SELINA Solutions for Class 9 Biology Chapter 15 - Hygiene - A Key To Healthy Life

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Chapter 15 - Hygiene - A Key To Healthy Life Exercise Ex. 1

Question A

No urination due to shortage of water in the body is a typical symptom of

(a) typhoid

(b) malaria

(c) dysentery

(d) cholera

2. Which one of the following is an unhealthy habit?  

(a) Removing wax from inside the ears  

(b) Keeping the mouth closed while breathing  

(c) Sleeping for only 6-7 hours  

(d) Sharing towels with others 

3. The protozoan that causes malaria is: 

(a) Entamoeba histolytica 

(b) Euglena 

(c) Paramecium 

(d) Plasmodium 

4. The chemical substance mainly responsible for tooth disorders is 

(a) Calcium 

(b) Chloride 

(c) Fluorides 

(d) Iodides 

5. Typhoid is caused by 

(a) Housefly 

(b) Bacteria 

(c) Virus 

(d) None of the above

6. The germ causing Hepatitis is transmitted through

(a) the bite of a mosquito

(b) contamination of food by a housefly

(c) personal contact with a patient

(d) contaminated water


Solution A

1. (d) cholera

2. (d) Sharing towels with others

3. (d) Plasmodium

4. (c) Fluorides

5. (b) Bacteria

6. (d) contaminated water

Question B.1

Match Column I with that which is most appropriate in Column II.

Column I

Column II

(a) Mosquito

(i) DDT

(b) Plasmodium

(ii) Dengue

(c) Entamoeba histolytica

(iii) Vector

(d) Aedes mosquito

(iv) Malaria

(e) Insecticide

(v) Dysentery


Solution B.1

Column I

Column II (Answers)

(a) Mosquito

(iv) Malaria

(b) Plasmodium

(iii) Vector

(c) Entamoeba histolytica

(v) Dysentery

(d) Aedes mosquito

(ii) Dengue

(e) Insecticide

(i) DDT


Question B.2

Name the following:

(a) Organisms that transmit microbes that cause disease.

(b) Organisms that cause disease.

(c) Science of maintaining good health.

Solution B.2

(a) Vectors (disease carriers)

(b) Pathogens

(c) Hygiene

Question B.3

Describe the different ways by which the housefly contaminates our food.

Solution B.3

The different ways by which the housefly contaminates our food:

(i) 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.

(ii) 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.

(iii) Excreta: While feeding on food items, houseflies may deposit their excreta on food, contaminating it.

(iv) 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.

Question B.4

Suggest any two methods of controlling flies.

Solution B.4

Two methods of controlling flies:

1. Spraying of insecticides

2. Elimination of breeding grounds

Question B.5

List any three effective methods for controlling mosquitoes.

Solution B.5

Effective methods for controlling mosquitoes:

(i) Spraying insecticides

(ii) Food should be protected by covering it

(iii) Eliminating breeding places of mosquitoes

Question B.6

Name the two common kinds of mosquitoes and the diseases they transmit.

Solution B.6

Kind of mosquito

Disease caused by it

Anopheles Malaria
Culex Filariasis
Question B.7

Mention any three ways by which potable water can be contaminated.

Solution B.7

Contamination of potable water can occur due to

 Improper disposal of sewage

 Defecation and urination near lakes, rivers or ponds

 Drainage of animal wastes and washings from dairies and poultries into water bodies

Question C.1

Give suitable explanations for the following :

(i) One should breathe by nose and never by mouth.

(ii) Hands must be washed before eating food.

(iii) Eating places must be kept free of flies.

Solution C.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.

Question C.2

How are cockroaches and rats harmful to humans?

Solution C.2

Cockroaches and rats are common household pests.

(i) Cockroaches are involved in spoiling food, paper and cloth. They may act as carriers of viruses, especially those which cause cancer.

(ii) 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.

Question C.3

Name the two types of dysentery and their causative germs and give one main precaution against them.

Solution C.3









1. Bacillary dysentery

Bacterium: Shigella dysenteriae 

Drinking safe (boiled) water

2. Amoebic dysentery

Protozoan: Entamoeba histolytica

Avoiding contaminated water and food


Question C.4

Mention three symptoms of the disease Hepatitis.

Solution C.4

Symptoms of Hepatitis:

 Body ache

 Yellow eyes

 Deep yellow urine

 Enlarged liver