–Suminder kaur, Academic Content Writer at Edumarz


  • Food is used by living organisms to get energy so that they can do their usual work. Hence, all living things need nutrition.

  • Nutrition is a life process through which an organism takes up food from the environment and utilizes it for body development, growth and repair.

  • Living things such as plants and animals use various modes of getting nutrition. 




  • There are two modes of nutrition. They are autotrophic and heterotrophic mode of nutrition.




  1. It is the nutrition in which organisms prepare their own food from simple inorganic substances like carbon dioxide, water, chlorophyll, in the presence of sunlight.

  1. It is the nutrition in which organisms get their food directly or indirectly from other organisms. 

  1. For example, All green plants are autotrophs and some bacteria.

2.  For example, Animals, all fungi and some bacteria.



  • The heterotrophic mode of nutrition is of three types further.

  •  SAPROPHYTIC – In this type of nutrition organisms get their food from dead and decaying organisms. They break down the food material outside their body then they absorb it to get nutrition. For example, mushrooms, bread mould, yeast.

  • PARASITIC – In this type of nutrition, organisms get its food from living organisms called as hosts, without killing them. For example, orchids, cuscuta, lice , etc.

  • HOLOZOIC – in this type of nutrition, an organism directly takes up the food and then digests and absorbs it. For example, amoeba, paramecium, humans,etc.




  • It is the method by which plants use carbon dioxide and water to manufacture food in the presence of sunshine and chlorophyll.


  •  Equation of photosynthesis :-

  •                                 Sunlight

  •  6CO2 + 12H2O         C6H12O6 + 6H2O + 6O2

  •                                Chlorophyll


Chlorophyll: is a green pigment present in the leaves. If we observe a cross section of a leaf under a microscope, we can see cells containing green dot-like structures called chloroplasts which contain chlorophyll.


Stomata: These are small holes found in the leaves that allow gases to pass through. A pair of guard cells regulates the opening and shutting of the stomatal hole in each stoma. When water enters the guard cells, it expands, opening the pore; when the guard cells lose water, it contracts, closing the hole.

  •  Process of photosynthesis :-


 Photosynthesis takes place in three main steps. They are :-

  i) Absorption of light energy by chlorophyll.

ii) Light energy is converted to chemical energy, and water molecules are divided into hydrogen and oxygen.

iii) Reduction of carbon dioxide by hydrogen to form carbohydrates.





  • Amoeba is a single celled organism that lives in water.

  • It takes in food by developing pseudopodia (finger-like extensions) and a feeding vacuole.

  • Food is processed and absorbed inside the food vacuole.The undigested meal is subsequently expelled via the cell’s surface.

  • This whole process is called phagocytosis.



  • Nutrition in human beings takes place in the digestive system.

  • The mouth, oesophagus, stomach, small intestine, large intestine, and anus are the primary organs of the digestive system.

  • Salivary glands, stomach glands, liver, pancreas, and intestinal glands are the primary glands.

  • The alimentary canal and glands that create enzymes that break down food into tiny molecules make up this system.


  • In the mouth, the teeth break down the meal into smaller particles, whi ch are then combined with saliva produced by the salivary glands. 

  • Saliva includes salivary amylase, an enzyme that transforms starch to sugar. The meal then travels down the throat and into the stomach.

  • Gastric juice, which comprises the enzyme pepsin, hydrochloric acid, and mucus, is produced by the gastric glands in the stomach.

  • Pepsin is a digestive enzyme that breaks down proteins. Pepsin’s function is aided by hydrochloric acid, which makes the medium acidic. The stomach’s walls are protected by mucus from the acid’s effect. The meal next enters the small intestine.

  • The meal is combined with bile from the liver and pancreatic juice from the pancreas in the top section of the small intestine called the duodenum. 

  • Bile is a digestive enzyme that breaks down lipids into smaller globules. Trypsin and lipase are enzymes found in pancreatic juice. Proteins are broken down by trypsin, whereas lipids are broken down by lipase.

  • In the small intestine, intestinal juice is produced by glands on the small intestine’s walls. 

  • Carbohydrates are converted to glucose by intestinal juice enzymes, lipids are converted to fatty acids and glycerol by intestinal juice enzymes, and proteins are converted to amino acids by intestinal juice enzymes. 

  • The small intestine’s walls have many finger-like extensions called villi that contain blood veins. It aids in the absorption of digested food by increasing surface area. The blood absorbs the digested food and transports it to all of the body’s cells. The undigested meal then travels to the large intestine.

  • Water is absorbed in the large intestine, while waste is expelled through the anus.

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