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P S Verma & V K Aggarwal (biology) Solutions for Class 9 Science Chapter 5 - Why Do We Fall Ill

P S Verma & V K Aggarwal (biology) Solutions for Class 9 Science Chapter 5 Why Do We Fall Ill are provided here with simple step-by-step explanations. These solutions for Why Do We Fall Ill are extremely popular among class 9 students for Science Why Do We Fall Ill Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the P S Verma & V K Aggarwal (biology) Book of class 9 Science Chapter 5 are provided here for you for free. You will also love the ad-free experience on Meritnation’s P S Verma & V K Aggarwal (biology) Solutions. All P S Verma & V K Aggarwal (biology) Solutions for class 9 Science are prepared by experts and are 100% accurate.

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Healthy Disease-free
It refers to a state of complete well-being (physical, social and mental). It refers to a state of absence of discomfort in any part of the body.
Besides an individual, it also depends upon the physical and socio-environmental factors. It depends only on the individual.
Performance of a healthy person is very high because of high energy. Performance of a disease-free person depends upon the environment and personal behaviour.

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Health problems subsequent to a disaster include infectious diseases such as diarrhoea, cholera, and typhoid. Disasters also lead to diseases caused by deficiency of nutrients because of the unavailability of proper food.

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Following are some provisions made by local authorities to provide clean drinking water:

(a) Ensuring routine checks on water leakage in the tanks
(b) Treating the water with chlorine if the water gets unhygienic for drinking

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Following are some provisions made by local authorities for solid waste management:

(a) Collecting the waste on a regular basis for its proper degradation
(b) Cleaning the local area regularly to collect the solid waste at one place

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Symptoms of a disease Signs of a disease
Symptoms of a disease indicate the presence of a disease. These indicate the presence of a specific disease. 
They are a collective indication of a number of diseases. They are specific for different diseases.

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Tuberculosis is caused by Mycobacterium tuberculosis.
Kala-azar is caused by Leishmania.
Malaria is caused by Plasmodium.
Measles is caused by Paramyxovirus.
Athlete's foot is caused by Trichophyton.
Cholera is caused by Vibrio cholerae.

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Following are the two means of physical contact by which AIDS does not spread:

(i) It does not spread by shaking hands with the infected person.
(ii) It does not spread by sitting or talking with the infected person.

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Vector Carrier
A vector is an organism that passes on a disease without getting infected. A carrier is an organism that itself does not have any symptoms of a disease, but the pathogen lives in its body and is passed on to others.

A vector may act as an intermediate host for the completion of part of the life cycle of the pathogen.

A carrier may or may not be needed by the pathogen to complete its life cycle.

Pathogen inhabits a vector usually for a short period of time. The carrier state may carry the pathogen for a  short or long duration (temporary or transient carrier or chronic carrier).
Example- Mosquito with malarial parasite Example- A human with HIV virus but not AIDS or a human with pathogen Salmonella typhi but not typhoid

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Organ-specific manifestation of a disease:

It refers to those types of diseases in which the pathogen infects a specific organ of an individual.
Example: In tuberculosis, the lungs of an individual are targeted.

Tissue-specific manifestation of a disease:
It refers to those types of diseases in which the pathogen infects a specific tissue of an individual.
Example: The HIV virus targets the tissue and cells of an individual, thereby decreasing the immunity.

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After the entry of microbes in the body, the immune system of the body gets activated and starts releasing antibodies against the microbes. The immune system comprises several WBCs that fight against the microbes. These cells kill the microbes before they cause much harm to the body.

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A person suffering from AIDS cannot fight even the minute infections because his/her immune system or self-defence gets weakened. The HIV virus attacks the WBCs of the host and reduces the immunity. Hence, a person suffering from AIDS usually dies of secondary infections as he/she cannot fight even minor infections.

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"We can treat an infectious disease by killing microbes".

An infectious disease is caused by pathogens such as bacteria, protozoa, fungi, worm and viruses. When these pathogens enter a body, they result in a certain dysfunction in the body. Such symptoms can be treated by taking medicines; however, medicines do not necessarily remove the pathogens.

To treat an infectious disease, the microbes have to be killed by taking medicines that either kill the microbes or block the microbial synthetic pathways without affecting the host cellular pathways.

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Prevention is better than cure because of the following reasons:

(a) Curing a disease takes time and the person suffering from a disease has to cut off his work and daily routines to get complete rest.
(b) A person once infected serves as a medium of spreading the disease to others.
(c) Once a person gets infected, his or her body gets affected and he or she may never recover completely.

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A vaccine is a small quantity of a weakened antigen that is injected into the body of an individual. Once the antigen gets into the body of a healthy person, his/her body synthesises antibodies against the antigen. Once the body encounters an infectious antigen, it develops a memory; and when that antigen enters that body again, a large amount of antibodies is secreted by the body to destroy the antigen. Hence, it prevents the disease from occurring.

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The following three diseases in human beings are caused by bacteria:

(a) Cholera
(b) Tuberculosis
(c) Typhoid

The following three diseases in human beings are caused by viruses:

(a) Influenza
(b) Dengue fever
(c) AIDS

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Dehydration sets in during diarrhoea because of excessive loss of water from the body tissues via discharge of semisolid or fluid faeces and vomiting. Dehydration may lead to the death of infants. Hence, the doctor tries to prevent dehydration from occurring during diarrhoea by advising liquid diet to the patient to compensate for the loss of water along with antibiotic treatment.

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The unhygienic conditions prevailing in a locality where people suffer from malaria are as follows:

(i) Stagnant water at various places, due to which mosquitoes continue breeding
(ii) No use of insect repellents and mosquito nets by the people

Doctors confirm malaria by taking blood test of the infected individuals.

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Malaria can be prevented by adopting the following measures:

(i) Using insect repellents to avoid mosquito bites
(ii) Sprinkling kerosene oil on large open water bodies
(iii) Introducing Gambusia in water bodies, as it feeds on mosquito larvae
(iv) Spraying insecticides to kill adult mosquitoes

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He is suffering from AIDS (acquired immunodeficiency syndrome). The microbe that is responsible for the disease is the retrovirus human immunodeficiency virus (HIV).

It spreads from one person to another by the following ways:

(a) Unprotected sexual contact with the infected person
(b) Transfusion of blood contaminated by HIV
(c) Use of injected needles or unsterilised needles
(d) From an infected mother to her child during pregnancy

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Diarrhoea refers to an abnormal and frequent discharge of semisolid or fluid faeces. It is caused by bacteria.
It is caused by infections via contaminated food, drinks, clothes, etc. 

The symptoms include discharge of semisolid or fluid faeces, vomiting, abdominal cramps and decreased appetite. It can be prevented by improving hygiene.

It can be cured by giving antibiotic treatment to the patient.

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Rabies is also referred to as hydrophobia because the person suffering from this disease develops a fear of water. The person finds difficulty even in drinking water.

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Pulse Polio Immunisation Programme (PPIP):

It was conducted in December 1995 for the first time to eradicate polio from India. In this programme, a dose (0.5 mL) of oral polio vaccine (OPV) is given to a child at different ages (1.5, 2.5 and 3.5 months), along with a booster dose given at 1.5 years of age (now up to 5 years of age). The vaccine helps to develop antibodies against the polio virus in the intestine and blood of the child. The days on which PPIP is conducted in the country are fixed and are known as national immunisation days (NIDS). 



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