples marine invertebrates  hagfishes,bony fishes.
Define Anhydrobiosis?
Terrestrial animals can tolerate dehydration and it differs in various animals.This characteristic is known as anhydrobiosis.
What is excretion?
The removal of nitrogenous wastes from the body is called excretion or the elimination of wasteful metabolites.mainly of the nitrogenous nature is called as excretion.
What are excretophore?
The falling of yellow leaves in autumn is the seasonal time for the plants to get rid of the accumulated wastes and because of this reason leaves are said to be excretophore.
In what form nitrogen is excreted by animals?
Mostly excess nitrogen is excreted by animals as ammonia urea or uric acid.Lower quantities of nitrogen are excreted in the form of creatinine creatine or trimethylamine oxide and in very small quantities as amino acids purine and pyrimidine.
What are ammonotelic ureotelic and uricotelic?
Animals excreting ammonia urea and uric acid are called as ammonotelic ureotelic and uricotelic respectively.
What are flame cells?
Tubular system is spread through out the body and branches are capped by a cellular setup termed as flame cell.Each flame cell has tuft of cilia whose beating propel interstitial fluid into the tubular system.
What are nephridiopores?
The tubular system is drained into excretory ducts,which open to the exterior through several nephridiopores.
What is metanephridium?
Earthworm is the ideal example of tubular excretory system called as metanephridium.This system has an internal ciliated opening nephrostome which is immersed in coelomic fluid and enveloped by a network of capillaries.Nephrostome collectes coelomic fluid.
What are malpighian tubules?
Terrestrial arthropods particularly in the insects the excretory structures are adapted to collect excretory products from haemolymph in sinuses through suspended tubular structures called malpighian tubules.
31.What is nephron?
The basic functional structure in the kidneys is nephron.
32.What are metabolic wastes?
The generation of wastes is primarily done at metabolic level and these are called metabolic wastes.These include urea creatinine uric acid bilirubin and toxins.
33.What is bilirubin?
The end products of haemoglobin breakdown and metabolites of various hormones is called bilirubin.
34.What is urea cycle?
The metabolic pathways involved in the production of urea are termed as urea cycle.Two ammonia and one carbon dioxide molecules are shunted into the cycle to generate one molecule of urea.
35.What is ureter?
Urine leaves the kidney through a duct ureter.The ureters of both tube called the ureters which empties near the vagina in females or through the penis in males.
36.What is ureter?
Urine leaves the body during urination from the bladder through a tube called the urethra which empties near the vagina in females or through the penis in males.
37.What are cortical nephrons?
The nephrons arranged along the cortex are called cortical nephrons.
38.What are Juxtamedullary nephrons?
The nephrons arranged along the border of cortex and medulla with their tubular system looping deep in inner medulla are juxtamedullary nephrons.These are specifically important in the production of concentrated urine.
39.What is Bowman’s capsule?
In each nephron inner end forms a cup-shaped swelling called Bowman’s capsule which surrounds glomerulus.
40.What is Glomerulus?
Bowman’s capsule is around a ball of capillaries called hlomerulus.Glomerulus circulates blood through capsule as it arrives through afferent arteriole and leaves the capsule by efferent arteriole.
41.What are peritubular capillaries?
The blood vessel arising from glomerulus subdivides again into another network of capillaries called the peritubular capillaries.
42.What is vasa recta?
In juxtamedullary nephrons additional capillaries extend down from a loop of vessels vasa rect.
43.What is glomerular filterate?
The filtrate appearing in glomerulus is called as glomerular filtrate which contains numerous useful substances such as glucose amino acids salts etc in aqueous solution.
44.What is counter-current multiplier?
This mechanism causes gradual osmotic outflow of water from the filtrate back to kidney as it passes downward in the descending loop of Henle.The ascending loop of Henle does not allow outflow of water from its filtrate instead actively transport Na+ into kidney interstitium to sustain its high concentration.
45.What is the role of aldosterone and antidiuretic hormones in kidney?
The active uptake of sodium in the ascending limb or thick loop of Henle is promoted by the action of ladosterone.Antidiuretric hormone (ADH) released from posterior pituitary act to actively transport water from filtrate to kidney’s interstitum.
46.What are hypercalcemia and hyperoxaluria?
Hypercalcemia is high level of circulating calcium in blood while Hyperoxalria is higher blood level of oxalates.Both are contributing factor in the formation of kidney stones.
47.What is the percentage of incidence of different types of stones?
The incidence of calcium oxalate types is 70% of all the kidney stones.The incidence of other types of stones of calcium phosphate and of uric acid is 15% and 10% respectively.These salts are precipitated out during urine formation and accumulate later to form stone.
48.What is the most common way of lithotripsy?
The most common way of lithotripsy is extracorporeal shock wave lithortripsy.High concentrations of X-ray or ultrasound are directed from a machine outside the body to the stone inside.The shock waves break the stone in tiny pieces or into sand which are passed out of the body in urine.
49.What is Dialysis?
In chronic renal failure dialysis is used to clean the blood either by passing it through an artificial kidney or by filtering it within abdomen.The wastes and excess water are removed during the treatment as being done by the healthy kidneys.
50.Name different types of dialysis
There are two types of dialysis haemodialysis and peritoneal dialysis.

Define homeostasis.

The protection of the internal environment of the organism from the harms of fluctuations in external environment is termed as homeostasis.

Which of the components of the internal environment of an organism may be affected by fluctuations in the external environment?

These are water, solutes and temperature.

What is osmoregulation?

Osmoregulation is the phenomenon of maintenance of the balance of water and salts within the body of an animal.

Give an exact definition of excretion?

The removal from the body of the waste products or other substances which are not needed is known as excretion.

What is the nature of the metabolic waste materials in plants and in animals?

The metabolic waste materials in plants are carbon dioxide and surplus water and in animals those are carbon dioxide, surplus water and nitrogenous compounds which may be ammonia, urea or uric acid.

Explain thermoregulation?

The ability of an organism to maintain its internal body temperature within a tolerable range is called thermoregulation. It includes morphological, physiological or behavioral adaptations within limits necessary for its survival.

Write down the names of the components of the living control system in animals meant for homeostatic regulations.

The components are the receptor, the control center and the effectors.

What do hypotonic, hypertonic and isotonic environment mean for a cell?

A hypotonic environment for a cell means the presence of a solution around it which is weaker than the cell concentration; hypertonic environment has a more concentrated solution; and the isotonic environment has a solution of the same strength as the cell solution itself.

What will happen if a living cell is surrounded by a hypotonic solution (weaker than the cell solution)?

The water will enter the cell by osmosis rendering it turgid.

What is the effect of hypertonic (solution) environment on a living cell?

The cell solution will get concentrated and the cell will shrink due to loss of water by osmosis.

What are hydrophytes? What are their important adaptations?

The hydrophytes (aquatic plants) are the plants which grow in water or in very wet places. The surface area of their leaves in very large so as to transpire water excessively. A large number of stomata are present on the upper surfaces of the floating or above water leaves in order to promote water loss.

Describe xerophytes and their adaptations?

The xerophytes are plants that grow in very dry places where the supply of water is limited and the environmental conditions favour a high rate of transpiration. These plants need to minimize rate of transpiration and for this purpose they show many adaptations such as small, thick loaves covered by a thick, waxy and leathery cuticle. Stomata are situated on the lower surface of the leaves.

Define mesophytes?

The mesophytes are the ordinary land plants which grow in an environment having average conditions of temperature and moisture.

What are osmoconformers, as animals? Quote examples.

In some of the animals the concentration of their body fluids follows change in the concentration of the environmental fluids e.g., both the internal and external environments of the animals are kept isotonic. Such animals exhibit little or no osmoregulation and are known as osmoconformers. Most marine invertebrates and hagfishes are the examples.

How do cartilaginous fishes maintain lower internal salt concentration than sea water?

The kidneys of the cartilaginous fishes excrete surplus salt through the gills and they also possess salt excretory organs called as rectal glands. These fishes lose salt by active transport.

What is the name of the chemical which is retained by some marine cartilaginous fishes the protection against urea?

The chemical is the trim ethylamine oxide.

What role has osmoregulation played in the distribution of plants and animals?

Osmoregulation has enabled the animals and plants to distribute themselves in wide range of habitats.

Name the structures of fresh water protozoans which are meant for osmoregulation?

These structures are the contractile vacuoles.

How do many fresh water animals including fishes remove excess water from the body?

These animals do so by producing large amounts of very dilute urine.

How do some desert mammals like kangaroo rat survive without drinking water?

These animals feed on seeds containing more carbohydrates that yield enough water during metabolism which is utilized internally by the animals.

Define anhydrobiosis with an example.

The characteristic of terrestrial animals to tolerate dehydration to varying extents is known as anhydrobiosis. The example is a group of tiny invertebrates, the Tardigrades.

Why are leaves said to be excretophores?

The falling of yellow leaves in autumn is the seasonal time for plants to get rid of the accumulated wastes and because of this reason, leaves are said to be excretophores.

Explain deamination?

The removal of amino group (N11₂) from an amino acid and loading to the formation of ammonia is called deamination.

In which forms in animals is excreted low quantity or very small quantity of nitrogen?

Low quantities of nitrogen are excreted in the form of creatinine, creating are Trim ethylamine oxide whereas very small quantities as amino acids, purine and pyrimidine.

Write down the names of the nitrogenous wastes produced in the animals from the metabolism of purines and pyrimidine’s?

These are hypoxanthine, xanthine, uric acid, allantoin, urea and ammonia.

In which animals is ammonia excreted as the chief nitrogenous waste?

Ammonia is excreted as the chief nitrogenous waste only in those animals which have a highly hypotonic internal environment, so that the ammonia concentration is kept low in view of its great toxicity.

How much water is needed to excrete one gram of ammonia nitrogen, one gram of urea nitrogen and one gram of uric acid nitrogen?

The volume of water needed is 500 ml, 50 ml and one ml, respectively.

Which groups of animals excrete nitrogenous waste in the form of uric acid?

These groups of animals are reptiles, birds and insects.

What are ammonia excreting, urea excreting and uric acid excreting animals and the processes called as?

The animals are called as ammonotelic, ureotelic and uricotelic, respectively and the processes as ammonotely, ureotely and uricotely.

Which one of the nitrogenous wastes is the most toxic?

Of the nitrogenous wastes, ammonia is the most toxic.


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  1. Kidney stones are removed by the method of lithotripsy, not by lithosphere. The lithosphere is a type of ecosystem. Please, correct.

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