NCERT Solutions for Class 7th: Ch 2 Nutrition in Plants Science
Page No: 20
Exercises
1. Fill in the blanks:
(a) The main steps of nutrition 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 small intestine has many finger-like outgrowths called _________.
(e) Amoeba digests its food in the ____________ .
Answera) The main steps of nutrition in humans are ingestion, digestion, absorption, assimilation and egestion.
(b) The largest gland in the human body is liver.
(c) The stomach releases hydrochloric acid and digestive juices which act on food.
(d) The inner wall of the small intestine has many finger-like outgrowths called villi.
(e) Amoeba digests its food in the 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)
(b) The tongue helps in mixing food with saliva. (T/ F)
(c) The gall bladder temporarily stores bile. (T/ F)
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (T/ F)
Answer
(a) F
(b) T
(c) T
(d) 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
(b) Water from the undigested food is absorbed mainly in the
(i) stomach (ii) foodpipe (iii) small intestine (iv) large intestine
Answer
(a) Fat is completely digested in the (iii) small intestine
(b) Water from the undigested food is absorbed mainly in the (iv) large intestine
Page No: 21
4. Match the items of Column I with those given in Column II:
| Column I Food Components | Column II Product(s) of digestion |
| Carbohydrates | Fatty Acids and Glycerol |
| 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 Glycerol |
5. What are villi? What is their location and function?
Answer
Villi are small finger-like outgrowths present that help in the process of absorption. These are located in the inner walls of the small intestine. Its function is to increase the surface area of the small intestinal wall for absorption of the digested food.
6. Where is the bile produced? Which component of the food does it help to digest?
Answer
The bile juice is secreted by the liver. Bile juice helps in the digestion of fats by breaking down the larger fat globules to smaller fat globules.
7. Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Answer
Cellulose is a type of carbohydrate that can be digested by ruminants and not by humans.
Ruminants have a large sac-like structure called rumen between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.
8. Why do we get instant energy from glucose?
Answer
Glucose is simple sugar which is formed when carbohydrate get broken. Also, the carbohydrate get digested into glucose. Since, glucose does not have 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 ________________.
(ii) chewing of food ________________.
(iii) killing of bacteria ________________.
(iv) complete digestion of food ________________.
(v) formation of faeces ________________.
Answer
(i) absorption of food small intestine.
(ii) chewing of food buccal cavity.
(iii) killing of bacteria stomach.
(iv) complete digestion of food small intestine.
(v) formation of faeces large intestine.
10. Write one similarity and one difference between the nutrition in amoeba and human beings.
Answer
Similarity:
Both Amoeba and human have holozoic type of nutrition.
Difference:
Human beings have complex structure for the ingestion, digestion and egestion of food while Amoeba has simple process in which it engulfs the with the help of pseudopodia and food get trapped in food vacuoles.
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 |
Page No: 22
12. Label Fig. 2.11 of the digestive system.
13. Can we survive only on raw, leafy vegetables/ grass? Discuss.
Answer
No, Humans cannot survive only on raw, leafy vegetables, or grass. It is because the grass is rich in cellulose, which is a type of carbohydrate that humans are not able to digest due to the absence of cellulose-digesting enzymes.
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