Class VII, CBSE (NCERT) Solutions of Science
Chapter 2, Nutrition in animals
Answers of NCERT Science Textbook Exercise Questions
Q.1: Fill in the blanks:
(a) The main steps of digestion in humans are _________ and ___________.
(b) The largest gland in the human body is _________.
(c) The stomach releases hydrochloric acid and ______ juices which act on food.
(d) The inner wall of the smaller intestine has many finger-like outgrowths called _________.
(e) Amoeba digests its food in the ____________.
Answer: (a) buccal cavity, oesophagus, stomach, small intestine and large intestine (b) liver (c) digestive juices (d) villi (e) food vacuole.
Q.2: Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) Digestion of starch starts in the stomach.
(b) The tongue helps in mixing food with saliva.
(c) The gall bladder temporarily stores bile.
(d) The ruminants bring back swallowed grass into their mouth and chew it for sometime.
Answer: (a) F (b) T (c) T (d) T
Q.3: Choose the correct option:
(a) Fat is completely digested in the
(i) stomach (ii) mouth (iii) small intestine (iv) large intestine
(b) Water from the undigested food is absorbed in the
(i) stomach (ii) food pipe (iii) small intestine (iv) large intestine
Answer: (a) – (iii). (b) – (iv).
Q.4: Match the terms of column I with those given in the column II:
Products of digestion
Fatty acids and glycerol
Answer: Carbohydrates => Sugar. Proteins => Amino acids. Fats => Fatty acids and glycerol.
Q.5: What are villi ? What is their location and function ?
Answer: The inner wall of the small intestine has thousands finger-like outgrowths called villi.
These are found in small intestine. The villi increase the surface area for absorption of food.
Q.6: Where is the bile produced ? Which component of the food does it digest ?
Answer: Bile is produced in liver and is stored in a sac called the gall bladder.
The bile plays an important role in the digestion of fats.
Q.7: Name the type of carbohydrates that can be digested by ruminants but not by humans. Give the reasons also.
Answer: Cellulose is the carbohydrate that can be digested by ruminants. Ruminants have large sac like structure between the small intestine and large intestine. The cellulose of the food is digested by the action of certain bacteria which are not present in human beings.
Q.8: Why do we get instant energy from glucose ?
Answer: Because glucose easily breakdown in the cell with the help of oxygen and give carbon dioxide, water and energy.
Q.9: Which part of the digestive canal is involved in:
(i) absorption of food __________.
(ii) chewing of food __________.
(iii) killing of bacteria _________.
(iv) complete digestion of food ___________.
(v) formation of faeces ____________.
Answer: (i) small intestine. (ii) mouth. (iii) stomach (iv) small intestine. (v) large intestine.
Q.10: Write one similarity and one difference between the nutrition in amoeba and human beings.
Similarity: During the digestion of food, in amoeba digestive juices are secreted into the food vacuole. They act on the food and break it into simpler substances. In human being, the inner walls of stomach and the small intestine also secrete the digestive juices. The digestive juices convert complex substances of food to simpler ones.
Difference: Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle. The food is trapped in a food vacuole. Human beings take food through the mouth, digest and utilize it. The food is gradually digested as food travels through the various compartments.
Q.11: Match the items of column I with suitable items of column II.
(a) salivary gland
(e) small intestine
(f) large intestine
(i) bile juice secretion
(ii) storage of undigested food
(iii) saliva secretion
(iv) acid release
(v) digestion is completed
(vi) absorption of water
(vii) release of faeces
Answer: (a)–(iii). (b)–(iv). (c)–(i). (d)–(ii). (e)–(v). (f)–(vi).
Q.13: Can we survive only on raw, leafy vegetables / grass? Discuss.
Answer: We know that including all animals, fungi, many bacteria, non-green plants and human being do not possess the ability to synthesize their own food. Therefore depend upon autotrophs for their food supply either directly or indirectly. The green plants (leafy vegetables / grass) trap solar energy and manufacture their food in the form of glucose. So, leafy vegetables and grass can provide sufficient energy required for the survival of human being.