TRANSPORTATION IN ANIMALS AND PLANTS 123Table 11.1 Pulse rateS. No. Name Pulse per minute1.2.3.4.5.Compare the values you obtained andinsert them in Table 11.1.Paheli explained that thepulmonary artery carries bloodfrom the heart, so it is called anartery and not a vein. It carriescarbon dioxide-rich blood to thelungs. Pulmonary vein carriesoxygen-rich blood from thelungs to the heart.Veins are the vessels which carrycarbon dioxide-rich blood from all partsof the body back to the heart. The veinshave thin walls. There are valves presentin veins which allow blood to flow onlytowards the heart.Refer to Fig. 11.3. Do you see thearteries divide into smaller vessels. Onreaching the tissues, they divide furtherinto extremely thin tubes calledcapillaries. The capillaries join up toform veins which empty into the heart.HeartThe heart is an organ which beatscontinuously to act as a pump for thetransport of blood, which carries othersubstances with it.Imagine a pump working foryears without stopping! Absolutelyimpossible. Yet our heart works like apump non-stop. Let us now learn aboutthe heart.The heart is located in the chestcavity with its lower tip slightly tiltedtowards the left (Fig. 11.1). Hold yourfingers inwards on your palm. ThatFig. 11.3 Schematic diagram of circulationCapillariesVein ArteryHeartLungsI am confused! I have learntthat an artery alwayscarries oxygen-rich blood.PulmonaryarteryPulmonaryveinSCIENCE124makes your fist. Your heart is roughlythe size of your fist.What will happen if the blood rich inoxygen and the blood rich in carbondioxide mix with each other? To avoidthis from happening, the heart has fourchambers. The two upper chambers arecalled the atria (singular: atrium) andthe two lower chambers are called theventricles (Fig. 11.4). The partitionbetween the chambers helps to avoidPaheli wonders which side ofthe heart will have oxygen-richblood and which side will havecarbon dioxide-rich blood.Fig. 11.4 Sections of human heartVena CavaRight atriumRight ventriclePartition completelyseparating the twohalvesLeft atriumLeft ventriclePulmonary arteryPulmonary veinmixing up of blood rich in oxygen withthe blood rich in carbon dioxide.To understand the functioning of thecirculatory system, start from the rightside of the heart in Fig. 11.3 and followthe arrows. These arrows show thedirection of the blood flow from the heartAortaTRANSPORTATION IN ANIMALS AND PLANTS 125to the lungs and back to the heart fromwhere it is pumped to the rest of thebody.HeartbeatThe walls of the chambers of the heartare made up of muscles. These musclescontract and relax rhythmically. Thisrhythmic contraction followed by itsrelaxation constitute a heartbeat.Remember that heartbeats continueevery moment of our life. If you placeyour hand on the left side of your chest,you can feel your heartbeat. The doctorfeels your heartbeats with the help ofan instrument called a stethoscope.A doctor uses the stethoscope as adevice to amplify the sound of the heart.It consists of a chest piece that carries asensitive diaphragm, two ear pieces anda tube joining the parts. Doctors canget clues about the condition of yourheart by listening through astethoscope.Let us construct a model of astethoscope with the materials that areavailable around us.Activity 11.2Take a small funnel of 6 ñ7 cm indiameter. Fix a rubber tube (50 cm long)tightly on the stem of the funnel. Stretcha rubber sheet (or a balloon) on themouth of the funnel and fix it tightlywith a rubber band. Put the open endof the tube on one of your ears. PlaceTable 11.2 Heartbeat and pulse rateName of student While resting After running (4 –5 minutes)Heartbeat Pulse rate Heartbeat Pulse rateFig. 11.5 Instrument to hear heartbeat(a) Stethoscope (b) Model ofstethoscopeChest PieceEar PieceTubeSCIENCE126the mouth of the funnel on your chestnear the heart. Now try to listencarefully. Do you hear a regularthumping sound ? The sound is that ofheart beats. How many times did yourheart beat in a minute ? Count againafter running for 4ñ5 minutes. Compareyour observations.Record your own pulse rate and heartbeat and that of your friends whileresting and after running and record inTable 11.2. Do you find any relationshipbetween your heart beat and pulse rate?Each heart beat generates one pulse inthe arteries and the pulse rate perminute indicates the rate of heart beat.The rhythmic beating of the variouschambers of the heart maintaincirculation of blood and transport ofsubstances to the different parts of thebody.Boojho wonders if sponges andhydra also have blood? Animals suchas sponges and Hydra do not posses anycirculatory system. The water in whichthey live brings food and oxygen as itenters their bodies. The water carriesaway waste materials and carbon dioxideas it moves out. Thus, these animals donot need a circulatory fluid like theblood.Let us now learn about the removalof waste other than carbon dioxide.11.2 E XCRETION IN A NIMALSRecall how carbon dioxide is removedas waste from the body through thelungs during exhalation. Also recall thatthe undigested food is removed duringegestion. Let us now find out how theother waste materials are removed fromthe body. You may wonder where theseunwanted materials come from!When our cells per for m theirfunctions, certain waste products arereleased. These are toxic and hence needto be removed from the body. Theprocess of removal of wastes producedin the cells of the living organisms iscalled excretion. The parts involved inexcretion forms the excretory system.Excretory system in humansThe waste which is present in the bloodhas to be removed from the body. Howcan this be done? A mechanism to filterthe blood is required. This is done bythe blood capillaries in the kidneys.When the blood reaches the two kidneys,it contains both useful and harmfulsubstances. The useful substances areabsorbed back into the blood. Thewastes dissolved in water are removedas urine. From the kidneys, the urinegoes into the urinary bladder throughThe English physician, William Harvey(A.D.1578 ñ1657), discovered thecirculation of blood. The currentopinion in those days was that bloodoscillates in the vessels of the body.For his views, Harvey was ridiculedand was called ìcirculatorî. He lostmost of his patients. However, beforehe died, Harveyís idea aboutcirculation was generally accepted asa biological fact.TRANSPORTATION IN ANIMALS AND PLANTS 127Sometimes a personís kidneys maystop working due to infection orinjury. As a result of kidney failure,waste products start accumulating inthe blood. Such persons cannotsurvive unless their blood is filteredperiodically through an artificialkidney. This process is called dialysis.tube-like ureters. It is stored in thebladder and is passed out through theurinary opening at the end of amuscular tube called urethra (Fig. 11.6).The kindeys, ureters, bladder andurethra form the excretory system.An adult human being normallypasses about 1ñ1.8 L of urine in 24hours. The urine consists of 95% water,2.5% urea and 2.5% other wasteproducts.We have all experienced that we sweaton a hot summer day. The sweatPaheli wants to knowwhether other animals alsourinate?The way in which waste chemicalsare removed from the body of theanimal depends on the availabilityof water. Aquatic animals like fishes,excrete cell waste as ammonia whichdirectly dissolves in water. Someland animals like birds, lizards,snakes excrete a semi-solid, whitecoloured compound (uric acid). Themajor excretory product in humansis urea.Fig. 11.6 Human excretory systemKidneyUreterUrinary bladderUrethracontains water and salts. Boojho hasseen that sometimes in summer, whitepatches are formed on our clothes,especially in areas like underarms.These marks are left by salts present inthe sweat.Does sweat serve any other function?We know that the water kept in anearthen pot (matka) is cooler. This isbecause the water evaporates from thepores of the pot, which causes cooling.Urinary openingSCIENCE128Similarly, when we sweat, it helps to coolour body.11.3 T RANSPORT OF S UBSTANCES INP LANTSIn Chapter 1 you learnt that plants takewater and mineral nutrients from the soilthrough the roots and transport it to theleaves. The leaves prepare food for theplant, using water and carbon dioxideduring photosynthesis. You also learnt inChapter 10 that food is the source ofenergy and every cell of an organism getsenergy by the breakdown of glucose. Thecells use this energy to carry out vitalactivities of life. Therefore food must bemade available to every cell of anorganism. Have you ever wondered howwater and nutrients absorbed by theroot are transported to the leaves? Howis the food prepared by the leaves carriedto the parts which cannot make food?Transport of water andmineralsPlants absorb water and minerals bythe roots. The roots have root hair.The root hair increase the surface areaof the root for the absorption of waterand mineral nutrients dissolved inwater. The root hair is in contact withthe water present between the soilparticles [Fig. 11.7 (a)].Can you guess how water movesfrom the root to the leaves? What kindof transport system is present in plants?Boojho thinks that plantsmay have pipes to transportwater to the entire plant likewe have in our homes for thesupply of water.(a)(b)Xylem vessels Fig. 11.7 Transport of water and minerals in(a) a section of root, (b) a treeRoot hairTRANSPORTATION IN ANIMALS AND PLANTS 129SugarsolutionPotatoWaterWell, Boojho is right. Plants havepipe-like vessels to transport water andnutrients from the soil. The vessels aremade of special cells, forming thevascular tissue. A tissue is a group ofcells that perform specialised functionin an organism. The vascular tissue forthe transport of water and nutrients in theplant is called the xylem [Fig. 11.7 (a)].The xylem forms a continuousnetwork of channels that connects rootsto the leaves through the stem andbranches and thus transports water tothe entire plant [Fig. 11.7 (b)].Paheli says her mother putsladyfinger and other vegetables inwater if they are somewhat dry.She wants to know how waterenters into them.Boojho wants to know whyplants absorb a large quantityof water from the soil, then giveit off by transpiration!Fig. 11.8 Transportation of water through cellsinto a dish containing a small amountof water. Make sure that the level of wateris below the level of the pin. Allow theapparatus to stand for a few hours.You would find an increase in thelevel of sugar solution. How did waterget inside the potato? For very shortdistances water can move from one cellto another. In the same way waterreaches xylem vessels of the root fromthe soil [Fig. 11.7 (a)].TranspirationIn Class VI you learnt that plants releasea lot of water by the process oftranspiration.Plants absorb mineral nutrients andwater from the soil. Not all the waterabsorbed is utilised by the plant. Thewater evaporates through the stomatapresent on the surface of the leaves byYou know that leaves synthesisefood. The food has to be transported toall parts of the plant. This is done bythe vascular tissue called the phloem.Thus, xylem and phloem transportsubstances in plants.Activity 11.3Take a large potato and peel off its outerskin. Cut one of its ends to make thebase flat. Now make a deep and hollowcavity on the opposite side. Fill half ofthe cavity with sugar solution and markthe level by inserting a pin in the wallof the potato (Fig. 11.8). Put the potatoPinSCIENCE130What you have learnt
In most animals the blood that circulates in the body distributes foodand oxygen to different cells of the body. It also carries waste products todifferent parts of the body for excretion.
Circulatory system consists of the heart and blood vessels.
In humans, blood flows through arteries and veins and the heart actsas a pumping organ.
Blood consists of plasma, RBC, WBC and platelets. Blood is red due tothe presence of a red pigment, haemoglobin.
The human heart beats about 70ñ80 times per minute in an adultperson. This is called heart rate.
Arteries carry blood from the heart to all parts of the body.
Veins carry blood from all parts of the body back to the heart.
Removal of waste products from the body is called excretion.
Excretory system of humans consists of two kidneys, two ureters, aurinary bladder, and urethra.
Salts and urea are removed along with water as sweat.the process of transpiration. Theevaporation of water from leavesgenerates a suction pull (the samethat you produce when you suckwater through a straw) which canpull water to great heights in thetall trees. Transpiration also coolsthe plant.KeywordsAmmoniaArteryBloodBlood vesselsCapillaryCirculatory systemDialysisExcretionExcretory systemHaemoglobinHeart beatKidneysPhloemPlasmaPlateletsPulseRed blood cellRoot hairStethoscopeSweatTissueUreaUreterUrethraUric acidUrinary bladderVeinWhite blood cellXylemTRANSPORTATION IN ANIMALS AND PLANTS 131
Fish excrete waste substances such as ammonia which directly dissolvein water.
Birds, insects and lizard excrete uric acid in semi-solid form.
Water and mineral nutrients are absorbed by roots from the soil.
Nutrients are transported along with water to the entire plant via thevascular tissue called xylem.
The vascular tissue for the transport of food to the various parts of theplant is phloem.
A lot of water is lost by plants in the form of vapour through stomataduring transpiration.
Transpiration generates a force which pulls up water absorbed by theroots from the soil, to reach the stem and leaves.Exercises1. Match structures given in Column I with functions given in Column II.Column I Column II(i) Stomata (a) Absorption of water(ii) Xylem (b) Transpiration(iii) Root hairs (c) Transport of food(iv) Phloem (d) Transport of water(e) Synthesis of carbohydrates2. Fill in the blanks.(i) The blood from the heart is transported to all parts of the body bythe .(ii) Haemoglobin is present in cells.(iii) Arteries and veins are joined by a network of .(iv) The rhythmic expansion and contraction of the heart is called.(v) The main excretory product in human beings is .(vi) Sweat contains water and .(vii) Kidneys eliminate the waste materials in the liquid form called.(viii) Water reaches great heights in the trees because of suction pullcaused by .SCIENCE1323. Choose the correct option:(a) In plants, water is transported through(i) xylem (ii) phloem(iii) stomata (iv) root hair(b) Water absorption through roots can be increased by keeping theplants(i) in the shade(ii) in dim light(iii) under the fan(iv) covered with a polythene bag4. Why is transport of materials necessary in a plant or in an animal?Explain.5. What will happen if there are no platelets in the blood?6. What are stomata? Give two functions of stomata.7. Does transpiration serve any useful function in the plants? Explain.8. What are the components of blood?9. Why is blood needed by all the parts of a body?10. What makes the blood look red?11. Describe the function of the heart.12. Why is it necessary to excrete waste products?13. Draw a diagram of the human excretory system and label the variousparts.Extended Learning — Activities and Projects1. Find out about blood groups and their importance.2. When a person suffers from chest pain, the doctor immediately takesan ECG. Visit a doctor and get information about ECG. You may evenlook up an encyclopaedia or the internet.Did you know?There is no substitute for blood. If people lose blood from surgery or injuryor if their bodies cannot produce enough blood, there is only one way toget it ó through transfusion of blood donated by volunteers. Blood isusually in short supply. Donating blood does not decrease the strength of