NCERT Solutions for Class 7 Science Chapter 2 Nutrition In Animal

Q.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 ___________ .

Answer :

(a) 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.

Q.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 sometime. (T/F)

Answer :

(a) Digestion of starch starts in the stomach. (F)
(b) The tongue helps in mixing food with saliva. (T)
(c) The gall bladder temporarily stores bile. (T)
(d) The ruminants bring back swallowed grass into their mouth and chew it for some time. (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) foodpipe (iii) small intestine (iv) large intestine

Answer :

(a) (iii) Small intestine

(b) (iv) Large intestine

Q.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

Answer :

Column- I → Column- II

Food components → Product(s) of digestion
Carbohydrates → Sugar
Proteins → Amino acids
Fats → Fatty acids and glycerol

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

Answer :

1.The inner walls of the small intestine have thousands of finger-like outgrowths.
These are called villi (singular villus).

2.The villi increase the surface area for absorption of the digested food.

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

4.The surface of the villi absorbs the digested food materials and carries them to the bloodstream.
It is hence from the bloodstream, the absorbed food is delivered to each and every cell of the body.

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

Answer :

1.Bile juice is produced in the liver.
It is a greenish-yellow alkaline (basic in nature) liquid, which is stored in the Gall Bladder.

2.Bile plays an important role in the digestion of fats.

3.It actually doesn't digest fats but breaks the fat molecules into smaller pieces
to make their digestion easy. This process is called fat emulsification.

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

Answer :

1.Cellulose is the type of carbohydrate that can be digested by ruminants but not by humans because
humans lack the cellulose enzyme required to digest the cellulose.

2.Ruminants have a large sac-like structure called rumen located between the small and large intestines.

3.In this structure, the food containing cellulose is digested by the action of certain bacteria. On the other hand, due to the absence of cellulose digesting enzymes, humans cannot digest cellulose.

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

Answer :

1.Glucose is a simple sugar that is the primary source of energy in living organisms.

2.Carbohydrates, when consumed, have to be digested into glucose. Glucose does not need digestion, it is directly absorbed into the blood.

3.Glucose is broken down in the presence of oxygen into CO2 and H2O releases instant energy.
Once inside, glucose undergoes oxidation, which results in the release of ATP, a high-energy molecule that provides energy for the cell.

4. Hence, when glucose is directly taken, it does not have to be digested and thus acts as an instant source of 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) Absorption of food : Small intestine.
(ii) Chewing of food : Mouth.
(iii) Killing of bacteria : Stomach.
(iv) Complete digestion of food : Small intestine.
(v) Formation of faeces: Large intestine.

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

Answer :

Similarities:

1.Both amoeba and human beings follow the holozoic type of nutrition.
2.The basic process of digestion of food and release of energy is the same in amoeba
as well as in human beings.
3.In amoeba, Digestive juices act on the food and break it down into simpler substances. Gradually, the digested food is absorbed.
Similarly, in human beings various digestive juices act on food and break it down into simpler substances.

Differences:

1.The digestion process in the amoeba is simple while in human beings it is a complex process.
2.Amoeba engulfs its food by surrounding the food particle with its pseudopodia.
The undigested food which is largely carbon dioxide gas is expelled outside by the vacuole.
While in human beings, food (which is a complex substance) is taken inside the mouth and
undergoes a complex process of digestion and absorption.
Finally, the undigested food was expelled in the form of feces.
3.Humans intake food through the buccal cavity. In amoeba, food is ingested through pseudopodia.

Q.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

Q.12 Label Fig. 2.11 of the digestive system.

Answer :

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

Answer :

No, we cannot survive only on raw, leafy vegetables because :

1.They mainly consist of Cellulose which cannot be digested by us due to lack of cellulose digesting enzyme in our body.
2. We cannot get all required nutrients, such as carbohydrates, proteins, lipids, vitamins, and minerals, from them.
3. Moreover raw vegetables may not be digested easily as compared to cooked vegetables.