NCERT CLASS 7 SCIENCE CHAPTER 2 NUTRITION IN ANIMALS
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NCERT CLASS 7 SCIENCE CHAPTER 2 NUTRITION IN ANIMALS
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NCERT CLASS 7 SCIENCE CHAPTER 2 NUTRITION IN ANIMALS
Question Answers

Q. 1. Paheli wants to know how food moves in the opposite direction during vomiting. (Page 15)

Ans. The food pipe runs along the neck and the chest. Food is pushed down by movement of the wall of the food pipe. Actually this movement takes place throughout the alimentary canal and pushes the food downwards. At times the food is not accepted by our stomach and is vomited out.

Q. 2. Paheli wants to know why these animals (ruminants) cannot chew food properly at the time they take it in? (Page 18)

Ans. The ruminants mainly feed on grass and bush which primarily contain cellulose or roughage. The grass is rich in cellulose, so lot of chewing and saliva are needed. Thus, the ruminants needed to chew the grass for long time. If they chew for long while eating, they will get less time to eat.

Q.3. Boojho wants to know why we cannot digest cellulose like the cattle do. (Page 18)

Ans. Ruminants have a large sac-like structure between the small intestine and large intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

NCERT TEXTBOOK EXERCISE

Q.1.  Fill in the blanks:

(a) The main steps of nutrition in humans are………

(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 small intestine has many finger-like outgrowths called …..

(e) Amoeba digests its food in the…….

Ans. (a) ingestion, digestion, absorption, assimilation and egestion; (b) liver;(c) digestive; (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 some time.

Ans. (a) False (F); (b) True (T); (c) True (T); (d) True (T).

Q.3. Tick mark the correct answer in each of the following:

(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 mainly in the:

(i) stomach (ii) food pipe

(iii) small intestine (iv) large intestine.

Ans. (a) (iii) small intestine (b) (iv) large intestine.

Q.4. Match the items given in Column I with those in Column II:

Column IColumn II
Food Components Product(s) of Digestion

(i) Carbohydrates

(a) Fatty acids and glycerol
(ii) Proteins
(b) Sugar
(iii) Fats(c) Amino Acid
  

Ans.

Column IColumn II
Food Components Product(s) of Digestion

(i)

Carbohydrates

(a) Sugar
(ii) Proteins
(b) Amino Acid
(iii) Fats(c) Fatty acids and glycerol
  

Q.5. What are villi? What is their location and function?

Ans. The inner walls of the small intestine have thousands of finger-like outgrowths and are called villi. They are situated in the small intestine.

Function of villi:

(i) The villi increase the surface area for absorption of the digested food.

(ii) Each villus has a network of thin and small blood vessels close to its surface.

(iii) The surface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body.

Q.6. Where is the bile produced? Which component of the food does it help to digest?

Ans. The liver secretes bile juice that is stored in a sac called gall bladder. Bile juice digests fat.

Q.7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.

Ans. The grass is rich in cellulose, a type of carbohydrate. Many animals including humans cannot digest cellulose. The cellulose can be digested by ruminants but not by humans because they have a large sac-like structure between the small intestine and large intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

Q.8. Why do we get instant energy from glucose?

Ans. We get instant energy from glucose because glucose is the simplest form of carbohydrate which can be broken down easily to give 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 faces………

Ans. (i) small intestine ;(ii) buccal cavity; (iii) stomach ; (iv) small intestine; (v) large intestine.

Q.10. Write one similarity and one difference between the nutrition in amoeba and human beings.

Ans. Similarity: Both amoeba and human uses the process of digestion involves ingestion, digestion, absorption, assimilation and egestion.

Difference: Human needs to chew food whereas in amoeba, there is no chewing.

Q.11. Match the items of column I with suitable items in column II

Column IColumn II
(a) Salivary gland(i) Bile Juice secretion
(b) Stomach
(ii) Storage of undigested food
(c) Liver(iii) Saliva secretion
(d) Rectum(iv) Acid release
(e) Small Intestine(v) Digestion is completed
(f) Large intestine(vi) Absorption of water
 (vii) release of faeces

Ans. 

Column IColumn II
(a) Salivary gland(iii) Saliva secretion
(b) Stomach
(iv) Acid release
(c) Liver(i) Bile Juice secretion
(d) Rectum(vii) release of faeces
(e) Small Intestine(v) Digestion is completed
(f) Large intestine(vi) Absorption of water

Q.12 Label the figure of the digestive system.

Digestive System                                        Fig. A part of human digestive system.

Ans.

Human Digestive System

Q.13. Can we survive only on raw, leafy vegetables/grass? Discuss.

Ans. No, because to live healthy life we need a complete balance of all nutrients. Raw green vegetables may have cellulose which cannot be digested by us. Thus, only green leafy vegetables will not solve the purpose.

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Class 7  Science 

  • Chapter 1. Nutrition in Plants

  • Chapter 2. Nutrition in Animals

  • Chapter 3. Fibre to Fabric

  • Chapter 4. Heat

  • Chapter 5. Acitds, Bases and Salts

  • Chapter 6. Physical and Chemical Changes

  • Chapter 7. Weather; Climate and Adaptations of Animals to Climate

  • Chapter 8. Winds, Storms and Cyclones

  • Chapter 9. Soil

  • Chapter 10. Respiration in Organisms

  • Chapter 11. Transportation in Animals and Plants

  • Chapter 12. Reproduction in Plants

  • Chapter 13. Motion and Time

  • Chapter 14. Electric Current and its Effects

  • Chapter 15. Light

  • Chapter 16. Water; a Precious Resource

  • Chapter 17. Forests; Our Lifeline

  • Chapter 18. Wastewater Story