life processes

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class 10-life processes

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Life processes

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WHAT ARE LIFE PROCESSES? The maintenance functions of living organisms must go on even when they are not doing anything particular. Even when we are just sitting in class, even if we are just asleep, this maintenance job has to go on. The processes which together perform this maintenance job are life processes. There are 4 major life processes : Nutrition Respiration Transportation excretion

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Modes of nutrition: 1.Autotrophic nutrition 2.Heterotrophic nutrition 3.Nutrition in single-celled organism 4.Nutrition in human beings .

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AUTOTROPHIC NUTRITION Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis . It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy . This material is taken in the form of carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll. Carbohydrates are utilised for providing energy to the plant. The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant.

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The following events occur during this process – ( i) Absorption of light energy by chlorophyll . (ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. (iii) Reduction of carbon dioxide to carbohydrates . PHOTOSYNTHESIS

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stomata are tiny pores present on the surface of the leaves. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. But it is important to note here that exchange of gases occurs across the surface of stems , roots and leaves as well. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis . The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink. STOMATA

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Cross-section of a Leaf (a) Open and (b) closed stomatal pore

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NUTRITION IN SINGLE-CELLED ORGANISM In single-celled organisms, the food may be taken in by the entire surface. But as the complexity of the organism increases, different parts become specialised to perform different functions. For example, Amoeba takes in food using temporary finger-like extensions of the cell surface which fuse over the food particle forming a food-vacuole (Fig. 6.5). Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out.

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NUTRITION IN HUMAN BEINGS or The alimentary canal is basically a long tube extending from the mouth to the anus . We eat various types of food which has to pass through the same digestive tract. Naturally the food has to be processed to generate particles which are small and of the same texture .

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This is achieved by crushing the food with our teeth. Since the lining of the canal is soft, the food is also wetted to make its passage smooth. When we eat something we like, our mouth ‘waters’. This is actually not only water, but a fluid called saliva secreted by the salivary glands. Another aspect of the food we ingest is its complex nature. If it is to be absorbed from the alimentary canal , it has to be broken into smaller molecules. This is done with the help of biological catalysts called enzymes . The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while chewing by the muscular tongue.

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From the mouth, the food is taken to the stomach through the food-pipe or oesophagus . The stomach is a large organ which expands when food enters it. The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices. These digestion functions are taken care of by the gastric glands present in the wall of the stomach. These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus. The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin. What other function do you think is served by the acid? The mucus protects the inner lining of the stomach from the action of the acid under normal conditions. STOMACH

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From the stomach , the food now enters the small intestine. This is the longest part of the alimentary canal which is fitted into a compact space because of extensive coiling. The small intestine is the site of the complete digestion of carbohydrates , proteins and fats. It receives the secretions of the liver and pancreas for this purpose. The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act. Bile juice from the liver accomplishes this in addition to acting on fats. Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile salts break them down into smaller globules increasing the efficiency of enzyme action. SMALL INTESTINE

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The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats. The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

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ABSORPTION The digested food is taken up by the walls of the intestine. The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues.

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LARGE INTESTINE The unabsorbed food is sent into the large intestine where more villi absorb water from this material. The rest of the material is removed from the body via the anus. The exit of this waste material is regulated by the anal sphincter.

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During the process of respiration, complex organic compounds such as glucose are broken Down to provide energy in the form of ATP. ATP is used to provide energy for other reactions in the cell . Diverse organisms RESPIRE in different ways – some use oxygen to break-down glucose Completely into carbon dioxide and water, some use other pathways that do not involve oxygen. In all cases, the first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This Process takes place in the cytoplasm.

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Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide. The other product is water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration . The release of energy in this aerobic process is a lot greater than in the anaerobic process. AEROBIC RESPIRATION

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The pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration . Sometimes, when there is a lack of oxygen in our muscle cells, another pathway for the break-down of pyruvate is taken . Here the pyruvate is converted into lactic acid which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps. ANAEROBIC RESPIRATION

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Break-down of glucose by various pathways

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RESPIRATION IN HUMAN-BEINGS In human beings, air is taken into the body through the nostrils . The air passing through the nostrils is filtered by fine hairs that line the passage. The passage is also lined with mucus which helps in this process. From here, the air passes through the throat and into the lungs . Rings of cartilage are present in the throat. These ensure that the air-passage does not collapse . Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli . The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood-vessels .

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The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body . respiratory pigments take up oxygen from the air in the lungs and carry it to tissues which are deficient in oxygen before releasing it. In human beings , the respiratory pigment is haemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles.

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TRAnsport of substances from one Part to other to meet the Requirements of the organism is Transportation .

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TRANSPORTATION IN HUMAN-BEINGS blood transports food, oxygen and waste materials in our bodies. Blood is a fluid connective tissue. Blood consists of a fluid medium called plasma in which the cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by the red blood cells. Many other substances like salts, are also transported by the blood. We thus need a pumping organ to push blood around the body , a network of tubes to reach all the tissues and a system in place to ensure that this network can be repaired if damaged.

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OUR PUMP-THE HEART The heart is a muscular organ which is as big as our fist Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide. The carbon dioxide-rich blood has to reach the lungs for the carbon dioxide to be removed , and the oxygenated blood from the lungs has to be brought back to the heart . This oxygen-rich blood is then pumped to the rest of the body.

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Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts , the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation .

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The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing. Such separation allows a highly efficient supply of oxygen to the body . This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature . In animals that do not use energy for this purpose, the body temperature depends on the temperature in the environment. it goes through the heart twice during each cycle in humans. This is known as double circulation . OXYGEN ENTERS THE BLOOD IN THE LUNGS

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THE TUBES - BLOOD VESSELS Arteries are the vessels which carry blood away from the heart to various organs of the body. Since the blood emerges from the heart under high pressure , the arteries have thick, elastic walls. Veins collect the blood from different organs and bring it back to the heart. They do not need thick walls because the blood is no longer under pressure, instead they have valves that ensure that the blood flows only in one direction. On reaching an organ or tissue, the artery divides into smaller and smaller vessels to bring the blood in contact with all the individual cells. The smallest vessels have walls which are one-cell thick and are called capillaries . Exchange of material between the blood and surrounding cells takes place across this thin wall. The capillaries then join together to form veins that convey the blood away from the organ or tissue .

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MAINTENANCE BY PLATELETS What happens if this system of tubes develops a leak? Think about situations when we are injured and start bleeding. Naturally the loss of blood from the system has to be minimised . In addition, leakage would lead to a loss of pressure which would reduce the efficiency of the pumping system. To avoid this, the blood has platelet cells which circulate around the body and plug these leaks by helping to clot the blood at these points of injury.

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There is another type of fluid also involved in transportation. This is called lymph or tissue fluid. Through the pores present in the walls of capillaries some amount of plasma, proteins and blood cells escape into intercellular spaces in the tissues to form the tissue fluid or lymph. It is similar to the plasma of blood but colourless and contains less protein. Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph vessels that finally open into larger veins. Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood. LYMPH

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Plant transport systems move energy stores from leaves and raw materials from roots. These two pathways are constructed as independently organised conducting tubes. One, the xylem moves water and minerals obtained from the soil. The other, phloem transports products of photosynthesis from the leaves where they are synthesised to other parts of the plant. TRANSPORTATION IN PLANTS

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In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant. At the roots, cells in contact with the soil actively take up ions. This creates a difference in the concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference. This means that there is steady movement of water into root xylem, creating a column of water that is steadily pushed upwards. TRANSPORT OF WATER

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Plants use another strategy to move water in the xylem upwards to the highest points of the plant body. Provided that the plant has an adequate supply of water, the water which is lost through the stomata is replaced by water from the xylem vessels in the leaf. In fact, evaporation of water molecules from the cells of a leaf creates a suction which pulls water from the xylem cells of roots. The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration. Thus, transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation.

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The transport of soluble products of photosynthesis is called translocation and it occurs in the part of the vascular tissue known as phloem. Besides the products of photosynthesis, the phloem transports amino acids and other substances. These substances are especially delivered to the storage organs of roots, fruits and seeds and to growing organs. The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward and downward directions. TRANSPORT OF FOOD AND OTHER SUBSTANCES

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the translocation in phloem is achieved by utilising energy . Material like sucrose is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have less pressure. This allows the phloem to move material according to the plant’s needs. For example, in the spring, sugar stored in root or stem tissue would be transported to the buds which need energy to grow.

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Biological process involved in the removal of these harmful metabolic wastes from the body is called excretion .

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EXCRETION IN HUMAN BEINGS The excretory system of human beings includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are located in the abdomen , one on either side of the backbone. Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra. EXCRETORY SYSTEM IN HUMAN BEINGS

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nitrogenous waste such as urea or uric acid are removed from blood in the kidneys. the basic filtration unit in the kidneys is a cluster of very thin-walled blood capillaries that collects the filtered urine. Each kidney has large numbers of these filtration units called nephrons. some substances in the initial filtrate , such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra . STRUCTURE OF A NEPHRON

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EXCRETION IN PLANTS Plants use completely different strategies for excretion than those of animals . Oxygen is also a waste product generated during photosynthesis. They can get rid of excess water by transpiration. For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. Other waste products are stored as resins and gums, especially in old xylem. Plants also excrete some waste substances into the soil around them.

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FOR WATCHING THE PRESENTATION

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PRESENTED BY - (GROUP-6) A Y E S H N A N d S H I T I j N I R U D H U B H A N K A R CLASS- X-C (II shift), K.V.No.2, Delhi Cantt .

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j AYESH MOHAN X-C (II shift) ANAND X-C (II shift) KSHITIJ MISHRA X-C (II shift) ANIRUDH TANWAR X-C (II shift) SUBHANKAR BRAHMA X-C (II shift)

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