Life Processes

Category : 10th Class

Life Processes


Life Processes

All the living organisms on this planet perform some basic functions to maintain their life on the earth. These functions are called life processes. It includes nutrition, respiration, excretion, control and coordination, growth, movement and reproduction. Food is the main source that provides energy to all the living things to carry out various life processes.



Nutrition is the process of intake of nutrients by an organism and the utilisation of these nutrients. It is a substance that is obtained by an organism from its surrounding and used as a source of energy. Our body needs different types of nutrients in right amount. They are carbohydrates, fats, proteins, vitamins, minerals and roughage.


Mode of Nutrition

Different organisms obtained their food in different ways. Thus the mode of nutrition among organisms is different. The following are the two modes of nutrition among the Organisms.


  • Autotrophic mode of nutrition: In this mode of nutrition, an organism makes its own food with the help of carbon dioxide, water and sunlight. Green plants have this mode of nutrition. Green plants make their own food by the process of photosynthesis in the presence of carbon dioxide, water and sunlight. Autotrophic bacteria also obtain their food by this mode of nutrition. The organisms that make their own food are called autotrophs. All the green plants are called autotrophs. The green plants contain a green pigment called chlorophyll that traps the sunlight. The green plants are also called producers because they make their own food.
  • Heterotrophic mode of nutrition: In this mode of nutrition, organisms depend on other organisms for their food. All the animals come in this category. Most of the bacteria and fungi have heterotrophic mode of nutrition because they cannot make their own food. Non green plants are also called heterotrophs. The organisms that cannot make their own food are called heterotrophs.


The following are the types of heterotrophic nutrition:


  • Saprophytic nutrition: In this mode of nutrition, an organism obtains its food from dead and decaying organic matters such as dead animals, plants, rotten bread, etc. They are called saprophytes. For example, fungi and bacteria. These organisms break down the complex organic molecule into simpler substances and absorb them as their food.
  • Parasitic nutrition: In this mode of nutrition, an organism obtains its food from the body of another living organism called host without killing that organism. In this mode of nutrition, the organism harms the host. For example, disease causing bacteria lives in the body of the humans and causes harm to them.
  • Holozoic nutrition: In this mode of nutrition, an organism takes the complex organic food materials in its body by the process of ingestion, the ingested food is digested and then absorbed into the body cells of the organism. For example, human beings, dog, amoeba, etc.


Steps of Nutrition


The following are the steps of nutrition in animals:


  • Ingestion: It is the process of taking food into the body. In this process, food is taken into mouth with the help of hands.
  • Digestion: It is the process of breaking down the food into simpler molecules that is absorbed by the body. The digestion of food takes place with the involvement of many physical and chemical processes.
  • Absorption: It is the process in which digested food passes through the intestinal wall into blood stream.
  • Assimilation: It is the process in which the absorbed food is taken in by the body cells and is used for energy, growth and repair.
  • Egestion: It is the process in which the undigested food is removed from the body.


Nutrition in Human Beings


Nutrition in human beings is a complicated process. The digestive system of humans is a complex series of organs and glands that help to process the food properly. The food that we eat is broken down into smaller molecules. Some parts of it is used by the body and some parts come out of the body as waste.

The organs which take part in the process of digestion are: mouth, stomach, intestine, liver, pancreas, etc.

The process of digestion starts in the mouth. Food is chewed in the mouth properly and thus broken down. Saliva mixes with the food in the mouth and helps in breaking and swallowing of the food. Saliva is produced by the Salivary glands and break down starch into sugar.

From the mouth, food enters into esophagus that is a long tube that runs from the mouth to the stomach. It uses rhythmic, wave-like muscle movements called peristalsis to force food from the throat into the stomach.

Stomach is a J-shaped organ that churns the food. The stomach wall contains three tubular glands in its walls. The glands present in the walls of the stomach secrete gastric juice contains three substances: hydrochloric acid, the enzyme pepsin and mucus. From the stomach the partially digested food enters the small intestine. The small intestine in human beings is the site of complete digestion of food. The small intestine receives the secretions of two glands: liver and pancreas. Liver secretes bile, a greenish yellow liquid made in the liver which is normally stored in the gall bladder. Bile breaks the fats present in the food. Pancreas lies beneath the stomach. Pancreas secretes pancreatic juice which contains digestive enzymes like pancreatic amylase, trypsin and lipase. The enzymes amylase, breaks down the starch, the enzyme trypsin digests the proteins and the enzyme lipase breaks down the emulsified fats.

The digested food which is absorbed through the walls of the small intestine, goes into our blood. The blood carries digested and dissolved food to all the parts of the body where it becomes assimilated as part of cells. The undigested food cannot be absorbed in the small intestine. So, the undigested food passes from the small intestine into a wider tube called large intestine. The walls of the large intestine absorb most of the water from the undigested food. Finally solid waste is then stored in the rectum until it is excreted through the anus.



Respiration is the process of taking oxygen into the cells, releasing of energy by burning food and eliminating the waste product from the body. The following are the types of respiration:


  • Anaerobic respiration: It is a kind of respiration that takes place in the absence of oxygen. In the respiration, food is broken down to release energy. For example, food is broken down into ethanol and carbon dioxide by yeast to release energy.
  • Aerobic respiration: It is a kind of respiration takes place in the presence of oxygen. In this respiration, food is broken down into water and carbon dioxide by the process of oxidation. The following chemical equation represents the process of aerobic respiration.

\[{{C}_{6}}{{H}_{12}}{{O}_{6}}+6{{O}_{2}}\to \,6C{{O}_{2}}+6{{H}_{2}}O+Energy\]



Transportation is a well -defined process inside the body of an organism to carry the essential substances to all its parts so that they reach each and every cell of the body.


Transportation in Humans

Blood is a connective tissue. It plays an important role in transportation of material within the body. It consists of fluid medium called plasma in which the cells are suspended. It is the plasma that transports food, carbon dioxide and nitrogenous wastes in dissolved form. Salts and other substances are transported by bloods. Red blood cells carry oxygen. The blood is pumped by an important organ called heart. The pumping of blood pushes it around the body through a network of tubes to reach all the tissues.



The heart is a muscular organ which is as big as our fist. It plays an important role in our body. The heart has different chambers to prevent the mixing of oxygen-rich blood with the blood containing carbon dioxide because both oxygen and carbon dioxide are transported by the blood. Blood rich in carbon dioxide reaches lungs for the removal of carbon dioxide and oxygen rich blood from the lungs are brought back to the heart. The oxygenated blood is then pumped to the rest of the body. Oxygenated blood from the lungs comes to the thin-walled upper chamber of the heart on the left that is left atrium. The left atrium relaxes while 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 deoxygenated blood is pushed into the right ventricle, which in turn pumps it to the lungs for oxygenation.


Blood Vessels

Arteries and veins are the important part of circulatory system. Arteries carry blood from the heart to various organs of the body whereas veins carry the blood from various organs of the body and bring it back to the heart. Arteries have thick elastic walls as they carry blood under pressure whereas veins 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. Arteries further divided into smaller vessels on reaching an organ or tissue to bring the blood in contact with the individual cells. The Capillary wall performs an important function by allowing nutrients and waste substance to pass across it. Capillaries help in exchange of materials between the blood and surrounding cells.



Platelets are the tiny fragments of special cells formed in bone marrow. Platelets do not have nuclei. Platelets help in the coagulation of blood in a cut or wound.


Transportation in Plants

Transportation of plants helps in transportation of food prepared in the leaves to the various part of the plants like stems, roots, etc. The plants have two types of conducting

Tissues and these are:

carries water and minerals

Phloem - Which carries the food materials which the plant makes.


Excretion in Humans

The excretory system of humans consists of pair of kidney, a pair of ureters, urinary bladder and a urethra. Urine produced in the kidney passes through the ureters into the urinary bladder where it is stored until it is released through the urethra. The skin of human is also an excretory organ as body gets rid of small amount of salt and urea through skin in the form of sweat. Liver also plays an important role in excretion. It removes the ammonia and converts it into the less toxic urea. It also chemically changes and filter out certain drugs such as penicillin and erythromycin. These substances are then picked up by the blood and transported to the kidneys, where they are put into the excretory system to undergo the complete process of excretion.

Other Topics

Notes - Life Processes
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