The process of taking in food and utilizing it is called
The term ‘nutrition’ comes from the word ‘nutrient’.
A nutrient is an organic or inorganic substance
required for the maintenance of life and survival of a
The food taken in by an organism contains a large
number of nutrients like carbohydrates, fats, proteins
The word ‘auto’ means ‘self’ and ‘trophe’ means
Autotrophic nutrition is that mode of nutrition in
which an organism makes its own food from the
simple organic materials like carbon dioxide and water
present in the surroundings (with the help of sunlight
Those organisms which can make their own food from
carbon dioxide and water are called autotrophs.
Green plant are autotrophs and synthesis their own
food by the process of photosynthesis.
‘Photo’ means light and ‘synthesis’ means build, thus
photosynthesis means ‘build up by light’.
The process by which green plants make their own
food from carbon dioxide and water by using sunlight
energy in the presence of chlorophyll is called
Raw material required are carbon dioxide and water.
Oxygen gas is released during photosynthesis.
The process of photosynthesis takes place in the green
leaves of a plant.
The food prepared by the green leaves of a plant is in
the form of a simple sugar called glucose.
The extra glucose is changed into another food called
The green plants convert sunlight energy into
chemical energy by making carbohydrates (food).
Site of photosynthesis is Chloroplasts.
6CO2 + 6H2O + Light Energy ---- C6H12O6 + 6CO2
The photosynthesis takes place in the following four
1. Absorption of sunlight energy by chlorophyll.
2. Conversion of light energy into chemical energy.
3. Splitting of water molecules into hydrogen and
oxygen by light energy.
4. Reduction of carbon dioxide to form carbohydrates
like glucose by utilising the chemical energy.
The conditions necessary for photosynthesis to take
3. Carbon Dioxide
The word ‘heteros’ means other and ‘trophe’ means
nutrition, thus heterotrophic means nutrition
obtained from others.
All animals have a heterotrophic mode of nutrition.
Those organisms which cannot make their own food
from inorganic substance like carbon dioxide and
water depend on other organism for their food are
Saprophytic nutrition is that nutrition in which an
organism obtains its food from decaying organic
matter of dead plants, dead animals, and rotten bread,
Saprophytes are the organisms which obtain their food
from dead plants, dead and decaying animal bodies,
and other decaying matter.
Saprotrophic nutrition is also called saprophytic
E.g. Mushroom, yeast, etc.
The parasitic nutrition is that nutrition in which an
organism derives its food from the body of another
living organism (called its host) without killing it.
A parasite is a organism which feeds on another living
organism called its host.
E.g Cuscuta, Plasmodium, etc
Holozoic nutrition means ‘feeding on solid food’.
The holozoic nutrition is that nutrition in which an
organism takes the complex organic food material into
its body by the process of ingestion, the ingested food
is digested and then absorbed into the body cells of the
E.g. Amoeba, frog, etc.
Animals obtain their food from plants and animals
thus are heterotrophs.
Animals can be divided into three groups on the basis
of their food habits:
The nutrition in human beings takes place through
human digestive system
The human digestive system consists of the alimentary
canal and its associated glands.
The various organs of the human digestive system in
sequence: Mouth, Oesophagus, Stomach, Small
Intestine, and Large Intestine.
The glands which are associated with the human
digestive system and form a part of the human
digestive system are: Salivary Glands, Liver, and
The process of releasing energy from food is called
The process of respiration involves taking in oxygen
into the cells, using it for releasing energy by burning
food, and the eliminating the waste products from the
Food + Oxygen ----- Carbon Dioxide + Water + Energy
Respiration is essential for life because it provides
energy for carrying out all the life processes which are
necessary to keep the organisms alive.
The respiration which uses oxygen is called aerobic