Life Processes Class 10 Notes Biology Science Chapter 6


What is living ?

‘Living’ is something that is alive, something that can grow, move, reproduce, respire, made up of cells and are capable of carrying out various cellular activities.

Biology is the study of life and all living organism that have the potential to carry out the basic process which may be called as the characteristics of life or life processes.

Some Of The Life Processes In The Living Beings Are Described Below:

Nutrition: The process of obtaining energy through consumption of food is called as nutrition.

Respiration: The process of acquiring oxygen through breathing and make it available to cells for the process of breaking down of organic substances into simpler compounds is called as respiration. 

Transportation: Transportation is the process by which the food and oxygen is carried from one organ to other organs in the body.

Excretion: It is the process by which the metabolic waste by-products are removed from the different organs and released out from the body

In unicellular organisms, all these processes are carried out by a single cell.

In multicellular organisms, well-developed systems are present to carry out the processes.


“Nutrition is the process of taking in food and converting it into energy and other vital nutrients required for life.”

What Is The Need Of Nutrition ?

    • Organisms need 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.

What Are 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.

Types Of Nutrition:

Types of Nutrition
Types of Nutrition

Autotrophic Nutrition: 

  • The mode of nutrition through which an organism prepares its own food is called autotrophic nutrition.
  • Green plants and blue-green algae follow the autotrophic mode of nutrition. These organisms are called photosynthetic because they process raw materials in presence of sunlight to make food.

  • Some organisms process certain raw materials through chemical reactions, without utilising the sunlight. Such organisms are chemosynthetic.

Heterotrophic Nutrition: 

  • The mode of nutrition through which an organism takes food from another organism is called heterotrophic nutrition.
  • Organisms, other than autotrophs, follow heterotrophic mode of nutrition. These organisms directly or indirectly depend on autotrophs for food.
  • For example, almost all the animals directly or indirectly take food from plants. Animals which eat plants are called herbivores, while flesh-eating animals are called carnivores.

  • Heterotrophic nutrition can be further divided into three types, viz. saprophytic nutrition , holozoic nutrition and parasitic nutrition.

Saprophytic Nutrition: In saprophytic nutrition, the organism secretes digestive juices on food. The food is digested while it is still to be ingested.

Digestion involves converting complex molecules into simple molecules so that they can be utilised by the organism. The digested food is then ingested by the organism.

All the decomposers follow saprophytic nutrition. Saprotrophs feed on dead remains of different organisms. By doing so, they help in decomposition of organic waste. This is an important process during various biogeochemical cycles. 

Many bacteria and all the fungi follow saprotrophic mode of nutrition.

Parasitic Nutrition : Organisms that lives in or on other organisms and also acquire food of its host are known as parasites.

Most parasites are harmful to the hosts health and sometimes, they even kill the host. Both animals and plants may serve as a host. Unlike commensalism, the parasite causes some harm to its host. A few examples of parasites are louse on a human head, Cuscuta plant. 

Holozoic Nutrition: In holozoic nutrition, the digestion happens inside the body of the organism, i.e. after the food is ingested. Animals and protozoa follow this mode of nutrition.

Nutrition in plants


Green plants are capable of manufacturing their own food in the form of carbohydrate in presence of light by using water and carbon-dioxide, this process is called photosynthesis.

Such mode of nutrition is termed as autotrophic nutrition. Carbohydrates provide energy to the plant and the ones not used are stored in the form of starch. Starch is the reserve food of plants whereas reserve food in case of animals in glycogen.

Photosynthesis is the process by which green parts of the plant synthesize organic food in the form of carbohydrates from CO2 and water in the presence of sunlight.

$$6\text{CO}_{2}+ 6\text{H}_2\text{O}\xrightarrow[\text{ChlorophyII}]{\text{Light}}\underset{(\text{Glucose})}{\text{C}_6\text{H}_{12}\text{H}_{6}+6\text{O}_{2}}$$

Mechanism Of Photosynthesis

    • Light reaction – Thylakoids of Grana
    • Dark reaction – Stroma

Events Occurring During Photosynthesis

    • Absorption of light energy by chlorophyll.
    • Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
    • Reduction of CO2 into carbohydrate.

Steps Of Photosynthesis :

During the process of photosynthesis, the following events occur :

    • Absorption of light energy by chlorophyll.
    • Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.


The above processes are considered as light reaction as it can take place only in the presence of light.

    • Reduction of carbon-dioxide to carbohydrates. This is also known as dark reaction as it does not require light.

Desert plants take up CO2 at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.

Conditions  Necessary For Photosynthesis

    • Sunlight
    • Chlorophyll
    • Carbon-dioxide
    • Water

These conditions are needed for autotrophic mode of nutrition.

Site of Photosynthesis: Leaf in the organ where maximum photosynthesis takes place. If you see the cross section of a leaf you will find some green dots. These green dots are cell organelles called chloroplasts which contain chlorophyll.

Chlorophyll containing organelles (chloroplasts) are found in large numbers in plant and algal cells.

Steps of photosynthesis
Steps of photosynthesis

Raw Materials For Photosynthesis

  1. Carbon dioxide: It is a gas, which is released into the atmosphere during respiration by all living organisms. This gas is utilized by autotrophic plants which enters the leaf through the stomata present on its surface during the process of photosynthesis.

  2. Water: It is another requirement for photosynthesis which is transported upward through xylem tissues to the leaves, from where it reaches the photosynthetic cells. Elements such as N, P, Fe and Mg are required by the plant to build their body is taken up from the soil along with water by roots. Nitrogen is the most important constituent of amino acid and nitrogenous bases. This is taken up in the form of inorganic nitrates or nitrites. It can also be taken as organic compounds which have been prepared by bacteria from atmospheric nitrogen.

  3. Chlorophyll: It is a green pigment in plants which act as a catalyst. It is responsible for absorption of sun’s energy. The chlorophyll pigments are photoreceptor molecules which play a key role in the photosynthetic process. The different types of chlorophyll molecules are chlorophyll a, b, c, d and bacteriochlorophyll; of which chlorophyll a and b are most common.

  4. Light: It affects the rate of photosynthesis by its intensity, quality and duration. In green light, the rate of photosynthesis is minimum, while in red and blue lights the rate of photosynthesis is maximum. Rate of photosynthesis is higher in plants getting average light of 10-12 hrs a day.
  5. Gaseous exchange during photosynthesis : Stoma are tiny pores present on the surfaces of the leaves (more on the lower surface and less on the upper surface). Stomata function in gas exchange between the plant and the atmosphere during photosynthesis. Each stoma is bordered by two bean / dumbbell shaped guard cells in dicots and monocots respectively. However exchange of gases also occurs across the surface of stems, roots etc.

Opening and Closing of Stomatal Pore : The opening and closing of the stomata is the function of 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. Since large amounts of water can also be lost through stomata the plant closes these pores when it does not need CO2 for photosynthesis.

Opening and Closing of Stomatal Pore

External Factors Affecting Photosynthesis

    • There are number of factors which affect the process of photosynthesis thereby affecting the productivity of a plants.
    • Each factor has three principal values i.e., minimum, optimum and maximum. Optimum means the process is taking place at its highest rate.
    • Maximum value means beyond which the process is adversely affected.

Important External Factors Are :

    • Light
    • Temperature
    • Water
    • Carbon dioxide


    • In photosynthesis light is converted into chemical energy in the form of food.
    • The rate of photosynthesis is affected by quality, intensity and duration of light.
    • The chlorophyll absorbs mostly the blue and red regions of the spectrum.
    • The green light has inhibitory effect. The low intensities of light increase the rate of photosynthesis while the higher intensities retard the rate of photosynthesis.
    • Plants getting average light of 10-13 hours a day exhibit higher rate of photosynthesis.


    • Temperature acts as a limiting factor under field conditions particularly on cool days.
    • The influence of temperature on photosynthesis depends on both light intensity and availability of CO2.
    • An increase in temperature above 30oC results in a fall in the rate of photosynthesis. Changes in temperature do not affect the light reactions of photosynthesis but markedly influence the rate of enzyme-mediated dark reactions.
    • However, the effect of temperature on the rate of photosynthesis varies from plant to plant.


    • Water deficiency may retard the rate of photosynthesis as it is one of the raw materials for the process.
    • Under water deficient conditions stomata remain closed to reduce the transpiration thereby affecting the entry of CO2.

Carbon dioxide

    • Carbon dioxide is present in low concentration and forms about 0.032% of the atmosphere. It enters the leaves through stomata.
    • The rate of photosynthesis increases with an increase in CO2 concentration up to a certain limit. Higher concentration of CO2 may prove toxic to plants.

Internal Factors Affecting Photosynthesis


Photosynthesis does not occur in etiolated and chlorophyll less leaves. In the variegated leaves, photosynthesis occurs only at the places which possess chlorophyll.

Anatomy of leaf

The amount of CO2 that reaches the chloroplast depends on structural features of the leaves like the size, position and behaviour of the stomata and the amount of intercellular spaces Some other characters like thickness of cuticle, epidermis, presence of epidermal hairs, amount of mesophyll tissue, etc., influence the intensity and quality of light reaching into the chloroplast.

Nutrition In Human Beings

Human beings are heterotrophic omnivorous organisms. They obtain their food from plants, animals and their products by holozoic modes of nutrition.

    • Ingestion: Process of taking food inside the body through mouth.
    • Digestion: Process of conversion of complex food particles into simpler ones by the action of enzymes.
    • Absorption: Process of diffusion of soluble food particles into the blood.
    • Assimilation: Process of utilization of absorbed food by the body cells.
    • Egestion: Process of removal of undigested food from the body.

Human Digestive System

    • The organs which are responsible for ingestion, digestion, absorption, assimilation and egestion constitute the digestive system.
    • The digestive system comprise the alimentary canal and associated digestive glands.
    • It consists of mouth, buccal cavity, oesophagus, stomach, small intestine, large intestine, rectum and anus.
    • Digestive glands are salivary glands, liver and pancreas.

Alimentary Canal

Alimentary canal in man is 9 meters long and consists of the following parts :


    • It leads into buccal cavity. Palate forms the roof of the buccal cavity and is differentiated into anterior hard and posterior soft palate.
    • The floor of the buccal cavity has a tongue bearing taste buds. Mucous membrane of the tongue contains taste buds which contain receptors sensitive to sweet, salty, bitter and sour taste.


There are 32 teeth of four different types, in human adult. These are:

Types of teeth Function Number of teeth
Incisors Used for biting 4
Canines Used for tearing 2
Premolars Used for grinding 4
Molars Used for grinding 6


    • It is a short, conical region that lies after the mouth cavity and connects it to the esophagus.


    • It is a long, narrow, muscular tube which leads to the stomach. No digestive glands are present in the oesophagus. It conveys the food (bolus) to stomach through peristalsis.
    • Peristalsis is a series of wave of contraction of muscles that passes from one end to the other. This pushes the food forward.


    • It lies below the diaphragm on the left side of abdominal cavity and is J-shaped.
    • It is divisible into cardiac and pyloric part. The food is stored and partially digested in the stomach.

Small Intestine:

    • From the stomach the food is moved to the small intestine. It is a very long tube (7 mt. long and 2.5 cm. diameter) which originates from the distal end of the stomach and extends to the large intestine.
    • The small intestine is the longest part of the alimentary canal and is greatly coiled and twisted. The small intestine is subdivided into three sections: the duodenum, the jejunum, and the ileum.


    • The duodenum (about 10 inches ) part of the small intestine is the main seat of digestion in the gut. The acidic chyme in the duodenum receives the bile secreted from the liver, the pancreatic juice secreted from the pancreas and the intestinal juice from the glands of the intestinal wall.
    • Bile is a yellowish-green in colour, bitter in taste, slightly alkaline fluid secreted from the liver.
    • Bile being alkaline in nature neutralises the acidic chyme. Bile emulsify fat into microscopic droplets and thus helps in the digestion and absorption of fat. So bile is called digestive juice though it does not contain enzyme.
    • Again the pancreas, a large gland located below the stomach, secretes pancreatic juice into the duodenum through the pancreatic duct. There are three enzymes namely amylase, pancreatic lipase and trypsin, in pancreatic juice that break down carbohydrates, fats, and proteins respectively.
    • Glands of intestine are present in the mucous layer of the intestinal wall. These glands secrete intestinal juice, which contains various enzymes.
    • The enzymes present in it finally convert the carbohydrates into glucose, proteins to amino acids and fats into fatty acids and glycerol.


    • The jejunum is about 8.2 feet (2.5 meters) long. The digested carbohydrates, fats, proteins, and most of the vitamins, minerals, and iron are absorbed in this section.
    • The inner lining of the small intestine is composed of up to five million tiny, fingerlike projections called villi. The villi increase the rate of absorption of nutrients into the bloodstream by greatly increasing the surface area of the small intestine.


    • The ileum, the last section of the small intestine, is the longest, measuring 11 feet (3.4 meters). Certain vitamins and other nutrients are absorbed here

Large Intestine

    • It has three parts – caecum, colon and rectum.
    •  Large intestine absorbs water and electrolytes.

Digestive Glands

Salivary Glands

    • The salivary glands secrete the first of the digestive juices, the saliva.
    • There are three pairs of salivary glands, namely the parotids, sub-maxillary and sublingual glands.

Gastric Glands:

    • They are branched tubular glands which lie in the mucus membranes of the stomach.
    • They secrete gastric juice, which is acidic, containing HCl, enzymes and mucus.


    • It is the largest gland in man and lies below diaphragm in the right upper part of abdomen.
    • Liver comprises of two lobes, right and left, the right lobe is much larger than the left lobe.
    • The cells of liver, i.e., hepatic cells, produce bile juice, which is stored in the gall bladder via cystic ducts.

Bile juice flows out of liver through hepatic ducts forming common bile duct and opens into the duodenum.



    • It is a soft lobulated gland present in between the loops of duodenum.
    • It secretes pancreatic juice containing enzymes which is poured into duodenum with the help of pancreatic duct.

What Are Life Processes ?

  • Living beings are complex organisations of molecules which perform various life processes like growth, respiration, digestion, reproduction, excretion etc., which makes them different from non-living.
  • The basic processes or functions performed by living organisms to keep them alive are called life processes.

Nutrition is defined as the process of intake of nutrients and its utilisation by an organism in various biological activities.

  • In autotrophic mode of nutrition, organisms prepare their own food and they are called autotrophs. Organisms prepare food by the process of photosynthesis.
  • Photosynthesis is the process by which chlorophyll containing cells prepare glucose using carbon dioxide and water in presence of light energy and oxygen gas is released as a by product during this process.
  • 6CO2 + 12H2O Sunlight/Chlorophyll C6H12O6 + 6O2 + 6H2O [Equation for photosynthesis]

Steps of nutrition in human beings

Organs of the digestive system

Nutrition in amoeba


  • Respiration is a biological process by which glucose is oxidized to release energy in the form of ATP which is the energy currency of the cell.

$$\text{C}_6\text{H}_{12}\text{O}_6\space+\space6\text{O}_2 \xrightarrow{\text{Sunlight}}6\text{CO}_2\space+\space6\text{H}_2\text{O}\space+\space\text{Energy}\space [\text{Equation\space for\space respiration}]$$

  • During aerobic respiration, 38 molecules of ATP are released whereas during anaerobic respiration only 2 molecules of ATP are released.
  • Tobacco is a plant and its leaves are smoked, chewed, or sniffed for a variety of effects. Tobacco contains nicotine, an addictive substance. Smoked tobacco products include cigarettes, cigars, bidis, and kreteks.
  • Smoking can destroy the cilia or tiny hairs in the airway that keep dirt and mucus out of lungs.

Breathing process in human beings


  • The essential substances like food, water, oxygen etc., need to be carried from one part of the body to another which is done by transport system.
  • Arteries carry oxygenated blood except pulmonary artery.
  • Veins carry deoxygenated blood except pulmonary vein.
  • Capillaries are thin walled blood vessels where exchange of gases and materials like food occurs.
  • Valves allow the blood to flow in one direction i.e., they prevent back flow of the blood.
  • When blood flows from atria to ventricles atria contracts and ventricle relaxes, this is called ventricular diastole.
  • When blood flows from ventricles to blood vessels, ventricles contract and atrium relaxes, this is called ventricular diastole.
  • The force exerted by blood on the walls of blood vessels is called blood pressure.
  • The normal blood pressure of human beings is 120/80 mm of Hg.
  • As blood flows in our heart twice so circulation in human beings is called double circulation.

Double Circulation


  • The process of removal of mainly nitrogenous waste substances from our body is called excretion.
  • In case of kidney failure due to infections or injury or other factors artificial kidney is used.
  • Artificial kidney is a device that removes nitrogenous wastes from our body by dialysis.
  • Organ donation is the donation of biological tissue or an organ of the human body, from a living or dead person to a living recipient in need of a transplantation. Organ transplantation is the only option to save lives in patients affected by terminal organ failures and improve their quality of life.
1. Life Processes: The processes like nutrition, respiration, growth, excretion etc. which together keep the living organisms alive and perform the function of body maintenance are called life processes. 9. Holozoic nutrition: It is the mode of nutrition in which an organism feeds on solid food which is a complex organic matter by the process of ingestion, then the food is subsequently digested and absorbed and finally undigested residue is removed from the body.
2. Autotrophic nutrition: It is the mode of nutrition in which organisms prepare their own food by utilising the raw materials from the surroundings and thus, do not depend on others for their food. 10. Peristalsis: The contraction and expansion movement of muscular wall of oesophagus when food (bolus) passes from mouth to stomach.
3. Photosynthesis: It is a biological process in which organisms prepare their own food by using inorganic raw materials like water, carbon dioxide in presence of chlorophyll and sunlight or light energy and oxygen is evolved as a byproduct during this process. 11. Chyme: It is the semi solid paste formed by the churning of partially digested food from the stomach mixed with gastric juice secreted by the stomach.
4. Chlorophyll: It is a green pigment found within the chloroplasts of green plants and some algae which traps solar energy for the process of photosynthesis. 12. Respiration: It is a complex process which involves gaseous exchange i.e., oxygen is taken in and carbon dioxide is given out as well as oxidation of glucose in cells to release chemical energy in the form of ATP.
5. Light reaction: The series of reactions which occurs only in presence of light inside the granum of chloroplast where there is formation of oxygen molecule due to photolysis of water and production of assimilatory powers like NADPH and ATP 13. Transportation: It is a life process in which a substance synthesized or absorbed in one part of the organism is carried to the other parts of the body.
6. Dark reaction: The series of reactions in which carbon dioxide is converted to glucose in absence of light utilising the assimilatory powers like NADPH and ATP in stroma of chloroplast. 14. Excretion: It is a biological process where there is removal of nitrogenous wastes from our body produced due to metabolism.
7. Photolysis: The reaction in which water splits to produce hydrogen , protons, electrons and oxygen by using light energy trapped by chlorophyll. 15. Osmoregulation: The process of maintaining a constant osmotic condition in the body by regulating the water and solute concentration of body fluids.
8. Heterotrophic nutrition: It is the mode of nutrition in which the organisms depends upon other organisms for food i.e., they obtain their food from autotrophs. 16. Dialysis: It is an artificial process of removal of metabolic wastes and excess water from the body by using a machine in order to maintain the normal water and solute concentration in our body.