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Chapter 15

Hygiene - [A Key to Healthy Life]

Class 9 - Concise Biology Selina


Multiple Choice Type

Question 1

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

  1. Typhoid
  2. Malaria
  3. Dysentery
  4. Cholera ✓

Question 2

Which one of the following is an unhealthy habit?

  1. Removing wax from inside the ears
  2. Keeping the mouth closed while breathing
  3. Sleeping for only 6-7 hours
  4. Sharing towels with others ✓

Question 3

The protozoan that causes malaria is:

  1. Entamoeba histolytica
  2. Euglena
  3. Paramecium
  4. Plasmodium ✓

Question 4

The chemical substance mainly responsible for tooth disorder is

  1. Calcium
  2. Chloride
  3. Fluorides ✓
  4. Iodides

Question 5

Typhoid is caused by

  1. Housefly
  2. Bacteria ✓
  3. Virus
  4. None of the above

Question 6

The germ causing Hepatitis is transmitted through:

  1. The bite of a mosquito
  2. Contamination of food by a housefly
  3. Personal contact with a patient
  4. Contaminated water ✓

Very Short Answer Type

Question 1

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

Column IColumn II
(a) Mosquito(i) DDT
(b) Plasmodium(ii) Dengue
(c) Entamoeba histolytica(iii) Vector
(d) Aedes mosquito(iv) Malaria
(e) Insecticide(v) Dysentery

Answer

Column IColumn II
(a) MosquitoMalaria
(b) PlasmodiumVector
(c) Entamoeba histolyticaDysentery
(d) Aedes mosquitoDengue
(e) InsecticideDDT

Question 2

Name the following:

(a) Organism that transmit microbes that cause disease.

(b) Organisms that cause disease.

(c) Science of maintaining good health

Answer

(a) Organism that transmit microbes that cause disease — Vectors

(b) Organisms that cause disease — Pathogens

(c) Science of maintaining good health — Hygiene

Question 3

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

Answer

The housefly is a natural scavenger involved in cleaning and consuming the left-overs of the food. But at the same time housefly poses dangers to human life which are really serious, that it often designated as Public Enemy and is responsible for spreading numerous diseases.

The manner in which the housefly spreads diseases are:

  1. Hairy body and legs pick up the filth — Spiny or hairy legs and body tend to pick up dirt containing germs from germ-infested places such as faecal matter, rotten material, infected wound. When these carriers/flies rest on our food, they rub their legs continuously dropping the particles of dirt on the food, causing it to get contaminated.
  2. Pouring out saliva — Food gets moist when housefly regurgitates on food or pours its saliva as a result pathogens get discharged on them causing the food to get contaminated.
  3. Direct transmission of germs — Houseflies directly transmit pathogens in some cases. In case of eye disease trachoma, pathogens are transmitted from an infected person to a healthy person, when a fly settled on an infected eye of person sits on the eyes of a healthy person.
  4. Excreta – It deposits its excreta while it feeds, thus contaminating human food.

Question 4

Suggest any two methods of controlling flies.

Answer

The two methods of controlling flies are:

  1. Elimination of breeding places of flies.
  2. Spraying houses and breeding places of flies with DDT and other insecticides.

Question 5

List any three effective methods for controlling mosquitoes.

Answer

The effective methods for controlling mosquitoes are:

  1. Elimination of breeding places for mosquitoes.
  2. Spraying on stagnant water with Kerosene or some other greasy oil to kill larvae and pupae. Spraying DDT and other insecticides to kill adult mosquitoes.
  3. Biological control by introducing certain fishes like Gambusia which selectively devour on mosquito larvae.

Question 6

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

Answer

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

  1. Anopheles — They transmit Malaria.
  2. Aedes — They transmit Dengue

Question 7

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

Answer

Contamination of potable (drinking) water can occur in several ways such as:

  1. Sewage, if improperly disposed, leaks into sub soil and may contaminate underground water supplies.
  2. Urination and defecation near water bodies such as ponds, lakes and rivers
  3. Contamination of water bodies by the drainage of animal washings and wastes from poultries and dairies.

Long Answer Type

Question 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.

Answer

(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. These germs can be picked by us when we touch these objects. They are then transmitted to the different parts of the body, through the water we drink or through the food we eat. Hence it becomes a necessity to wash hands thoroughly before consuming food as it protects us from the diseases that could be spread through these germs/vectors.

(iii) Eating places must be kept free of flies as flies carry bacteria and germs that cause various diseases.

Question 2

How are cockroaches and rats harmful to humans?

Answer

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

  1. Cockroaches eat and spoil food, paper and clothes. They are also suspected to be carriers of certain viral diseases, possibly including a cancer-causing virus.
  2. Rats eat grains and other foods. They also spread germs of certain diseases. Rat-fleas is a parasite that lives on rat's skin. It may carry germs of plague.

Question 3

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

Answer

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

Type of DysenteryCausativePrecaution
BacillaryBacterium – ShigellaConsume safe(boiled) drinking water.
AmoebicProtozoan – Entamoeba histolyticaAlways check for food and water contamination before consumption.

Question 4

Mention three symptoms of the disease Hepatitis.

Answer

The three symptoms of Hepatitis disease are:

  1. Body ache
  2. Eyes turn yellowish, due to the bile pigments – urine turns to deep yellow
  3. Enlarged liver
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