NCERT Solutions for Class 7 Science Chapter 2 Nutrition in Animals

1.Fill in the blanks:

(a) The main steps of nutrition in humans are __________, __________,__________, _________ and __________.

Answer: Ingestion, digestion, absorption, assimilation, egestion.

(b) The largest gland in the human body is __________.

Answer: liver.

(c) The stomach releases hydrochloric acid and ___________ juices which act on food.

Answer: digestive

(d) The inner wall of the small intestine has many finger-like outgrowths called _________.

Answer: villi

(e) Amoeba digests its food in the ____________ .

Answer: food vacuole

2. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) Digestion of starch starts in the stomach. (T/F)

Answer: False (F). [ Digestion of starch starts in the mouth. ]

(b) The tongue helps in mixing food with saliva. (T/F)

Answer: True (T).

(c) The gall bladder temporarily stores bile. (T/F)

Answer: True (T).

(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/F)

Answer: True (T).

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

Answer: Small intestine

(b) Water from the undigested food is absorbed mainly in the

(i) stomach (ii) food pipe (iii) small intestine (iv) large intestine

Answer: Large intestine.

4. Match the items of Column I with those given in Column II: Column I Column II Food components Product(s) of digestion Carbohydrates Fatty acids and glycerol Proteins Sugar Fats Amino acids

Column I Food Components	Column II Product(s) of digestion
Carbohydrates	Fatty acids and Glycerols
Proteins	Sugar
Fats	Amino Acids

Answer:

Column I Food Components	Column II Product(s) of digestion
Carbohydrates	Sugar
Proteins	Amino Acids
Fats	Fatty acids and Glycerols

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

Answer: Villi are small finger like outgrowths, located in large numbers on inner wall of small intestine. It increases surface area for absorption of digested food. Each villus ( singular form of villi ) is connected with network of thin blood vessels. Absorbed food material from surface of villus, is transferred through these blood vessels to various organs.

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

Answer: Bile or bile juice is produced in liver which are stored in gallbladder. Bile helps in digestion of fats.

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

Answer: Carbohydrates like cellulose can only be digested by ruminants but not by humans. This is because, ruminants have a large sac like structure between small intestine and large intestine. This sac like structure contains certain bacteria which have ability to digest cellulose. These bacteria are absent in humans. Thus, humans cannot digest cellulose.

8. Why do we get instant energy from glucose?

Answer: The simplest carbohydrates is glucose. Digestion of carbohydrates in body forms glucose, which can be easily absorbed in blood, thereby providing energy. When glucose is taken directly, it does not need to be digested and thus acts as an instant source of energy.

9. Which part of the digestive canal is involved in:

(i) absorption of food ________________.

Answer: small intestine

(ii) chewing of food ________________.

Answer: buccal cavity

(iii) killing of bacteria ________________.

Answer: stomach

(iv) complete digestion of food ________________.

Answer: small intestine

(v) formation of faeces ________________.

Answer: large intestine

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

Answer:

Similarity:

1. In both, digestive uses are used to break complex food in simplest form.
2. Both carry out digestion in several steps like, ingestion, digestion, absorption and assimilation.

Difference:

Humans	Amoeba
Have complex digestive system	Digestive system is absent
Food is taken inside the body with help of mouth	Food is engulf inside the body with the help of pseudopodia
Buccal cavity, stomach and small intestine secretes digestive juices	Food vacuole secrets digestive juices
Carbohydrates, proteins and fats are digested in separate regions of digestive system	All food components are digested in food vacuole of amoeba

11. Match the items of Column I with suitable items in Column II

Column I	Column 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

Answer:

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

12. Label Fig. 2.11 of the digestive system.

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

Answer: To live alive human body need balanced containing all essential components of food like proteins, vitamins, carbohydrate, etc. Raw leafy vegetable and grasses contains cellulose, which human body cannot digest.

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