NCERT Exemplar Solutions- Class 7 Science- Chapter 2 - Nutrition in Animals - CBSE Class Notes Online

Chapter 2 Nutrition in Animals This chapter explains how animals, including humans, obtain and process their food. Key concepts included in the chapter –

Different Ways of Taking Food- Exploring how various animals ingest their food, ranging from simple to complex methods.
Digestion in Humans- Understanding the human digestive system, including the process of digestion and the role of different organs.
Digestion in Other Animals- Learning about the digestive processes in other animals, including ruminants and simple organisms like Amoeba.
Feeding and Digestion in Amoeba- A detailed look at how single-celled organisms like Amoeba ingest and digest food.

NCERT Exemplar – Class 7 Science- Chapter 2 – Nutrition in Animals – Solved

Question 1 – Which of the following food items will give a blue-black color when tested with iodine?

(i) Boiled and mashed potato

(ii) Glucose solution

(iii) A slice of bread

(iv) Mustard oil

Options-

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (iii) and (iv)

Answer- (b) (i) and (iii). Both boiled and mashed potato and a slice of bread contain starch, which reacts with iodine to produce a blue-black color. Amylase present in saliva starts the chemical digestion of carbohydrates like starch in the bread into simpler sugars.

Also Check – Rapid Revision – Class 7 Science -Chapter 2 – Nutrition in Animals – Complete Notes

Question 2 – Which pair of teeth differ in structure but are similar in function?

Options-

(a) canines and incisors

(b) molars and premolars

(c) incisors and molars

(d) premolars and canines

Answer- (b) molars and premolars. Both molars and premolars are involved in grinding and crushing food, although they differ in structure.

Also Check – Nutrition in Animals – Definition and Explanation of Important Keywords

Question3 – Which set of organs do not carry out any digestive functions?

Options-

(a) Oesophagus, Large Intestine, Rectum

(b) Buccal cavity, Oesophagus, Rectum

(c) Buccal cavity, Oesophagus, Large Intestine

(d) Small Intestine, Large Intestine, Rectum

Answer- (a) Oesophagus, Large Intestine, Rectum. These organs are involved in the transportation and excretion of food, but they do not carry out the chemical or mechanical digestion of food. The oesophagus, for example, uses peristalsis to propel food but does not contribute to its digestion.

Also Check – Chapter 2 – Nutrition in Animals Textbook Exercise -(Solved)

Question 4 – Why does swallowed food move downwards in the alimentary canal?

Options-

(a) Force provided by the muscular tongue

(b) The flow of water taken with the food

(c) Gravitational pull

(d) The contraction of muscles in the wall of the food pipe

Answer- (d) The contraction of muscles in the wall of the food pipe. This process, known as peristalsis, ensures the smooth movement of food from the oesophagus to the stomach.

Also Check – Class 7- Chapter 2 – Nutrition in Animals – 4 Worksheets Solved and Unsolved

Question 5 – The acid present in the stomach

Options-

(a) kills the harmful bacteria that may enter along with the food.

(b) protects the stomach lining from harmful substances.

(c) digests starch into simpler sugars.

(d) makes the medium alkaline.

Answer- (a) kills the harmful bacteria that may enter along with the food. Acidic environment in the stomach helps to kill harmful bacteria.

Question 6 – The finger-like outgrowths of the human intestine helps to

Options-

(a) digest the fatty food substances.

(b) make the food soluble.

(c) absorb the digested food.

(d) absorb the undigested food.

Answer- (c) absorb the digested food. Villi, in the human intestine, their primary function is the absorption of digested nutrients.

Question7 – With reference to the villi of the small intestine, identify the statements which enable the villi to absorb digested food.

Options-

(a) (i), (ii) and (iv)

(b) (ii), (iii) and (iv)

(c) (iii) and (iv)

(d) (i) and (iv)

Answer- (a) (i), (ii) and (iv).

Villi are known to have very thin walls and a network of thin and small blood vessels close to the surface, enabling efficient absorption of nutrients.

Question 8 – The false feet of Amoeba are used for

Options-

(a) movement only.

(b) capture of food only.

(c) capture of food and movement.

(d) exchange of gases only.

Answer- (c) capture of food and movement. Amoeba uses its pseudopodia for both capturing food and moving.

Also Check – Activity – Effect of saliva on starch – Class 7

Question 9 – The enzymes present in the saliva convert

Options-

(a) Fats into fatty acids and glycerol.

(b) Starch into simple sugars.

(c) Proteins into amino acids.

(d) Complex sugars into simple sugars.

Answer- (b) Starch into simple sugars. Saliva contains enzymes like amylase, which initiate the breakdown of complex carbohydrates (starches) into simpler sugars.

Question10 – Cud is the name given to the food of ruminants which is

Options-

(a) Swallowed and undigested.

(b) Swallowed and partially digested.

(c) Properly chewed and partially digested.

(d) Properly chewed and completely digested.

Answer- (b) Swallowed and partially digested. Cud is regurgitated food that has been swallowed but not completely digested, allowing ruminants to chew it again for further digestion.

Question 11- Choose the correct order of terms that describes the process of nutrition in ruminants.

Options-

(a) Swallowing → partial digestion → chewing of cud → complete digestion

(b) Chewing of cud → swallowing → partial digestion → complete digestion

(c) Chewing of cud → swallowing → mixing with digestive juices → digestion

(d) Swallowing → chewing and mixing → partial digestion → complete digestion

Answer- (a) Swallowing → partial digestion → chewing of cud → complete digestion. Ruminants first swallow the food, which undergoes partial digestion, then they regurgitate it as cud, chew it, and swallow again for complete digestion.

Also Check- Chewing the Cud- The Ruminant Digestive System

Question 12- Cellulose-rich food substances are a good source of roughage in human beings because

Options-

(a) Human beings do not have cellulose-digesting enzymes.

(b) Cellulose gets absorbed in the human blood and converts into fibres.

(c) The cellulose-digesting bacteria convert cellulose into fibres.

(d) Cellulose breaks down into smaller components which are egested as roughage.

Answer- (a) Human beings do not have cellulose-digesting enzymes. Humans lack the enzymes necessary to digest cellulose, making it a source of roughage in the diet.

Question 13 – Name the parts of the alimentary canal where

(i) water gets absorbed from undigested food.

(ii) digested food gets absorbed.

(iii) the taste of the food is perceived.

(iv) bile juice is produced.

Answer-

(i) The large intestine is where water gets absorbed from undigested food.
(ii) The small intestine is where digested food gets absorbed.
(iii) The taste of food is perceived in the mouth, particularly by the tongue.
(iv) Bile juice is produced in the liver.

Question 14 – Mark the following statements as True or False. If false, write the correct statements.

(a) Tongue is attached to the roof of the mouth cavity at the back.
(b) The large intestine is longer and wider than the small intestine of the human alimentary canal.
(c) Mucus protects the stomach lining from damage.
(d) All heterotrophs have a similar basic process of nutrition.

Answer-

(a) False. The correct statement is- The tongue is not attached to the roof of the mouth cavity at the back.
(b) False. The correct statement is- The large intestine is shorter but wider than the small intestine.
(c) True. Mucus does protect the stomach lining from damage.
(d) False. The correct statement is- Not all heterotrophs have a similar basic process of nutrition. There is a diversity in the nutritional processes among different heterotrophic organisms.

Question 15 – Choose the odd one out from each group and give reasons.

(i) liver, salivary gland, starch, gall bladder
(ii) stomach, liver, pancreas, salivary gland
(iii) tongue, absorption, taste, swallow
(iv) oesophagus, small intestine, large intestine, rectum

Answer-

(i) Starch. Reason– Liver, salivary gland, and gall bladder are organs involved in the process of digestion, while starch is a type of carbohydrate that is a subject of the digestive process.
(ii) Salivary gland. Reason- Stomach, liver, and pancreas are organs involved in the production and secretion of digestive enzymes or substances aiding in digestion. The salivary gland, while involved in digestion, primarily secretes saliva that begins the digestive process in the mouth, differing in function from the other organs.
(iii) Absorption. Reason- Tongue, taste, and swallow are all functions or actions related to the mouth and the initial process of digestion, whereas absorption is a process that occurs in the intestines, particularly the small intestine where nutrients are absorbed.
(iv) Oesophagus. Reason- The small intestine, large intestine, and rectum are all part of the lower gastrointestinal tract involved in the absorption and excretion of digested food. The oesophagus is part of the upper gastrointestinal tract, primarily serving as a conduit for food to reach the stomach.

Question 16 – You were blindfolded and asked to identify the drinks provided in two different glasses. You could identify drink A as lime juice and B as bitter gourd juice. How could you do it despite being blindfolded?
Answer- You could identify the drinks based on their distinct tastes. The tongue, with its taste buds, can detect different flavors such as the sourness of lime juice and the bitterness of bitter gourd juice, even without the aid of sight. This ability to perceive taste is not hindered by being blindfolded.

17. Fill in the blanks with suitable words-

(a) The alimentary canal stretches from mouth to anus.

(b) Teeth are rooted in separate sockets in between the gums.

(c) Digestion of food starts in the mouth and gets completed in the small intestine.

(d) Liver is the largest gland in the human body.

18 . One word for each statement describing the five steps in animal nutrition-

(a) Transportation of absorbed food to different parts of the body and their utilization.
- Assimilation.
(b) Breaking of complex food substances into simpler and soluble substances.
- Digestion.
(c) Removal of undigested and unabsorbed solid residues of food from the body.
- Egestion.
(d) Taking food into the body.
- Ingestion.
(e) Transport of digested and soluble food from the intestine to blood vessels.
- Absorption.

Question 19- Match the animals in Column I with their mode of feeding listed in Column II.

Column I	Column II
a) Housefly	i) Biting and chewing
b) Cockroach	ii) Suckling
c) Mosquitos	iii) Sponging
d) Infants	iv) Sucking

Answer-

a) Housefly matches with iii) Sponging. Houseflies feed by sponging up liquids since they can’t chew solid food.
b) Cockroach matches with i) Biting and chewing. Cockroaches are known to chew their food.
c) Mosquitos matches with iv) Sucking. Mosquitoes suck blood or nectar using their proboscis.
d) Infants matches with ii) Suckling. Human infants feed by suckling milk.

Question 20 – Boojho took some grains of boiled rice in test tube ‘A’ and Paheli took boiled and chewed rice in test tube ‘B’. Both of them poured 1 – 2 drops of iodine solution into the test tube and observed the color change. What color change would they have observed? Give reasons for your answer.

Answer-

In test tube ‘A’ with boiled rice, they would observe a blue-black color change upon adding iodine, indicating the presence of starch.
In test tube ‘B’ with boiled and chewed rice, the color change might be less pronounced or absent. This is because the salivary amylase in Paheli’s saliva would have begun breaking down the starch into simpler sugars during chewing, reducing the amount of starch available to react with the iodine.

21. ‘A’ got her gallbladder removed surgically as she was diagnosed with stones in her gallbladder. After the surgery, she faced problems in the digestion of certain food items when consumed in bulk. Can you tell which kind of food items would they be and why?

Answer- After ‘A’ had her gallbladder removed, she would likely face problems digesting fatty foods. This is because the gallbladder stores and releases bile into the small intestine, which is essential for the emulsification of fats. Bile breaks down large fat globules into smaller ones, increasing the surface area for digestive enzymes to act upon. Without the gallbladder to store and concentrate bile, the bile flows directly from the liver into the small intestine, but not in the same concentrated amounts. This reduced capacity to handle large amounts of fat at once can lead to difficulty in digesting high-fat foods, causing discomfort and indigestion. After gallbladder removal, it’s commonly advised to limit the intake of high-fat foods to avoid these issues.

Question 22- Match the organs in Column I with the words listed in Column II.

Column I	Column II
a) Rectum	i) Mucous
b) Gall bladder	ii) Villi
c) Stomach	iii) Taste Buds
d) Tongue	iv) Faeces
e) Small Intestine	v) Bile Juices

Answer-

a) Rectum matches with iv) Faeces. The rectum stores the faecal matter before it is eliminated from the body.
b) Gall bladder matches with v) Bile Juices. The gall bladder stores bile produced by the liver.
c) Stomach matches with i) Mucous. The stomach lining secretes mucous to protect itself from acidic gastric juices.
d) Tongue matches with iii) Taste Buds. The tongue has taste buds that help in perceiving different tastes.
e) Small Intestine matches with ii) Villi. The small intestine is lined with villi which aid in the absorption of nutrients.

Question 23 – Ruminants such as cows and buffaloes swallow their food hurriedly and then sit restfully and chew their food. Can you reason why?

Answer- Ruminants like cows and buffaloes have a unique digestive system that allows them to quickly swallow the grass and store it in a specialized stomach compartment called the rumen. Here, the food is partially digested. Later, when they rest, they regurgitate this partially digested food, known as cud, and chew it thoroughly. This process is essential for breaking down cellulose in the grass, which requires both mechanical action (chewing) and chemical action (digestive enzymes and rumen bacteria) for efficient digestion.

Question 24 – Boojho and Paheli were eating their food hurriedly so that they could go out and play during the recess. Suddenly, Boojho started coughing violently. Think of the reasons why he was coughing and discuss with your friends.

Answer- Boojho’s violent coughing while eating hurriedly could be due to food entering his windpipe instead of the food pipe (oesophagus). This is known as choking. When we eat quickly, we might not chew the food properly, and there is a higher risk of accidentally inhaling small pieces of food. This triggers a cough reflex to expel the food from the windpipe to prevent it from going into the lungs. Chewing food properly and eating slowly are important to avoid such situations.

Question 25- Fill in the blanks using the words listed below.

water, front, intestinal, salts, pseudopodia, back, vacuole
(a) The digestion of all food components is completed by the ____________ juice.

(b) Large intestine absorbs ___________ and some __________ from the undigested food.

(c) Tongue is attached at the _____________ to the floor of the mouth cavity and is free at the _____________.

(d) Amoeba pushes out _____________ around the food and traps it in a food _____________.

Answer-

(a) The digestion of all food components is completed by the intestinal juice. (Intestinal juices are mentioned as digestive juices that break down food into simpler substances).
(b) Large intestine absorbs water and some salts from the undigested food. This is a well-known function of the large intestine.
(c) Tongue is attached at the back to the floor of the mouth cavity and is free at the front. The back of the tongue is anchored to the mouth, allowing the front part to move freely.
(d) Amoeba pushes out pseudopodia around the food and traps it in a food vacuole. Amoebas use pseudopodia to move and capture food, which is then enclosed in a food vacuole for digestion.

26. Label the below-given Figure 2.1 as directed below in (i) to (iv) and give the name of each type of teeth.

(i) The cutting and biting teeth as ‘A’

(ii) The piercing and tearing teeth as ‘B’

(iii) The grinding and chewing teeth as ‘C’

(iv) The grinding teeth present only in adults as ‘D’

Also Check – Activity -Arrangement of teeth and different type of teeth

Answer-

A. Incisors

B. Canines

C. Premolars

D. Molars

27. Read the following passage carefully and answer the questions that follow it. Bile juice is stored in a sac called the gallbladder, located near its organ of secretion, the liver. The gall bladder releases the bile juice into the small intestine whenever food reaches there. Though bile juice is devoid of any digestive enzymes, it is required for the digestion of fats. The fats cannot be digested easily because they are insoluble in water and are present as large globules. Bile juice breaks down big fat droplets into smaller droplets. These are then easily digested by the enzymes released from the pancreas

(a) Which organ secretes the bile juice?

The liver secretes bile juice.

(b) Why is the digestion of fats difficult as compared to that of other nutrients?

The digestion of fats is difficult because fats are insoluble in water and are present as large globules, making them less accessible to digestive enzymes.

(c) How does bile juice help in the digestion of fat?

Bile juice helps in the digestion of fat by breaking down big fat droplets into smaller droplets. This process, known as emulsification, increases the surface area of the fats, making them easier to be digested by enzymes.

(d) Where is the digestion of fat completed?

The digestion of fat is completed in the small intestine. This is where the emulsified fats are acted upon by enzymes from the pancreas.

(e) Does bile juice digest fat completely?

No, bile juice does not digest fat completely. It only aids in the digestion of fat by emulsifying it, making the fats more accessible to digestive enzymes. The actual digestion of fats into fatty acids and glycerol is carried out by enzymes from the pancreas.

28. Label the following parts in Figure 2.2 and name them.

(a) The largest gland in our body.

(b) The organ where protein digestion starts.

(c) The organ that releases digestive juice into the small

intestine.

(d) The organ where bile juice gets stored.

NCERT Exemplar Solutions Class 7 Science Chapter 2-sol-4

Answer –

NCERT Exemplar Solutions Class 7 Science Chapter 2-sol-5

(a) Liver

(b) Stomach

(d) Gallbladder

29. Open your mouth, look into a mirror and try to count the different types of teeth in your mouth. Compare them with Figure 2.3 on page 13 of your NCERT textbook. Record your observations in the table below:

NCERT Exemplar Solutions Class 7 Science Chapter 2-sol-6

(a) Did you observe any difference in the number of teeth? If yes, could you identify which type of teeth showed the difference?

(b) Compare the number and type of teeth in an adult (say your parents or cousins who have reached the age of 25–30 or more). Note your observation.

Answer-