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Life Processes Chapter Notes - Science Class 10

In this Class 10 chapter on life processes, we will learn about how life springs into action through concealed motions and vibrant growth. Explore the significance of understanding the mechanisms that keep living beings flourishing, from plants to animals.

Life Processes Chapter Notes | Science Class 10These chapter notes summarize the important parts, so that you can quickly understand and remember the main ideas related to this chapter.

What are Life Processes?

These simple points capture the basic ideas that explain what life processes are in living things. 

  • Continuous Maintenance: Even when at rest, living organisms require ongoing maintenance processes to prevent damage and breakdown.
  • Energy Source: Energy for maintenance comes from external sources called food. The process of transferring energy from food to the body is called nutrition.
  • Growth Requirements: For growth, additional raw materials are needed from the environment, often carbon-based substances.
  • Nutritional Diversity: Different organisms use various nutritional processes based on the complexity of carbon sources.
  • Energy Transformation: External energy sources vary, so they are broken down or transformed into a uniform energy source for sustaining cellular functions and growth.
  • Chemical Reactions: Chemical reactions inside the body are necessary for breaking down molecules. Oxidising-reducing reactions are common, often involving oxygen, known as respiration.
  • Multi-cellular Challenges: As organisms grow larger and more complex, specialized tissues handle food and oxygen uptake. This complexity requires a transportation system to distribute these essentials.
  • Waste Management: Energy-generating reactions produce waste by-products. Specialized tissues for waste elimination require a transportation system to remove waste from cells.

Question for Chapter Notes: Life Processes
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What is the process by which energy is transferred from food to the body called?
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  • Nutrition: The process by which an organism takes food and utilizes it, is called nutrition.
  • Need for Nutrition: Organisms need the energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
  • Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
  • Modes of Nutrition
    • Autotrophic Nutrition
    • Heterotrophic Nutrition

Life Processes Chapter Notes | Science Class 10

Autotrophic Nutrition

The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.

  • The organisms which carry out autotrophic nutrition are called autotrophs (green plants).
  • Autotrophic nutrition is fulfilled by the process, by which autotrophs intake CO2 and H2O, and convert these into carbohydrates in the presence of chlorophyll, sunlight is called photosynthesis.

Photosynthesis EquationPhotosynthesis Equation

Nutrition in Plants: Green plants prepare their own food. They make food in the presence of sunlight. Sunlight provides energy’, carbon dioxide and water are the raw materials and chloroplast is the site where food is made.

Question for Chapter Notes: Life Processes
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Which mode of nutrition involves an organism preparing its own food?
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What is Photosynthesis?

Photosynthesis: The process by which green plants prepare food is called photosynthesis.

  • During this process, the solar energy is converted into chemical energy and carbohydrates are formed.
  • Green leaves are the main site of photosynthesis.
  • The green portion of the plant contains a pigment chloroplast, chlorophyll (green pigment).

Raw Materials for Photosynthesis

  • Sunlight
  • Chlorophyll: Sunlight absorbed by chloroplast
  • CO2Enters through stomata, and oxygen (O2) is released as a byproduct through stomata on the leaf.
  • Water: Water + dissolved minerals like nitrogen, phosphorous etc., are taken up by the roots from the soil.

Process of PhotosynthesisProcess of PhotosynthesisHow do raw materials for photosynthesis become available to the plant?

  • Water comes from the soil, through the xylem tissue in roots and stems.
  • Carbon dioxide comes in the leaves through stomata.

Site of Photosynthesis: Chloroplast in the leaf. Chloroplast contains chlorophyll (green pigment)

Main Events of Photosynthesis

  • Absorption of light energy by chlorophyll.
  • Conversion of light energy into chemical energy + splitting (breaking) of water into hydrogen and oxygen.
  • Reduction of CO2 to carbohydrates.
  • Sunlight activates chlorophyll, which leads to splitting of the water molecule.
  • The hydrogen, released by the splitting of a water molecule is utilized for the reduction of carbon dioxide to produce carbohydrates.
  • Oxygen is the by-product of photosynthesis.
  • Carbohydrate is subsequently converted into starch and is stored in leaves and other storage parts.
  • The splitting of water molecules is a part of the light reaction.
  • Other steps are part of the dark reaction during photosynthesis.


Stomata are tiny pores in the epidermis of leaf or stem through which gaseous exchange and transpiration occur.

Functions of stomata

  • Exchange of gases, O2 and CO2.
  • Loses a large amount of water (water vapour) during transpiration.


Opening and closing of stomatal pores

  • The opening and closing of stomatal pores are controlled by the turgidity of guard cells.
  • When guard cells uptake water from surrounding cells, they swell to become a turgid body, which enlarges the pore in between (Stomatal Opening).
  • While, when water is released, they become flaccid shrinking to close the pore (Stomatal Closing).

Significance of Photosynthesis

  • Photosynthesis is the main way through which solar energy is made available for different living beings.
  • Green plants are the main producers of food in the ecosystem. All other organisms directly or indirectly depend on green plants for food.
  • The process of photosynthesis also helps in maintaining the balance of carbon dioxide and oxygen in the air.

Heterotrophic Nutrition

Heterotrophic nutrition refers to the mode of nutrition where an organism obtains its food from other living organisms, excluding green plants and blue-green algae. This type of nutrition is observed in various organisms. It can be classified into three categories: saprophytic nutrition, holozoic nutrition, and parasitic nutrition.

  1. Saprophytic Nutrition: In this mode of nutrition, organisms release digestive juices onto the food source, digesting it externally before ingestion. Decomposers primarily employ saprophytic nutrition, while some insects, such as houseflies, also follow this method.
  2. Holozoic Nutrition: Holozoic nutrition involves the digestion of food inside the organism's body after ingestion. This mode of nutrition is predominant among most animals.
  3. Parasitic Nutrition: Parasites are organisms that live either inside or outside another organism (host) and obtain their nutrition from it. This mode of nutrition is known as parasitic nutrition and is exemplified by organisms like Cuscuta and ticks.

How do Amoeba Obtain their Nutrition?

  • Amoeba is a unicellular animal which follows the holozoic mode of nutrition.
  • In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism.
  • Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.

Nutrition in AmoebaNutrition in Amoeba

  • The cell membrane of amoeba keeps on protruding into pseudopodia.
  • Amoeba surrounds a food particle with pseudopodia and makes a food vacuole. 
  • The food vacuole contains food particle and water. 
  • Digestive enzymes are secreted in the food vacuole and digestion takes place. 
  • After that, digested food is absorbed from the food vacuole. 
  • Finally, the food vacuole moves near the cell membrane and undigested food is expelled out.

Question for Chapter Notes: Life Processes
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How do green plants obtain the raw materials required for photosynthesis?
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Nutrition in Human Beings

Human beings possess a sophisticated digestive system, consisting of both an alimentary canal and several accessory glands. The alimentary canal is a long, hollow tube that is divided into various parts, including the esophagus, stomach, small intestine, large intestine, rectum, and anus. Meanwhile, the accessory glands, namely the salivary gland, liver, and pancreas, are located outside the alimentary canal and play essential roles in the digestive process.

Structure of the Human Digestive System

The human digestive system comprises of the alimentary canal and associated digestive glands.

Human Digestive SystemHuman Digestive System

Alimentary Canal

It comprises of mouth, oesophagus, stomach, small intestine and large intestine.

1. Mouth or Buccal Cavity

  • The mouth has teeth and tongue. Salivary glands are also present in the mouth.
  • The tongue has gustatory receptors which perceive the sense of taste.
  • The tongue helps in turning over the food so that saliva can be properly mixed in it.
  • Teeth help in breaking down the food into smaller particles so that, swallowing of food becomes easier.
  • There are four types of teeth in human beings. The incisor teeth are used for cutting the food.
  • The canine teeth are used for tearing the food and for cracking hard substances.
  • The premolars are used for the coarse grinding of food. The molars are used for fine grinding of food.

2. Oesophagus

  • Taking food from mouth to stomach by Peristaltic movement.
  • Rhythmic contraction of muscles of the lining of the alimentary canal to push the food forward is called Peristaltic movement.

Life Processes Chapter Notes | Science Class 10

3. Stomach

  • Stomach is a bag-like organ. Highly muscular walls of the stomach help in churning the food.
  • The walls of the stomach secrete hydrochloric acid. Hydrochloric acid kills the germs which may be present in food.
  • Moreover, it makes the medium inside the stomach as acidic. The acidic medium is necessary for gastric enzymes to work.
  • The enzyme pepsin, secreted in the stomach, does partial digestion of protein.
  • The mucus, secreted by the walls of the stomach saves the inner lining of the stomach from getting damaged from hydrochloric acid.

Life Processes Chapter Notes | Science Class 10

4. Small Intestine

  • The highly coiled, tube-like structure known as the small intestine is longer than the large intestine, although its lumen is smaller in comparison. 
  • The small intestine can be further divided into three parts: the duodenum, jejunum, and ileum.

5. Large Intestine

  • Large intestine is smaller than the small intestine.
  • Undigested food goes into the large intestine.
  • Some water and salt are absorbed by the walls of the large intestine. After that, the undigested food goes to the rectum, from where it is expelled out through the anus.
  • Large Intestine bbsorb excess of water. The rest of the material is removed from the body via the anus. (Egestion).

Associated Glands

The main associated glands are the Salivary gland, Gastric Glands, Liver and Pancreas.

1. Salivary glands

  • Saliva makes the food slippery which makes it easy to swallow the food. 
  • Saliva also contains the enzyme salivary amylase or ptyalin. Salivary amylase digests starch and converts it into sucrose, (maltose).

2. Liver

  • Liver is the largest organ in the human body. 
  • The liver manufactures bile, which gets stored in the gall bladder. 
  • From the gall bladder, bile is released as and when required.

3. Pancreas

  • Pancreas is situated below the stomach. 
  • It secretes pancreatic juice which contains many digestive enzymes.
  • The duodenum receives both bile and pancreatic juice through a common duct called the hepatopancreatic duct. 
  • Bile plays a crucial role in breaking down fats into smaller particles, a process known as emulsification. 
  • Following this, the enzyme lipase acts on the emulsified fats, breaking them down into fatty acids and glycerol. 
  • Moreover, the enzymes trypsin and chymotrypsin are responsible for digesting proteins into amino acids, while complex carbohydrates are broken down into glucose. 
  • The duodenum is the primary site for these digestive processes, where the major part of digestion occurs.

No digestion occurs in the jejunum: Inside the ileum, the inner wall has numerous finger-like structures known as villi. These villi serve two important functions: first, they increase the surface area of the ileum, allowing for efficient nutrient absorption. Second, they help reduce the lumen of the ileum, which allows food to stay inside for a longer time, facilitating better absorption. The digested food is then absorbed through these villi.


Respiration is the process through which living beings use food to obtain energy. It involves the oxidation of carbohydrates to produce energy. Mitochondria are the sites where respiration takes place, and the energy released during this process is stored in the form of ATP (adenosine triphosphate). ATP is stored in mitochondria and released as needed by the body.

Types of Respiration

  • Aerobic respiration: This type of respiration happens in the presence of oxygen. Pyruvic acid is converted into carbon dioxide. Energy is released and water molecule is also formed at the end of this process.
  • Anaerobic respiration: This type of respiration happens in the absence of oxygen. Pyruvic acid is either converted into ethyl alcohol or lactic acid. Ethyl alcohol is usually formed in case of anaerobic respiration in microbes, like yeast or bacteria. Lactic acid is formed in some microbes as well as in the muscle cells.

Exchange of gases

  • For aerobic respiration, organisms need a continuous supply of oxygen, and carbon dioxide produced during the process needs to be removed from the body.
  • Diffusion is the method which is utilized by unicellular and some simple organisms for this purpose.
  • In plants also, diffusion is utilized for exchange of gases.
  • In complex animals, respiratory system does the job of exchange of gases.
  • Gills are the respiratory organs for fishes. Fishes take in oxygen which is dissolved in water through gills. Since, availability of oxygen is less in the aquatic environment, so the breathing rate of aquatic organisms is faster.
  • Insects have a system of spiracles and trachease which is used for taking in oxygen.
  • Terrestrial organisms have developed lungs for exchange of gases. Availability of oxygen is not a problem in the terrestrial environment so breathing rate is slower than in fishes.

Human respiratory system

The human respiratory system consists of a pair of lungs connected to a network of tubes that open to the outside through the nostrils.

Life Processes Chapter Notes | Science Class 10

Following are the main structures in the human respiratory system:

  • Nostrils: There are two nostrils which converge to form a nasal passage. The inner lining of the nostrils is lined by hair and remains wet due to mucus secretion. The mucus and the hair help in filtering the dust particles out from inhaled air. Further, air is warmed up when it enters the nasal passage.
  • Pharynx: It is a tube-like structure which continues after the nasal passage.
  • Larynx: This part comes after the pharynx. This is also called voice box.
  • Trachea: This is composed of rings of cartilage. Cartilaginous rings prevent the collapse of trachea in the absence of air.
  • Bronchi: A pair of bronchi comes out from the trachea, with one bronchus going to each lung.
  • Bronchioles: A bronchus divides into branches and sub-branches inside the lung.
  • Alveoli: These are air sacs at the end of bronchioles. The alveolus is composed of a very thin membrane and is the place where blood capillaries open. This is alveolus, where the oxygen mixes with the blood and carbon dioxide exits from the blood. The exchange of gases, in alveoli, takes place due to the pressure differential.

Passage of air through the respiratory system in human beings: 

Life Processes Chapter Notes | Science Class 10

Breathing Mechanism

  • The breathing mechanism of lungs is controlled by the diaphragm and the intercostalis muscles.
  • The diaphragm is a membrane which separates the thoracic chamber from the abdominal cavity.
  • When the diaphragm moves down, the lungs expand and the air is inhaled.
  • When the diaphragm moves up, the lungs contract and air are exhaled.

Question for Chapter Notes: Life Processes
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What is the main role of the salivary glands in the digestive system?
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Circulatory system of human being, transportation in plants. Human beings like other multicellular organism need a regular supply of foods, oxygen etc. This function is performed by a circulatory system or transport system.

Transportation in Human Beings

The circulatory system is responsible for transport of various substances in human beings. It is composed of the heart, arteries, veins and blood capillaries. Blood plays the role of the carrier of substances.

1. Heart: Heart is a muscular organ, which is composed of cardiac muscles.

  • It is so small that, it can fit inside an adult’s wrist. The heart is a pumping organ which pumps the blood.
  • The human heart is composed of four chambers, viz. right atrium, right ventricle, left ventricle and left atrium.
  • Systole: Contraction of cardiac muscles is called systole.
  • Diastole: Relaxation of cardiac muscles is called diastole.

2. Arteries

  • These are thick-walled blood vessels which carry oxygenated blood from the heart to different organs.
  • Pulmonary arteries are exceptions because they carry deoxygenated blood from the heart to lungs, where oxygenation of blood takes place.

3. Veins

  • These are thin-walled blood vessels which carry deoxygenated blood from different organs to the heart, pulmonary veins are exceptions because they carry oxygenated blood from lungs to the heart.
  • Valves are present in veins to prevent back flow of blood.

4. Capillaries: These are the blood vessels which have single-celled walls.

Blood: Blood is a connective tissue which plays the role of the carrier for various substances in the body. Blood is composed of 1. Plasma 2. Blood cells 3. Platelets.

  • Blood plasma: Blood plasma is a pale coloured liquid which is mostly composed of water. Blood plasma forms the matrix of blood.
  • Bloods cells: There are two types of blood cells, viz. Red Blood Cells (RBCs) and White Blood Cells (WBCs).
    (a) Red Blood Corpuscles (RBCs): These are of red colour because of the presence of haemoglobin which is a pigment. Haemoglobin readily combines with oxygen and carbon dioxide. The transport of oxygen happens through haemoglobin. Some part of carbon dioxide is also transported through haemoglobin.
    (b) White Blood Corpuscles (WBCs): These are of pale white colour. They play important role in the immunity.
  • Platelets: Platelets are responsible for blood coagulation. Blood coagulation is a defense mechanism which prevents excess loss of blood, in case of an injury.


  • Lymph is similar to blood but RBCs are absent in lymph.
  • Lymph is formed from the fluid which leaks from blood capillaries and goes to the intercellular space in the tissues. This fluid is collected through lymph vessels and finally return to the blood capillaries.
  • Lymph also plays an important role in the immune system.
  • Lymph a yellowish fluids escape from the blood capillaries into the intercellular spaces contain less proteins than blood.
  • Lymph flows from the tissues to the heart assisting in transportation and destroying germs.

Double circulation: In the human heart, blood passes through the heart twice in one cardiac cycle. This type of circulation is called double circulation. One complete heartbeat in which all the chambers of the heart contract and relax once is called cardiac cycle. The heart beats about 72 times per minute in a normal adult. In one cardiac cycle, the heart pumps out 70 mL blood and thus, about 4900 mL blood in a minute. Double circulation ensures complete segregation of oxygenated and deoxygenated blood which is necessary for optimum energy production in warm-blooded animals.

Transportation in plants

Plants have specialized vascular tissues for transportation of substances. There are two types of vascular tissues in plants.

Transport of Water

  • Xylem: Xylem is responsible for transportation of water and minerals. It is composed of trachids, xylem vessels, xylem parenchyma and xylem fibre. Tracheids and xylem vessels are the conducting elements. The xylem makes a continuous tube in plants which runs from roots to stem and right up to the veins of leaves.
  • Carry water and minerals from the leaves to the other part of the plant.

Transport of food and other substances

  • Phloem: Phloem is responsible for transportation of food. Phloem is composed of sieve tubes, companion cells, phloem parenchyma and bast fibers. Sieve tubes are the conducting elements in phloem.
  • Carries product of photosynthesis from roots to other part of the plant.
  • Root pressure: The walls of cells of root hairs are very thin. Water from soil enters the root hairs because of osmosis. Root pressure is responsible for movement of water up to the base of the stem.
  • Transpiration pull: Loss of water vapour through stomata and lenticels, in plants, is called transpiration. Transpiration through stomata creates vacuum which creates a suction, called transpiration pull. The transpiration pull sucks the water column from the xylem tubes and thus, water is able to rise to great heights in even the tallest plants.
  • Transport of food: Transport of food in plants happens because of utilization of energy. Thus, unlike the transport through xylem, it is a form of active transport. Moreover, the flow of substances through phloem takes place in both directions, i.e., it is a two-way traffic in phloem. Transpiration is the process of loss of water as vapour from aerial parts of the plant.

Question for Chapter Notes: Life Processes
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What is the function of platelets in the circulatory system of human beings?
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Other metabolic activities generate nitrogenous materials which need to be removed. The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion. Different organisms use varied strategies to do this. 

Excretion in human beings

  • Removal of harmful waste from the body is called excretion.
  • Many wastes are produced during various metabolic activities.
  • These need to be removed in time because their accumulation in the body can be harmful and even lethal for an organism.
  • The human excretory system is composed of a pair of kidneys.
  • A tube, called ureter, comes out of each kidney and goes to the urinary bladder.
  • Urine is collected in the urinary bladder, from where it is expelled out through urethra as and when required.

Excretory system of human beings includes


  • Kidney is a bean-shaped organ which lies near the vertebral column in the abdominal cavity.
  • The kidney is composed of many filtering units, called nephrons.
  • Nephron is called the functional unit of kidney.


  • It is composed of a tangled mess of tubes and a filtering part, called glomerulus.
  • The glomerulus is a network of blood capillaries to which renal artery is attached.
  • The artery which takes blood to the glomerulus is called afferent arteriole and the one receiving blood from the glomerulus is called efferent arteriole.
  • The glomerulus is enclosed in a capsule like portion, called bowman’s capsule. The bowman’s capsule extends into a fine tube which is highly coiled.
  • Tubes from various nephrons converge into collecting duct, which finally goes to the ureter.

Urine formation in the kidney

The urine formation involves three steps:

  • Glomerular filtration: Nitrogenous wastes, glucose, water, amino acid filter from the blood into bowman’s capsule of the nephron.
  • Tubular reabsorption: Now, useful substances from the filtrate are reabsorbed back by capillaries surrounding the nephron.
  • Secretion: Extra water, salts are secreted into the tubule which opens up into the collecting duct and then into the ureter.

Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.

The purpose of making urine is to filter out waste product from the blood i.e., urea which is produced in the liver.

Haemodialysis: The process of purifying blood by an artificial kidney. It is meant for kidney failure patient.

Excretion in Plants

  • Other wastes may be stored in leaves, bark etc. which fall off from the plant.
  • Plants excrete some waste into the soil around them.
  • Gums, resin → In old xylem
  • Some metabolic wastes in the form of crystals of calcium oxalates in the leaves of colocasia and stem of Zamikand.
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