29 July 2014

IX Bio. Why do we fall ill? NCERT solved questions

Q. What is an antibiotic? Give its one example 

Ans: Antibiotic is a chemical substance that kill bacteria, secreted by microorganismswhich can kill the pathogens Example – Penicillin 

Q. (i) Which disease is more harmful : Acute or Chronic disease ? Why? 
(ii) Why are we advised to take bland and nourishing food when we are sick? 

Ans: (i) Chronic disease 

Because chronic diseases have drastic long term effects on people’s health as compared to acute disease


(ii) (a) Such food does not contain oil or fat and spices so it is digested easily

(b) It provides sufficient energy for recovery after the disease

(c) It provides adequate amount of nutrients required for regeneration of cells and tissues.

Q. (i) How atmospheric inert nitrogen gas is converted into usable nitrogenous form for the various life forms? (ii) Draw a labelled diagram to show nitrogen cycle in nature
Ans: (i) (i) By the help of free living nitrogen fixing bacteria or nitrogen fixing bacteria found in roots of legumes.

(b) Physical process : During lighting, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain.

Q. (i) What are the consequences of Global warming (ii) Why is water essential to life?
Ans: (i) Rise in temperature (ii) Melting of glacier

(ii) (a) All life processes require water. (b) Water is needed for transportation of substances from one part of body to other in dissolved farm.

Q. Name the causal organism of AIDS. Why a person suffering from AIDS cannot fight even very minor infections ?
Ans: HIV (virus)

The virus goes to the immune system and damages its function. So the body can no longer fight off even minor infections.

Q. Write the symptoms when following organs are targeted by microbes. (a) Lungs (b) Liver (c) Brain.
Ans: Lungs – cough , breathlessness. Liver – Jaundice Brain – Headache, vomiting, fits

Q. What is immunization? List two diseases against which vaccines are available.
Ans: Immunization is the process in which a person's immune system is enhanced by giving inactive form of the disease causing agent ( immunogen). This agent develops the human immune system to fight against that agent and if attacked again by the same agent the immune systems give a more stronger response and eliminate the disease.

Two diseases for which vaccines are available are Polio and Diphtheria.

Q. Write the full form of AIDS. List four modes of transmission of virus of this disease.
Ans: Aquired Immuno Deficiency Syndrome

Modes of transmission of virus of this disease

a) Through sexual contact

b) Through blood trsnsfusion From mother to child

c) Through infected needled or syringes

Q. Health workers are exposed to more sick people than others in the community. Writeany four preventive measures they take to avoid sickness.
Ans: Preventive measures:

(i) Hand washing after any direct contact with patients

(ii) Wearing gloves while treating or examining the patient.

(iii) Proper disposal or sterilizing the instruments.

(iv) Immunisation.

Q. Same drug does not work against the microbes belonging to different groups. Why? State the mechanism of antibiotics in killing bacteria.
Ans: Every micro organism has its own biochemical cycle. So one type of antibiotic can stop or block biochemical cycle of one type of micro organism only but not all type of micro organisms. Antibiotic destroy the cell wall during the asexual reproduction cycle hence the bacteria can be easily killed.

Q. “Water is essential for living organisms”. State two reasons to justify this statement.
Ans: Water is needed by organisms to maintain their body temperature. Water is needed by organisms to perform many biochemical reactions.

Q. List the names of three diseases caused by virus stating their mode of communication in each case.
Ans: (1) Influenza (2) Hepatitis (3) AIDS

Mode of communication

(1) Blood transfusion (2) Unprotected sexual contact (3) Use of contaminated needles syringes etc. (4) From mother ‘to foetus thmyh’ placenta

Q. List four preventive measures against communicable diseases.
Ans: 1. Health education 2. Isolation 3. Proper sanitation 4. Sterilization of articles used by patients 5. Vaccination 6. Provision of safe water supply

Q. A person has lost his power to fight infections. Name the disease the person is suffering from. State the pathogen and modes of transmission of this disease.
Ans: Suffering from AIDS Name of pathogen is a virus known as HIV. Mode of transmission of HIV is :

1. Intimate sextual contact

2. Blood transfusions

3. Contaminated needles, syringes or razors (Any 2 points)

Check it out

Class IX Biology Chapter - Why do we fall ill?   NCERT Solutions
CCE Test Paper Biology     Chapter:  Why do we fall ill?   Solved Questions
NCERT Solved Board Questions 9th Science: Ch-13.  Why do we fall ill?
Class IX  Biology Ch-13.Why do we fall ill-Chapter Notes

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