Science PDF - Transportation in Animals and Plants

7 Transportation in Animals and Plants Y ou have learnt earlier that all organisms need food, water and oxygen for survival. They need to transport all these to various parts of their body. Further, animals need to transport wastes to parts...

7 Transportation in Animals and Plants Y ou have learnt earlier that all organisms need food, water and oxygen for survival. They need to transport all these to various parts of their body. Further, animals need to transport wastes to parts from where they can be removed. Have you wondered how all this is achieved? Look Heart at Fig. 7.1. Do you see the heart and the blood vessels? They function to Vein transport substances and together form the circulatory system. In this chapter, you shall learn about transport of Artery substances in animals and plants. 7.1 CIRCULATORY SYSTEM Blood What happens when you get a cut on your body? Blood flows out. But what is blood? Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports waste for removal from the body. How does the blood carry various substances? Blood is composed of a fluid, called plasma in which different types of cells are suspended. Why is the colour of Fig. 7.1 Circulatory system blood red ? (Arteries are shown in red colour and veins in blue) Reprint 2024-25  One type of cells are the red blood Since the blood flow is rapid and at a cells (RBC) which contain a red pigment high pressure, the arteries have thick called haemoglobin. Haemoglobin elastic walls. binds with oxygen and transports it to Let us perform an activity to study all the parts of the body and ultimately the flow of blood through arteries. to all the cells. It will be difficult to Activity 7.1 provide oxygen efficiently to all the cells of the body without haemoglobin. The Place the middle and index finger of presence of haemoglobin makes blood your right hand on the inner side of your appear red. left wrist (Fig. 7.2). Can you feel some The blood also has white blood cells throbbing movements? Why do you (WBC) which fight against germs that think there is throbbing? This may enter our body. throbbing is called the pulse and it is Boojho fell down while playing a due to the blood flowing in the arteries. game and his knee got injured. Blood Count the number of pulse beats in one was coming out from the cut. After some minute. time, he noticed that bleeding had How many pulse beats could you stopped and a dark red clot had plugged count? The number of beats per minute the cut. Boojho was puzzled about this. is called the pulse rate. A resting The clot is formed because of the person, usually has a pulse rate between presence of another type of cells in the 72 and 80 beats per minute. Find other blood, called platelets. places in your body where you can feel the pulse. Blood vessels Record your own pulse beats per There are different types of blood vessels minute and those of your classmates. in the body. You know that during Insert the values you obtained in inhalation a fresh supply of oxygen fills Table 7.1 and compare them. the lungs. Oxygen has to be transported to the rest of the body. Also, the blood picks up the waste materials including carbon dioxide from the cells. This blood has to go back to the heart for transport to the lungs for removal of carbon dioxide as you have learnt in Chapter 6. So, two types of blood vessels, arteries and veins are present in the body. (Fig. 7.1) Arteries carry oxygen-rich blood from the heart to all parts of the body. Fig. 7.2 Pulse in the wrist TRANSPORTATION IN ANIMALS AND PLANTS 71 Reprint 2024-25  Table 7.1 Pulse rate S. No. Name Pulse per minute 1. 2. I am confused! I have learnt 3. that an artery always 4. carries oxygen-rich blood. 5. Paheli explained that the Veins are the vessels which carry pulmonary artery carries blood carbon dioxide-rich blood from all parts from the heart, so it is called an of the body back to the heart. The veins artery and not a vein. It carries have thin walls. There are valves present carbon dioxide-rich blood to the in veins which allow blood to flow only lungs. Pulmonary vein carries towards the heart. oxygen-rich blood from the Lungs lungs to the heart. Pulmonary Pulmonary artery vein Refer to Fig. 7.3. Do you see the Heart arteries divide into smaller vessels? On reaching the tissues, they divide further Vein into extremely thin tubes called Artery capillaries. The capillaries join to form veins which empty into the heart. Heart Capillaries The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other Fig. 7.3 Schematic diagram of circulation substances with it. Imagine a pump working for Blood Donation years without stopping! Absolutely Hundreds of people die due to impossible. Yet our heart works like a unavailability of blood. Voluntary pump non-stop. Let us now learn about blood donation is harmless and painless and can save precious lives. the heart. Blood can be donated at hospitals and The heart is located in the chest other places authorised by the cavity with its lower tip slightly tilted government. Donated blood are stored towards the left (Fig. 7.1). Hold your with special care in Blood Banks. fingers inwards on your palm. That 72 SCIENCE Reprint 2024-25 makes your fist. Your heart is roughly chambers. The two upper chambers are the size of your fist. called the atria (singular: atrium) and What will happen if the blood rich in the two lower chambers are called the oxygen and the blood rich in carbon ventricles (Fig. 7.4). The partition dioxide mix with each other? To avoid between the chambers helps to avoid this from happening, the heart has four Vena Cava Aorta Pulmonary artery Pulmonary vein Right atrium Left atrium Partition completely separating the two Left ventricle halves Right ventricle Fig. 7.4 Sections of human heart mixing up of blood rich in oxygen with the blood rich in carbon dioxide. Paheli wonders which side of To understand the functioning of the the heart will have oxygen-rich circulatory system, start from the right blood and which side will have side of the heart in Fig. 7.3 and follow carbon dioxide-rich blood. the arrows. These arrows show the direction of the blood flow from the heart TRANSPORTATION IN ANIMALS AND PLANTS 73 Reprint 2024-25 to the lungs and back to the heart from heart by listening through a where it is pumped to the rest of the stethoscope. body. Let us construct a model of a stethoscope with the materials that are Heartbeat available around us. The walls of the chambers of the heart are made up of muscles. These muscles Activity 7.2 contract and relax rhythmically. This Take a small funnel of 6 –7 cm in rhythmic contraction followed by its diameter. Fix a rubber tube (50 cm long) relaxation constitute a heartbeat. tightly on the stem of the funnel. Stretch Remember that heartbeats continue a rubber sheet (or a balloon) on the every moment of our life. If you place mouth of the funnel and fix it tightly your hand on the left side of your chest, with a rubber band. Put the open end you can feel your heartbeat. The doctor of the tube on one of your ears. Place 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 and a tube joining the parts. Doctors can get clues about the condition of your Tube Chest Piece (a) Stethoscope (b) Model of stethoscope Ear Piece Fig. 7.5 Instrument to hear heartbeat Table 7.2 Heartbeat and pulse rate Name of student While resting After running (4 –5 minutes) Heartbeat Pulse rate Heartbeat Pulse rate 74 SCIENCE Reprint 2024-25 the mouth of the funnel on your chest as it enters their bodies. The water near the heart. Now try to listen carries away waste materials and carbon carefully. Do you hear a regular dioxide as it moves out. Thus, these thumping sound ? The sound is that of animals do not need a circulatory fluid heart beats. How many times did your like the blood. heart beat in a minute ? Count again Let us now learn about the removal after running for 4–5 minutes. Compare of waste other than carbon dioxide. your observations. 7.2 EXCRETION IN ANIMALS Record your own pulse rate and heart Recall how carbon dioxide is removed beat and that of your friends while as waste from the body through the resting and after running and record in lungs during exhalation. Also recall that Table 7.2. Do you find any relationship the undigested food is removed during between your heart beat and pulse rate? egestion. Let us now find out how the Each heart beat generates one pulse in other waste materials are removed from the arteries and the pulse rate per the body. You may wonder where these minute indicates the rate of heart beat. unwanted materials come from! The rhythmic beating of the various When our cells perform their chambers of the heart maintain functions, certain waste products are circulation of blood and transport of released. These are toxic and hence need substances to the different parts of the to be removed from the body. The body. process of removal of wastes produced Boojho wonders if sponges and in the cells of the living organisms is hydra also have blood? Animals such called excretion. The parts involved in as sponges and Hydra do not possess excretion form the excretory system. any circulatory system. The water in which they live brings food and oxygen Excretory system in humans The waste which is present in the blood The English physician, William Harvey has to be removed from the body. How (A.D.1578 –1657), discovered the can this be done? A mechanism to filter circulation of blood. The current the blood is required. This is done by opinion in those days was that blood the blood capillaries in the kidneys. oscillates in the vessels of the body. When the blood reaches the two kidneys, For his views, Harvey was ridiculed it contains both useful and harmful and was called “circulator”. He lost substances. The useful substances are most of his patients. However, before absorbed back into the blood. The he died, Harvey’s idea about wastes dissolved in water are removed circulation was generally accepted as as urine. From the kidneys, the urine a biological fact. goes into the urinary bladder through TRANSPORTATION IN ANIMALS AND PLANTS 75 Reprint 2024-25  contains water and salts. Boojho has seen that sometimes in summer, white Kidney patches are formed on our clothes, especially in areas like underarms. These marks are left by salts present in the sweat. Does sweat serve any other function? We know that the water kept in an earthen pot (matka) is cooler. This is because the water evaporates from the Ureter pores of the pot, which causes cooling. Paheli wants to know whether other animals also urinate? Urinary bladder The way in which waste chemicals Urethra are removed from the body of the animal depends on the availability of water. Aquatic animals like fishes, Urinary opening excrete cell waste as ammonia which Fig. 7.6 Human excretory system directly dissolves in water. Some land animals like birds, lizards, tube-like ureters. It is stored in the snakes excrete a semi-solid, white bladder and is passed out through the coloured compound (uric acid). The urinary opening at the end of a major excretory product in humans muscular tube called urethra (Fig. 7.6). is urea. The kindeys, ureters, bladder and urethra form the excretory system. Sometimes a person’s kidneys may An adult human being normally stop working due to infection or passes about 1–1.8 L of urine in 24 injury. As a result of kidney failure, hours. The urine consists of 95% water, waste products start accumulating in 2.5% urea and 2.5% other waste the blood. Such persons cannot products. survive unless their blood is filtered We have all experienced that we sweat periodically through an artificial on a hot summer day. The sweat kidney. This process is called dialysis. 76 SCIENCE Reprint 2024-25 Similarly, when we sweat, it helps to cool The root hair increase the surface area our body. of the root for the absorption of water and mineral nutrients dissolved in 7.3 TRANSPORT OF SUBSTANCES IN water. The root hair is in contact with PLANTS the water present between the soil In Chapter 1 you learnt that plants take particles [Fig. 7.7 (a)]. water and mineral nutrients from the soil Can you guess how water moves through the roots and transport it to the from the root to the leaves? What kind leaves. The leaves prepare food for the of transport system is present in plants? plant, using water and carbon dioxide during photosynthesis. You also learnt in Chapter 6 that food is the source of energy Boojho thinks that plants and every cell of an organism gets energy may have pipes to transport water to the entire plant like by the breakdown of glucose. The cells we have in our homes for the use this energy to carry out vital activities supply of water. of life. Therefore food must be made available to every cell of an organism. Have you ever wondered how water and nutrients absorbed by the root are transported to the leaves? How is the food prepared by the leaves carried to the parts which cannot make food? Transport of water and minerals Plants absorb water and minerals by the roots. The roots have root hair. Root hair (b) (a) Fig. 7.7 Transport of water and minerals in Xylem vessels (a) a section of root, (b) a tree TRANSPORTATION IN ANIMALS AND PLANTS 77 Reprint 2024-25  Well, Boojho is right. Plants have pipe-like vessels to transport water and nutrients from the soil. The vessels are made of special cells, forming the vascular tissue. A tissue is a group of cells that perform specialised function in an organism. The vascular tissue for the transport of water and nutrients in the plant is called the xylem [Fig. 7.7 (a)]. Fig. 7.8 (a) Stem placed in coloured water The xylem forms a continuous network of channels that connects roots to the leaves through the stem and branches and thus transports water to the entire plant [Fig. 7.7 (b)]. (b) (c) Fig. 7.8 (b) Water moves up in the stem (c) Enlarged view of open end of stem Paheli says her mother puts Does any part of the herb appear ladyfinger and other vegetables in red? If yes, how do you think the colour water if they are somewhat dry. reached there? She wants to know how water You can cut the stem across and look enters into them. for the red colour inside the stem (Fig. 7.8(b) and 7.8(c)). You know that leaves synthesise From this activity we see that water food. The food has to be transported to moves up the stem. In other words, stem all parts of the plant. This is done by conducts water. Just like the red ink, the vascular tissue called the phloem. minerals dissolved in water also move Thus, xylem and phloem transport up the stem, along with water. Water substances in plants. and minerals go to leaves and other Activity 7.3 plant parts, through narrow tubes We would require a glass tumbler, water, (xylem) inside the stem (Fig. 7.7(b)). red ink, a tender herb (e.g., Balsam), and a blade for this activity. Pour water to fill one-third of the Boojho wants to know why tumbler. Add a few drops of red ink to plants absorb a large quantity the water. Cut the base of the stem of of water from the soil, then give the herb and place it in the glass as shown it off by transpiration! in Fig. 7.8(a). Observe it the next day. 78 SCIENCE Reprint 2024-25 Transpiration on the surface of the leaves by the process In Class VI you learnt that plants of transpiration. The evaporation of water release a lot of water by the process of from leaves generates a suction pull (the transpiration. same that you produce when you suck Plants absorb mineral nutrients and water through a straw) which can water from the soil. Not all the water pull water to great heights in the absorbed is utilised by the plant. The water tall trees. Transpiration also cools evaporates through the stomata present the plant. Keywords Ammonia Heart beat Tissue Artery Kidneys Urea Blood Phloem Ureter Blood vessels Plasma Urethra Capillary Platelets Uric acid Circulatory system Pulse Urinary bladder Dialysis Red blood cell Vein Excretion Root hair White blood cell Excretory system Stethoscope Xylem Haemoglobin Sweat 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 from different 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 acts as a pumping organ. Blood consists of plasma, RBC, WBC and platelets. Blood is red due to the presence of a red pigment, haemoglobin. The human heart beats about 70–80 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. TRANSPORTATION IN ANIMALS AND PLANTS 79 Reprint 2024-25  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. Fish excrete waste substances such as ammonia which directly dissolve in 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 the plant 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 the roots from the soil, to reach the stem and leaves. Exercises 1. 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 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 pull caused by. 80 SCIENCE Reprint 2024-25  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 the plants (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 various parts. Extended Learning — Activities and Projects 1. Find out about blood groups and their importance. 2. When a person suffers from chest pain, the doctor immediately takes an ECG. Visit a doctor and get information about ECG. You may even look 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 to get it — through transfusion of blood donated by volunteers. Blood is usually in short supply. Donating blood does not decrease the strength of the donors. TRANSPORTATION IN ANIMALS AND PLANTS 81 Reprint 2024-25