Selina Textbook Solutions: Hygiene | Biology Class 9 ICSE PDF Download

 Page 1


Chapter 15. Hygiene – A Key To Healthy Life
Exercise 1
Solution A.
1. (d) cholera
2. (d) Sharing towels with others
3. (d) Plasmodium
4. (c) Fluorides
5. (b) Bacteria
Solution B.1.
Column I Column II
(a) Eggs (iii) White cylindrical
(b) Adult (i) Sucking proboscis
(c) Pupa (ii) Barrel-shaped
(d) Larva (iv) Legless
Solution B.2.
The different ways by which the housefly contaminates our food:
1. Hairy body and legs: Hairy or spiny body and legs easily pick up dirt containing 
germs from unhygienic places such as rotten materials, infected wound 
or faecal matter. When these flies sit on our food, they rub their legs continuously 
dropping the particles of dirt onto the food, thereby contaminating it.
2. Pouring out saliva: When the housefly pours its saliva or regurgitates on food, 
foodstuffs get moistened and pathogens get deposited on them. This results in their 
contamination.
3. Excreta: While feeding on food items, houseflies may deposit their excreta on food, 
contaminating it.
4. Direct transmission of germs: In some cases, houseflies directly transmit the 
pathogens. In case of eye disease trachoma, pathogens are transferred from an 
infected person to a healthy person, when a fly settled on an infected eye of a 
person sits on the eyes of a healthy person.
Solution B.3.
Two methods of controlling flies:
1. Spraying of insecticides
2. Elimination of breeding grounds
Solution B.4.
Page 2


Chapter 15. Hygiene – A Key To Healthy Life
Exercise 1
Solution A.
1. (d) cholera
2. (d) Sharing towels with others
3. (d) Plasmodium
4. (c) Fluorides
5. (b) Bacteria
Solution B.1.
Column I Column II
(a) Eggs (iii) White cylindrical
(b) Adult (i) Sucking proboscis
(c) Pupa (ii) Barrel-shaped
(d) Larva (iv) Legless
Solution B.2.
The different ways by which the housefly contaminates our food:
1. Hairy body and legs: Hairy or spiny body and legs easily pick up dirt containing 
germs from unhygienic places such as rotten materials, infected wound 
or faecal matter. When these flies sit on our food, they rub their legs continuously 
dropping the particles of dirt onto the food, thereby contaminating it.
2. Pouring out saliva: When the housefly pours its saliva or regurgitates on food, 
foodstuffs get moistened and pathogens get deposited on them. This results in their 
contamination.
3. Excreta: While feeding on food items, houseflies may deposit their excreta on food, 
contaminating it.
4. Direct transmission of germs: In some cases, houseflies directly transmit the 
pathogens. In case of eye disease trachoma, pathogens are transferred from an 
infected person to a healthy person, when a fly settled on an infected eye of a 
person sits on the eyes of a healthy person.
Solution B.3.
Two methods of controlling flies:
1. Spraying of insecticides
2. Elimination of breeding grounds
Solution B.4.
Effective methods for controlling mosquitoes:
1. Spraying insecticides
2. Food should be protected by covering it
3. Eliminating breeding places of mosquitoes
Solution C.1.
Kind of mosquito Disease caused by it
Anopheles Malaria
Culex Filariasis
Solution C.2.
Page 3


Chapter 15. Hygiene – A Key To Healthy Life
Exercise 1
Solution A.
1. (d) cholera
2. (d) Sharing towels with others
3. (d) Plasmodium
4. (c) Fluorides
5. (b) Bacteria
Solution B.1.
Column I Column II
(a) Eggs (iii) White cylindrical
(b) Adult (i) Sucking proboscis
(c) Pupa (ii) Barrel-shaped
(d) Larva (iv) Legless
Solution B.2.
The different ways by which the housefly contaminates our food:
1. Hairy body and legs: Hairy or spiny body and legs easily pick up dirt containing 
germs from unhygienic places such as rotten materials, infected wound 
or faecal matter. When these flies sit on our food, they rub their legs continuously 
dropping the particles of dirt onto the food, thereby contaminating it.
2. Pouring out saliva: When the housefly pours its saliva or regurgitates on food, 
foodstuffs get moistened and pathogens get deposited on them. This results in their 
contamination.
3. Excreta: While feeding on food items, houseflies may deposit their excreta on food, 
contaminating it.
4. Direct transmission of germs: In some cases, houseflies directly transmit the 
pathogens. In case of eye disease trachoma, pathogens are transferred from an 
infected person to a healthy person, when a fly settled on an infected eye of a 
person sits on the eyes of a healthy person.
Solution B.3.
Two methods of controlling flies:
1. Spraying of insecticides
2. Elimination of breeding grounds
Solution B.4.
Effective methods for controlling mosquitoes:
1. Spraying insecticides
2. Food should be protected by covering it
3. Eliminating breeding places of mosquitoes
Solution C.1.
Kind of mosquito Disease caused by it
Anopheles Malaria
Culex Filariasis
Solution C.2.
Solution D.1.
(i) One should breathe by nose and never by mouth because nose contains hair and 
mucous to trap dust and micro-organisms, so that the inhaled air becomes pure and the 
Page 4


Chapter 15. Hygiene – A Key To Healthy Life
Exercise 1
Solution A.
1. (d) cholera
2. (d) Sharing towels with others
3. (d) Plasmodium
4. (c) Fluorides
5. (b) Bacteria
Solution B.1.
Column I Column II
(a) Eggs (iii) White cylindrical
(b) Adult (i) Sucking proboscis
(c) Pupa (ii) Barrel-shaped
(d) Larva (iv) Legless
Solution B.2.
The different ways by which the housefly contaminates our food:
1. Hairy body and legs: Hairy or spiny body and legs easily pick up dirt containing 
germs from unhygienic places such as rotten materials, infected wound 
or faecal matter. When these flies sit on our food, they rub their legs continuously 
dropping the particles of dirt onto the food, thereby contaminating it.
2. Pouring out saliva: When the housefly pours its saliva or regurgitates on food, 
foodstuffs get moistened and pathogens get deposited on them. This results in their 
contamination.
3. Excreta: While feeding on food items, houseflies may deposit their excreta on food, 
contaminating it.
4. Direct transmission of germs: In some cases, houseflies directly transmit the 
pathogens. In case of eye disease trachoma, pathogens are transferred from an 
infected person to a healthy person, when a fly settled on an infected eye of a 
person sits on the eyes of a healthy person.
Solution B.3.
Two methods of controlling flies:
1. Spraying of insecticides
2. Elimination of breeding grounds
Solution B.4.
Effective methods for controlling mosquitoes:
1. Spraying insecticides
2. Food should be protected by covering it
3. Eliminating breeding places of mosquitoes
Solution C.1.
Kind of mosquito Disease caused by it
Anopheles Malaria
Culex Filariasis
Solution C.2.
Solution D.1.
(i) One should breathe by nose and never by mouth because nose contains hair and 
mucous to trap dust and micro-organisms, so that the inhaled air becomes pure and the 
respiratory passage is free of dust and micro-organisms.
(ii) We handle a variety of things like books, coins, furniture, tools and machinery in 
workshops, seats and supporting rods in buses and even pets and other domestic animals 
in our day-to-day life. Many of these objects carry germs. These germs can be picked up 
by us, when we touch these objects and get transferred to other parts of our body or into 
our mouth, when we eat our food. Therefore, it is necessary to wash our hands before 
eating food to avoid the spread of diseases caused due to these germs.
(iii) Flies are carriers of many disease-causing germs and bacteria. Therefore, eating 
places must be kept free of flies to avoid possible contamination of food.
Solution D.2.
Cockroaches and rats are common household pests.
1. Cockroaches are involved in spoiling food, paper and cloth. They may act as carriers 
of viruses, especially those which cause cancer.
2. Rats eat grains and other foods. They also act as carriers of certain pathogens. A 
parasite named rat-fleas lives on rat’s skin. It possibly carries the germs of plague.
Solution D.3.
TYPE OF 
DYSENTERY
CAUSATIVE GERM PRECAUTION
1. Bacillary 
dysentery
Bacterium: Shigella dysenteriae
Drinking safe 
(boiled) water
2. Amoebic 
dysentery
Protozoan: Entamoeba histolytica
Avoiding 
contaminated 
water and food