REVISION CONCEPTS
Nutrition: It is the mode of taking food by an organism and its utilization by the body.
• Nutrients: The components of food that provide nourishment to the body.
• All organisms take food and utilise it to get energy for the growth and maintenance of their bodies.
• Green plants synthesise their food themselves by the process of photosynthesis. They are autotrophs.
• Photosynthesis: Green plants prepare their own food with the help of carbon dioxide and water tekn from the environment in presence of sunlight called chlorophyll (found in green plants) for the manufacture of food. This process is known as photosynthesis.
• Plants use simple chemical substances like carbon dioxide, water and minerals for the synthesis of food.
• Chlorophyll and sunlight are the essential requirements for photosynthesis.
• Complex chemical substances such as carbohydrates are the products of photosynthesis.
• Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
• Oxygen is produced during photosynthesis.
• Oxygen released in photosynthesis is utilised by living organisms for their survival.
• Fungi derive nutrition from dead, decaying matter. They are saprotrophs. Plants like Cuscuta
are parasites. They take food from the host plant.
• A few plants and all animals are dependent on others for their nutrition and are called heterotrophs.
• Parasitic: Organisms that live on the body of other organisms.
• All parasitic plants feed on other plants as either:
(i) Partial Parasites: Obtain some of their nutrition from the host, e.g. painted cup.
(ii) Total Parasites: dependent completely on the host for nutrition, e.g. mistletoe.
• Saprophytic: Organisms that obtain nutrition from dead and decaying plant and animal matter.
• Mushrooms, moulds and certain types of fungi and bacteria.
Insectivorous Plants: Green plants which obtain their nourishment partly from soil and atmosphere and partly from small insects. Example: pitcher plant, bladderwort, and venus fly trap.
• Symbiosis: Mode of nutrition in which two different individuals associate with each other to fulfil their requirement of food.
• Lichens found on tree trunks is the association between alga and fugus. Alga obtains water from fungus and it in turn obtains food from alga.
NCERT SOLUTIONS
Q1 : Why do organisms need to take food?
Answer : All living organisms require food to survive. It gives them energy to perform various activities. All activities such as playing, running, walking, studying, etc. require energy. The various components present in our food such as carbohydrates, proteins, fats, vitamins, and minerals provide energy to our body. These are also important for growth and development of the body.
Q2 : Distinguish between a parasite and a saprotrophytic.
Answer :
