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Page No 27:

Question A:

Solve the following crossword puzzle:

figure

Across
3. It is the false feet of amoeba
4. A type of teeth use for tearing of food
6. Excretion of undigested food

Down
1. Taking in of food
2. Finger-like projection in small intestine
5. An enzyme produced in mouth

Answer:

Page No 27:

Question B.1:

The false feet in amoeba are
(a) vacuole
(b) pseudopodia
(c) proboscis
(d) tentacle

Answer:

(b) pseudopodia

Pseudopodia are the false feet in Amoeba.

Page No 27:

Question B.2:

The process of breaking down complex food into simpler one is
(a) digestion
(b) absorption
(c) excretion
(d) assimilation

Answer:

(a) Digestion

Digestion is the process in which solid and complex food substances are converted into simpler soluble forms.

Page No 27:

Question B.3:

Which of the following organs produces bile?
(a) liver
(b) pancreas
(c) gall bladder
(d) gastric gland

Answer:

(a) Liver

Liver is a digestive gland that produces bile, which is stored in the gall bladder.

Page No 27:

Question B.4:

Digestion in amoeba is
(a) intracellular
(b) extracellular
(c) intercellular
(d) none of these

Answer:

(a) intracellular

Digestion in Amoeba is intracellular, as it takes place within the cell.

Page No 27:

Question B.5:

Ptyalin helps in the digestion of
(a) sugar
(b) fat
(c) protein
(d) starch

Answer:

(d) starch

Ptyalin, which is present in saliva, converts starch into sugar.

Page No 27:

Question B.6:

Small intestine have this to increase the surface area of absorption.
(a) villi
(b) glands
(c) liver
(d) pancreas

Answer:

(a) Villi

Villi present in the small intestine increase the surface area of absorption.

Page No 27:

Question B.7:

Which of the following helps in partial digestion of fats?
(a) bile
(b) gastric juice
(c) pancreatic juice
(d) amylase

Answer:

(a) Bile

Bile juice secreted by the liver helps in the partial digestion of fats; it breaks down fats into fatty acids and glycerol.

Page No 27:

Question B.8:

The part of digestive system which helps in mixing food with saliva is
(a) teeth
(b) oesophagus
(c) tongue
(d) stomach

Answer:

(c) tongue

Tongue is the part of the digestive system that helps in mixing saliva with food.



Page No 28:

Question C:

Fill in the blanks:
1. ........................... movement pushes the food down towards the stomach.
2. Bile breaks down fats into ........................... and ........................... .
3. ........................... increase the area of absorption for food.
4. In amoeba ........................... are used for procuring food.
5. The excessive loss of water from the body is called ............................ .

Answer:

1. Peristaltic movement pushes the food down towards the stomach.
2. Bile breaks down fats into fatty acids and glycerol.
3. Villi increase the area of absorption for food.
4. In Amoeba, pseudopodia are used for procuring food.
5. The excessive loss of water from the body is called dehydration.

Page No 28:

Question D:

Match the items in Column A with the items in Column B:

Column A Column B
1. Diarrhoea (a) Digestive gland
2. Pancreas (b) Proteins
3. Tentacles (c) ORS
4. Amylase (d) Hydra
5. Trypsin (e) Paramecium
  (f) Mouth

Answer:

  Column A Column B
1. Diarrhoea (c) ORS
2. Pancreas (a) Digestive gland
3. Tentacles (d) Hydra
4. Amylase (f) Mouth
5. Trypsin (b) Proteins

Page No 28:

Question E:

Write True (T) or False (F) against the following statements in the given brackets:
1. Rumen in cow is actually the true stomach. ( )
2. Digestion of food starts in the mouth. ( )
3. Gastric juice is secreted by the small intestine. ( )
4. An enzyme called ptyalin is present in saliva. ( )
5. Villi helps in digestion of food. ( )

Answer:

1. False (F)
Abomasum in cow is the true stomach.

2. True (T)

3. False (F)
Gastric juice is secreted by the stomach.

4. True (T)

5. False (F)
Villi help in the absorption of food.

Page No 28:

Question F:

Look at the diagram and label the parts with these words and write their function:

Molar, Canine, Incisor, Premolar

figure

Answer:


a. Incisors: They are used for cutting and biting food.

b. Canine: They are used for tearing food.

c. Premolars: They are used for grinding and crushing food.

d. Molars: They are used for grinding food.



Page No 29:

Question 1:

Why is goat milk much simpler to digest as compare to cow's milk?

Answer:

Goat's milk is much simpler to digest, as it contains less lactose (glucose + galactose) compared to cow's milk. In addition to this, goat's milk also contains riboflavin (vitamin B2), which helps in the faster metabolism of proteins and carbohydrates.

Page No 29:

Question 2:

On skipping meals, problem of acidity develops. What is the reason behind this?

Answer:

The inner walls of the stomach secrete digestive juices (such as hydrochloric acid), which are acidic in nature. These juices help in the break down of food into simpler forms. When we are hungry, digestive juices are secreted; and if we do not consume food for a long period of time, these juices tend to corrode the protective lining of the stomach, thereby causing ulcers. Therefore, it is important to eat meals at regular intervals to avoid acidity.

Page No 29:

Question 3:

Digestion needs the help of two more systems in the body to provide energy from food. Which are these systems and how do they help?

Answer:

1. Respiratory system: The respiratory system (airways and lungs) works closely with the digestive system, as it provides oxygen for the complete breakdown of food in the body.

2. Circulatory system: The digestive system breaks down food into nutrients that are transported to all parts of the body through the circulatory system. Thus, the body derives energy from the nutrients absorbed to carry out various life processes.

Page No 29:

Question 4:

How regular intake of green leafy vegetables can present constipation?

Answer:

Constipation is a condition in which an individual has infrequent bowel movements. It is generally caused by consuming refined foods that do not contain enough roughage (fibre). This condition can be prevented by the regular intake of green leafy vegetables. Green leafy vegetables contain a good amount of roughage along with other important nutrients. Roughage is an indigestible fibrous material found in vegetables; it helps in proper digestion and improves the functioning of the bowel system. Therefore, regular intake of green leafy vegetables can help avoid digestive disorders.



Page No 30:

Question A.1:

Define holozoic nutrition.

Answer:

The process in which organisms obtain nutrition by ingesting solid or liquid food materials is known as holozoic nutrition.

Page No 30:

Question A.2:

Which type of carbohydrate cannot be digested by humans?

Answer:

Cellulose is a carbohydrate that cannot be digested by humans.

Page No 30:

Question A.3:

What is the role of hydrochloric acid in the stomach?

Answer:

Hydrochloric acid helps in the effective digestion of food, as it provides an acidic medium for the breakdown of complex food substances into simpler forms.

Page No 30:

Question A.4:

Define digestion.

Answer:

The process of breaking down of complex food substances into simpler forms is known as digestion.

Page No 30:

Question A.5:

Which organ helps to sense different tastes?

Answer:

Tongue is the organ that helps to sense different tastes.

Page No 30:

Question A.6:

Differentiate between ingestion and egestion.

Answer:

Ingestion Egestion
Consumption of food is called ingestion. Elimination of undigested food from the body is called egestion.
Food is taken into the body through the mouth. Undigested food is eliminated from the body through the anus.

Page No 30:

Question A.7:

What is villi?

Answer:

Villi are the small, finger-like projections present in the inner walls of the small intestine; they increase the surface area in the small intestine.

Page No 30:

Question B.1:

Define intracellular digestion. Give one example of an animal where this type of digestion takes place.

Answer:

Intracellular digestion is the digestion that takes place within the cells, in the cytoplasm of an organism. The enzymes present in the cytoplasm help in the process of intracellular digestion.

For example, Amoeba is a unicellular organism in which digestion of food takes place in the food vacuole within the cells.

Page No 30:

Question B.2:

What is the difference between milk teeth and permanent teeth?

Answer:

Milk Teeth Permanent Teeth
Milk teeth develop in a child from the age of about five months to about two years. Permanent teeth develop after the milk teeth fall out between the age of 6 and 8 years.
They are temporary teeth, which are 20 in number. They fall out between the age of 6 and 8 years. They last throughout the life or fall out during old age. There are 32 in number, 16 each in upper and lower jaws.



Page No 31:

Question B.3:

How can diarrhoea be fatal?

Answer:

Diarrhoea is a condition in which an individual passes frequent loose or watery stools. It is caused as a result of the infection of water-borne bacteria, indigestion or food poisoning. As it involves frequent passing of loose, watery stools, a large amount of water and salt is lost from the body, which can be fatal. Dehydration can affect the metabolism of the body, and the body may not be able to carry out its normal functions.

Page No 31:

Question B.4:

Why does rice on chewing give sweet taste?

Answer:

The process of digestion of food begins in the mouth. The mouth contains salivary glands, tongue and teeth.  As the food is chewed, a watery liquid called saliva is released by the salivary glands in the mouth. This saliva helps in the digestion of food; it also converts the starch present in the food to sugar even before the food reaches the stomach. That is why rice tastes sweet on chewing.

Page No 31:

Question B.5:

Which is the largest chamber of the ruminant stomach? What is its role?

Answer:

Rumen is the largest chamber in a ruminant's stomach. It is mainly used for storing food. Ruminants are mostly grass-eating animals. Grass and leaves are rich in cellulose. Cellulose is partially digested in the rumen because it contains special cellulose-digesting bacteria and protozoa. The semi-digested food called cud then leaves the rumen and enters the reticulum chamber of the ruminant's stomach.

Page No 31:

Question B.6:

What is the juice secreted by the liver called? What does it do?

Answer:

The juice secreted by the liver is called bile juice; it is stored in the gall bladder. Bile juice helps in the breakdown of fats into simpler food substances.

Page No 31:

Question B.7:

What is constipation and how can it be prevented?

Answer:

Constipation is a condition in which the bowel movements of a person become infrequent. The stool is difficult to pass and is generally hard. Constipation is usually caused by the intake of over-refined food or food that lacks roughage.

Prevention: Constipation can be prevented by eating food adequate in roughage.

Page No 31:

Question B.8:

What is the role of pancreas in digestion?

Answer:

The pancreas is a digestive gland in the body that helps in the breakdown of complex food substances into simpler food forms. It secretes pancreatic juice, which helps in the breakdown of carbohydrates into sugar, proteins into amino acids and fats into fatty acids.

Page No 31:

Question C.1:

Which digestive juice is secreted in the mouth? What enzyme does it contain and what is its function?

Answer:

Saliva is the digestive juice secreted by the salivary glands in the mouth. Saliva contains the enzyme amylase or ptyalin, which helps in the breakdown of starch present in food into simple sugar.

Page No 31:

Question C.2:

Draw a diagram to show the different steps involved in the process of nutrition in amoeba.

Answer:

                              Nutrition in Amoeba 

Page No 31:

Question C.3:

Explain the role of rumen in the digestion process in ruminants.

Answer:

Rumen is the largest chamber of the stomach in ruminants; it is mainly used for storing food. Ruminants are mostly grass-eating animals. Grass and leaves are rich in cellulose. Cellulose digestion partially takes place in the rumen because of the presence of special cellulose-digesting bacteria and protozoa in it. The food that is partially digested is called cud; it enters the reticulum chamber and is sent back to the mouth for further chewing.

Page No 31:

Question C.4:

Draw a labelled diagram of the alimentary canal of humans.

Answer:


  
       Alimentary Canal of Humans

Page No 31:

Question C.5:

What are digestive glands? Name three such glands that are present in the human body. What are their secretions called?

Answer:

Digestive glands are special glands in the body that produce various digestive juices. These digestive juices help in the breakdown of complex food substances into simpler forms.

The three digestive glands present in the human body are:

1. Salivary gland: The salivary gland secretes saliva that contains the enzyme amylase, which converts starch into simple sugar.

2. Liver: The liver secretes bile juice, which helps in the breakdown of fats into simpler forms.

3. Pancreas: The pancreas secretes pancreatic juice, which digests and converts carbohydrates, proteins and fats into simpler substances.

Page No 31:

Question C.6:

How do the following animals procure their food?
Paramecium, hydra, butterfly, lizard, hawk and elephant.

Answer:

1. Paramecium: It is a unicellular organism; it procures food with its hair-like projections called cilia, which take in the food particles and water into its body.

2. Hydra: It is a multicellular organism; it has finger-like projections called tentacles, which put food into its mouth.

3. Butterfly: It has a feeding tube that is used to suck nectar from flowers.

4. Lizard: It uses its long sticky tongue to procure its prey.

5. Hawk: It uses its curved beak and sharp claws to get hold of its prey and tear it to pieces.

6. Elephant: It uses its long trunk to reach out to the leaves of tall trees.

Page No 31:

Question C.7:

What is the role of stomach in the digestion process?

Answer:

The stomach is a J-shaped bag-like structure made of muscles; it stores and mixes the food received from the food pipe with the help of gastric juice. The digestive juices secreted by the inner walls of the stomach are as follows:
1. Mucus: It guards the lining of the stomach.
2. Hydrochloric acid: It kills microorganisms and creates an acidic medium.
3. Gastric juice: It is secreted by the gastric glands in the stomach and contains the enzyme pepsin, which breaks down proteins  into simpler forms.

The semi-digested food remains in the stomach for one to four hours before it enters the small intestine.

Page No 31:

Question C.8:

What happens to the food in the small intestine?

Answer:

The semi-digested food that leaves the stomach enters the small intestine, where the food is digested completely. The food in the small intestine is mixed with the bile and pancreatic juices secreted by the liver and the pancreas, respectively.
a. Bile juice helps in the digestion of fats; it breaks down the fats into fatty acids and glycerol.
b. Pancreatic juice helps in the breakdown of carbohydrates into sugars, proteins into amino acids and fats into fatty acids.

The inner walls of the small intestines contain finger-like projects, known as villi, which help in the absorption of food. These absorbed nutrients are then transported to various parts of the body through the blood stream for assimilation. The food that remains undigested is passed into the large intestine.

Page No 31:

Question C.9:

Which chamber in ruminant's stomach is known as true stomach? Why?

Answer:

Abomasum is the chamber which is called the true stomach in a ruminant's stomach. This is because the digestion of food takes place in this chamber with the help of gastric juices secreted by the walls of the abomasum. This is similar to the digestion that takes place in the human stomach. The digestion gets completed by the action of enzymes, and the digested food is passed into the small intestine where the absorption of nutrients takes place.



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