81.34 ,/ CBSE Science Self-hrtor-X/

Q./ Wnirh chemical reactions cffe necessary to prod,uce energy rich compound,s?

Ifis. Oxidising-reducing reactions are the most common reactions which causebreakdown of food to produce energy rich compounds. Oxygen obtained fromoyaiside the body is used for sueh reactions.,/

Q./Wn, do unicellular organisms not require specific organs for taking in food,/ exchange of gases, transport of substances and, remoual of wastes?

Ans. Since, the entire surface of unicellular organisms remains in contact with theenvironiaent, specifrc organs for these functions are not required. Their general body

,surface helps in procurement of food, exchange of gases and removal of waste.

-Q75. Wich process helps in producing carbon-based food? Which source of energy isutilised to produce food.? Name the organisms which are inuolued in the process.

Ans. The process is known as photosynthesis" Solar energy is utilised in convertingCO2 and water into the form of carbon-based food like carbohydrates by greenplants, r..e., autotrophs.

Q. 6. Do all organisms fulfil requirement of food in the same way?

Ans. Plants use inorganic substances like carbon dioxide and water to produce foodand other substances. Other organisms like animals take complex food moleculesfrom plants or animal sources and break them into simpler substances so thatthey are absorbed easily.

Q. 7. Giue examples of parasitic organisms.

Ans. Cuscula, orchids, ticks, mosquitoes, leeches, tapeworm and lice.

Q. 8. flou.r d.oes Paramecium obtain food?Ans. Poromecium is a unicellular organism with a definite slipper-shaped body. The

fiodis taken from a specific point called the oral groove. Cilia are present all over

/ t}l,e surface of the body which direct food towards the oral groove.

{5. Carbon d.ioxid.e is consid.ered, essential for photosynthesis. How d,o the aquaticgreen plants obtain it?

An7 Carbon dioxide remains dissolved in water, which is directly absorbed by the

/ aquatic green plants.

,Q..tO. Tlace the path of food in human alimentary canal.Ans. Buccal cavity -+ oesophagus -t stomach -+ small intestine -+ large intestine

-) anus.

Lif'

6

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g/'- Ans.

4. rr.Ans.

what is the mode of nutrition in fungi like bread, mould,s, yeast and mushroom,s?The mode of nutrition in these organisms is that they obtain nutrients from thedead and decaying organic matter by breaking them into simpler substances andthen absorbing the digested food. This mode of nutrition is called saprophyticnutrition-What would be the effect if all the green plants u)ere to disappear front. the earth?Green plants are the only producers of food and oxygen. No living organism wouidsurvive as food is needed to be oxidised by oxygen to obtain energy.What are the sources of energy aua,ilable for organisnts?Food is the main source of energy available to living organisms. Plants use solarenergy to produce food. This food is eaten by animals to obtain energT.

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Q' 19' Hout ma,ny types of substances are released. by the gastricSland.s of stomach of ahuman being? What do they form collectiuely? _/Ans' Three types of substances are released by the gastrie giands present in th.e wallsof a human stomach. They secrete (r) hydrochloric acid, (ir) digestive enzyme

), called pepsin, and (iir) mucus, all of which collectively form gastric juice.O la. zd) wnat is the function of pclnrreas?

\ *#" Pancreas secretes digestive enzymes: ,_-'

Lr,fe Processes ,a,/ 81'35

{A. uJar* {intur*ed,iate compound. produced. d,uring night in desert plants? How is it'"-*J changed to food during day?

Ans' Desert plants absorb CO2 during night and fix it in an intermediate compoundknown as malic acid. During d.ay, the solar energ:y absorbed by chlorophylr*$>{urcs he}ps in changing the intermediate compound into food.

Q. 15. ffh,y d.o heterotrophic organisms d,epend. for food, on autotrophs?Ans' Heterotrophic organisms cannot prepare their own food and thus depend on

autotrophs, which are also known as producers. The only food "rr"il"bl. to

herbivores are plants and plant parts. The carnivores, in turn, feed. on herbivores*- and other carnivores for their fo,:d.r7l

Q. to. jlo* is oxygen prodyred d.uring photosynthesis? What happens to the oxygen thus-Jproduced,? ,/Ans" Water splits during photosynthesis into hydrogen and oxygen. Whi1e hydrogen is

needed for reducing carbon dioxide, oxygen escapes into the atmosphere to beutilised by the living organisms to produce energv.

Q' 17' Wy are uariegated legtvs chosen to proue that chlorophyu is necessary forphotosynthesis? -/Ans. Variegated leaves show two regions, one green region containing chlorophyll, and

the other nor,-gry)n region that does not contain chlorophyll.Q. 18. why do plants'fequire minerars rike nitrogen, phosphorus, iron and, m,agnesium?Ans' These are required to produce proteins and other chemical substances needed by

plants. These are components of cells and enzymes.

(i) Trypsin digests proteins into small molecules mad.e up of a few amino acids.(il) Amylase digests starch into sugars.(iii) Lipase digests fats into fatty acids and glycerol.wich d'igestiue glands help in d,igestion though food, neuer enters tbem?The glands are liver, pancreas and salivary glands. -.'

q,.22.

Ans.

Wy is assimilation of food essential?

Assimilation or utilisation of food is essential for building up processes, properfunctioning of life by producing useful materials, for ryit of worn out parts, andfor obtaining energy.

_/-

81.36

,d rr.'/ Ans.

CBSE Science Self-futor-X

Wh,at is the role of intestinal ju,ice secreted, by intestinat gland,s?

In the small intestine. the intestinai juice completes the digestion of proteins intoamino acids, carbohydrates into glucose and fats into fatty acids and glycerol.What are the end products of digestion of carbohydrates, fo,ts and proteins?

(i) Carbohydrates --+ glucose.

Fats -r fatty acids and glycerol.

Proteins -+ amino acids"

[aw d,o stomata aperu and clase?

Wheruryrater flows into guard cells, they swell up and thus open the stornata.the stomata.phen the guard cells lose water, they shrink and close

'ow does ruitrogen enter the plant?(i) Roots absorb nitrogen in the form of nitrates or nitrites.

t fii) Bacteria use atmospheric nitrogen (Nr), incorporating it in organic

/ compounds:

tA.rr. Nonte the enzymes for protein digesti,on present in the gastri.c; pancreo,ti.c a,nd,

Ans.

intestinal juices, the substra,te they digest, and the products of their action.

Juice Enzym,e Substrate Produ.ct

(i) Gastric juice

(ri) Pancreatii juicr(iii) Intestinal juice

Pepsin

TrypsinErepsin

Protein

ProteinContain very fewamino acids (peptidesand peptones)

Small molecules madeup of a few amino acids(peptones)PeptidesAmino acids

Where does exchange of gases occwr in plants?Massive exchange of gases occurs through stomata present on leaves during theproces$- of photosynthesis. Exchange of gases also occurs through the surface ofstems and roots"

Define parasitic nutrition. What are these organisms known as?

The mode of nutrition in which an organism obtains food synthesised by the otherorganism, called host, is termed, parasitic nutrition and the organisms exhibitingthis mode of nutrition are called parasites.Hout does the food moue in a regulated me,rLner along the d,igestiue tract?Small regulated amounts of food should move, so that food is properly p*oc"""edin the various parts of the digestive tract. The muscular sphincter present at thejunction of the stomach and the small intestine allows only small amount of food

i-jubstances are broken down into simpler substances here. The digested fooddffuses lnto the cytoplasm and is assimilated. The undigested food is thrown outthrr-,ugh the cell surface"

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Life Processes ,a. B1.B?z-"F*q */

{, {ir" $* ao ii" orgrn, of alimerutary canal help in thte forwarcl mouement of food?#n"walls of the organs of the alimentary canal like small andlarge intestine are

81.37

muscular in nature which contract rhythmically to push fbod forward bypylstaltic movements.

ss""fih.y is photosynthesis regarded, as the sole mechanism for the conuersion af solar

Ans"

energy into oth,er suitable forms of energy?

This is the oniy process where the chlorophyll molecules present in the leaves canconveri solar energy to chemical energy which is stored in the food molecules.The food thus produced is utilised by aII organisms in one way or the other. Noop* o,*sanism can perform this process as they do not contain chlorophyll.

"When d.o planrs clo,se stomata?

when the plants do not use carbon dioxide the stomata is closed, i.e.. at nightwhen photosynthesis does not occur. In d.esert plants, the carbon dioxide rs takenat nieht. thus in such plants stcmata is open at night"

(Q" ar' lLook at the figure giuen below" What euents haue occurred. in them? Expktirt.

Guard cells

Stomatal pore

Chloroplast

Fig. 1.5: Open and close stomata

Ans' Fig. 1.5 (o) depicts an open stomata. It shows the gaseoqs cxcha,ge betweeri C(.r,and 02, and the process of photosynthesis is taking piace. since. guard. ceilscontain glucose it has absorbed water from the surrounding epidermal ceils 4ueto which the stomata open.

Fig. 1-5 (b) depicts closed stomata which shows that exchange of gascs andphotosynthesis do not occur. Since, glucose is not present waier co,ce,t'ationdecreases and the stomata close.

Q. 36. Wat are gill slits and in which process d,o they help?

Ans. Gill slits are openings of gilrs to the outside and arerespiratior in fishes.

istaltic movements.

a.

Q.34.

Ans.

(a) (b)

meant for the process of

CBSE Science Self-Tutor_X

between anaerobic respiration in yeast and, in muscles-

Life Prol,

between erternal and internal respiration,

rnal

muscles causes cram

Cellular respiration is the oxidation

$ e.4G.Ans.

q.47.Ans.

Q.48.Ans.

Q.4e.

Ans.

,Q.',rii.Ans.

Q. 51.

Ans.

Q.52.

Ans.

Q.53.Ans.

Q. 54.

Ans.

dioxide, through the respiratory organs,into the surroundins mcdirrm

are red blood, corpuscles consid,ered, the best transporters of oxygeru?

1:=1Pt:,:*:11yctes contain a pigment calted haemoglobin. Haemoglobin hasgreat affinitv for oxygen. It combines with oxygen to be-carrie;;;;il"

"tJffiffi"body.

Breathing is intake of atmosphericErich in oxygen, and release oicarbon ofstored food to release energy in

the presence or absence ofoxygeninside the cell.

Q. 40. How is carbon d,ioxid.e transported. in the human bod,y?Ans' carbon dioxide is more soluble in water. Hence, it is transported. in a dissolved_- --fqrm in the plasma of the blood.z---. I

'4 +t' )that path is taken by air when. it tra,uels from the nostrils to the lungs in thel,/hurnan beings?

Ans' Air from the nostrils reaches the alveoli in lungs by taking the following paththrough the various organs:

(@:::";:::':";;r'tr#;:;;:T;::;:::;n::::;:es+a've.'i\-AEil6' The air enters and fills the alveoli and. increases the oxygen concentration in thealveoli, than.the- surrounding brood capillaries. Ti;;";;;;;;;;;;;iffuse intothe blood-' The blood capillaries havJ more

"."bo, dioxide concentration thanalveoli- Therefore, carbon dioxide from the capillaries diffuses into the alveoli.(t Q' 43' Is concentration of carbon d.ioxid,e in the enuironment more d,uring night or d,o,y?Ans' During the night, plants respire and produce carbon dioxide which is not utiiisedby them, as photosynthesis does not occur due to the absence oflight, thus oxygenis not produced' Therefore, carbon dioxide concentration is more during the night" as compared to the day.q. 44. How is the energy released, d.uring respiration?Ans' Energy is released in steps d'uring respiration, so that the temperature of the cellsdoes not rise' very little amount of energy is'lost as heat during this process.

$ Q' 45' Haw is oxygen carried, to the-tissues, consid,ering that d,iffusion pressure is notsufficient to carry olcygen to d,ifferent parts oy tn"'6o417Ans' Diffusion pressure is not sufficient to carry oxygen to different parts of the body"The respiratory pigment, haemoglobin, is efficle"nt to carry oxygen to the differentparts of the body.

Life Processes

Ans.

Q.50.Ans"

81.39

Q' 46' Why does aerobic respiration prod,uce ntore energy than anaerobic respiration?Ans' During aerobic respiration, there is complete oxidation of glucose .molecules"

Therefore, large amount of energy is released whereas in ana-erobic respiration.glucose is only partially oxidised, releasing little amount c( energy.

q. 47. How does the breathing process help us?Ans' ' It provides oxygen for aerobic respiraiion in the cells to produce energy.

' It excretes out toxic carbon dioxide along with excess of water vapour fromthe body.

Q. 48. Name the respiratory orgarus of (i) fish and, (ii) dog.Ans. (i) Fish : Gilts

(ii) Dog : LungsQ' ag' Wat are the characteristics of root cells which remain in close conto,ct with soil forabsorption of water and for exchange of gases?

The root cells are very thin and extend to become elongated, thus increasing theirsurface area. The root cells remain in contact with oxygen and water, *rri.tmakes them more suitable for exchange of gases ana for a'bsorption of water.Describe the diaphragm.A diaphragm is a muscular partition separating thoracic cavity from theabdominal cavity. It helps in the process of inhalation and exhalation. Whenmuscles of diaphragm, along with rib muscles contract, the volume of the thoraciccavity increases. As a result, air rushes in. When their muscles relax. the volumedecreases and air moves out.

Q. 51. what are the respiratory structures and, their role in flowering plant?Ans' The main respiratory structures in a flowering plant are stomata present on the

leaves. Stomata are small openings, present o" Uott the surfaces of the leave*q.Oxygen Tovef into stomata by diffusion. This oxygen is absorbed by the leaf cells.Carbon dioxide has more concentration in tissue-spaces than the surroundings.When no photosynthesis occurs, carbon dioxide diffuses out through the stomata.

Q' 52. Differentiate between aerobes and, aruaerobes. Giue examples of the two types oforganisms.

Ans' Aerobes are the organisms which utilise oxygen and undergo aerohic respiration"Examples of aerobes are green plants and animals. In contrast, anaerobesperform anaerobic respiration without utilising oxygen, as in yeast and somebacteri.a.

6 Q. 5s. what is the ad.uantage of ruose breathing ouer mouth breathing?Ans' The air passes directly from the-mouth to the pharynx during mouth breathrng

while, during nose breathing, the air passes ihrough nasal lassages and getsfiltered, warmed up and moistened because of the presence of mucus *hich trapsdirt and foreign objects.

Q. 54" Explairu exchange of gases through stomata.Ans. ' The gases which diffuse in or out are carbon dioxide and oxygen.

' Large intercellular spaces in the leaf are full of air and all the cells remarn rndirect contact with the air.

' Environmental conditions decide the dilection of diffusion of these gases.

B1.40 CBSE Science Self-Tutor-X

$ Q. 55. What will happen to aquatic animals if there is oil spilt in tlrc ocean?Ans. OiI spill spreads on the surface of water in the ocean, which d.oes not allow oxygen

to enter and get dissolved in water. Aquatic animals will die in such cond.itrons asno oxygen will be available to them.

Ans.

Q"57.Ans.

Q.58.

Life Proce

p

d

(, Q. 56. Food. and. oxcygeru, both are necessary for life. Will man be able to suruiue withoutfood and oxygen? Why?

Man can survive without food for a few days as the stored food molecules can beoxidised to give energy. But without oxygen, energy rich compound ATp cannotbe produced and energy will not be available to carry on the life processes.How are minerals and water absorbed by the roots in the plants?The cells of the roots remain in contact with soil and take ions actively" A differenceis created in the concentration of ions between the root cells and the soil. So waterfrom the soil moves into the root cells and reaches the xylem vessels.Does food, enter the uarious plant parts accord,ing to their need,s? Giue one exampleto proue it.

Ans. Food enters the various parts of the plant according to their requirements. Forexample, the food is transferred to the buds in the spring season. Buds need foodto get energ'y to grciw.

Q. 59. Name the cells which are present along with the sieue tubes in the phloem tissue.Are they liuing cells?

Ans. The companion cells are present along with sieve tubes. The cells contain cytoplasmand nucletis and therefore they are living cells and help in the conduction of food.

Q. 60. How do water and, minerals from the roots enter the leaues?Ans. Xylem vessels are placed one above the other, forming long channels from the

roots to the leaves. Xylem of the roots remains in direct contact with that of thestem, branches, petioles ofthe leaves and other parts ofthe plant. So, through thexylem, the water from the roots enter the leaves.

Q. 61. Wa,t is blood,? What are its components?Ans. Blood is a fluid connective tissue. Its matrix, also known as plasrna, contains the

foliowing cell components-red blood corpuscles, white blood corpusclesand platelets. Plasma transports dissolved organic and inorganic substances likefood, carbon dioxide and nitrogenous wastes.

Q" 62. Wat is haemoglobin and what function d,oes it perform?Ans. Haemoglobin is a red-coloured respiratory pigment, present in the RBCs of the

blood. It carries oxygen from the lungs to tissues and brings carbon dioxide fromthe tissues to lungs.

Q. 63. How does blood come back to the heart from different parts of the bod,y?Ans. Oxygenated blood from the lungs comes to the left atrium through the pulmonary

veins and deoxygenated blood from different parts ofthe body comes Lack to theright atrium throu5;h the superior and inferior venae cavae"

Q" 64. which euents occur in the capillaries present in the tissues?Ans. Capillaries are the ultimate branches of the arteries. These are one cell thick. The

exchange ofgases occurs between the cells ofthe tissues and the capillaries by the

Q.65. .r

u

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tr

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ab

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Life Pracesses

process of diffusion. Oxygen diffuses into thedioxide enters the blood capillaries.Is the pressure deueloped, du,e to d,ifference in con centration, of ions enough to p*shwater up in tall trees?

The pressure so developed is not enough to push water up in the tall trees. Thetranspiration pull, created by the ioss of water, helps to push water up in tall trees.\Ih.at are blood platelets? Wat function do they perforru?tslood platelets are suspended in the plasma of the blood. whenever an injury o*a leah in a blood vessel occurs, the bleeding must stop. To minimise the losc ofblood the plateiets circulating in the brood plug the leakage by forrning a clot.\44r,y sh"ould bieeding or leahage af btood. be stopped,?Bleeding should stop for the following reasons:

' Loss of biood should be minirnised so that the amount of nutrients and. oxygenshould not decrease in our body.

' Loss of blood from blood vessels wil reduce the efficiency of the pumping sysrem.Describe the structure of capillari,es. IW,at function d.a th,ey perform?capillaries are one cell thick. Being extremely thin, the exchange of gases, foodmaterials and wastes takes place easily through them.

Q' 69' llhat are the wastes prod,u,ced d,urirug metabolic actiuities? Ifaut are these u;a.stestro,n sported?

Ans' Carhon dioxide and nitrogenous wastes are produced. These are transported in adissolved form irr the plasrna.

Q' 70. Mett"tian the etsents accurring in the lelt sid,e of the heart when blood, is poured intrtthe left atrium by th,e pulmonary uein,s.

Ans" When cxygenated blood is brought by the pr.rlmonary veins frona the lungs tr-r 1,1ieIeft atri um, the left atrium and left ventricle are in a relaxed conditron. lVhen theleft atrium contracts, blood is pushed into the left ventricle, which expands toreceive Lrlood.

Wat is blaod pressure?

'Ihe pressure exerted by blc,od against the waII of the vessej. is called bloodpressure" The presstrre of blood in the arteries is mucir greater than in the vei's"What are systolic and diq,stolic blood, pressures?The blood pressure in the arteries during ventricular systole, i.e., cturi*gcontraction of ventricles is called systolic blood pressure. The blood p*.**"u"!rn the arteries during ventricular cli.astole, i.e., d.uring relaxation of ventricLes iscalled diastolic blood pressure.What is high blood pressure?

High blood pressure or hypertension is caused. by the consLriction ofthe arterieswhich causes resistance to biood flow. Hypertension can rupture an artery, Iearlingto incernai bleeding.

8i.41

cells of the tissues and carbon

6

6

Q. 65.

Ans.

Q. 66.

Ans"

Q. 67.

Ans.

Q.68"Ans.

Q. 71.

Ans.

q.72.Ans.

81.42 CBSE Science Self-Tutor-X

q. 7 4. Wat happens in the right sid.e of the heart when d,eoxygenated blood, is brought tothe right atriurn by the two uenae cauae?

Ans. When the two venae cavae bring deoxygenated blood to the right atrium, itremains relaxed and the blood pours into it. The ventricle also remains in arelaxed condition. Once the right atrium contracts, the right ventricle expand.s toreceive deoxygenated blood. When the right ventricle contracts, blood is pushedinto the pulmonary arteries to carry it to the lungs for oxygenation.

Q. 75. Why are energy need,s low in, plants?

Ans. Energy needs in plants are low because

(i) plants do not move so energy is not required.(zr.) plants contain large proportion of dead cells, which reduce the use of energy.

Q. 76. How do unicellular organisms remoue nitrogenous waste?

Ans. Many unicellular organisms remove the nitrogenous waste from the body surface,into the surrounding environment, by diffusion.

q. 77. What is excretion?

Ans. Excretion is a process by which metabolic wastes are removed from the body andan osmotic balance is maintained by controlling the water content and saltamount of the body fluid.

Q. 78. State two uital functions of kidrueys.

Ans. (i) Kidneys remove toxic wastes from the body.

(ii) They control water balance and levels of minerals in the body.

Q. 79. Where a.re the kidneys located in our body? How are they protected?

Ans.-Kidneys are located in the abdominal cavity, one on either side of the vertebralcolumn. They are protected by the ribs.

Q. 80. What are the major parts of the human excretory system?

Ans. Kidneys, ureters, urinary bladder and urethra.

Q. 81. What are the major nitrogenous waste products in hwrnan beings? How are theseremoued frorn the body?

Ans. urea and uric acid are the major nitrogenous waste products in human beings.These are removed by the nephrons as urine by the process of filtration of blood.The urine is collected in the kidneys, is carried by the ureters, and collected in theurinary bladder to be released outside the body.

Differentiate between ureter and, urethra,.Q.82.Ans.

Ureter is the duct which passes urinefrom the kidneys to the urinarybladder.

Ureter Urethra

Urethra is the muscular tubethrough which the urine is releasedto the exterior from the urinarybladder.

Life Processes

Q.83. How isAns. A braac

very fi-n

Q. 84. How hhigh or

Ans. Kidneystissues ikidneys

Q. AA. Wat isAns. The Bor

Produce,The uri:Bowmarnephron

Q. 86. Wy is u

Ans. Human.to maint

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Ans. Several I

. failure. I(, e. 88. wy is tt

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salts frorQ. Ag. Wat slxAns. In case o

device wprocess it

Q. 90. Write a s,

Ans. Urinary. through t

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Life Processes Bl.4B

Q. 83. How is glomerulus formed?Ans. A branch of renal artery enters the Bowman's capsule and divides profusely into

very fine capillaries. This structure is called glomerulus.Q' 84. How do kidneys maintain the water balance when water conterut in the bod,y is

high or low?Ans. Kidneys excrete more dilute urine when the water content is more in the body

tissues and blood, and excrete more concentrated urine when water is less. Thus,kidneys maintain a water balance in our body.

Q. 85. What is the function of Bowman's capsule? Explain.Ans. The Bowman's capsule contains glomerulus, which is a cluster of capillaries

produced by the renal artery. In glomerulus, blood is filtered and urine is formed..The urine contains important substances like glucose, amino acids and salts.Bowman's capsule receives this filtrate which enters the tubular part of thenephron.

Q. 86. wy is water reabsorbed by the excretory system of human beings?Ans. Human beings take less amount of water. So, water is reabsorbed to conserve it

to maintain the osmotic balance of blood.

Q. 87. How d.oes kidney failure occur?Ans. Several factors like infections, injury or restricted blood flow may cause kidney

failure. Since kidneys are vital organs, their failure may lead to death also.It Q. 88. Wy is the tubular part of the nephron surrcwnd,ed, by blood, capillaries?

Ans. Blood capillaries reabsorb useful substances like glucose, amino acids, water andsalts from the tubular part ofthe nephron.

Q. 89. Wat should be done when kidney failure occurs?Ans. In case of kidney failure, an artificial kidney may be used. Artificial kidney is a

device which helps in removing the nitrogenous wastes from the blood. Thisprocess is known as dialysis.

Q.e0.Ans.

Write a short note on the urinary blad.d.er.

Urinary bladder is a muscular structure. It receives urine from the kidneys)- through two ureters which is stored in it. It is under the nervous control.O Q. 91. what strategy is ad.opted, by the plants to remoue the wastes?

Ans. Plants use different ways to get rid of waste materials. Carbon dioxide and oxygenare removed through stomata, excess water escapes as water vapour. Other wastematerials may be stored in the vacuoles. Gums and resins may be removed in thefalling leaves or waste may be excreted out into the surrounding soil.

Q- l. why are processes like intake of food,, exchange of gases, remoual of wastes notpossible through the general surface when the bod,y size increases and, beconresrnore complex?

Ans. Multicellular bodies are more complex as they are mad.e up of a large number ofcells. Complexity increases with the increase in the size of the body. Cells are

81"44 CBSE Science Self-Tutor__X

organised in groups called tissues. All the cells can not be in direct contact withthe outside environment, and through diffusion, it will take a torrg li*" fo" *molecule to reach its place ofaction. Therefore, such processes, defrnite organisedsystems are necessary.

Q- 2. How d,o mu.lticellular orga,nis,nrs accomplish the uarious life processes?Ans' In multicellular organisms, there are various body parts or organs which are

specific in their functions. These organs have specialised tissues which aresuitabie for specific functions. Intake offood and oxygen from outside is also thefunction of specialised tissues. Intake of food ant digestion occurs in thealimentary canal while the intake of oxygen occurs through the rungs.

Q.3. Wh,at are maintenance processes?

Ans' Maintenance processes are the processes to perform various functions in theliving organisms. These are (i) nutrition, (ri) respiration, (ilr) transportation and(lu) excretion. For this, organisms need energy, *t l"f, is mad.e avaiLble from thefood obtained through the process of nutrition. Oxygen is taken in and the food isoxidised to provide energy. Oxidation-reduction p"o.u*."" help in producingessentral molecules needed for the- growth and development of the body. Tru.rspo"lof the molecules fuifils the needs of the actively growing cells of the body" Un*untudsubstances are excreted outside the body.

Q. 4. What is the importance of photosynthesis?Ans' ' Photosynthesis is the process of food production by green plants. They are known

as prirnary producers, as they provide food to alt living organisms.' Solar energy is trapped as chemical energy, which is stored in food molecules

only try the process of photosynthesis. This energy is then distributed to allliving organisms to sustain life.

'Photosynthesis is the only natural process during which carbon dioxideis taken in and life sustaining oxygen is released.. This helps in baiancing theconcentrations ofboth the gases.

6Co, + 6H2o ffilf, C6Hr2o6 + 6o2tQ. 5. Wh,y is the process of nutrition necessury for liuing organisms?Ans' Nutritron is necessary for living organisms because of the foilowing reasons:

' It provides substances which release energ-y needed to do work.. It helps rn the growth and development of the body.. It provides materials to repair worn out cells of the body.' It provides substances to the body which help to fight diseases.' It provid.es substances which regulate different body processes an4" maintains

life"

' Essential cellular products, such as enzymes, and other important substanceslike hormones are produced from the food molecules.

Q. 6. Differentiate between the following:(i) Parasitic and saprophytic ruutrition.(ii) Herbiuores and carniuores.

Life Processc

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(b) l1

Wabso,

. Vil

. vildig

. Bltpal

MafuQ. a.

Ans.

vb

O e.z"

Life Processes

Ans" (r)

Q.8.Ans.

res

animals which feed

. deer are

81"45

rasitic Nutrition ic Nutrition(o) Parasitic mode of nutrition involves Saprophytic nutrition is the mode ofobtaining food synthesised by other

organisms. known as host. Theorganism obtaining food is called aparasite. It lives in intimatecontact with the host.

(b) Holozoic nutrition, ingestive typetaken in solid state, and digestionis internal.

(c) Cuscuta, orchids, tapeworms,leeches, ticks and lice exhibit thismode of nutrition.

nutrition in which the organismobtains food from dead ancl decayingorganic matter"

(ii)

(o) Herbivores areon plants only.

(b) Rabbit, grasshopper andherbivores.

Absorptive nutrition, food obtainedin liquid state and digestron isexternal"Fungi and bacteria exhibit this modeof nutrition.

CarniuoresCarnivores are anrmals which feedon herbivores and other animals.

Waxy cuticle

Upper epidermis

Chloroplasts

Lower epidermis

Frog, hawk and tiger are carnivores.

6 e"7. wy are uilli, present in the inner lining of the smail intestine, most suitabLe fo,absorption of food?Ans. . Vilii are only one cell thick.

'villi increase surface area considerably, thus increasrng the absorption ofdigested food.Blood vessels present in them are meant to carry absorbed food to differentparts of the body.

Make a labelled sketch of a cross section of a teaf.

Air spaces

Guard cell

Fig. 1.6

81.46 C BSE Science Self-Tutor-X

Q.9. lWy is the leaf considered the most suitable plant organ for photosynthesis?

Ans. . Leaves are the site of photosynthesis. The palisade tissue present below theupper epidermis is made up of cells having chloroplasts. These cells obtaincarbon dioxide through stomata and water through xylem of the veins.

. Sunlight is absorbed by chlorophyll pigments of the chloroplasts.

. The solar energy is used to combine carbon dioxide and water in thechloroplasts, with the help of enzymes, to produce sugar. Sugar is stored in theform of starch. Oxygen produced during photosynthesis is released throughstomata into the atmosphere.

Q. f0. How do plants obtain food? Giue the equation for photosynthesis.

Ans. Green plants are autotrophs and synthesise their own food by the process ofphotosynthesis. It means synthesis offood in the presence of sunlight. It is a processin which plants use sunlight, chlorophyll, carbon dioxide and water to synthesisefood.

Life Proce

Q. 14. li

Ans. F

Q. 15.

Ans.

Q"17"Ans.

Q. 18. .r

Ans. Ip

Sl

e

a

a

Ii

a

6CO, + 12H2O Tffir C6H12O6 + 6O2t + 6H2O

Carbon dioxide Water Glucose Oxygen Water

v

tc.

va

a

Ia

S Q. ls.

Ans.

S Q. 11. Answer the following:(i) Which is the first simple m.olecule produced by photosynthesis?

(ii) What happens to these sintple molecules in the leaues later?

(iii) In which molecules, produced, during photosynthesis, is solar eruergy storedas chemical energy?

Ans. (i) Glucose is the first simple molecule prod.uced during photosynthesis"

(n) Giucose molecules combine to produce starch, which is stored in variousparts ofthe plant.

(iii) Solar energy is stored in the glucose molecules as chemical energy.

Q. 12. Mention. the action of enzymes which hetp in d,igestion of starch in the alimentarycanal.

Ans. In mouth ; starch salivarv am-r'hse , Maltose

Pancreatic juice : Starch Amvlase , sugar

In small intestine : Sugar ^".ffirk*

Glucose

Answer the following questions based on experirnents on pho"tosynthesis:

(D VAry are the leaues boiled in alcohol while testing for starch?(ii) Why is the plant kept in dark for about three days while perform,ing an

experiment to show that chlorophyll is necessary for photosynthesis?(iii) Why should the leaues be kept in boiling water for a few minutes before

putting them in alcohol for testing for starch?(i) Leaves are boiled in alcohol so that chlorophyll from the leaves leaches out

into alcohol.(ii) The plant should be kept in the darh for three days to destarch the leaves.

(ai) Leaves are boiled in water so that the enzymes are destroyed and they donot show further activity.

8m

Life Processes

Q. f4. Wy is there a need for digestiue process in the orgaruisms?Ans. Food is masticated and digested in the digestive system by:

' the complex food molecules are broken down into simpler substances with thehelp of enzymes.

. the digested products offood are absorbed by the villi in' absorbed food is assimilated to form substances which are

development, repair and production ofenergy.

' undigested toxic waste is released outside the body through anus.Q. 15. wat happens to partly d.igested, food, in the smail intestine?Ans' ' Small intestine has intestinal glands which prod.uce intestinal juice containing

enzymes. The enzymes are rereased in the intestinar cavity.' Complete digestion ofcarbohydrates, fats and proteins occurs here.

' The products formed are glucose , fatty acids, glycerol and amino acids. Foocl isthen absorbed by villi in the small intestine.

6 /ft] Wat happens to absorbed. food in our bod,y? Wy should. food, be assintilated.?

'*-/ Utilisation of absorbed food by the cells of the body takes place to produce thechemical substances which are need.ed by our body for gro*ih, development andvarious other activities. Assimilation is important to. build or replace old and worn out cells in the body.. obtain energy from the assimilated food.. build substances for growth and development.Enumerate the euents which occur in the stomach when food reaches it"' when food enters the stomach it expands. stomach is a large organ, which

receives food from the food pipe. The muscular walls of the stomach crush andmix, the food thoroughly with digestive juices released by gastric glandspresent in the wall of the stomach.

' when the food enters the stomach, the cells of gastric glands, present in thewali of the stomach, secrete the gastric juice which contains hydrochloric acid,the enzyme pepsin and mucus.

' Hydrochloric acid makes the medium of the food acidic and activates theenzyme pepsin which acts on proteins and breaks them.into smaller molecules.Bacteria and other microbes are destroyed by HCl. Mucus protects the 1ining ofthe stomach from the action of HCl.

Haw is the food digested by the intestinar juice in the small intestine?The partially digested proteins, carbohydrates and emulsified fats from the firstpart of small intestine move further into small intestine. The intestinal juice issecreted from the glands present in the walls of the smali intestine and it containsenzymes. Here, intestinal juice completes the digestion of proteins into aminoacids, carbohydrates into glucose and fats into fatty acids and glycerol.

81.41

the small intestine.

required for growth

Q" 17"

Ans.

Q. 18"

Ans"

)

I

Food particle

Fig. i.7Q' 20' How is d'erutal caries caused? w hat precaution s should you obserue to *uoitl d,entalcaries? rilhot wil happen if praqui formation is *ot remoued.?Ans' Bacteria.acting on sugars produce acids that softens or demineralises the enamel.Bacteual cells together wiih food particl""

"ri"r. r, the teeth to form i""rrr piaque.saliva cannot reach the tooth .,rrfr"" t" """irlile the acid as plaque covers theteeth' As a result dental carle1 or tooth a".uy o."rrrs. Brushing the teeth aftereating removes the plaque. If plaque ror^uiiorrl" ,rot remored, micr.orgarusmsmav invade the pulp causing inflammatior, *oJ infection.

6 Q' 21' tf o s'""n plant is placed. in air, free af oxygen, utou,ld, it liue longer in tight or indarhness? \Alty?

$ q,"22.

The green plant would live ronger in 1ight even rvithout oxygen in air as it can usecarbon dioxrde and water du"ir;rg phoiosynthesis and uroiru oxygen rn the air.This will be utilised du,ng *".piiriio., io ,ui".uu carbon aio*iau and energy. Butin the dark, there wiil be no ptoto"yrrttesis and no evolution of oxygen. sinceoxygen is not present in air, the prant wil not u,dergo resprration. Energy rvil notbe made available for various activities and the prant *itt die after some time"Merution, th,e euen'ts which occur d,uri*g the proeess of aerobic respi,ration.Represent the process in the fornt of word equation.Aerobic respiration is a multi-step process which involves:

(i) Absorption of atmospheric oxygen,(il) Oxiclation of fbocl (glucose, etc.),(lli) Elimination of carbr:n dioxide produced. during oxidation, and(i,) Production and conservation of energy released dtrring oxidarion in usefulforms such as ATp.

^ ^^--:x for the form of word equation, refer to point 6 of Brief R6suur6 on Fage BJ.4q. 23. Ila'ta is breathing d,ifferent froru r.espi,t ation?

Ans. Breathin(i) It ls an extracelluiar phvsrcal

iratian

process, performed by specificorgans"

(ii) Iio energy is releasecl.

(iii) Exchange of gases takes placewithotlt the action of enz

J1."{8

Q. 1e.

Ans.

Ans.

Ans.

CBSE Science Self-Tutor_X Life Proc,.

With the h.elp of sketches, show nutrition in Amoeba.

Food particle Pseudopodia

& q.24. LAns.

Q. 26.

Ans.

Q" ao"

Ans.

(ii

r\-c

Gilan(Ox:

dio:

outthe

Des

Thethebroalr.ebl,b[he i

It is anprocess"

intracellular biochemicali

Q.27. Dif;tAns. Dun

anci t

of an

In 1.e

GIucr(6- e;i,molr,r:

Anae:glucoi

Glucc(6-ca:'inr o lt.c:;.

Energy is released. and stored in theform of ATP rnolecules.Food is oxidised with the heip ofenzymes.mes"

Di fferentiate betw een respir atiorc and photosyn thesis.

Life Proce.sses

Q"24.Ans" Respiration

(l) It is a destructive process in whichfood is broken down into simpleinorganic forms like carbon dioxideand water with the release of energy.

(ri) It does not require light but, d,uringaexoHg-r"es.pirat"ion, require oxygen.

(iii) h takes place in cytoplasm andmitochondria of the cell.

81.49

osynthesis

It rs a constructive process in whichsimple inorganic molecules likecarbon dioxide and water combine toform food as complex organic molecules.

Carbon dioxide and water are usedto produce glucose try utilising solarenergy. It is a light-dependent, processand oxygen is produced as a by-product.

It takes place in the chloroplast ofthe celi.

Q' 25. Name the organ of respiration in fishes. How d,oes it help in the process of respiratiort?Ans. Gills are the respiratory organs of fishes. The water enters through the mouth

and spreads over the gills, which are richly supplied with blood capillaries.Oxygen dissolved in water diffuses into the blcod. The blood contains carbondioxide, brought from the various parts ofthe body. This carbon dioxide diffusesout in water" Water containing carbon dioxide is expelled out of the gills through

-'"-'1the gilt siits.

Q. 26. iDescribe the structure of human lungs.Ang' The lungs are situated in the thoracic cavity. Each lung receives a bronchus from

*. s'' the trachea. Elach bronchus branches into many smal.Ier and smaller tubes calledbronchioles. Each bronclr.iole terminates into a balloon-like structure calledalveolus or alveolar sac. The alveoli have ver], thin walls which are surroundedby blood capillaries. The exchange of gases occurs between the alveolar walls andthe walls of the capillaries.

q" 27 . Differentiate' between an aerobic respiration in yeast cells an d, in ou7 bod,y mwtcles.Ans' During anaerobic respiration in yeast cells, glucose is converted into pyruvate

and then into ethanol (ethyl alcohol) rvith the release of carbon dioxide. This typer:f anaerobic respiration is known as fermentation.In yeast cells;

Glucose [n c-vtoplasnt t pyruvate ------]

Ethanol +, Carbon dioxide + Energl,(6- calhon ii]*carbon (2_ca r.br';nmolt,cule) rnolecule) molecule)

Anaerobic respiration in body muscles involves lactic acid formation w,hereglucose, after conversion to pyruvate, is reduced. to lactic acid.

Glucose In cl'toplasm , pyruvic acid or pyruvate --------+ Lactic acicr + Itrner,gy(6--carbon (il-calbon rnolecnler) (jJ__calhonnrolt'cule) nroltrcuk_,)

81.50 CBSE Science Self-Tutor-X

Ans. n Aquatic respiration occurs through organs like gills, as in fishes. In terrestrialrespiration, lungs are the respiratory organs.

' Very little oxygen is dissolved in water as compared to the oxygen present in theatmosphere. Thus, the rate of breathing is much higher in aquatic organisms ascompared to in terrestrial organisms.

' Gills, which are the organs for aquatic respiration, are exposed to the outsidebut are covered with operculum. Lungs, which are the organs for terrestrial

' respiration, are placed inside the organism and are protected by the chestcavity.

Q. 29. What should be the characteristics of a gcaeous exchange surface?

"Ans. ' It should be a thin, delicate surface and should allow exchange of gases.

. It should have a large surface area.

i It should be richly supplied with blood vessels for easy transport of gases.

Q. 30. .besc ribe the role of trachea in respiration in humans.

An+: Trachea or wind pipe is a tube made up of rings of cartilage. It serves as an air.'r"' passage between the throat (pharynx) and bronchi. It remains moist due to the

presence of mucus which holds back the dust and bacteria.-This ensures entry ofdust and bacteria-free clean air to the lungs. Pharynx leads into the trachea.

Jrachea runs down the neck and branches into two bronchi.

A. Fl Wry is tlrc internal respiratory system considered efficien t?

Ans. ' Internal respiratory organs have very frne, delicate membranes which provideextensive surface area for exchange of gases. These remain in contact with theenvironment full of air. Being internally placed, these are protected.

' Efficient separate,respiratory passages have been provided and are protected.

' A well-developed internal mechanism for moving the air in and out from thisarea is also provided.

Q. 32. What is comrLon to the structures of gills and, lungs that mahes the efficientexchange of gases possible?

Ans. ' W'alls of gills and those of alveoli of lungs are thin and are meant for easydiffusion of gases.

' In both, a large surface area is available for absorption of enough oxygen.

" Gills and alveoli in lungs are richly supplied with blood capillaries.

Q. 43. Q) Draw a well-labelled diagram of a human lung showing its internalstructure.

(ii) Enlarge a part of the lung showing the respiratory bronchioles, alueolar d,uctand alueoli.

Life hocesses

Ans.

Q.34.

Ans.

Q.35.Ans.

,€.g0.An

Wat i^s

Discuss.

The funYeast prfermenfirst cordioxide.

Glucose

ExplainTissuesenergy.blood cz

leavingconcentr

ntr

,s

Loss ofrwater isto contirpulls wz

,'^, moveme'\ Thi" "^,

Q. 3?. i ta wz

, ,j (ii) Ho\*-,' (ii) tlaAns" (r) Pn

r(x(li) Ior

en(ceI

(lir) Tt a

-

Life Processes

Ans.

' (iii) Wat are its benefits?Ans. (j) Pressure exerted by water on the rigid wals of the xyrem cerls is canedroot pressure.

(ii) Ions are taken up by the roots from the soil actively with the expendirure ofenergy' A difference is created in the concentration ofthese ions in the rootcells and soil. This causes water to enter the roots and deverop root pressure.

(iii) Water rises in small plants due to root pressure.

81.5r

Fls. 1.8

Q' ga' What is comm,on between anaerobic respiration and, the functioning of a brewery?Discuss.Ans' The functioning of a brewery is based on anaerobic respiration shown by yeast"

Yeast produces ethanol during anaerobic respiration. This is known as alcoholicfermentation or yeast fermentation. In t-he cytoplasm of yeast cell, glucose isfirst.converted into pyruvate, which is then reauced to ethyi alcohol and carbonc[oxr€l.e.

Glucose ln citoplasm , Pyruvate-------+Ethanol or ethyl alcohol + carbon dioxideQ. 35" Explain gaseous exchange between tissues artd blood, in humans.Ans' Tissues are in constant need of oxygen for the oxidation of stored. food to getenergy' The cells of the tissues have low concentration of oxygen than theblood capillaries, which are rich in oxygen. So, oxygen diffuses into tissues,leaving the blood. In exchange of thls,"th"

"a.borrtioxide, fro* ,t" higherconcentration in tissues, diffuses into blood having lower carbon dioxrde, -...,poncentration.

Q' s6. !w"t is the rore of transpiration in the cond,uction of water?Ans,"'Loss of water d'ue to transpiration occurs continuously from the leaves. .Ihe lost

-/ water rs replenished by the movement of a fresh supplyof water to the leaves. Dueto contrnuous transpiration, a suction force is created in the xylem vessels whichpulls water up from the xylem cells of the roots. Transpiraiio" rr"rp" upward-' movement of water and the dissolved minerals (sap) from the roots to the leaves.' '' This causes continuous absorption of water from the soil by the root hairs.

S e. s7. i (, what is root pressure?

,j (ii) How d,oes it d.euelop?

4

81.52 CBSE Science Self-Tutor-X

Q. 38. Mention three uses of transpiration.

Ans. . Transpiration helps in conduction of water in tall trees.

r It helps to transport minerals, which are needed for various metabolic

activities, to the leaves at the top ofthe plant'

o It regulates temPerature'

Q. 39. Show the path of water during its transport in plants'

Ans. t

y't{/ \ Water vapour

Movement of water

Fig. 1.9

Life Processes

$ q.42. wy d.o ttentperotut

Ans. Amphibiaratria anC c

atria comtoxygenate(amount ofThese orgrtemperatu_

Q. 43. Desuibe b;

Ans. Fishes har-,pumped rcthe giIls. It

_ water, carlonly once ri

Q" s+. How does ,

r. - . minerals?Ans. . Stomata

. This io,"rvessels c,i

. Leaves d-

absorb ir':a suction

Q. 45. Describe onAns. (l) Take r

(ll) Take r

(lii) in the(iu) The su

so tha:(u) Coverl

(ui) Place r

(url) After tpot whthe inr

{bt e. 4O. Wk1 are there two pathways in plants to cond.uct food, and' raw materials like

water and minerals? Describe them in brief.

Ans: Plants have two independent pathways for conducting enerry store, i.e., food and

raw materials like water and minerals. The conducting system needed totransport raw materials like water and minerals consists of dead cells known as

xylem vessels and tracheids. Transport ofthese raw materials in trees occurs

due to root pressure, *'hich is an active process, and transpiration puil, which is

a passive pro.""r. Another conducting system consisting of live cells like the sieve

tube cells of the phloem tissue translocates the food s5rnthesised in leaves to

different parts of the plant. This process involves use of enerry'

6. +t. Define transpiration. Draut a diagram of thepa,rt of the leaf front where transpiration takesplace.

Ans. Loss of water vapour into the atmosphere fromthe stomata present on the leaves of a plant iscalled transpiration.

Water drc

Epidermal cell

Guard cell

Stomatal openingChloroplasts

-

Life Processes 81.53

$ q'42. Wy d.o animals lilze amphibians and. reptiles not haue a constant borlytentperature?Ans' Amphibians and many reptiles have a three-chambered heart, consisting of twoatria and one ventricle.The oxygenated blood and d.eoxygenated bloocl fio* tt

"atria come into a single ventricre. This causes the mixed bloo4, ;"r., -purtrv

oxygenated and partly deoxygenated blood, to be circulated. This leave-s*tessamount of oxygen to be circulated, causing less arnount of energyi" U- pr."a.,*a"These organisms do not have a constint body temperature as their hodytemperature depends upon the temperature of thl environment.Describe blood. circula,tian in fishes.Fishes have-on1y a two'chambered heart-one atrium, one ventricie. The blood isq"orqg"d to_the gills for oxygenation. water carrying dissolved oxygen passes overthe gills. Here, blood takes up oxygen and .ellas6"

"urtu"-ai""ia". aro.,g- r"iinwater, carbon dioxide is removed through the gill slits. Blood enters the"heartonly once during one cycle of passage thiough tire body.r{o.w do-es suctiort force created, in the prants trclp in cond.uction o{ ws,ter and,min erals?

Ans. ' Stomata remain open during the day and water is lost from them.. This lost amount of water is compensated by taking ,,vater from the xylem

vessels of the leaves.

'Leaves draw water from the branches and branches from the roots. Rootsabsorb water from the soil, which has an adequate supply of water. This createsa suction force that helps in the conductton of water and rninerals.

Q. 45" Describe an experiment to d.emonstrate that plants transpire wqter.Ans" (l) Take two pots of the sarne size having the same amount of same soil.

(ii) Take a plant in one pot.(iii) In the other pot, take a stick of the same height as that of thc plant.(iu) The surface of the soil in boththe pots should be covered with a plastic sheet,

so that no water evaporates frornthe surface of the soil.(u) Cover both the pots with plastic bags in such a way that no leakage of air r:ccurs.

(ul) Place the tu,o pots in bright sunlight for half an hour.(uri) After haif an hour, water droplets-will appear on the inner side of bag in thepot which had the plant. In the other poi, there wlu b" ;;;;;. a"ffiut. o"

the inner side of the bag.

Q.43.Ans.

Q" 44:

Water droplets

Piastic sheel

CBSE Science Self-Tu.tor_X

tf e' 46' Giue a schentatic representation af transport and exchange of oxygen an cl carbondioxide i.n human beings.Ans.

Lung capillaries

Pulmonary artery to lungs(Deorygenated blood)

Capillaries in body organsapart from the lungs

. ,.- '..\i Fig. 1.12

a'2' 47 ' Yr!r:;

bload circulation in human heart caltert d,ouble circulatio*? Explaini43q-4'*o venae cavae bring deoxygenated blood to the right atrium, from where theblood flows into.the right ventricle. The brood is pi*pua in,o the pulmonarytrunk and is carried to the two lungs for oxygenation" The left atrium receivesoxygenated blood frorn the iungs through thepulmonary veins. It then flows intothe left ventricle from where it is pushed into the aorta for distribution rn the body.since blood ci"rculates twice in the heart, it is known as double circulation"

Q. 48. Giuen below is a sketch of a human orgarl system.(i) Name the system.

(ii) Label the uarious parts of the system.Ans.

Right kidney Left renal artery

l-eft kidney

Left renal vein

Vena cava Aorta

Left ureter

Urinary bladder

Urethra

Fig. 1.13: Human excretory system

B1.54

Vena cava from body(Deoxygenated blood)

Pulmonary vein from lungs(Oxygenated btood)

Aorta to body(oxygenated blood)

Li:e h.":r.;,,r;

Q. rg .[I.:; a.{as- . -i _s

i-- ---! J

. Ifutftreabi

. FiltriQ. 50. tthat lt

{i) Bou

.{ns, (ii Rr

(ri) Rr

frf(il') L r

ur

Q. 51. Ilhat qr

Ans. . planft

con,.rci

. Ox-r-ge

. Carbo:

. Escesi

. Lcss o:

Q" 52. Describe

Ans. Blood fi_li

tryo kidnrof rena_l

filtrate cThese suurine.

Q. 53. How is thAns. Excretion

reactionsorgans kr.:

hody throrthe bod_v.

Q. 54. W,at is tt.Ans. . The prc

product;. It reguie

and salt,

" It help--

Life Processes B1.bb

Q' ag' How is it beneficial to h,aue large number of highly coiled. nephrons in our lzid,neys?Ans' ' A large number of nephrons in the kidneys helps in increasing the su*face areafor proper filtration.

' Highly coiled nephrons further increase the surface area which heips in properreabsorption of, useful substances.

. Filtration becomes more effective and fast.Q' 50' wo't fuructions are performed by the fortawing parts of nephrons?

(i) Bouman's capsure (ii) Tuburar part (iii) coilecting d.u.ctAns. (i) Refer to e. gb on page 81.48.

(li) Reabsorption of substances like glucose, amino acids and salts occurs in thetubular part ofthe nephrons.(ili) Urine gets collected in the collecting d.uct and is then released into the

ureters.

Q. 5f. What are the d,ifferent waste prod,u,cts prod,uced by plaruts?Ans' ' Plants produce many substances like gum, rubber ancl resin, which are

considered as waste products.

' Oxygen may be taken as a waste product prod.uced during photosynthesis.' carbon riioxide produced during respiration is arso a waste product.n Excess water, which is not utilised by plants, is taken as a waste product"o Loss of leaves periodically may be considered as loss of waste parts.

Q' 52. Describe hriefly the m.ecrrunism of uri,ne formatiott i,n *ephrons.Ans' tsiood filtration occurs in the nephrons rvhich are present in large number in thetll'o kidneys. Abunch of capillaries, known as glomerulus, is procluced by a branchof renal artery in the Bowman's capsule. Blood is filtered in glomerulus. Thefiltrate contains useful substances iike glucose, amino acids, .salts and water.These substances are selectively reabsorbed by blood. The filtrate forrns theurine.

Q' 53' How is the process of excretion d.ifferent fram that of egestion?Ans' Excretion is the removal of nitrogenous waste products produced by biochemicalreactions occurring in the body. These waste products are removed by excretoryorgans known as kidneys. Egestion is the removal of undigested fooa from thetrody through the anus. The faecal matter is not produced by metabolic activity inthe body.

Q" 54. Wat is the significance of excretion?Ans' ' The process of excretion helps in the removal of toxic nitrogenous was1,products from the body.

. It regulates the cornposition ofthe bodv fluid by controlling the leveJs of u,at,and salts in it"

. It helps in conserving useful substances lilte glucose, arnino acids and salts

81'56 CBSE Scien'ce Self'Tutor-X

Q. 55. Describe the uarious organs of excretory system of human beings-

Ans. The excretory system of huinan beings consists of two bean-shaped kidneys.

These are located in the abdomen, one on either side of the backbone. Each kidney

contains a large number of closely placed tubular structures called nephrons"Urine formed in the kid.neys enters the ureters. The two excretory tubes or

ureters, one from each kidney, open into a urinary bladder. A muscular tube,

called urethra, eilIows the urine to be thrown out through an opening.

Q.3.Ans.

S Q. 56. Explain the circulation af blood. in the hid,neys.

Ans. Renal artery brings oxygenated blood which is rich in nitrogenous wastes, to the

kidneys. A branch of renal artery enters the Bowman's capsule of a nephron and

forms the glomeru}rs where blood gets filtered and urine is formed. The tubularpart of the nephron is surrounded by the capillaries which reabsorb substances

like glucose, amino acids, salts, water, etc. The capillaries join to form rena] veins

which join to form the inferior vena cava which collect blood from the lower part

of the body.

t criteria do we trse to decide whether sorneone is aliue or not? Expl,ain.

lfferent types of moveraents can be taken as the criteria to decide whether an

organism is alive or not" The following movements are observed in livingorganisms:. Animals move from one place to another.

. Piants show growth movements.

. During breathing, the movement of chest cavity is visible in animals"

. Al1 organisms, whether plants or animals, show invisible molecularmovements. Plants and animals are made up of tissues, and tissues are made

up of cells and their components. Cells are made up of molecules. These

molecules must move so as to maintain and repair the structure of cell

components and tissues.. waste molecules are moved out of the body by the excretory system.

Q.2" \$th.y is there q, need for a transportation system and ant excretory system? Wh'o:

relationship exists between the tuto systems?

Ans. Food and oxygen are taken in frorn specific points such as alimentary canal an:

respiratory system respectively. But nutrients and oxygen are needed by all th.other parts of the body. The transportation system helps in carrying thes=

substances to ail the tissues and cells.

Whep chemical reactions use carbon source and oxygen molecules are brok::'down during oxidation along with energy generation in the cells, certain b-''

products, which may prove toxic to the body, are also produced. To remove the=.

substances, a specialised excretory system is involved. Transportation syste-

carries these wastes to the excretory organs from where they are excreted cu:

Life Processes

Can uisible r,

Visible movtrnovements lStructures ofmade up of ctorgan systefiis such thatprocesses ov€their structu:worn out paiEven unicelhthemselves.

enancethese processt

Organisms a<

carried out. Tthe body is L

when the sizeon carbon-babased.

Q.5, Wich euentsof carbohydrc

Ans. The following(l) Absorpr

(fti) Conversmolecuii

(iil) Heductlatmospl

Excess carbolstorage organExcess carboL

During d,ru elthat chloroS,phatosynthesi.steps taken:

(il il/hy ucuariegott

(ii) Why u'asthree do-

(iii) Wy uc;sunlight

(iu) Why u'erboiled tn

(u) llhy uer,iodine?

Long Answer Questions (5 Marks)

$ Q. 56. Explain the circulation of blood, in the kid,neys.

Ans. Renal artery brings oxygenated blood which is rich in nitrogenous wastes, to the

kidneys. A hranch of renal artery enters the Bowman's capsule of a nephron and

forms the glomeruhos where blood gets filtered and urine is formed. The tubular

part of the nephrorr is surrounded by the capillaries which reabsorb substances

like glucose, amino acids" salts, water, etc. The capillaries join to form renal veins

which join to form the inferior vena cava which collect blood from the lower part

of the body.

criteria d,o we t!,se ta d,ecide whether sotneone is aliue. or not? Explain'.

/lfferent types of moveraents can be taken as the criteria to decide whether an

trganism is alive or nol. The following movements are observed in livingorganlsms:. Animals move from one place to another'

. Plants show growth movements.

. During breathing, the movement of chest cavity is visible in animals.

. AI1 organisms, whether plants or animals, show invisihle molecular

movements. Plants and. animals are made up of tissues, and tissues are made

up of cells and their components. Cells are made up of molecules. These

molecules must move so as to maintain and repair the structure of cell

components and tissues.. Waste molecules are moved out of the body by the excretory system.

e. Z, Wh.y i,s there a need, for a transportation system arud an.excretory system? What

relatioruship exists between, the two systerns?

Ans. Food and oxygen are taken in from specific points such as alimentary canal and

respiratory system respectively. But nutrients and oxygen are needed by all the

other parts of the body. The transportation system heips in carrying these

substances to all the tissues and cells.

When chemical reactions use carbon source and oxygen molecules are broken

down during oxidation along with energy generation in the cells, certain by'

products, which may prove toxic to the body, are also produced. To remove these

substances, a specialised excretory systern is involved. Transportation system

carries these was;es to the excretory organs from where they are excreted out.

81.56 CBSE Science Self'Tutor-X

Q. 55. Describe the uarious orgctns of excretory system of human. beings.

Ans. The excretory system of human beings consists of two bean-shaped kidneys.

These are located in the abdomen, one on either side of the backbone. Each kidney

contains a large nurnber of closely placed tubular structures called nephrons"

Urine formed in the kidneys enters the ureters. The two excretory tubes or

ureters, one from each kidney, open into a urinary bladder. A muscular tube,

called urethra, atrlows the urine to be thrown out through an opening.

Life Prot

Q.3.Ans.

Q.5.I

Ans. '

6.

l(

l)I

IC

J

Life Processes

Q. 3. con uisible ntouements arone be ind.icatiue of tife? Justify yoar answer.Ans' Visible movements may be indicative of life in some cases. But there aremovernents like molecular movements which are surely indicatir.e of life.

Excess carbohydrates, which are notstorage organs of the plants.Excess carbohydrates in animals are

81.57

used by plants, are storecl as starch in the

stored as glycogen.

Leal

Leaf boiled in Leaf boiledwater in alcohol

Structures of all living organisms are well organised.. Multicellular 6rganisms aremade up of cells which are organised into tissues, tissues into organs, organs intoorgan systems and then the individual as a rvhole. The effect of the env[onmentis such that the organised ordered iiving structures, *uy ,rro* breakdownprocesses over time, leading to death. Organisms require molecules to maintaintheir structures intact' Therefore, molecules must be availabie for repair of theirworn out parts. This is made possible by molecular: movements through diffusion.Even uniceliular organisms need. a "orrtirr.rorr*

supply of morecures, to maintainInemselves.

4'. lMaintenance

processes require energy to preuen t d,amage an,d, breahd,outn. IIow d,o/these processes ocqu,ire eruergy?

Organisms acquire energy from outside sources for ma.intenance processes to becarried out. The process which provrdes a source of energy, a.e., food from or.rtsid.ethe body is known as r-rutrition. organisms require #.iitlorut raw materialswhen the size of the body increases, i,e", growth o"o*rr*. As life on earth depe,dson^carbon-based molecules, the sources, i.e., food *n,rr*r,",-r"e mostly carbon-Dased.

Q" 6. which euents accur _during th,e proce.ss of ph,ettosyntrr,esis? what happens ta excossof carbohydrates uthich are not utilised" by prants and uruirrtars?Ans. The following events occur during the process of photosynth*sis:

Absorption of .l.ight energy by chlorophyll molecules.conversion of light energy into chemical energy and sprittlng of wate,r:molecules into hydrogen and oxygen.

(ir'il Reduction of carbon dioxir{e to carbohydrates and release of oxygen into tireatmosphere.

(i)(r,)

Durirug art experirnen,t to d,em,onstrateth:tt chlorophyll r.s essenti,al forphotosynthesis, wlty were tlre following

(i) VIlry uia,s a potted plant withuariegated leantes taken? i(ii) Why was the plant kept in d,ark farthres d.QY5?

(iii) Wy was the potted, plant kept insunlight for si,x hours?

(iu) Why utere the experimental leaueshoiled. in alcahal?

(.u) Wy were these leaues t;rea.ted, withiodin e?

:

Blue black

Variegated leaf Starch test of leaf

Fig. 1.14

' 81.58 CtsSE Scieruce Self-Tu,tor_-X

Ans. (l) Variegated leaves have some green areas containing chlorophyll and sornenon-green areas which are without chlorophyll"

(il) Since the potted plant was actively photosynthesising, it was kept rn darkf,or three days to destarch the leaves.

(iir) After destarching, the potted plant was kept in sunlight for six hours so th;rtstarch could be produced by photosynthesis.

(ru) Experimental leaves were boiled in alcohoX to dissolve chlorophyil fromthem.

(u) These leaves were treated with iodine to show the presence of si,arch rngreen areas r:f the leaves. Blue-black colour appears in the chlorophyll

/8. 7. Describe an, experiment to demonstrate that saliuary atmylase d,igests starch.\{ry/ (i) Take two test tubes A and B and take 1 mL of starch soiution in each

test tuhe.(ii) in test tube A, add 1 rnl, of saiiva. Keep the two test tubes undistr.rrbed at

roorn temperattrre fbr 20 to 30 minutes.(rfl Adcf a few drops of iodine in each test tube.(lu) Blue-black colour wiil appear only in test tube B. There wiil be no colour in

test tube A.(u) This shows that salivary amylase from saliva in test tube A has acrr:d on

,r-/-\-.-\ starch and changed ii to sugar. Hence, there is no colour.' / q.tA. )escribe an experiment to proue that carban d,iorid,e i,s essential for ph,otosynthesis.

( a"". ) O f"Uu two potted plants, nearly of the same size.\---/ (li) Keep ttrrena in the dark for three days to destarch theru"

(lil) Take two separate glass plates and put one pi,:tted plant on each of tirem.(lu) Put a petri dish or watch glass containiug potassium hydroxide on one of the

glass plates aiong with the potted plant, as seen in the experimental setup A.(u) Cover both plants separately with bell jars.

(ul) Apply vaseline i:o seal the bottorn of the beii jar to avoiti leakage of thecarborr dioxide prnd uced.

(uri) 'i'he experimentatr setups should be kept for about twc hours in sunlight"(c;il,i) Pluck one leaf each from the two piants and test for the presence of star:ch

b3'Lroiling first in water, then in alcohol nnd finally, treating it ivith rodine.

(ir) A leaf {rom experi.menlal setup B showed blue-blar:k colciur.

Potassiumhydroxide

Life Processes

(x) 1

:n

Q" 9. Explaiphotos.

Ans. Refer r

Q. 10. Ansue(, ir

(,,) I(,,,) u(iu) Il(t'1 11

Ans. Refer t

th q. t"!. obser-,(i) II

(ii.r tt(iii; -1:

(it.t Gt

(rl -{'r€(

Ans. (r) P,:'

(ilt \-a(izi) \r(fuI C:

cal

(c) Inber

,---\ L,.ugl

Ct ql rz. rritot a,

\

-l

Lif'e Processes

&)

Ans.

Q. 10"

Q" 9. Explain an, experiment to tlem,onstrate that chlorctpltytl r,s necessnry forphatosyrtthesis.

Refer to Q. 6 on Page Bl.bT.

81.59

The leaf from experimeatar setup A, containing potassium hydroxide, dirinot show any blue-black colour. potassium hyJroxide abso*bs co, whichwas not availabre for_photosynthesis, proving that carbon dioxide isnecessary for photosynthesis.

Answer the following questions based. on the a.boue experiment.(i) W'h,y raere uariegates leaues taken for the experirnent?(ii) ll/h,y was plarut hept in dark for tuto to threi d,ays?(iii) Why was the plant hept again, in sunligh.t?(iu) Why was the teaf sailed, in alcohol?(u) Why was the leaf later treatecl, with iod,ine?

.., Ans. Refer to Q. 6 on page B1.b7.{t e' 1!' obserue the set-up prouid,ed for Ans. I carefully a,nd answer the following questions:

(i'1 wy is potassiunt. hyd,roxid.e sorutioru kepr in one of the bey jat"s?(ii)

(iii)why should uaseline be opptied, arau,nd, the rnottth of the bert jars?After testing for starch with iocline, what do you obserue?

(iu) Giue d, reason for th,e sa,nte.

(u) After testing for starch on. leaf from setup B, what d.o you obserue? Giue ureason for the satrle.Ans' (i) Potassium hydroxide was kept in one of the bell jars to absorb carbon dioxide.

(il) vaseline is applied to make the experimental setup air tight.(ijj) No blue-black corour appeared in the experimentar setup A.(iu) Colour did not appear in the leaf taken from experimental setup A becausecarbon dioxide was absorbed by putting potassium h5rdroxicle.(u) In setup B, the leaves showed. biue-black colour when tested with iodine

because carbon dioxide was present in the air of the beli jar and was arsobeing produced by the plant.wpat ore the different modes of heterotrophic nutrition? Describe thent.fleterotrophic nutrition: Organisms which derive food from the other organismsshow heterotrophic nutrition. such organisms are called heterotrophs. Allanirnals, inciuding man, are exannples of heterotrophs.Heterotrophic nutrition is of the following types:

(i) Pctrasitic nwtrition: organisnas caltred parasites live on or insiile the bocty ofother living organisms, calred the host and absorh food. from them. This isseen in plants like orchids, custuta and animals rike ticks, tiou, tup"*orr*(ii) Saprophytic n utrition : Tnsaprophytic nutrition, the iiving organism s thriveon dead and decaying organic matter of piant ,"a o"i*i orlgin. ,rhi. ;;p;of nutrition is seen in fungi, suctr as bread *o.,tj., *,r.irroonas ancl yeast.(iii) trIolozoic n'utrition ' some animars eat whole plants, whore animars or theirparts arrd digest thern' The digested materiai is subsequerrtly al:sorbed andutilised" Holozoic nutrition is seen in most of the ani*uls like Amaeba,

cc,ckroach, man, and. also some pl,ants.

. 12.

81.60 CBSE Science Self-Tutor-X

escribe the process of nutrition in Amoeba.'Amoeba engulfs food in solid form. Following are the steps in the process ofnutrition by Amoeba:

' Amoeba captures its prey by means of the pseudopodia (faise feet). It forms twopseudopodia encircling the prey. The tw,o pseudopodia fuse completely,forming a bag like structure containing the food particle or prey. This is calledthe food vacuole.

. The enzymes present in the food vacuole digest the food.

' The digested material diffuses into the cytoplasm, where it is assimilated toform new protoplasm.

' The food vacuole also known as residual vacucle containing undigested waste isbrought to any point on the surface ofthe cell and then it is released outside.

For figure refer to Q. 19 on Page 81.48.wy is photosynthetic process considered, the most irnportant process in thebiosphere? Explain.Photosynthesis is considered the most important process in the biosphere due tothe following reasons:

' Fhotosynthesis is the only process on earth, where solar energ"y is trapped byar'rtotrophic organisms and converted into chemical energy, which gets stored. infood molectrles for all the organisms present on earth.

' Photosynthesis is the only method to produce food from inorganic rawmaterials^ All photosynthetic organisms are producers.

. Plant and plant products are used as food, fodder, firewood, timber, fibres, oilsand drugs, which are produced as a result ofphotosynthetic process.

' Fossil fuels, such as coal, petroleum, and natural gas, are also prod.ucts ofphotosynthetic organisms which lived millions of years ago.

{iii) wh'y is ntuctts necded, duri,ng the process of d,igestian in the stomach?(.iu) W'hy is the small i,ntestine richty swpplied. with btoael, t.:t:ssel.s?

(u) Why is there a need for absorption of d,igested" foadiAns. (i) Small tntestine is very long because complete digesrit.,rr of food must occur

and then te foliowed by complete absorption of the digested fbod.(rr) A sieeping person requires energy because processes like respiratiou,

transp0rtation-, :flormation of waste products and growth occtrr even whenasleep.

(lii) hlucus in the stomach protects the iining of the stomach from ihe action ofHCI and facilitates srnooth movement of food"

(iu) Small intestine is richly supplied with blood vessels to absorb all the digestedfood products so that they can be distributed to all parts of the body.

Life Processes

;--16.

Ans.

.j

Ans.

t7 templ

(i) wtorl

(ii) w'l

(iii) w1

(iu)

(,)

(ii)IF

L

Bfc

G

L1

AI

!\:CO

fo:

(u) NI

of

AItprowh:

(il) Druprogivt

(iil) Ext(iu) Des

anienel

(u) Nitrobtaatm,

IS

at

I(

(iii)(iu)

(u)

(,)

,{\

{:^)

(ii)(iii)

(iu)

Hodo:

In(u)

(i)

Life Processes 81.61

(u) Digested food must be absorbed so that it is assimilated in the form of usefulsubstances needed for growth and maintenance of the body.

'plain the following:(i) Emulsification of fats.(ii) Gall bladder.

(iii) Function of the large intestine.(iu) Peristaltic mouements.

(u) Use of muscular sphincter in the stomach.Ans. (t) Bile salts break large fat globules in the small intestine into smaller molecules

for better action of the enzymes" This process is called emulsification of fats.(li) GaiI bladder is a sac-like structure present in the liver. It stores bile juice.(iii) Large intestine is meant for absorption of water from the undigested food

and making it more solid. This waste is then excreted through the anus.(iu) Wails of the organs of the alimentary canal are provided rvith muscles which

contract rhythmically causing peristaltic movements which push the foodforward-

(u) Muscular sphincter, located at the end of stomach, regulates the movementof small amounts of food into the intestine -for its proper digestion.

ttempt the following:(i) why is photosynthesis acnsirlered the most beneficial process for liuing

organisms?

(ii) Why is there a need for openirug of stornata in, leaues, d,uring d,ay?

(iii) What happens to ertra carbohydrates produced by leaues?

(iu) How is food prod,uced, by desert plants, as the stom,d,ta remain close duringdav?

Ans.

(u)

(,)

In which form is nitrogen taken up by plants?AII the food needed by living organisms is produced by plants through theprocess of photosynthesis. During this process, oxygen is also produced,which is essentially needed by organisms to procluce energy.During the day, carbon dioxide enters the leaves through stomata for theprocess of photosynthesis and oxygen produced during photosynthesis isgiven out into the atmosphere.

Extra carbohydrates produced by leaves are stored as starch in plant parts.Desert plants take carbon dioxide through stomata during night to preparean intermediate compound, which is then changed into food by utilising theenerg'y absorbed by the chlorophyll pigments during the day.

Nitrogen is taken in irrorganic forms, such as nitrites and nitrates, or it isobtained as an organic compound which is produced by the bacteria fromatmospheric nitrogen.

(ii)

(iii)(iu)

(u)

81.62,],..

.,1 CBSE Scieruce Self-Tutor_X/I

\. L8. fExplain.

the foltowing aspects of photosynthesis i,t plants:\_/ (i) The role of chlorophyil.

(ii) Euen"ts which occur d.urin4 photosyruth.esis.(iii) go* is excess of carbohydrates stored, in prants and. animars?Ans' (i) chtorophyll pigments absorb light energy and convert this energy intochemical energy, which is storeiin the fJoci morec*les.(li) Events occurring during photosynthesis are;

(o) Chlorophyil pigments absorb light energy which is converted intochemical energy and stored. in the food mollcuies. wut"" ,r*o.prits intohydrogen-and oxygen. oxygen is then rereased into the atmosphere.spJittingof Hro into oxvgen and hydrogenis known r" pi"l"iy"i}i;"t*.

(b) The hydrogen released. is used for reduction ofcarbon dioxide to producecarbohydrates like glucose. This process does not require light ancloccurs during and at night.(iii) Itrxcess ofcarbohydrates, which are not utilised by the plants, are changed-into starch and get stored. in their organs.

- -- vJ v'rv r^a*vD, o" ttt , ,,

es

Ans. f)i.gestiue Secretian Enzymes Substro,te ProductsSalivary giands(in buccal cavity)

Saiiva orsalivary jui.ce

Salivaryaurylase

Starch Sugar

Gastric glands(in stomach)

Gastric juice Pepsin Fyoteins Partly digestedprr:teinmolecules

Liver Bile juice No enzyrne Fat Srnall moleculesof fat

Pancreas Pancreaticjuice

(r) Amytrase(ii) Trypsin

(iii) Lipase

StarchProteinsFat

SugarPeptides

{atty acids andgiycerol%

Amino acids

Glucose

Fatty acidsand glycerol

Intestinalglands(in smallintestine)

Intestinaljuice(succusentericus)

(i) Enzyraeforpeptidasesproteindigestion

(ii) Enzyrnefor sugare.g. r,naltosedigestion

(ili) Lipase

Peptides

Sugar

Fat

Describ

The alimouth 1

$)M,:fsa

(ii) O(

frt(,,il sa

skdasp,

(lu) SrtatFo

(o) Inwa

(ui) An

---l\ sPI

,.' Ffu figu

fi. zy6)",,ia"\AEx/ G) Mo

carinr

(li) StoglaHCdorfror

(iii) Sntintrwh:ThtofrcoIIglu,bvl

(iu) Larabs,thrr

Q.32" \Mtat isorgonismbatlt, the 1

Ans. Respu.atiThere arr(i) aerobir

{

Describe the path of food, in th.e alimentary canal of man.

81.63

man is nearly nine metres long, extending from theThe alimentary canal ofmouth to the anus.

(i) Mou,th (buccal) cauity: Food is rnasticated. in the buccal cavity wirh the helpof teeth. Tongue, present in the mouth, herps in *i.i"i "r

rrre food with thesaliva secreted by the salivary glands.(ii) oesophagus: A long muscular tube. also known as food pipe, carries f,oodfrom the buccal cavity to the stomach.(iii) stomach.' st.mach is a rarge muscular organ" The muscr.Iar ri*ing of thestomach helps in mixing the food thorou-ghlj, with gaJic juice whiclih"lp indigestion. passage of food into the smarfiniesti"";;;;;Iated by m*scularsphincter.(irt) small intestine: It is a coiled narrow tube and the rargest part of the arimen-tary canal. The food enters here and-the process or iig"*tro., rs compreted.Food is absorbed by villi present in the iniestinar *ur]?-

Large intestine: It is a wider tube than the small intesti,e and excess ofwater from the undigested food is absorbed here. It is also known as coron.An'us: The faeces is egested out of the anus which is regulated by anarsphincter.

(u)

(ui)

(r)

(,i)

figure, refer to Fig. 1.1 on page B1.8"ribe the process af d,igestion of foact in ntan.Mou,th, (buccal) cauity: Three pairs of salivary grands present in the buccalca'ity secrete salivary juice which mixes with fooa. sdi"r6;yhse presentin saliva tligests starch into sugar.stomach,: Fnod enters the stomach through the oesophagus" The gastricglands present in the ,r'all of the stomach secrete c;;;i; j;"e contarnrngHCl, which provides acidic medium for the r"tioo o? p"f

"lri" p*p"i., breaksdown proteins into smalrer mr:recules. Muctrs protects the iining of stomachfrom the action of HCI. Food now enters srnall intestine"

(iii'1 gn'o1'1 in't'estine: Fancreatic juice contains trypsin, which breaks proteinsinto smaller molecules' amylase, which digests itur.t into sugar, and 6pase,which changes f,ats, emursified by bile sJlts. lnlo fatty ,"id ;;; gjyceror.The bile salts secreted by the liver make tt e ,neclium alkaline for the actionof pancreatic enzymes. The intestinar juice *"".,;l;;;;il;;u iri*.tirru,completes the digestion of proteins into amino acids, carbohyJrates intoglucose -and fats into fatty acids and glyceror- i;" digested foorl is absorbedb5' blood vessers present in the ringei-iike p"ojo"aiorr" known as vi1i.(iu) Large intestine: Excess water, from the unabsorbed and undigested fcrod., isabsorbed by the walls of the large intestine. Cndigested foocl is removedthrough the anus.Q' 22' W1w't is respiration? Mention the two types of respiration, ocatrri*g in tiuingotga'ruisrns' Descrihe briefly the two typesif respi,raiions. lvrite th,e equcttions forbath th,e prlcesses.Ans' Respiration is a biocliemical process rvhich results in the production of energy,There are two types of respirations occur:ring in tiving r:rganisms" These are:(r.) aerobic respiration and (ir) anaerobic

"uupiiutio.r.

-

81.64 CBSE Science Self-Tutor-.X

(.i,) Aerobic respirati.ou Aerobic resprration occurs when food (glucose) iscompleteiy oxidised by oxygen into carbon dioxide and water with release oflot of energ'y stored in ATP (Adenosine tri-phosphate) molecules. Thisprocess occurs in mitochondria.Equation for aerobic respiration:

No oxl,gen Oxygen rs

Glucose 't'qtr,'e(l ts Pvruvate .cquired , Carbcln clioxrd^e * Wrtclln c\ t{,pla{lr * ln rnitur,hrrndlra

+ Enet.gy(ii) Anaerobic respiralr.orlr '1'n" process occurring in the cytoplasm, rvrtholrt

utilising oxygen is known as anaerobic respiration. Food i-< partialill"oxidised into either ethyl aicohol or lactic acid. Bacteria and yeast undergofermentation, producing ethyl alcohol and carbon droxide, as shown in theequation.

No oxygen No ('\ygerl

Glucose . r'eqrrirj'd r Pyruvate .. r't'qur'ed > Ethyl alcohol + Carbon dioxide

ln cr lrrplasnt - l"er'rncntirtron f Energy

Our muscles also undergo anaerobic respiration during vigorous exercrseand produce lactic acid.

No oxygcn No oxYgon

Glucose Fyruvate 'S!!lfg--> Lactic acid + EnergyIn cvtopl:rsrr

will happen when

yeast cells are ad,d,ed ta sugan' solution?

cluring actiue exe'r'cise, lat:tic acid q,ccum,ulates in th.e muscl,es?

grease is applied, auer th,e upper and, lower surface of leaues?

glucose is com.pletely oxidised, in th,e body of an organism,?

air enters the nasal ca,uities?

Anaerobic respiration or fermentation will take place due to the absence ofoxygen. The sugar is converted into ethanol.

^ Nrj o\\'uer')Susar -_:'Y'-:1=-_> Ethanol + Carbon dioxide" l,'r:i r,rr,nfrr1 rrrt

Life Processe

t 'rtl

.T.'Ti

Q,,25. De-,

Ans. Brer

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ir ii

i::

l::

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I Ansz'P-'--r: a-

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( ;- _

& e.23.

Ans.

What(,)

(,,)

(iii)(iu)

(u)

(,)

(li) Accumulation of lactic acid in the muscles causes muscle cramps. Later on,lactic acid reduces and the cramps stop.

(rrr) At1 the stomata wiil close, which will stop exchange of gases rn the leaves.(lu) It will lead to aerobic respiration. It releases carhon dioxide, water and

energy.(r,) The arr is filtered and moistened by the hairs present in the nasal cavities.

q,. 24" How does the process of breutltirug au.t of air or expit"atioll accur in hum,an beings'!Explain.

Ans. Erpiration: It is the process of brealhing out of erir. The following events occurduring expiration: - ^{ns'. Diaphragm comes back to its original dorne shape as the muscles of the

diaphragna relax". Simultaneously, the rib muscles also relax.

6 e.2;

!

Life Processes rJ1.{15

",'he thoracic cavity comes back to its original size.

' The volurne of the thoracic cavity decreases, while its air pressure increases.The air, rich in carbon dioxide, is expelled out.

Qt es.' Descri.he the euents occurring during the process of breatfi,ing in lt,un-rans.'Ans. Breathing involves exchange of gases in the lungs and tissues.

It rnvoh,es the following processes:(i) Inhalatlon.' During this process, air, rich in oxvgen, enterr, the ::ostrils and

passes rnto alveoii of the lungs as a result of the contractlon cf rib musclesand diaphragm"

(ii) Excho,nge of gases in the lungs: A s alveoli have higher oxygen concentrationand lower carbon dioxide c(,ncentration, in cornparison to the blood, theoxygen diffuses into blood tr.nd carbon dioxrde diffuses into ah,eoli.

(iii) Exchange of gases in, the tisswes: The cells produce carbon dioxrd.e 'lue tometabolic activities" Carbon dioxicte concentration is rnore in the tissues andso it is reieased into the blood. Oxygen from the blood diffuses into thetissues because of difference in concentration.

(iu) Exhalatian: LL is caused by the relaxation of the rib muscles and thediaphragm. which causes the expulsion of carbon dioxide fi,om the l*ngsthrough the nostrils.

wtat is pyruuate? How is it produced? what is its function in a cell?Pyruvate is a three carhon rnolecule. trt is produced by the breakdown of glucosemolecules in the cytopl.asm"

Furtction: Pyruvate, driring aerobic respiration, enters into mitochond.ria, whereit is oxidised by oxygen to produce carbon clioxide and water. accompanied byrel.ease of a large amount of energy.

In mitochondria

,'-a:,/Q.2d.\

[ry/

n1 [n cl'torrlirsnttTIUCOSe

l\o r)xr gonPyruvate

+ Energy

0rvgen present

In yeastNo Oxlgen

In our musclc r:cll-c

-+

i\() o\yBen

Carlron dioxrde + Water+ Ener:glEthanol + Carbon dic xirle+ Energyl,actie acid + Energv

l+ q,. 27.

During anaerollic respiration, in the yeast cell, pyruvate prod.uces ethyl alcoholand carbon dioxide and, in our muscles, pyrr"rvate is converted. into laciic acid. Atrittle arnount of energy is released during anaerobic respiration..Aruswer the following:

(i) wat happens to the air in nasal cauities before it reaches the trachea?(ii) \Yhy rloes the exchange of gases occur continuousry in the lungs?(iii) Why are lungs made up of rnillion s of alueoli?(iu) What is the role of hair in the nasa,l cauity?(u) During uigorous exercise, oxygerL is u"sed up faster than it is mad,e auailable

to the m,uscles. rlow do muscles obtain energy for contraction, and, expan,sion?Ans.

(

(,)ii)

Refer to Q. 41 on Page 81.38.some air is left in the lungs, which is known as residual volume" It gi.vessufficient time for oxygen uptake by tire blood riue to which exchrrxge *fgases occllr coni.rnucuslv.

81.66 C BSE Science Self-Tu,tor--X

(iil) Miilions of alveoli Lncrease surface area tremenclouslv for effective exchangeof gases.

(ll') Hair present in the nasal cavity catch dust particles and any other foreignmaterial present in the air.

(u) During vigorous exercise, the muscles uncl"ergo anaerobic respiration andproduce lactic acid, accompanied with release of energy. This energy is usedfor contraction and expansion of muscles.

Q. 28. Describe u.n, experintent to proue that carlson dioxid,e releqsed. by us clurin"grespi,ration is ntuch nl,ore as compared ta that present in the atmospl,eye.

Ans. (l) 'rake equal. arnounts of lime water in two test tubes A and B.(ii) In test tube A blow air. Nore the

time taken by lime water to turnmilky.

(ili) in the other test tube B pass arrthrough a pic,h.hari or a syringe.

(lu) Note the time taken by lime war,erto tu;r:n milky.

(u) Time taken by lime water to turnmiihy in test tuhe A is much lessas compared to test tube B.

(r.,i) I'his experirnent shows that theamount of carbon dioxide blownout is more than the amountpresent in air.

Q. 2e. (i) wh.y is hl*od can si,dered, the n,r,st effici,ent tissae to cat ry oxygen ta d,ifferentparts of f,he bocly?

(ii) Horu is c.orban dioxide cqrried to Lungs?(.iii) Ilout da iungs cornntunicate with the outside?

{itt) Haut da fi,shes bt"eath,e?

(u) lYhot h,appens to energy released d.uring oxid,ution, af glu,cose?(i) Blood is the most efficient tissue as it carries oxygen by combining it with

the haernoglokrin rnolecule present in the red biood corpuscles.(il) Biood carries carbon dioxide dissolved in plasma, for its removal through

the Lungs.

(lli) Lungs cornmunicate rvith the outside through the respiratory passageconsisting of nostrils, rlasal cavities, pharynx, trachea. bronchi. bronchiollsand alveoli.

(iu) Fishes take in water through their motrth and force it over the grlls. Here,dissolved oxygen passes into the blood.

(u) As glucose is being oxrdised. the energy released is used i1 synthesising ATprnolecules, which are utih.sed to provide energy for various functions ofthe body"

Ans"

L:ts Prlcesses

B

Fig. 1.16

{t* Q so" 'Respiratit

-{ns. The proce. It provir

through. Oxygen

annount. Oxidatic

highly ti. During t

extra de

. Vital orgrespirati

Q. 3i. Differeruti.ainhaled an

Ans. Refer to eMuscles atcavity causthe lungs.cavity to nsqueezirrg r

Q. 32. Desuibe th

Ans. The transpvesseis (fbr

(i) Aortadiffer,

(ii) Pwlmtright

(iii) Superbody r

(iu) Inferirbody t

(tt) pul,mc

Q. 33. Y\lh.ich aninAns. Birds and n

. The blood

. Left atrrr"ventricle.

. From theblood to C

. From thethe right :

Rubbertube

Test tubecontaininglime rrvater

b

!

Life Processes 81.67

S Q. 30. 'Respiration is the uital functian of the bod.y.'Justify.Ans. The process of respiration is the vital function of the body because;

' It provides oxygen which is vital for life. Air, rich in oxygen, enters our bodythrough the process of breathing, which is an essential step of respiration.

' Oxygen oxidises food (giucose) in the cells, resulting in the production of largeamount of energy, which is vital to perform the various trody activities.

' Oxidation of food results in production of large amount of carbon dioxrde, ahighly toxic gas, which is expelled out by the proce ss of breathing.

' During excessive need of energy, the rate of respiration increases to meet theextra demand.

" Vital organs like the heart and the brain require oxygen, which is provided byrespiration.

Q. 41. Differentiate beh.ueen breathing and respiration. Explain. clearly how the air isinhaled. a,nd exhaled during breathing in, humaws.

Ans. Refer to Q. 23 on Page 81.48.

Muscles attached to the ribs and those of the diaphragm contract and lift the chestcavity causing its volume to increase and thus resulting in inhalation of air iirtothe lungs. The rib muscles, along with the diaphragm, relax, trringing the chestcavitS, tc' normal condition. This causes an increase in the air pressure, causingsqueeziiig of the trungs, which results in exhalation of air.

Q. 32. Describe the tru,nsportation system of the human heart.Ans. The transportation system of the human heart consists of the following blood

vessels (for figure refer to Fig. 1.3 on Page 81.7):(i) Aorta: It arises from the left ventricle and carries oxygenated blood to

different parts of the body.(.ii) Pulmonary arteries.'There are two pulmonary arteries which arise from the

right ventricle and carry deoxygenated. blood to the lungs for oxygenation.(iii) Superiar uena cou,c. brings deoxygenated biood from the upper part of the

body to the right atrium.(iu) Inferior uerLCL couo brings deoxygenated blood from the lower part of the

body to the right atrium.

,t. (u) Pulmonary uein s bring oxygenated blood from the iungs to the left atrium.O Q. SS. Which anima,ls show d,ouble circulation of bLood. and, why?

Ans. Birds and rnamrnals show douhle circulation of blood.

" The blood flows trvice from the heart.

' Left atrium receives blood from the lungs, which is pushed intr: the leftventricle.

' From the left ventricle, blood enters aorta, a big vessel, which distributes theblood to different parts of the body"

' Front the body, blood is collected by two big veins and they pour the blood intothe right atrium. Thus, blood enters and leaves the heart trn ice.

S e.sb.

81.68 CBSE Science Self-Ttr,tor-X

Q. 34. Mention the functions of blood.

Ans. The following functions are performed by the blood:

(i) Transportation: Biood transports various substances to different parts ofthe body such as:

(o) The digested food and other nutrients from the intestine are absorbedby the blood and transported to aII parts ofthe body.

(b) After the air enters the lungs, the oxygen from alveoli diffuses into theblood capillaries. It is then transported by the blood to every cell ofthebody. Carbon dioxide, produced in the tissues due to metabolicactivities, is brought to the lungs so that it can be released outside.

(ii) Waste products like urea are produced in the various tissues of the body dueto metabolism. of proteins. These are brought to the kidneys by the blood so

that they can be expelied out.

(rii) Blood regulates body temperature.

(iu) It prevents loss of blooct by coagulating it during an injury.Explain the following:

(i) Why d.oes an artery d,iuid,e into smaller and. smaller uessels on entering atissue?

How is bacleward flow of blood from th,e uentricles to the auricles preuented?

How is double circulation beneficial to us?

Why ,ioes our transport system require a heq,rt o,nd a network of blood

uessels?

Why are the ueins thin-walled and why do they possess ualues?

Arteries divide into smaller and smaller vessels so that blood comes in close

contact with the cells of the tissue for effieient exchange of materials.

Backward flow of blood from the ventricles to the auricles is prevented byvalves present between them"

During double circulation, oxygenated and deoxygenated blood circulateseparately. This allows efficient supply of oxygen to meet the demand forhigh energy required to maintain the body temperature and for variousother activities of the body.

Heart is required to pump the blood into a network of blood vessels whichare required for distribution and collection of blood, to and from differentparts of the body, and for efficient exchange of gases and materials.

Blood pressure reduces considerably in the veins so they do not have thickwalls. The valves present at intervals in the veins allow movement of blood

. only in one direction.(f; Q. s6. Answer the foltowing:

(il Why do plants require less energy?

(ii) Does the d,istance between the soil contacting orgcln, i.e", the root, ccichlarophyll containing organ, i.e., leaf , affect the trunsport af ruul ntateric.:und" energy stare?

Life Processes

(iii) Hot(iu) Wtt

tu) w,Ans. (l) pla

less

(ii) wh,conldiffiroot

(jjl) Soilmag

(lu) Duecellsfrou

(u) Wat.

. ox)'E

6 e. g7. what are,substance

Ans. . In plantmineralcells. T1

water. a

. Sieve tuhelp rn r

form.. The cir

substanrhaemoglsuitableflows thu

Q. 38. W\r.y d,o pttAns. Plants ner

found in ththe soil. Tleaves. Thsmall. In r

so processorganised r

a dead tisrffiat is lj,tthe body?

Write a notc

Ans. Lymph is arof blood cell

(ii)(iii)(iu)

(u)

Ans. (r)

(ii)

(iii)

(iu)

(u)

Life Pracesses

(iii)(iu)

(u)

Ans. (r)

B1.69

How d,oes soil fulfitl the main reqwirernents of a plant?

W4ra,t wil,l be the rate of tra,nspirati,on' wh,eru the air is dry ar'd, Eoil is wet?

V/h.at would. be the fate of a water molecule in'the cells of a leaf?

Plants do not move and, also, they contain many dead cells" So, they requu'eless energy.

When the distance is less between the soil-contacting organ and chlolophyllcontaining organ, then the conduction can occllr by the simple process ofdiffusion. When the distance is more, as in the case of tall trees, then eitherroot pl:er sure or transpiration pull help in the process"

Soil contains water and minerais iike nitrogen, phosphorrrs, irc;n and

magnesium"(iu) Due to the diff'erence in the concentration of water vapour in air and rn the

cells of leaf, transpiration rate wiil be high, leading to absorption of rvaterfrom wet soil.

(u) Water molecule, on reaching the cells of a leaf, will split into hydrogen andoxygen in the presence of sunlight.

{b Q. BT. Whot are the characteristics features and. special tissues or orgoru$ tt;lti.ch transportsu,bstances in plants an'd artintals?

Ans. . In plants, xylem is the most suitable tissue to transport rvater, with dissolvedminerals, to all the parts ofthe plant. The xylem vessels and tracheids are dead

cells" They have great affinity for water molecules. Since, plants transpirewater" a suction force is created, which pulls the water up.

. Sleve tubes of the phloem trssue are living and, along with r:ompanion cells,

help in translocation of food in all directions. Food is translocated rn aquectls

form.. The circulatory system in animals, including man, rapidly transports

substances to each part of the body aird removes the wasle efficiently. The

haemoglobin present in the RBCs has great affinity for O2 and is the mostsuitatrle and efficrent molecule to carrlr oxygen. The blood pumped b5, the heartflows through the vessels"

Q. 38. llrh,y do plants n,eed a well organised con,du,cting systern?

Ans. Plants need raw material like nitrogen, phosphorus and other minerals are

found in the soil. These substances are taken up by roots which are in contact wrththe soil. These substances must reach the photosynthesising organ, namelyleaves. This may be achieved by simple process of diffusion if the plant size is

small. In tall plants, i.e., trees the distance between roots and leaves is bigso process of diffusron cannot be possible. For this there is a need of a wellorganised conducting system. This system is made up of xylern tissue which rs

./:.,-,..''. a dead tissue "

,&,:,,9C,"'rfuat is lymph? What functiorus d.oes it perform? IIow does l-v*Lplt. ci.rtttLute itthe bocly?

OrWrite a note on lymphatic system in htlmqti l:eings, statirug fun cti.or+s *{ t,h,e l),mph.

Ans. Lymph is another fluid connective tissue In ilur circulator;, systeffi. Scrme amountof blood cells (lymphocytes), plasma, proteins, gases and nutrienLs escape from

(,,)

(rrr)

81.70 CBSE Science Self-Tutor-X

very fine poresr present in the capillaries, into the interceliular spaces presentbetween the cells. This forms the tissue fluid or lymph. Red blood corpuscles arenot present in lymph. As it lies outside the cells, it is also called extracellularfluid"Function,s of lymph:. Lymph drains excess fluid from the extracellular spaces irrto the blood.

. Lymph returns proteins and fluid to the tissues through circulation.

. Digested and absorbed fats are carried by the lymph.

Circulation of lym.ph: From intercellular spaces, the lymph is drained intolymphatic capillaries v,'hich join to form lymph vessels. Vessels open into the bigvein, superior vena cava, thus returning the fluid to the blood. It is purified by thelungs along with bLood.

Q. 40. Draw a diagram of tke heart and show the flow of blood, with the help of arrou-ts,

in the uarious chq,rnbers of the heart. Label the parts through, wh,ich the blood

will flow.Ans. R,efer to Fig. 1.3 on Page 81.7.

Q" 41. Differentiate between: (One difference only)

(i) Lymph and, blood

(i,i) RBCs and platelets(.iii) Plasma and blood

(iu) Xylem arud, phloem

(u) Root pressure and transpiration pullAns. (l)

Lym.ph BIood

Life Processes

(iu)

X1,'lemx1-lemfor corfrom tthe plr

(u)

Root pis effetthe rc,<{l

Lymph is plasma without RBCs. Itcontains blood ceiis Qymphocytes),proteins, gases and nutrients.

RBCs

RBCs are spherical disc-shapedcelis, without nucleus, but containha-emoglobin, which can transportoxygen to different parts of the body.

Plasma

Plasma is a colourless fluid matrixof blood containing proteins, salts,hormones and vitamins.

Blood contains RBCs. It is red incolour as RBCs containhaemogiobin, which carries oxygento dif[t,rent parts of the body.

Platelets

Platelets are very small blood cellsand help in clotting of blood at thesite o{ injury and, thus, stopbleeding.

Blood,

Blood is plasma containing RBCs,WBCs and platelets. It is red incolour due to the presence ofhaernoslobin.

(l q.42. Exptain li(l) IIlo(ii) Hou'(iiil II no

(iu,) Is:h(i- ) II7: *

Ans. (l) AJl c-.,L -.

*-cri(li) O:*-;

ent€l

(lii) -{m:(lu) In ra

bet*-

(u) On e

srte c

Q. 43. Draw a dirof the faii.a

(i) Puln;

(ii) Aortc

(iii) Puln(iu) \:er'.a

Ans. Refer to Fi

q.44. Answer tht(i) Ment

(ii) trlent(iii) llhat

(i,ii)