Nutrition in Human Beings 1. What is the basic strategy used by complex multicellular organisms? Complex multicellular organisms have evolved specialised organ system called digestive system that performs the process of nutrition. Events that take place in this system are.(i) Taking in of food (ingestion)
(ii) Breakdown of complex food to simple form (Digestion)
(iii) Absorption of simple form of food (Absorption)
(iv) Removal of waste material or undigested food (Egestion) 2. Name the parts of human digestive system.
Human digestive system has a long continuous tube called alimentary canal and associated glands.
Alimentary canal is made up of following parts:
Mouth (buccal cavity)
Oesophagus
Stomach
Small intestine (duodenum, jejunum and ileum)
Large intestine (colon)
Rectum and
Anus
Major glands associated with alimentary canal are:
Salivary glands
Liver
Pancreas. 3. Draw a labelled diagram of human alimentary canal and the associated glands. 
4. We eat diverse type of food that is complex in nature. How is this food processed in the same digestive tract? In our digestive tract (alimentary canal) various parts or organs are present. They perform specialised task. As a result, the diverse food we eat get processed at each location to produce the small particles required by our body. 5. What is the need for crushing the food by our teeth? We eat complex food material. Food needs to be crushed for following reasons
(i) To produce small particles of similar texture.
(ii) Crushed food helps the enzymes to act on large area of food molecules.
(iii) Small size and uniform texture protects the delicate lining of our digestive tract. 6. Why is our food wetted? Food gets wet when it comes in contact with saliva. Wetting of food is required for following reasons
(i) It helps makes the passage of food smooth and protect the lining of digestive canal.
(ii) It helps in swallowing of food.
(iii) Saliva also contains enzyme salivary amylase that breaks down starch to sugar. 7. Name the fluid secreted in our mouth at the time of eating food or sometimes even at the thought of food. Saliva 8. How the complex food material is broken down in the form of absorbable molecules? Complex food material is first crushed into smaller particles. The particles are then broken down by biological catalysts called enzymes into simpler forms. 9. What are enzymes? Enzymes are biological catalysts that help in carrying out biochemical reaction taking place in living organisms.
For example, salivary amylase is an enzyme that breakdown starch to sugar. 10. Name the enzyme present in saliva. What is its role? Salivary amylase or ptyalin is the enzyme present in saliva. It is secreted by salivary glands present in the mouth region. It breaks down starch to sugar. 11. How does food move in the alimentary canal? Food moves in the alimentary canal due to peristaltic movements.
Peristaltic movements are rhythmic contraction of the muscles lining the alimentary canal that pushes the food forward.
12. Name the pipe that takes food from mouth to
stomach. Oesophagus or food pipe. | 
