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Samacheer Kalvi 9th Science Books English Medium World of Microbes

Science : Chapter 22 : World of Microbes

I . Choose the correct answer.

1. Mycology is the branch of biology that deals with the study of

  1. algae
  2. virus
  3. bacteria
  4. fungi

Ans : fungi

2. The major constituent of vinegar is

  1. citric acid
  2. acetic acid
  3. oxalic acid
  4. hydrochloric acid

Ans : acetic acid

3. Bacteria involved in curd formation is

  1. Lactobacillus acidophilus
  2. Nitosomonas
  3. Bacillus ramous
  4. none of the above

Ans : Lactobacillus acidophilus

4. Which of the following is transmitted through air?

  1. Tuberculosis
  2. Meningitis
  3. Typhoid
  4. Cholera

Ans : Tuberculosis

5. The most fatal form of Malaria is caused by

  1. Plasmodium ovale
  2. Plasmodium falciparum
  3. Plasmodium malariae
  4. Plasmodium vivax

Ans : Plasmodium falciparum

6. One of the means of indirect transmission of a disease is

  1. sneezing
  2. coughing
  3. vectors
  4. droplet infection

Ans : vectors

7. Syphilis is caused by

  1. Treponema pallidum
  2. Leptospira
  3. Pasteurella
  4. Vibrio cholerae

Ans : Treponema pallidum

8. Mosquito borne viral diseases are

  1. malaria and yellow fever
  2. dengue and chikungunya
  3. filariasis and typhus
  4. kala azar and diptheria

Ans : dengue and chikungunya

9. Diptheria affects the

  1. Lungs
  2. Throat
  3. Blood
  4. Liver

Ans : Throat

10. Which one of the following is a pair of viral disease?

  1. Filariasis, AIDS
  2. Common cold, AIDS
  3. Dysentry, Common cold
  4. Typhoid, Tuberculosis

Ans : Common cold, AIDS

11. Which of the following disease is spread by animal bite?

  1. Pneumonia
  2. Tuberculosis
  3. Cholera
  4. Rabies

Ans : Rabies

12. The primary organ infected during tuberculosis is

  1. bone marrow
  2. intestine
  3. spleen
  4. lungs

Ans : lungs

13. Microbes that generally enter the body through nose are likely to affect

  1. gut
  2. lungs
  3. liver
  4. lymph nodes

Ans : lungs

14. The organ affected by jaundice is

  1. liver
  2. lungs
  3. kidney
  4. brain

Ans : liver

15. Severity of disease symptom depends upon

  1. number of microbes
  2. target organ
  3. both a and b
  4. none of these.

Ans : both a and b

16. Poliomyelitis virus which causes infantile paralysis enters the body through

  1. skin
  2. mouth and nose
  3. ears
  4. eye

Ans : mouth and nose

II. Fill in the blanks.

1. ______________ break down organic matter and animal waste into ammonia.

Ans : microbes

2. The hyphae with branches form a complex network called ______________.

Ans : mycelium

3. First antibiotic ______________ was developed by ______________.

Ans : pencillin, Alexander Fleming

4. Baker’s yeast is ______________.

Ans : Saccharomyces cerevisiae

5. The two non symbiotic nitrogen fixing bacteria are ______________ and ______________.

Ans : Nitrosomonas, Nostoc

6. Typhoid fever is caused by _____________.

Ans : Salmonella typh

7. H1N1 virus causes ______________.

Ans : Swine flu

8. ______________ is a vector of viral disease dengue.

Ans : Acedes aegypti mosquito

9. _____________ vaccine gives considerable protection against tuberculosis.

Ans : BCG (Bacillus Calmette Guerin)

10. Cholera is caused by ______________ and malaria is caused by ______________.

Ans : acteria – Vibrio cholerae, Protozoan parasite -Plasmodium

III. Expand the following.

1. ORSOral Rehydration Solution
2. HIVHuman Immunodeficiency Virus
3. DPTDiptheria Pertussis Tetanus
4. WHOWorld Health Organisation
5. BCGBacillus Calmette Guerin

IV. Pick out the odd one from the following.

i) AIDS, Retrovirus, Lymphocytes, BCG,

Ans : BCG

ii) Bacterial disease, Rabies, Cholera, Common cold and Influenza

Ans : Cholera

iii) Sporozoites, Merozoites, Trophozoites, Gametocytes (Infective stages of plasmodium in human)

Ans : Gametocytes

V. State whether True or False. If false write the correct statement.

1. Glycogen and oil globules are stored form of food in fungi. ( True )

2. One of the differences between virus and viroid is the presence of protein coat in viroid and its absence in virus. ( False )

Ans : protein coat is absent in viroid.

3. Rhizobium, associated with root nodules of leguminous plants fixes atmospheric nitrogen. ( True )

4. Lophotrichous is a cluster of polar flagellae. ( True )

5. Non- infectious diseases remain confined to the person who develops the disease and do not spread to others. ( True )

6. The process of vaccination was developed by Jenner in the year 1796. ( True )

7. Hepatitis B is more dangerous than Hepatitis A. b. Common cold, AIDS ( True )

IV. Match the following.

Column AColumn B
1. Swine fluHuman Papilloma virus
2. Genital wartsHuman Immunodeficiency Virus
3. AIDSMycobacterium
4. TuberculosisInflueuza virus H1N1

Ans : 1 – D, 2 – A, 3 – B, 4 – C

VII. Analyze the table and select the option given below that correctly fills the blank.

DiseaseCausative organism Symptoms
HepatitisVirusInflammation of the liver
ElephantiasisFilarial wormSwelling of legs
MalariaProtozoanFever, Chills and Sweating
DiarrhoeaRota virusNausea, Vomitting, Dehydration

VIII. Answer the following in a word or a sentence.

1. Name the chronic diseases associated with respiratory system.

Tuberculosis,Diptheria,Influenza, Measles are the chronic diseases associated with respiratory system.

2. Name the scientist who first discovered penicillin antibiotic. Can you name any other known antibiotic?

  1. Alexander fleming
  2. Cephalosporin

3. Name the organism causing diarrhoeal diseases and give one precaution against it.

  1. Causative organism -Rota virus
  2. Precausion -Proper sanitation and Hygine

4. Name two common mosquitoes and the diseases they transmit.

Mosquito nameThe diseases they transmit 
Aedes aegyptiChickunguniya, dengue
Culex mosquitoFilaria

5. Name one disease that is transmittedby houseflies. Mention their causative pathogen.

DiseaseCausative pathogen
TyphoidSalmonella typhi
Amoebic dysentryEntamoeba histolytica

IX. Define the following.

1. Pathogen

A pathogen is a biological agent that causes disease to its host.

e.g. bacteria,virus etc.

2. Bacteriophages

Virus that infect bacterial cells.

e.g. T4 bacteriophage.

3. Plasmid

A small extra chromosomal circular DNA called plasmid.It is found in the cytoplasm of bacteria.

4. Vaccines

Vaccines are preparation of living or killed microorganisms or their products used for prevention or treatment of diseases

5. Prions

Prions are viral particles which contain only proteins. They do not contain nucleic acid. They are infectious and smaller than viruses.

X. Answer the following in brief.

1. Distinguish between Virion and Viroid.

DiseaseCausative pathogen
1. It is a nucleo protein particleIt is an RNA particle
2. Nucleic acid can be DNA or RNAViroid is formed only of RNA
3. A protein covering of coat is presentA protein coat is abesent
4. They have a large sizeThey have a smaller size
5. Virions infect all types of organisms.Viroid infect only plants.

2. A baby is suffering from diarrhoea, while other babies in the same locality do not. Mention the possible causes that you think. What would be the possible solutions for this?

possible causes for diarrhoea is drink of contaminated water and unhygienic contaminated food. This result infection of intestine proper sanitation and hygiene would be possible solutions for this

3. Name the vector of the malarial parasite. Mention the species of malarial parasite which cause malignant and fatal malaria.

Anopheles female mosquito is the vector of malarial parasite. Plasmodium falciparum species is malignant and fatal malaria.

4. What is triple antigen? Mention the disease which can be prevented by using the antigen.

Triple antigen is a vaccine used to protect against three disease (DPT).

Dipetheria, Pertussis (wooping cough) and Tetanus can be prevented by using triple antigen.

5. Sanjay had an attack of chicken pox and has just recovered. The health officer of his locality says that the disease would not occur again for him. What would be the reason for this?

Sanjay got natural active immunity from Chicken box virus that is .It is a type of aquired immunity in which the body produces its own antibodies against disease causing agent.

XI. Assertion and Reason.

Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of reason (R) is given just below it. Mark the correct statement as.

  1. If both A and R are true and R is correct explanation of A
  2. If both A and R are true but R is not the correct explanation of A
  3. If A is true but R is false
  4. If both A and R are false.

1. Assertion : A patient with cholera is given oral rehydration therapy for rapid replacement of fluid and electrolytes.

Reason : Cholera can be diagnosed by the microscopic examination of the stool to identify the bacteria.

Ans : If both A and R are true but R is not the correct explanation of A

2. Assertion: Chicken pox is a disease indicated by scars and marks in the body.

Reason: Chicken pox causes rashes on face and further spreads throughout the body.

Ans : If both A and R are false.

3. Assertion: Dengue can be treated by intake of antibiotics.

Reason: Antibiotics blocks the multiplication of viruses.

Ans : If both A and R are true and R is correct explanation of A

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