Class 10 Class 10 Science Notes

CBSE Class 10 Science Chapter 6 Life Processes

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Life Processes

Life Processes

Life Processes


Living beings are the organisms which show all the characteristics of life i.e growth, movement, reproduction, respiration etc.
Living beings are made up of cells, which form tissues, tissues form organs and organs form organ systems which ultimately form a living body and this organization should be maintained by movement of molecules around all the time as all the structures are made up of molecules.

Life processes are the maintenance functions which take place even when the organisms are in rest to keep the living organisms alive.
Nutrition, respiration, transportation, excretion are all basic life processes in order to remain alive.


  • Nutrition is the process of intake of source of energy from outside the body in order to grow, develop and synthesize proteins.
  • Nutrition in different organisms is fulfilled in different ways.
  • Some organisms use simple food material in the form of carbon dioxide and water and some use complex food materials which is first broken down in to simpler ones and is then used by the body.
  • Enzymes are the biocatalysts which help in the breaking down of complex substances into simpler ones.
  • The method of obtaining food is different in different organisms.
  • Mode of nutrition can be classified into autotrophic and heterotrophic nutrition based on the method of obtaining food.
  • Autotrophic organisms prepare their own food by the process of photosynthesis. Example- plants.
  • Heterotrophic organisms depend on autotrophic organisms for food. Example- human beings.


Autotrophic Nutrition

The nutrition in which organisms prepare their own food from inorganic raw materials like carbon di oxide and water is called autotrophic nutrition.
Green plants produce their food by the process of photosynthesis.
Photosynthesis is the process of production of food from carbon dioxide and water in the presence of sunlight and chlorophyll.
Events of photosynthesis-
  1. Chlorophyll absorbs light energy.
  2. Light energy is converted to chemical energy.
  3. Water molecule splits into hydrogen and oxygen.
  4. Carbon dioxide reduces to carbohydrates.
  5. Green dots present in some cells of leaves are calledchloroplasts which contain chlorophyll.
  6. The site of photosynthesis in a cell of the leaf is chloroplasts.
  7. The plants obtain carbon dioxide by tiny pores called as stomata present on the surface of the leaves of plants.
  8. The carbon dioxide gas enters into the leaves through the stomata.
  9. Stomatal pores are surrounded by a pair of guard cells and guard cells regulate opening and closing of stomata.
  10. Water can be lost through stomatal hence the pores are closed when not needed for photosynthesis.
  11. When water flows into guard cells these swell causing the stomatal pores to open and the pores close if the guard cells shrink.
  12. The raw materials such as water, nitrogen, phosphorous etc. used in photosynthesis are also taken up by the plants from different sources.
  13. Water is absorbed by plants from the soil by the roots in terrestrial plants.
  14. Nitrogen, phosphorous, iron, magnesium is taken up from soil.
  15. Nitrogen is either taken in the form of inorganic nitrates or as organic compounds prepared by bacteria from atmospheric nitrogen.
  16. Nitrogen is used in the synthesis of proteins.

Heterotrophic Nutrition

Heterotrophic nutrition is the mode of nutrition in which an organism depends on other living organisms for food.
Depending on the type of food, heterotrophs can be divided into 3 types-
  1. Carnivores- organisms which eat only animals. Example- lion, snake.
  2. Herbivores- organisms which eat only plants. Example- rabbit, elephant.
Omnivores- organisms which eat both plants and animals. Example- crow, dog.
Some organisms break down the food material outside the body and then absorb it. Example- yeast and mushrooms.
Some other animals break the food inside the body before absorbing. Example- human, cat.
Some organisms derive their food from the body of other organisms without killing them. Example- ticks, leeches.

Nutrition in Unicellular Organisms

In unicellular organisms, the food is taken by the entire surface.
Amoeba, is an unicellular organism which takes in food using temporary finger like projections of the cell which fuse over the food particle to form a food vacuole and the food is broken down inside the food vacuole and diffuse into cytoplasm.
The undigested food is taken to the cell surface and excreted.
Paramecium, another unicellular organism has a definite spot in the body to take in food.
Food is moved to the spot by the movement of hair like structure called cilia in the body of paramecium.

Nutrition in Human Beings

  • Nutrition in human beings takes place through parts like mouth, stomach, small intestine, large intestine, anus
  • The process of nutrition takes place through an alimentary canal which is a long tube extending from the mouth to the anus.
  • Complex foods should be converted to smaller ones by crushing the food with teeth and by the enzyme salivary amylase of saliva secreted by salivary glands.
  • Salivary amylase breaks down starch which is a complex molecule into sugar.
  • As the canal lining is soft so food is made wet to make the passage smooth.
  • The alimentary canal has different parts and the food should be moved in a regulated manner along the digestive tube so the food is processed properly in each part.
  • The canal has muscles that contract rhythmically to push the food forward and this movement of food is called peristaltic movement which occurs all along the gut.
  • The food is taken to the stomach through the food pipe or oesophagus from mouth.
  • The muscular wall of stomach mixes the food with more digestive juices secreted by the gastric glands present in the wall of the stomach.
  • Gastric gland releases hydrochloric acid, a protein digesting enzyme called as pepsinmucus.
  • Enzyme pepsin acts on the food and hydrochloric acid facilitates the action of pepsin.
  • Mucus protects the inner lining of the stomach from the action of acid under normal conditions.
  • From stomach acidic food enters small intestine, the longest part of alimentary canal and this is regulated by sphincter muscle.
  • Complete digestion of carbohydrates, protein and fats take place in the small intestine by the secretions of liver and pancreas.
  • Bile secreted by liver makes the acidic food alkaline and acts on large globules of fat into smaller globules so that the enzymes can act on easily.
  • The process of breakdown of large fats globules into small globules which increases the efficiency of the pancreatic enzymes is called
  • Pancreas secrete pancreatic juice which contains enzyme trypsin to break for digesting proteins, lipase for digesting emulsified fats.
  • The walls of the small intestine contain glands secreting intestinal juice which converts finally complex carbohydrates into glucose, proteins to amino acids and fats into fatty acids and glycerol.
  • The inner wall of small intestine has finger like projections called villi which are richly supplied with blood vessels and these take absorbed food to all the cells of the body.
  • The unabsorbed food is sent to the large intestine where more villi absorb water from this undigested material and the rest of the material is excreted from the body by anus.
  • The excretion of waste materials by anus is regulated by the anal sphincters.



Respiration is a process in which glucose is broken down with the help of oxygen and energy is released along with the production of carbon dioxide and water.
There are two types of respiration i) aerobic respiration ii) anaerobic respiration.
Aerobic respiration- the process of respiration that takes place in the presence of oxygen.
Example- glucose(a 6-carbon molecule) breaks into pyruvate(a 3-carbon molecule)  and in the mitochondria pyruvate is broken down into 3 molecules of carbon dioxide and water with the release of energy.
Glucose –> pyruvate + energy à carbon dioxide + water + energy.
Anaerobic respiration- the process of respiration that takes place in the absence of oxygen.
  • In yeast cells, glucose (a 6-carbon molecule) breaks into pyruvate (a 3-carbon molecule) and pyruvate is then converted to ethanol(a 2-carbon molecule) and carbon dioxide.
Glucose –> pyruvate + energy –> ethanol + carbon dioxide + energy.
  • If there is a lack of oxygen in our muscle cells, pyruvate breaks in a different pathway. Glucose (a 6-carbon molecule) breaks into pyruvate (a 3-carbon molecule) and pyruvate is then converted to lactic acid (a 3-carbon molecule) along with the release of energy.
Glucose –>pyruvate + energy –>  lactic acid + energy.
The energy released during the process of respiration is immediately used to synthesize another molecule called as ATP.
ATP is made from ADP and inorganic phosphate with the help of energy released during respiration.
ATP is broken down into a fixed amount of energy and then drive the endothermic reactions in the cell.

Respiration in plants

  • Plants exchange gases through stomata.
  • The large inter-cellular spaces ensure that all the cells are in contact with air.
  • Carbon dioxide and oxygen are exchanged in and out of the cells by the process of
  • Diffusion is directed by environmental conditions and the requirements of the plants.
  • During night, in the absence of sunlight photosynthesis do not take place and hence carbon dioxide is released but not used up by the plants.
  • During the day, there is no carbon dioxide release because the released carbon dioxide is used up by the plants for photosynthesis.
  • Oxygen is released instead of carbon dioxide during the day.

Respiration in animals

  • In aquatic animals, rate of breathing is fast due to the less amountof dissolved oxygen in water
  • Fishes take in water through their mouths and force it to the gills from where the dissolved oxygen is absorbed by blood.
  • Terrestrial organisms use atmospheric oxygen and different animals use different organs for breathing.
  • The surface of the organs is very fine and delicate and placed within the body.
  • Passages are there in the body which takes the oxygen rich air to the area of respiration.

Respiration in human beings

  • Air is taken in through nostrils and the air is filtered while passing through the nostrils by fine hairs and mucus that line the passage.
  • From nostrils air passes to throat where rings of cartilages are present to ensure that air passage does not collapse.
  • Air reaches lungs from throats and within the lungs the passage divides into smaller and smaller tubes ending into balloon-like structure called alveoli.
  • Network of blood vessels are present in the alveoli.
  • During breathing air is sucked into the lungs and fills the expanded alveoli.
  • The oxygen in the alveolar air is taken by the blood vessels after releasing carbon dioxide collected from all the cells of the body in the alveoli.
  • Lungs contain a residual volume of air during the breathing cycle.
  • Respiratory pigments present in the body take up oxygen from lungs and transport to all the cells of the body.
  • Hemoglobin is the respiratory pigment of human beings present in the red blood cells which has high affinity for oxygen.
  • As carbon dioxide is more soluble in water than oxygen so it is transported mostly in the dissolved form in our blood.

Transportation in Animals

  • Transportation can be defined as the movement of any substance from one place to another.
  • Water and nutrients required for all metabolic activities should be transported in the body of plants and animals.
  • The waste material or excretory products should also move to the region of excretion.
  • Transportation in animal takes place through circulatory system which includes blood, blood vessels and heart.
  • Blood is a fluid connective tissue consists of fluid medium called plasma.
  • Functions of blood are to transport food, oxygen, carbon dioxide, nitrogenous wastes, salts.
  • A pumping organ is necessary to push the blood around the body.
  • Heart is the muscular pumping organ which pushes the blood around the body.
  • Tube like structure through which carry blood to cells, tissues and organs are called as blood vessels.
  • Two special blood vessels are arteries and veins.
  • After reaching the organs, the arteries divide in to small branches called as capillaries.
  • Heart in another component of circulatory system which is also known as pumping organ.
  • Heart consists of four chambers separated by a partition to avoid mixing of oxygenated and deoxygenated blood.


  • Heart is the muscular pumping organ which pushes the blood around the body.
  • Blood transports carbon dioxide to the lungs for oxygen from the cells for removal and carries oxygen from the lungs to the heart and heart pump the blood to all the cells of the body.
  • Heart has different chambers such as right atrium, left atrium, right ventricle, left ventricle to prevent the mixing of oxygenated blood and carbon dioxide rich blood.
  • The thin walled upper chamber, left atrium, relaxes and oxygenated blood enters it.
  • Left atrium then contracts and the next chamber left ventricle, expands and thus blood enters it.
  • When the left ventricle contracts the blood is pumped out to all the cells of the body.
  • Deoxygenated blood from the body reaches the right upper chamber, right atrium when it expands.
  • As the right atrium contacts, the lower chamber, right ventricle, dilates.
  • Separation of right and left side of heart allows efficient supply of oxygen to the body and useful for animals that have high energy needs to maintain their body temperature.
  • In some animals, body temperature depends on the temperature in the environment and thus they do not use energy to maintain body temperature.
  • Amphibians and reptiles have three chambered heart and allows some mixing of oxygen and deoxygenated blood.
  • Fishes have two chambered heart and the blood is pumped to the gills for oxygenation and transported directly to all the cells of the body.
  • When blood goes through the heart twice during each cycle, the process is called as double circulation.
  • In fish, blood goes only once through the heart and thus fish shows single circulation.

Blood Vessels

  • Blood vessels are the tube like structures which carry the blood through cells, tissues and organs.
  • Two types of blood vessels are arteries and veins which are connected to the heart for transporting blood.


  • Carry blood rich in oxygen from the heart to all the cells of the body.
  • The pressure exerted by the arteries while blood leave heart is rapid and thus wall walls of arteries are thick.


  • Veins carry blood rich in carbon di oxide from all the cells of the body to the heart.
  • The pressure exerted by the walls of the veins is less and have thin walls.
  • Valves present in the veins ensure that the blood flows only towards the heart.
  • The arteries divide in to extremely small thin branches on reaching the tissues. These small branches are called as capillaries.
  • Capillaries have walls and are one-cell thick through which the exchange of materials between the blood and surrounding cells take place across his thin wall.


  • Platelets are the colorless tiny blood cells without nucleus, circulate through the blood stream.
  • During injury, the bleeding needs to minimize naturally.
  • Leakage of blood can also reduce the efficiency of the pumping system due to the loss of pressure.
  • Platelet cells are present in the body to plug the leaks and to stop bleeding by clotting the blood at the points of injury.
  • Platelets circulate around the body and clot the blood whenever wherever necessary.


  • Lymph is another fluid involved in transportation.
  • Some amount of plasma, proteins and blood cells escape into the intercellular spaces in the tissues to form lymph or tissue fluid.
  • Lymph is similar to blood plasma but colorless and contains less protein.
  • Lymph drains into lymphatic capillaries which join to form large lymph vessels and which open into larger veins.
  • Function of lymph is to carry absorbed digested fat from intestine and it also drains excess fluid from extra cellular space back into the blood.

Composition of Lymph

1) Water
2) Solids: The solid content found in the lymph is as follows:
  • Proteins: Three varieties of proteins are found–albumin, globulin and fibrinogen.
  • Fats
  • Carbohydrates
  • Other Constituents: Urea,creatinine, chlorides, inorganic phosphorus, calcium, enzymes and antibodies are also present.

Functions of Lymph

1) It supplies nutrition and oxygen to those parts where blood cannot reach.
2) It drains away excess tissue fluids.
3 Lymph returns proteins to the blood from the tissue spaces.
4) Fats from the intestine are also absorbed through the lymph.
5) The lymphocytes and monocytes of lymph act as defensive cells of the body.
6) The lymph also removes bacteria from tissues.

Transportation in Plants

Soil is the natural and richest source of raw material for plants.
Raw materials like nitrogen, phosphorous and other minerals are absorbed by plants from soil by roots.
Plants absorb water and minerals from soil by roots and transport to the leaves.
As the distance between roots and leaves is large, diffusion is not sufficient to provide raw materials to leaves and energy to roots.
Plants use slow transport system but large as required in tall plants to transport energy from leaves and raw materials form roots.
A group of special cells forming vascular tissue transport water and nutrients to all the cells of the plants.
Two types of vascular tissues are xylem and phloem.
Xylem transports water and minerals obtained from the soil.
Phloem transports products of photosynthesis from the leaves to other parts of the plant.
Vessels, tracheids of the roots, stems and leaves are connected to form a continuous system in xylem cells to transport water to all the parts of the plants.
Cells in the roots which are in contact with the soil take up ions which creates a difference of concentration between the roots and the soil and therefore water moves to the roots to eliminate the difference.
Water is moved into xylem of roots and from where it is pushed upward.
Plants use different mechanisms to pull water upwards through xylem like-
  • Water which is lost through stomata is replaced by water absorbed by the roots.
  • Evaporation of water from leaf creates a suction force which pulls water.
The loss of water in the form of water vapor is called
Importance of transpiration-
  • Regulates temperature.
  • Helps in absorption of water and upward movement of water and minerals.
When stomata are open during the day, large amount of water is lost and thus upward movement of water also becomes more.
Phloem transports soluble products of photosynthesis, amino acids, and other substances.
The transport of soluble products of photosynthesis is called translocation.
The substances are transported to the storage organs of roots, fruits and seeds.
The translocation takes place in the sieve tubes with the help of adjacent companion cells.
The movement of substances is bidirectional i.e both upward and downward.
Energy from ATP is utilized for translocation.
Materials like sucrose move to phloem using energy, increasing the osmotic pressure of the tissue causing water to move and materials in the phloem to tissues according to the plant’s needs.
Example- when the buds grow these need energy and sugar stored in the root or stem would be transported to the buds as sugar is an energy giving molecule.
  • The biological process of removal of harmful nitrogenous metabolic waste from the body is called excretion.
  • Unicellular organisms excrete by diffusion and multicellular organisms use specialized organ to perform same function.

Excretion in Human Beings

  • A pair of kidneys, a pair of ureters, a urinary bladder and a urethra constitutes the human excretory system.
  • Kidneys are present on either side of the backbone in the abdomen.
  • Kidneys produce urine and urine from kidney passes through the ureters into the urinary bladder and remains stored their until it is released through the urethra.
  • Urine is produced to filter out waste products from the blood.
  • Nephrons are basic structural and functional unit of kidney.
  • Cluster of thin walled blood capillaries called glomerulus in the nephron filtrate the urine and each cluster is associated with cup shaped end of a tube called Bowman’s capsule.
  • Substances like glucose, amino acids, salts and a major amount of water is selectively reabsorbed from the initial filtrate as the urine flows along the tube.
  • Reabsorption depends on the amount of excess water in the body and dissolved waste to be excreted.
  • The urine from kidney enters the long tube called ureter.
  • Ureter connects the kidney with the urinary bladder and urine from the kidney is passed to urinary bladder and stored in the bladder.
  • When the pressure in the expanded bladder leads to the urge to urinate, the urine is passed out through urethra.

Excretion in Plants

  • Oxygen, a waste product of photosynthesis is released.
  • Excess water is removed by transpiration.
  • Some waste products may get stored in the leaves which fall off.
  • Many waste products are stored in vacuoles.
  • Some waste products are stored as resins and gums in old xylem.
  • Plants excrete some waste materials into the soil around them.


SCIENCE Revision Notes

Chapter:01  Chemical Reaction & Equation
Chapter:02  Acid Base & Salt
Chapter:03  Metals & Non Metals
Chapter:04  Carbon & its Components
Chapter:05  Periodic Classification of Elements
Chapter:06  Life Processes
Chapter:07  Control & Coordinates
Chapter:08  How do Organisms Reproduce
Chapter:09  Heridity & Evolution
Chapter:10  Light Reflection Refraction
Chapter:11  The Human Eye & the Colourful World
Chapter:12  Electricity
Chapter:13  Magnetic Effect of Electric Current
Chapter:14  Source Of Energy
Chapter:15  Our Environment
Chapter:16  Management of Natural Resource

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