Carbohydrates, proteins, fats, vitamins and minerals are components of food.
These components of food are necessary for our body and are called nutrients.
Nutrition is the mode of taking food by an organism and its utilisation by the body.
The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic
(auto = self; trophos = nourishment) nutrition. plants are called autotrophs.
Animals and most other organisms take in readymade food prepared by the plants. They are called
heterotrophs (heteros =other).
the bodies of living organisms are made of tiny units called cells.
Cells can be seen only under the microscope.
Some organisms are made of only one cell.
The cell is enclosed by a thin outer boundary, called the cell membrane cell membrane.
Most cells have a distinct, centrally located spherical structure called the nucleus.
The nucleus is surrounded by a jelly-like substance called cytoplasm.
Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves.
These pores are surrounded by ‘guard cells’. Such pores are called stomata.
The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This
energy is used to synthesise (prepare) food from carbon dioxide and water.
Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light;
synthesis : to combine).
So we find that chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of
photosynthesis.
During photosynthesis, chlorophyll containing cells of leaves in the presence of sunlight, use carbon dioxide
and water to synthesize carbohydrates.
During the process oxygen is released.
The carbohydrates ultimately get converted into starch.
The presence of starch in leaves indicates the occurrence of photosynthesis.
The starch is also a carbohydrate. You often see slimy, green patches in ponds or in other stagnant water
bodies.
These are generally formed by the growth of organisms called algae.
They contain chlorophyll which gives them the green colour.
Algae can also prepare their own food by photosynthesis.
The carbohydrates are made of carbon, hydrogen and oxygen.
These are used to synthesise other components of food.
proteins are nitrogenous substances which contain nitrogen.
Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil.
These soluble forms are absorbed by the plants along with water.
Farmers adding fertilisers rich in nitrogen to the soil.
In this way the plants fulfill their requirements of nitrogen along with the other constituents.
Plants can then synthesise components of food other than carbohydrates such as proteins and fats.
humans and animals such plants depend on the food produced by other plants.
They use the heterotrophic mode of nutrition.
Yellow tubular structures twining around the stem and branches of a tree? This is a plant called Cuscuta
(Amarbel).
It does not have chlorophyll.
It takes readymade food from the plant
The plant on which it climbs is called a host.
Pitcher plant showing lid and pitcher
The apex of the leaf forms a lid which can open and close the mouth of the pitcher.
Inside the pitcher there are hairs which are directed downwards.
When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair.
The insect is digested by the digestive juices secreted in the pitcher. Such insect-eating plants are called
insectivorous plants
SAPROTROPHS
cotton-like threads spread on the piece of bread
These organisms are called fungi.
They have a different mode of nutrition.
They secrete digestive juices on the dead and decaying matter and convert it into a solution.
Then they absorb the nutrients from it.
This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is
called saprotrophic nutrition saprotrophic nutrition.
Plants which use saprotrophic mode of nutrition are called saprotrophs
Fungi also grow on pickles, leather, clothes and other articles that are left in hot and humid weather for long time
Some organisms live together and share shelter and nutrients. This is called symbiotic relationship.
For example, certain fungi live in the roots of trees.
The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil.
This association is very important for the tree.
In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together.
The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form.
But Rhizobium cannot make its own food.
So it lives in the roots of gram, peas, moong beans and other legumes and provides them with nitrogen.
Most of the pulses (dals) are obtained from leguminous plants.
Social