NCERT Class 7 Science Chapter 2 Nutrition in Animals

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NCERT Class 7 Science Chapter 2 Nutrition in Animals

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Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 7 Science Solutions are part of All Subject Solutions. Here we have given NCERT Class 7 Science Chapter 2 Nutrition in Animals and Textbook for All Chapters, You can practice these here.

Nutrition in Animals

Chapter: 2

NCERT TEXT BOOK EXERCISES

Q. 1. Fill in the blanks:

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

Ans: Ingestion, digestion, absorption, assimilation, 

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

Ans: Liver.

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

Ans: Digestive.

(d) The inner wall of the small intestine has many finger like out-growths called __________.

Ans: Villi.

(e) Amoeba digests its food in the __________ .

Ans: 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.

Ans: False.

(b) The tongue helps in mixing food with saliva 

Ans: True.

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

Ans: False.

(e) The gall bladder temporarily stores bile. 

Ans: True. 

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.

Ans: (a) (i) Small intestine.

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

(i) stomach

(ii) food pipe

(iii) small intestine

(iv) large intestine.

Ans: (b) (iv) Large intestine. 

Q. 4. Match the items of Column I with those given in Column II:

Ans: 

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

Ans: The finger like projections in the inner walls of the small intestine is called villi. These are found in small intestine. 

Function: The villi decrease the surface area for absorption of the digested food.

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

Ans: The liver secretes bile juice that is stored in a sac called the gall bladder. The bile plays an important role in the digestion of fats.

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

Ans: Cellulose is the carbohydrate that can be digested by ruminants. Ruminants have large sac like structure between the small intestine and large intestine. The cellulose of the food is digested by the action of certain bacteria which are not present in humans. 

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

Ans: We get instant energy from glucose, because in the cells, glucose breaks down with the help of oxygen into carbon dioxide and water and energy is released. 

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

(i) absorption of food.

Ans: Small intestine. 

(ii) chewing of food.

Ans: Buccal cavity.

(iii) killing of bacteria

Ans: Stomach.

(iv) complete digestion of food.

Ans: Small intestine.

(v) formation of feces.

Ans: Large intestine.

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

Ans: Similarity: In both the cases digestive juices break down the complex food particles into simpler substances which can be absorbed.

Difference: Amoeba has no mouth and no digestive system whereas a human being has a mouth and a digestive system made up of many organs. 

Q. 11. Match the items of column I with suitable items in column II:

Ans:

Q. 12. Label Fig 2.16 of the digestive system.

Ans. 

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

Ans: We know that the animals, fungi, bacteria, non-green plants and human beings do not have the ability to make their own food. They depend upon the autotrophs for their food directly or indirectly. The green plants (leafy vegetables, grass) trap solar energy and make their own food in the form of glucose. So we can say that leafy vegetables and grass can provide sufficient energy to survive us.

ADDITIONAL IMPORTANT QUESTIONS

Very Short Answer Questions 

Q. 1. What is the scientific name of the process of ‘taking food into the body’?

Ans: Ingestion.

Q. 2. Name the substance which mixes with food in the mouth during chewing by teeth.

Ans: Saliva.

Q. 3. Name the process which moves the food forward in the food pipe as well as the whole alimentary canal.

Ans: Peristalsis.

Q. 4. (a) Where is the water from undigested food absorbed in the body? 

Ans: (a) Large intestine.

(b) Where is the digested food absorbed into the blood?

Ans: (b) Small intestine.

Q. 5. What is the other name of food pipe?

Ans: Esophagus.

Q. 6. What is the special name of the animals which can chew the cud?

Ans: Ruminants. 

Q. 7. Which substance is absorbed in large intestine?

Ans: Water.

Q. 8. Why food is crushed and wetted before it makes its passage into the alimentary canal?

Ans: Since the lining of the canal is soft, the food is crushed and wetted to make its passage smooth.

Q. 9. Name the enzyme present in saliva. What is its role?

Ans: The saliva contains an enzyme salivary amylase that breaks starch to give sugar. 

Q. 10. Name the longest part of the alimentary canal.

Ans: The small intestine. 

Q. 11. What is the mode of nutrition in human beings?

Ans: Holozoic.

Q. 12. In which part of digestive tract does no digestion take place?

Ans: Oesophagus.

Q. 13. Food from mouth enters which organ of digestive tract through oesophagus?

Ans: Stomach.

Q. 14. Name the end products of digestion of fat.

Ans: Fatty acids and glycerol.

Q. 15. What regulates the exit of waste material from the body?

Ans: The exist of waste material is regulated by the anal sphincter.

Short Answer Questions

Q. 1. What is emulsification? Name the organ where fat is emulsified in the alimentary canal of human beings.

Ans: Emulsification is the breakdown of the large droplets into smaller ones. It occurs in the small intestine.

Q. 2. What is the role of hydrochloric acid in human digestive system?

Ans: Hydrochloric acid secreted inside the stomach, makes the medium acidic for digestion of protein. Hydrochloric acid also causes disinfection of the food.

Q. 3. What is the function of salivary glands? Where are these glands located in the digestive system of man?

Ans: Salivary glands secrete saliva which contains water, salt, mucin and an enzyme ptyalin. The enzyme ptyalin splits starch and glycogen into maltose. These glands are located in the buccal cavity of man.

Q. 4. Name the intestinal juice and write its functions.

Ans: Intestinal juice secreted in jejunum and ileum is succus entericus. It completes the digestion of proteins into amino acids, carbohydrates into glucose and fats into fatty acids and glycerol.

Q. 5. Name the organs where the following enzymes are secreted in human digestive system. 

(i) Pepsin. 

Ans: Stomach.

(ii) Ptyalin. 

Ans: Human saliva in Buccal cavity.

Trypsin.

Ans: Pancreas.

(iv) Gastric lipase.

Ans: Stomach.

Q. 6. Some crushed boiled rice is put in water in a test tube and a few drops of dilute iodine solution are added to it. A blue-black colour is produced which shows the presence of X in rice. If, however, the crushed boiled rice and water are first warmed with saliva for some time and then dilute iodine solution is added, then no blue-black colour is produced. This shows that saliva converts X into product Y which does not produce blue black colour with dilute iodine solution

(a) Name. 

(i) X. and 

(ii) Y.

Ans: (i) Starch 

(ii) Sugar (Maltose) 

(b) What does the above activity tell us about the role of saliva in the digestion of food?

Ans: Saliva helps in digesting starch carbohydrate present in food.

Q. 7. What are peristaltic movements? Why do they occur? 

Ans: The rhythmic contraction of muscles that takes place all along the alimentary canal is referred to as peristaltic movements. These movements help to push the food forward. 

Q. 8. What is the unique feature of stomach?

Ans: The stomach is a large organ which expands when food enters into it. The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices.

Q. 9. Why length of the small intestine differs in various animals?

Ans: The length of the small intestine depends on the type of food they eat. Herbivores need a longe smaller intestine to allow the cellulose present in all plants to be digested.

Carnivores like tigers have a short intestine as meat is easier to digest. 

Q. 10. It is said that, ‘small intestine is the site of the complete digestion’. Why is it so?

Ans: The small intestine receives the secretions of the liver and pancreas which helps in the complete digestion of carbohydrates, proteins and fats.

Short Answer Questions 

Q.1. The digested food in small intestine is absorbed into blood vessels in the walls of small intestine through millions of tiny finger-like outgrowths called W. The undigested and unabsorbed food from the small intestine enters into another organ X. The organ X absorbs most of the water from the undigested waste food material making it semi-solid. The semi-solid waste is stored in part Y of organ X for some time. It is passed out from the body through part Z in the form of faeces.

(a) What are, 

(i) W 

(ii) X 

(iii) Y and 

(iv) Z? 

Ans: (i) Villi. 

(ii) Large intestine. 

(iii) Rectum. 

(iv) Anus. 

(b) What is the name of the process in which undigested waste is thrown out of the body?

Ans: Egestion.

Q. 2. How does Amoeba engulf the food? 

Ans: Amoeba engulfs its food by forming pseudopodia around it. When the food gets completely surrounded from all the sides the tips of encircling pseudopodia fuse with each other and the food is encaptured along with a few lysosomes into the cell in the form of a bag called food vacuole.

Q. 3. What are the functions of the liver and pancreas?

Ans: Functions of liver: Liver secretes bile which contains bile pigments and bile salts. The bile is stored in the gall bladder and secreted into the duodenum through common duct.

Functions of Pancreas: The pancreas is both an endocrine and an exocrine gland. The exocrine region secretes sodium bicarbonate and many digestive enzymes. The endocrine region of pancreas secrete hormones insulin and glucagon.

Q.4. What is saliva? State its role in the digestion of food.

Ans: Saliva is a watery liquid, which is produced by the salivary glands in our mouth.

Saliva helps in the following ways in the digestion of food:

(i) The saliva helps in thorough mixing of food which further helps in the easy movement of food in the food pipe as well as in the alimentary canal.

(ii) The saliva contains an enzyme called salivary amylase (ptyalin) which helps in the breakdown of starch (a complex molecule) to give maltose (a simple sugar).

Q. 5. Draw a diagram of human alimentary canal and label it.

Ans:

Long Answer Questions 

Q.1. When food is put in our mouth, the teeth cut, chew and grind it. The gland A present in mouth secrete a watery liquid B which helps to digest component C present in the food partially. The partially digested food then passes through tube D into an organ E. The inner walls of organ E secrete mucus, hydrochloric acid and digestive juices.

a.  What are: 

(i) A 

(ii) B 

(iii) C 

(iv) D and 

(v) E?

Ans: (a) (i) Salivary glands. 

(ii) Saliva. 

(iii) Starch.

(iv) Oesophagus (or food pipe). 

(v) Stomach. 

(b) Name the component of food which is broken down by the digestive juices secreted by E.

Ans: (b) Proteins.

Q. 2. Explain the process of nutrition in Hydra.

Ans: Hydra is a multicellular animal which ingests its food with the help of tentacles. The tentacles help in catching small aquatic animals by killing them with the help of sting cells present in them.

The food material is then ingested inside the body cavity through the mouth. The food material on entering the body cavity is digested with the help of the enzymes secreted by the cells of the cavity wall of the body. This digested food is absorbed by diffusion through the cavity walls and is assimilated in the cells of the body.

Q.3. What is dental plaque? What harm can it do? How can the formation of plaque be prevented?

Ans: If the teeth are not cleaned regularly, they become covered with a sticky, yellowish layer of food particles and bacteria cells called dental plaque. Since plaque covers the teeth forming a layer over them, the alkaline saliva cannot reach the tooth surface to neutralize the acid formed by bacteria and hence tooth decay sets in. Brushing the teeth regularly, after eating food, removes the plaque before bacteria produces acids. This will prevent tooth decay.

HOTS QUESTIONS

Q.1. Give reason why the milk teeth in children are replaced by permanent teeth. 

Ans: In growing children, the milk teeth become progressively inadequate as the head grows and therefore are replaced by permanent teeth.

Q.2. At times, we feel burning sensation in our throat due to indigestion. Give the possible reason. 

Ans: Sometimes, the acidic contents of stomach enter into esophagus which causes burning sensation in the throat.

Q.3. If we do not clean our teeth and mouth after eating food, then many harmful microorganisms called A begin to grow and live on the tooth. These microorganisms iet on the substance B present in the left-over food particles sticking to the tooth to form C. The Ceats up the parts D and E of the tooth gradually and ultimately make a hole in the tooth. When this hole reaches part F of the tooth, our tooth becomes painful and we get toothache.

(a) What are 

(i) A 

(ii) B 

(iii) C

(iv) D 

(v) E and 

(vi) F? 

Ans: (i) Bacteria.

(ii) Sugar. 

(iii) Acid.

(iv) Enamel.

(v) Dentine.

(vi) Pulp cavity. 

(b) What name is given to the process in which the tooth becomes rotten due to the formation of holes in it?

Ans: (b) Tooth decay.

SKILL BASED QUESTIONS

Q.1. Identify the following figure and label the regions of salt, bitter, sweet and our sensation on the given figure.

Fig. 2.20

Ans: The given figure is the tongue of human mouth. 

1. Salt. 

2. Sour.

3. Sweet. 

4. Bitter. 

Q.2. (a) Label marks 1 and 2 in the diagram of digestive system of ruminant animal.

Ans: 1. Rumen.

2. Stomach. 

Fig. 2.21

(b) Name the partially digested food in rumen. 

Ans: Partially digestive food in rumen is called cud.

FORMATIVE ASSESSMENT

1. Fill in the following blanks with suitable words:

(i) The largest gland in the human body is _________.

Ans: Liver, 

(ii) The stomach releases hydrochloric acid and _________ juices which act on food.

Ans: Digestive.

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

Ans: Villi.

(iv) When the digestion of food is completed, the carbohydrates get broken down into ________, proteins into ______ and fats into ________ and ________.

Ans: Glucose, amino acids, fatty acids, glycerol.

(v) The alimentary canal together with the associated glands constitutes the _______ system. 

Ans: Digestive.

(vi) Permanent teeth grow in place of ________ teeth.

Ans: Milk.

(vii) Tooth decay happens when the bacteria present in mouth turn the sugar present in our food into _________.

Ans: Acid.

(viii) The partially digested food which is brought back from stomach to mouth of an animal for re-chewing is known as _________.

Ans: Cud.

(ix) An example of the animal which can chew the cud is _________.

Ans: Cow.

(x) The finger-like projections on the body of Amoeba are called __________.

Ans: Pseudopodia.

2. State whether the following statements are true or false: 

(i) The tongue helps in mixing saliva with food. 

Ans: True.

(ii) Digestion of starch starts in the stomach.

Ans: False.

(iii) The fall bladder stores bile temporarily.

Ans: True.

(iv) The ruminants bring back swallowed grass into their mouth and chew it for some time.

Ans: True.

(v) The process of taking in food by an animal and its utilization in the body is called digestion. 

Ans: False.

(vi) The aquatic animal which ingests food with the help of pseudopodia is fish.

Ans: False.

(vii) The site of complete digestion and absorption of food in the human digestive system is small intestine. 

Ans: True.

(viii) The millions of tiny outgrowths on the inner surface of small intestine are called villi.

Ans: True.

(ix) The length of small intestine in adult human beings is about 1.5 m.

Ans: False. 

(x) Water from the undigested food is absorbed mainly in the stomach.

Ans: False.

3. Matching Type Questions: Match the items of column I with those given in column II.

Ans: 

4. Multiple Choice Questions:

(i) Tongue helps in:

(a) mixing saliva with food. 

(b) swallowing the food.

(c) speaking.

(d) all the above.

Ans: (d) All the above.

(ii) The process by which organisms take in food is called:

(a) ingestion

(b) assimilation

(c) digestion

(d) egestion

Ans: (a) Ingestion.

(iii) The total number of teeth in a permanent set is:

(a) 32

(b) 30

(c) 29

(d) 16

Ans: (a) 32.

(iv) Bile helps to:

(a) digest carbohydrates

(b) digest proteins

(c) digest fats

(d) digest cellulose

Ans: (c) Digest fats.

(v) Partially digested food in the rumen is called:

(a) rumen

(b) cud

(c) saliva 

(d) grass

Ans: (b) Cud.

(vi) In amoeba, food particle is trapped inside a cavity called:

(a) food vacuole

(b) pseudopodia

(c) villi

(d) cud

Ans: (a) Food vacuole.

(vii) The proboscis is present in:

(a) housefly

(b) cockroach

(c) butterfly

(d) lizard

Ans: (c) Butterfly.

(viii) The sting cells are present in:

(a) Amoeba 

(b) Paramecium

(c) Euglena 

(d) Hydra

Ans: (d) Hydra.

(ix) Which of the following are called the tearing teeth?

(a) Incisors

(b) Canines

(c) Molars

(d) Premolars

Ans: (b) Canines.

(x) Ruminants can: 

(a) digest the cellulose

(b) not digest the cellulose

(c) sometimes digest and sometimes do not

(d) all of the above 

Ans: (a) Digest the cellulose.

5. Write one word for the following:

(i) The act of getting and eating food.

Ans: Ingestion.

(ii) The white part of the tooth containing calcium salts. 

Ans: Enamel.

(iii) The digestive system from esophagus to anus. 

Ans: Alimen- try canal.

(iv) The fleshy muscular organ that helps in speaking.

Ans: Tongue.

(v) Large sac-like structure between small intestine and large intestine in the body of a ruminant.

Ans: Caecum.

(vi) The contraction and expansion of muscles of the esophagus which help in movement of food to the stomach.

Ans: Peristalsis.

(vii) Excretion of undigested food. 

Ans: Egestion.

(viii) False feet of amoeba.

Ans: Pseudopodia.

(ix) Finger like projections on the inner walls of small intestine.

Ans: Villi.

(x) An animal with four chambered stomach that regurgitates.

Ans: Ruminant.