Class-7 Science, Chapter-2 Nutrition in Animals / NCERT book / CBSE Syllabus

Chapter 2

Nutrition in Animals

Exercises from textbook

Additional Exercises

Activities/Projects

 

Exercises from Textbook

Fill in the blanks:

 

1)    The main steps of nutrition in humans are ingestion, digestion, absorption, assimilation and egestion.

2)   The largest gland in human body is liver.

3)   The stomach releases mucous, hydrochloric acid and digestive juices which act on food.

4)    The inner wall of the small intestine has many finger-like outgrowths called villi.

5)   Amoeba digests its food in the food vacuole.

 

Mark (✓) if the statement is true and (✗) if it is false:

1)   Digestion of starch starts in the stomach.(✗)

2)   The tongue helps in mixing food with saliva.(✓)

3)   The gall bladder temporarily stores bile. (✓)

4)   The ruminants bring back swallow grass into their mouth and chew it for some time. (✓)  

 

Tick (✓) mark the correct answer in each of the following:

1)   Fat is completely digested in the 

a)   Stomach

b)   Mouth

c)    Small intestine (✓)

d)   Large intestine

2)   Water from the undigested food is absorbed mainly in the 

stomach

a)   Food Pipe

b)   Small intestine

c)    Large intestine  (✓)

 

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

Ans-

 

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

 

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

Ans- Villi are thousands of finger-like outgrowths in the wall of the small intestine. 

The villi increase the surface area for absorption of the digested food. The surface of villi absorbs the digested food and through the network of blood vessels it reaches to various organs.

 

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

Ans- Bile is a digestive juice secreted by the liver and is stored in gall bladder. It helps to digest fats in the food into fatty acids and glycerol.

 

Q. Why do we get instant energy from glucose?

Ans- Glucose is a simple carbohydrate which our digestive system need not to break further. It gets absorbed in the blood directly and provides energy during respiration.

 

Which part of the digestive canal is involved in:

a)   Absorption of food

b)   Chewing of food

c)    Killing of bacteria

d)   Complete digestion of food

e)   Formation of faces

 

Absorption of food	Small Intestine
Chewing of food	Buccal Cavity
Killing of bacteria	Stomach
Complete digestion of food	Small Intestine
Formation of faces	Large Intestine

 

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

Ans- Similarity-

Both amoeba and the human digestive system have steps of ingestion, digestion, absorption, assimilation and ingestion.

Difference-

Digestion of food in amoeba is a simple cellular process while in humans digestion occurs via a complex process in the alimentary canal.

 

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 faces 

 

Column I	Column II
Salivary gland	Saliva Secretion
Stomach	Acid release
Liver	Bile juice secretion
Rectum	Storage of undigested food
Small intestine	Digestion is completed
Large intestine	Absorption of water
Anus	Release of faces

Label the digestive system.

 

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

We can survive only on raw fruits and leafy vegetables for a shorter period.

Raw fruits and vegetables / grass have cellulose which the human body is not able to digest. Cooking makes the food easily digestible. In fact, we should try to incorporate raw fruits and vegetables also in a well-balanced diet.

 

Additional Exercises

 

Choose the correct option:

Amoeba captures its food by the movement of finger-like projections called__________

      a)   Villi

      b)   Pseudopodia (✓)

      c)    Food vacuole

      d)   Bristles

 

Which is the widest part of our digestive system?

     a)   Stomach (✓)

     b)   Large Intestine

     c)    Rectum

     d)   Pancreas

 

Grass is rich in _________, a type of carbohydrate which humans are not able to digest.

     a)   Lactose

     b)   Fructose

     c)    Sucrose

     d)   Cellulose (✓)

 

Which of these process is characteristic of grass-eating animals?

     a)   Rumination (✓)

     b)   Rehydration

     c)    Sucking

     d)   Swallowing

 

Which of these animals sucks the nectar of the plant?

     a)   Mosquito

     b)   Humming bee (✓)

     c)    Ant

     d)   Lice

 

Plants can prepare their own food by the process of _________

     a)   Photosynthesis (✓)

     b)   Digestion

     c)    Transpiration

     d)   Respiration

 

Give one word for the following:

(1) The process of breakdown of complex components of food into simpler substances.

Digestion

(2) The process of taking food into the body.

Ingestion

(3) The first set of teeth that grows during infancy and they fall off at the age between six to eight years.

Milk teeth

(4) It is the largest gland in the body.

Liver

(5) Finger-like outgrowths in the inner walls of the small intestine.

Villi

(6) Removal of faecal matter through anus.

Egestion

(7) A condition in which watery stool is passed frequently because of infection, food poisoning or indigestion.

Diarrhoea

(8) Finger-like projections in amoeba which are used for movement and capture of food.

Pseudopodia

(9) A special strong thread which is moved between two teeth to take out the trapped food particles.

Dental floss

Fill in the blanks:

1)   The digestive tract and associated glands together constitute the digestive tract.

2)   The food is pushed down in the alimentary canal by the movement of the wall all of the food pipe.

3)   The large intestine is about 1.5 metre in length. 

4)   The digested food passes into blood vessels in the wall of the intestine.

5)   The saliva breaks down the starch into sugars.

6)   The digestive juices convert complex substances of food into simpler ones.

7)   Infants of humans and many other animals feed on mother’s milk.

8)   The end of the stomach opens into the intestine only after the digestion of the food inside the stomach is completed.

 

State whether the following statements are true or false:

     1)   The basic process of digestion of food and release of energy is the same in all animals. (T)

     2)   The largest intestine is wider and shorter than the small intestine. (T)

     3)   The bile plays an important role in the digestion of carbohydrates. (F)

     4)   The digestive tract begins at the buccal cavity and ends at the anus. (T)

     5)   Some aquatic animals filter tiny food particles floating nearby and feed upon them. (T)

 

Select the odd one:

      a)   Salivary gland, liver, pancreas, pseudopodia

      b)   Buccal cavity, oesophagus, pancreas, stomach, intestine, rectum

      c)    Ingestion, digestion, absorption, assimilation, rumen, egestion

      d)   Incisor, canine, piercing, premolar, molar

      e)   Mucous, hydrochloric acid, digestive juices, bile

 

Answer these questions:

Que- Why do animals need food?

Ans- Animals need food their growth, repair and functioning of the body.

 

Que- What is digestion? Why is it necessary for organisms to digest their food?

Ans- The breaking down of complex components of food into simpler substances is called digestion.

The components of food such as carbohydrates are complex substances. These complex substances cannot be utilized as such, so it is necessary for organisms to digest food.

 

Que- What is the role of villi in the process of digestion?

Ans- Villi are thousands of finger-like outgrowths in the wall of the small intestine. 

The villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of villi absorbs the digested food and through the network of blood vessels it reaches to various organs.

 

Que - How does starfish eat its food?

Ans- Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested.

 

Que - Explain feeding and digestion of food in amoeba.

Ans- Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole. Inside these food vacuoles, digestive juices are secreted and the food is broken down into simpler substances. The digested food gets absorbed and the absorbed substances are used for growth, maintenance and multiplication. The undigested residue of food is expelled outside by the vacuole.

 

Que- Humans cannot digest cellulose. How does the digestion of cellulose occur in grass-eating animals?

Ans- Grass-eating animals (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.

 

Que- Why are cows, buffaloes and other grass-eating animals called ruminants?

Ans- Grass-eating animals quickly swallow the grass and store it in a part of the stomach called rumen. In rumen, food gets partially digested and is called cud. Later the cud returns to the mouth in small lumps and the animal chews it. This process is called rumination. Thus, these animals are called ruminants.

 

Tables from Textbook

Table 2.1 Various modes of feeding

Name of animal	Kind of food	Mode of feeding
Snail	Insects	Scraping
Ant	Grains	Scraping, chewing
Eagle	Fish	Capturing, swallowing
Humming-bird	Nectar	Sucking
Lice	Blood	Sucking
Mosquito	Blood	Sucking
Butterfly	Nectar	Siphoning
Housefly	Liquid food	sponging

(Scraping, chewing, siphoning, capturing and swallowing, sponging, sucking etc.)

 

Wash your hands. Look into the mirror and count your teeth. Use your index finger to feel the teeth. How many kinds of teeth could you find? Take a piece of an apple or bread and eat it. Which teeth do you use for biting and cutting, and which one for piercing and tearing? Also find out the ones that are used for chewing and grinding? Record your observations in the table below:

Table 2.2

Type of teeth	Number of teeth		Total
	Lower jaw	Upper jaw
Cutting and biting teeth
Piercing and tearing teeth
Chewing and grinding teeth

(Students should count their own teeth to fill in this table)

 

Extended Learning - Activities and Projects

1.    Visit a doctor and find out:

a)   Under what conditions does a patient need to be on a drip of glucose.

b)   Till when does a patient need to be given glucose.

c)    How does glucose help the patient recover?

Write the answers in your notebook.

2.            Find out what vitamins are and get the following information.

a)   Why are vitamins necessary in the diet?

b)   Which fruits or vegetables should be eaten regularly to get vitamins?

3.            Write one-page note on the information collected by you. You may take help of a doctor, a dietician, your teacher or any other person, or from any other resource.

 

Back to Table of Contents

 

Image attribution

Human Digestive System - OpenStax College / CC BY https://creativecommons.org/licenses/by/3.0)

Starfish - Alain Feulvarch / CC BY (https://creativecommons.org/licenses/by/2.0)

Phagocytosis in Amoeba - Kate Taylor / CC0