Nutrition :
Nutrition is the mode of taking food by an organism and its utilisation by the body.
- Nutrition is very important as the nutrients from the food consumed enables living organisms to build their bodies and grow.
- Nutrition helps to repair damaged parts and organs.
- Nutrition also provides energy for carrying out various functions
Autotrophs and Heterotrophs :
Organisms that make food themselves are called autotrophs.(auto = self; trophos = nourishment)
- Plants are an example of autotrophs as they make their own food using carbon dioxide, water and light energy.
Animals
and most other organisms take in food
prepared by plants. They are called
heterotrophs (heteros = other).
- Animals and human beings are an example of heterotrophs as they depend on plants in many ways for their food.
Photosynthesis (Photo: light , synthesis : to combine).
Photosynthesis is the process of synthesis of food by green plants.
- This process usually takes place in the leaves of plants.
- The process requires chlorophyll , sunlight, carbon dioxide and water.
Chlorophyll - Chlorophyll is a green pigment that is responsible for the synthesis of food in green plants.
Sunlight- Chlorophyll helps the leaves use the energy from the sunlight to prepare food(Thus, sun is
the ultimate source of energy for all
living organisms.)
Carbon dioxide is taken in through tiny pores on the leaves called stomata.
Water and minerals that are required for the process are transported to the leaves from the roots through the stem.
Process of Photosynthesis :
The process of photosynthesis takes place in the leaves, the “food factory” of the plants.
During photosynthesis, chlorophyll
containing cells of leaves in
the presence of sunlight, use carbon
dioxide and water to synthesise
carbohydrates . During the process oxygen is
released. The food synthesised by plants is stored as starch.
Other Modes of Nutrition :
Parasites
A parasite is a heterotroph that completely depends on another organism for its food.
- Host-The organism to which the parasite latches onto is called the host.
- The host, in the process, is deprived of all nutrients for its own growth as they are consumed by the parasite.
- For example, Cuscuta (Amarbel) is a nongreen plant that takes readymade food from the plant on which it is growing.
Insectivorous Plants :
Plants that feed on insects are called Insectivorous plants.
- These plants are green and carry out photosynthesis. But, they grow in nitrogen-deficient soils. So, in order to get nitrogen, they feed on insects. These insectivorous plants have their parts modified for attracting and catching insects.
- For example, The pitcher plant, Venous flytrap
Saprotrophs :
Organisms which take dead and decaying matter for their food are called Saprotrophs. This mode of nutrition is called saprotrophic nutrition
- For example, Fungi. Fungi secrete digestive juices on the dead and decaying matter and convert it into a solution. Then they absorb the nutrients from it.
Symbiotic Relationship :
Organisms that live together and share their shelter and nutrients are said to be in a symbiotic relationship.
- 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 works well for both the fungi and the tree.
- Rhizobium bacteria is a most common example of symbiotic relationship .They reside in the root nodules of leguminous plants. The bacteria provide a plant with nitrogen that they fix and in turn, they get shelter and food from the plant. This association is of great significance for the farmers. They can reduce the use of nitrogenous fertiliser where leguminous plants are grown. Most of the pulses (dals) are obtained from leguminous plants
- In lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and minerals to the alga and, in return, the alga prepares and provides food to the fungus.
