ICSE Solutions for Chapter 15 Hygiene: A Key to Healthy Life Class 9 Biology Selina

Progress Check

1. Fill in the blanks

(i) Cleanliness, rest and sleep, and physical exercise are a part of _____ hygiene
(ii) One must always breathe by the ____ and never by the _____
(ii) Fresh air brings ____ into the living rooms.
(iii) One must never put a sharp-pointed object into the ____ it may rupture the ____
(v) For adults 6-7 hours of continuous undisturbed ____ is sufficient.
(vi) The municipal bodies must ensure the supply of clean germ-free _____ and an efficient ____ disposal.


(i) Personal
(ii) Nose, mouth
(iii) Oxygen
(iv) Ear, eardrum
(v) Sleep
(vi) Drinking water, sewage


2. List any three advantages of a daily bath.


The three advantages are as follows:

(i) It keeps the skin clean and germ-free
(ii) Eliminates body odours given out by perspiration
(iii) Keeps the sweat pores open
(iv) To keep the body warm


3. Tick-mark the correctly matched pairs of certain animals and the related diseases/habits.

(i) Culex ____ yellow fever
(ii) Aedes ____filarial
(iii) Anopheles _____malaria
(iv) Gambusia ____ eat up mosquito larvae
(v) Rat flea _____diarrhea
(vi) Cockroaches _____breed in man-holes


Culex _____ yellow fever

Aedes _____filarial

Anopheles ____malaria

Gambusia _____ eat up mosquito larvae

Rat flea _____diarrhea

Cockroaches ____breed in man-holes


4. Mention if the following statements are true (T) or false (F)

(i) Contamination means entry of germs by insect bite T/F
(ii) Sewage is the commonest source of contamination of water in the cities T/F
(iii) Cholera is marked by acute diarrhea and no urination T/F
(iv) Typhoid is caused by a type of worm T/F
(v) Mosquitoes are the source of dysentery germs T/F


(i) False. Contamination means the entry of germs into drinking water or edible foods.

(ii) True.

(iii) True.

(iv) False. Typhoid is caused by a bacteria

(v) False. Dysentery can be caused by bacteria or protozoans.


Review Questions

A. Multiple Choice Type

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

(a) Typhoid
(b) Malaria
(c) Dysentery
(d) Cholera


It is because urea accumulates in the blood, which is highly poisonous and fatal.


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 6-7hours
(d) Sharing towels with others


(d)Sharing towels with others
Trachoma and conjunctivitis are two common eye diseases caused by sharing towels and others.


3. The protozoan that causes malaria is:

(a) Entamoeba histolytica
(b) Euglena
(c) Paramecium
(d) Plasmodium


Malaria is caused by the protozoan Plasmodium


4. The chemical substance mainly responsible for tooth disorder is

(a) Calcium
(b) Chloride
(c) Fluorides
(d) Iodides


(c) Fluorides
Presence of fluorides in drinking water causes tooth disorders.


5. Typhoid is caused by

(a) Housefly
(b) Bacteria
(c) Virus
(d) None of the above


(b) Bacteria
Typhoid is caused by Salmonella typhi, a bacterium.


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


(d) Contaminated water
Hepatitis A is infectious hepatitis transmitted through contaminated water.


B. Very Short Answer Type

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


Column I

Column II





Entamoeba histolytica





2. Name the following:

(a) Organism that transmits microbes that cause disease.
(b) Organisms that cause disease.
(c) Science of maintaining good health.


(a) An organism that transmits microbes that cause disease – Vectors

(b) Organisms that cause disease – Pathogens

(c) Science of maintaining good health – Hygiene


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


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.


4. Suggest any two methods of controlling flies.


Two methods of controlling flies:

  1. Spraying of insecticides
  2. Elimination of breeding grounds


5. List any three effective methods for controlling mosquitoes.


Effective methods for controlling mosquitoes: 1. Spraying insecticides 2. Food should be protected by covering it 3. Eliminating breeding places of mosquitoes


C. Short Answer Type

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


The two common kinds of mosquitoes and the diseases they transmit are as follows:

Kind of Mosquito

Disease caused by it






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


Potable water can be contaminated in the following three ways:

  • Urination and defecation near water bodies such as ponds, lakes and rivers
    • Sewage disposed improperly
    • Contamination of water bodies by the drainage of animal washings and wastes from poultries and dairies


3. Write the difference between stages of life cycle of Culex and Anopheles mosquito.


Stages of Life Cycle

Culex Mosquito

Anopheles Mosquito


Eggs have no air spaces and are laid in rafts.

Eggs have small air spaces on their either sides, which makes them buoyant.


Larva floats obliquely with its head hanging downward.

Larva floats parallel to the surface of water.


Adult Culex keeps its body more or less parallel at rest.

Adult Anopheles always rests with its straight body, making an angle against the surface.


D. Long Answer Type

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.


(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 files to avoid possible contamination of food.


2. How are cockroaches and rats harmful to humans?


Cockroaches and rats are common household pests. They are harmful to humans in the following ways:

  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


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


The table below depicts the two types of dysentery, their causatives and precautions:

Type of Dysentery

Causative Germ


Bacillary dysentry

Bacterium – Shigella dysenteriae

Drink safe(boiled) drinking water

Amoebic dysentry

Protozoan – Entamoeba histolytica

Avoid having contaminated food and water for consumption.


4. Mention three symptoms of the disease Hepatitis.


The three symptoms of Hepatitis disease are:

(i) Body ache
(ii) Eyes turn yellowish, due to the bile pigments – urine turns to deep yellow
(iii) Enlargement of liver

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