1. Name any two factors on which the form of nutrition may depend. Form of nutrition in animal depends on -
(i) Type and availability of food material
(ii) Mode of obtaining the food material. 2. Give one example to show that form of nutrition in animals is dependent on type, availability and how food material is obtained. The parts of body used for obtaining nutrition is different in animals. For example, cow eats grass which is a stationary source and contains cellulose. So the alimentary canal of cow , including the mouth parts, teeth, length of intestine etc. is adapted and evolved to digest grass. In contrast, the corresponding body parts are different in an animal like lion whose source of food is generally mobile and consists of meat. 3. Explain giving examples the three different ways of intake of food material by a living organism. Three different ways of intake of food material by heterotrophic organisms are as follows:
(i) Some organism breakdown the food material outside their body. They release some chemicals called enzymes and breakdown the complex food material present outside. Once the complex food is converted to simple forms, absorb these materials inside their body. (Saprophytic nutrition)
Example: bread moulds, yeast, mushrooms, some bacteria, etc.
(ii) Some organisms take the whole complex material inside their body and then break it down in usable simpler form (Holozoic nutrition)
Example: Amoeba, Paramoecium, birds, human beings, etc.
(iii) Some organisms directly derive nutrition from other living organisms by living inside or outside their bodies. Such organisms are called parasite(Parasitic nutrition)
Example: Cuscuta (amar-bel), orchids, ticks, lice leeches, tapeworm, roundworm etc. 4. Why is the digestive system different in various organisms? The source and type of food consumed by various animals is highly variable. Therefore, the digestive system is different in various organisms to suit their requirement. 5. How do single celled organisms obtain nutrition? - In a single celled organism intake of food occurs by the body surface. In most of the cases, food enters through diffusion but in some complex organisms specialised parts of cell helps in food intake for e.g. pseudopodia (finger like extensions) in Amoeba .
- Once the food is taken in, it is broken down into simpler form inside food vacuole.
- These simple molecules diffuse to cytoplasm and are used for various life processes.
- The waste material produced is thrown out from body surface. 6. Explain the process of nutrition in Amoeba.
Amoeba feeds on microscopic animals and plants that float in a water body. Its mode of nutrition is holozoic. The various steps of nutrition are:
(i) Ingestion : Amoeba engulfs the food by forming pseudopodia. When the food is completely encircled and the tips of encircling pseudopodia touch each other, the membrane at that point dissolves and the food is enclosed inside forming a food vacuole. This intake of food is called ingestion.
(ii) Digestion : Inside the food vacuole, food gets digested by digestive enzymes. The digested food diffuses into the cytoplasm.
(iii) Assimilation : The digested food is utilised by the cell. This is termed assimilation.
(iv) Egestion : The
undigested food remains in the food vacuole and is thrown out of the
body. This process is called egestion. 
7. Explain the process of nutrition in Paramoecium .
- Paramoecium is a unicellular organism
- Food is taken in at a specific spot because the body has specific shapes, which do not change as in case of Amoeba .
- Whole complex food is pushed by movement of cilia on the body surface to the entry point of food tube.
- Once inside the body, the food enters food vacuole
- Food is broken down into simple forms.
- Simple molecules are absorbed inside cytoplasm and used.
- Waste material is
removed from body surface.  | 
