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Transportat ion in Animals

and Plants1 1 Y ou have learnt earlier that allorganisms need food, water andoxygen for survival. They need totransport all these to various parts of their body. Further, animals need totransport wastes to parts from wherethey can be removed. Have you

wondered how all this is achieved? Look at Fig. 11.1. Do you see the heart andthe blood vessels? They function totransport substances and together formthe circulatory system. In this chapter

you shal l learn about transpor t of substances in plants and animals.

11 . 1 C IRCULATORY S YSTEM

Blood

What happens when you get a cut on your body? Blood flows out. But what is blood? Blood is the fluid whichflows in blood vessels. It transportssubstances like digested food from thesmall intestine to the other parts of the

body. It carries oxygen from the lungsto the cells of the body. It also transports

waste for removal from the body.How does the blood carry various

substances? Blood is a liquid, which hascells of various kinds suspended in it.

Heart

Vein

Artery

Why is the colour of blood red ?

F i g . 1 1 . 1 Circulatory sy stem

(Arteries are show n in red colour an d vein in blu e)

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The fluid part of the blood is calledplasma .

One type of cells are the red blood

cel ls (RBC) which contain a red pigment called h a e m o g l o b i n . Haemoglobin binds with oxygen and transports it toall the parts of the body and ultimately to all the cells. It will be difficult toprovide oxygen efficiently to all the cellsof the body without haemoglobin. Thepresence of haemoglobin makes bloodappear red.

The blood also has white blood ce l ls

(WBC) which fight against germs that may enter our body.

Boojho fell down while playing a game and his knee got injured. Blood

was coming out from the cut. After sometime, he noticed that bleeding hadstopped and a dark red clot had pluggedthe cut. Boojho was puzzled about this.

The clot is formed because of thepresence of another type of cells in the

blood, called plate le ts .Blood vesse ls

There are different types of blood vesselsin the body. You know that duringinhalation a fresh supply of oxygen fillsthe lungs. Oxygen has to be transportedto the rest of the body.

Also, the blood picks up the wastematerials including carbon dioxide from

the cells. This blood has to go back tothe heart for transport to the lungs for removal of carbon dioxide as you havelearnt in Chapter 10. So, two types of

blood vessels, arteries and v e i n s arepresent in the body. (Fig. 11.1)

Arte r ies carry oxygen-rich bloodfrom the heart to all parts of the body.Since the blood flow is rapid and at a

high pressure, the arteries have thick elastic walls.Let us perform an activity to study

the flow of blood through arteries.

Act iv i ty 11 .1

Place the middle and index finger of your right hand on the inner side of your left wrist (Fig. 11.2). Can you feel somethrobbing movements? Why do you

think there is throbbing? Thisthrobbing is called the pulse and it isdue to the blood flowing in the arteries.Count the number of pulse beats in oneminute.

How many pulse beats could youcount? The number of beats per minuteis called the p u l s e r a t e . A restingperson, usually has a pulse rate between72 and 80 beats per minute. Find other

places in your body where you can feelthe pulse.

Record your own pulse beats per minute and those of your classmates.

F i g . 1 1 . 2 Pulse in the w r i s t

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T RANSPORTATION IN A NIMALS AND P LANTS 1 2 3

Table 1 1 .1 Pulse ra te

S. No . Na m e Puls e pe r m in ut e

1.2.3.4.5.

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 carries

carbon dioxide-rich blood to thelungs. Pulmonary vein carries

oxygen-rich blood from thelungs to the heart.

Veins are the vessels which carry carbon dioxide-rich blood from all partsof the body back to the heart. The veinshave thin walls. There are valves present in veins which allow blood to flow only towards the heart.

Refer to Fig. 11.3. Do you see thearteries divide into smaller vessels. Onreaching the tissues, they divide further into extremely thin tubes calledcapillaries . The capillaries join up toform veins which empty into the heart.

Heart The heart is an organ which beatscontinuously to act as a pump for thetransport of blood, which carries other substances with it.

Imagine a pump working for years without stopping! Absolutely impossible. Yet our heart works like a pump non-stop. Let us now learn about

the heart. The heart is located in the chest

cavity with its lower tip slightly tiltedtowards the left (Fig. 11.1). Hold your fingers inwards on your palm. That F i g . 1 1 . 3 Schema tic diagram of circulation

Capillaries

Vein Artery

Heart

Lungs

I am confused! I have learnt that an artery alwayscarries oxygen-rich blood.

Pulmonary artery

Pulmonary vein

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makes your fist. Your heart is roughly the size of your fist.

What will happen if the blood rich in

oxygen and the blood rich in carbondioxide mix with each other? To avoidthis from happening, the heart has four

chambers. The two upper chambers arecalled the atria (singular: atrium) andthe two lower chambers are called the

v e n t r i c l e s (Fig. 11.4). The partition between the chambers helps to avoid

Paheli wonders which side of the heart will have oxygen-rich

blood and which side will havecarbon dioxide-rich blood.

F i g . 1 1 . 4 Sect ions of hu man heart

Vena Cava

Right atrium

Right ventricle

Partition completely separating the twohalves

Left atrium

Left ventricle

Pulmonary artery

Pulmonary vein

mixing up of blood rich in oxygen with

the blood rich in carbon dioxide. To understand the functioning of thecirculatory system, start from the right side of the heart in Fig. 11.3 and follow the arrows. These arrows show thedirection of the blood flow from the heart

Aorta

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T RANSPORTATION IN A NIMALS AND P LANTS 1 2 5

to the lungs and back to the heart from where it is pumped to the rest of the body.

Hear tbea t The walls of the chambers of the heart are 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 place

your hand on the left side of your chest, you can feel your heartbeat. The doctor feels your heartbeats with the help of an instrument called a stethoscope.

A doctor uses the stethoscope as a device to amplify the sound of the heart.It consists of a chest piece that carries a sensitive diaphragm, two ear pieces anda tube joining the parts. Doctors canget clues about the condition of your

heart by listening through a stethoscope.

Let us construct a model of a

stethoscope with the materials that areavailable around us.

Act iv i ty 11 .2

Take a smal l funnel of 6 7 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 tightly

with a rubber band. Put the open end

of the tube on one of your ears. Place

Table 1 1.2 Heartbeat and pulse ra te

Nam e o f s t ude n t Wh ile re s t in g Aft e r run n in g (4 5 m in ut e s )He art be a t Puls e rat e He art be a t Pu ls e rat e

F i g . 11 . 5 Instrument to hear h eartbeat

(a) Steth oscope (b) Mod el of stethoscope

Chest Piece

Ear Piece

Tube

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the mouth of the funnel on your chest near the heart. Now try to listencarefully. Do you hear a regular

thumping sound ? The sound is that of heart beats. How many times did your heart beat in a minute ? Count againafter running for 45 minutes. Compare

your observations.Record your own pulse rate and heart

beat and that of your friends whileresting and after running and record in

Table 11.2. Do you find any relationship between your heart beat and pulse rate?

Each heart beat generates one pulse inthe arteries and the pulse rate per minute indicates the rate of heart beat.

The rhythmic beating of the variouschambers of the heart maintaincirculation of blood and transport of substances to the different parts of the

body.Boojho wonders if sponges and

h y d r a also have blood? Animals such

as sponges and H y d r a do not posses any circulatory system. The water in whichthey live brings food and oxygen as it

enters their bodies. The water carriesaway waste materials and carbon dioxideas it moves out. Thus, these animals do

not need a circulatory fluid like the blood.Let us now learn about the removal

of waste other than carbon dioxide.

11 . 2 E XCRETION IN ANIMALSRecall how carbon dioxide is removedas waste from the body through thelungs during exhalation. Also recall that the 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 form their functions, 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 is

called excre t ion . The parts involved inexcretion forms the excre to ry sys t em .

Excre to ry sys t em in humans The waste which is present in the bloodhas to be removed from the body. How can this be done? A mechanism to filter the blood is required. This is done by the blood capillaries in the k i d n e y s .

When the blood reaches the two kidneys,it contains both useful and harmfulsubstances. The useful substances areabsorbed back into the blood. The

wastes dissolved in water are removedas urine . From the kidneys, the urinegoes into the urinary bladder through

The English physician, William Harvey (A.D.15781657), discovered thecirculation of blood. The current opinion in those days was that bloodoscillates in the vessels of the body.For his views, Harvey was ridiculed

and was called circulator. He lost most of his patients. However, beforehe died, Harveys idea about circulation was generally accepted asa biological fact.

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T RANSPORTATION IN A NIMALS AND P LANTS 1 2 7

Sometimes a persons kidneys may stop working due to infection or injury. As a result of kidney failure,

waste products start accumulating inthe blood. Such persons cannot survive unless their blood is filteredperiodically through an artificialkidney. This process is called dialysis .

tube-like ure te r s . It is stored in the bladder and is passed out through theurinary opening at the end of a muscular tube called urethra (Fig. 11.6).

The kindeys, ureters, bl adder andurethra form the excretory system.

An adult human being normally

passes about 11.8 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 sweat on a hot summer day. The sweat

Paheli wants to know whether other animals also

urinate?

The way in which waste chemicalsare removed from the body of theanimal depends on the availability of 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.

F i g . 11 . 6 Hum an excretory system

Kidney

Ureter

Urinary bladder

Urethra

contains 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 ( m a t k a ) is cooler. This is

because the water evaporates from thepores of the pot, which causes cooling.

Urinary opening

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Similarly, when we sweat, it helps to coolour body.

11 . 3 T RANSPORT OF S UBSTANCES IN

P LANTSIn Chapter 1 you learnt that plants take

water 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 of energy 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 how

water and nutrients absorbed by theroot are transported to the leaves? How is the food prepared by the leaves carriedto the parts which cannot make food?

Transport of water andminera lsPlants absorb water and minerals by the roots. The roots have root hair.

The root hair increase the surface area of the root for the absorption of water and mineral nutrients dissolved in

water. 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 transport

water to the entire plant like we have in our homes for the

supply of water.

(a )

(b )

Xylem vessels F i g . 1 1 . 7 Transpor t of w a te r and m inera l s in (a) a s ection of r oot, (b) a tr ee

Root hair

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T RANSPORTATION IN A NIMALS AND P LANTS 1 2 9

Sugar solution

Potato

Water

Well, Boojho is right. Plants havepipe-like vessels to transport water andnutrients from the soil. The vessels are

made of special cells, forming thevascular t i ssue . A t i s s u e is a group of cells that perform specialised functionin an organism. The vascular tissue for the transport of water and nutrients in theplant is called the x y l e m [Fig. 11.7 (a)].

The xylem forms a continuo usnetwork of channels that connects rootsto the leaves through the stem and

branches and thus transports water to

the entire plant [Fig. 11.7 (b)].

Paheli says her mother putsladyfinger and other vegetables in water if they are somewhat dry.

She wants to know how water enters into them.

Boojho wants to know why plants absorb a large quantity

of water from the soil, then giveit off by transpiration!

F i g . 1 1 . 8 Transp ortat ion of w ater through cel ls

into a dish containing a small amount of water. Make sure that the level of water is 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 water get inside the potato? For very short distances water can move from one cellto another. In the same way water reaches xylem vessels of the root fromthe soil [Fig. 11.7 (a)].

Transpi ra t ion

In Class VI you learnt that plants releasea lot of water by the process of transpiration.

Plants absorb mineral nutrients and water from the soil. Not all the water absorbed is utilised by the plant. The

water evaporates through the stomata present on the surface of the leaves by

You know that leaves synthesisefood. The food has to be transported toall parts of the plant. This is done by the vascular tissue called the phloem .

Thus, xylem and phloem transport substances in plants.

Act iv i ty 11 .3

Take a large potato and peel off its outer

skin. Cut one of its ends to make the base flat. Now make a deep and hollow cavity on the opposite side. Fill half of the cavity with sugar solution and mark the level by inserting a pin in the wallof the potato (Fig. 11.8). Put the potato

Pin

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What you have learnt

In most animals the blood that circulates in the body distributes food

and 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 7080 times per minute in an adult person. 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, a urinary 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 same

that you produce when you suck

wa ter through a st raw) which canpull water to great heights in thetall trees. Transpiration also cools

the plant.

Keywords

Ammonia Artery BloodBlood vesselsCapillary Circulatory system

DialysisExcretionExcretory systemHaemoglobin

Heart beat KidneysPhloemPlasma PlateletsPulse

Red blood cellRoot hair StethoscopeSweat

TissueUrea Ureter Urethra Uric acidUrinary bladder

Vein White blood cell

Xylem

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T RANSPORTATION IN A NIMALS AND P LANTS 1 3 1

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 the vascular 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 stomata during transpiration.

Transpiration generates a force which pulls up water absorbed by theroots from the soil, to reach the stem and leaves.

Exerc ises

1. Match structures given in Column I with functions given in Column II.

Co lum n I Co lum n 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 carbohydrates

2. Fill in the blanks.

(i) The blood from the heart is transported to all parts of the body by the .

(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 .

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3. 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 bag

4. 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.

Exte nde d Learning Act ivi t ie s an d Project s

1. 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 injury or if their bodies cannot produce enough blood, there is only one way toget it through transfusion of blood donated by volunteers. Blood isusually in short supply. Donating blood does not decrease the strength of the donors.