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VIII-EM-Microorganisms
MICROORGANISMS
TEXTBOOK EXERCISES
I. CHOOSE THE BEST ANSWER.
1. Microorganisms are measured in _______.
a) cm
b) mm
c) micron
d) meter.
Ans: c) micron
2. _______ shows both living and nonliving characteristics.
a) Protozoa b) Virus c) Bacteria d) Fungi
Ans: b) Virus
3. ______ is a prokaryotic microorganisms.
a) Virus b) Algae c) Fungi d) Bacteria
Ans : d) bacteria
4. Based on shape, the bacteria are classified
into _______ types.
a) two b) three c) four d) five
Ans: c) four
5. Common cold in human is caused by ______.
a)plasmodium
b) influenza
c) vibrio cholera
d) aphthovirus
Ans: b) influenza
II. FILL IN THE BLANKS.
1. _______ is prepared from a mould called penicillium.
Ans: Penicillin
2. _______ are the infectious protein particles.
Ans:Prions
3. The infecting virus particle found outside the host cell is _______.
Ans: virion
4. Microorganism can be seen with the help of a _______.
Ans: microscope
5. Bacteria, which has a flagellum at one end is classified as _______.
Ans : mono trichous
III. STATE TRUE OR FALSE. IF FALSE, CORRECT THE STATEMENT.
1. Disease causing microorganisms are called pathogens.
Ans: True
2. Female anopheles mosquito is a carrier of dengue virus.
Ans: False. Correction statement Female anopheles mosquito is a carrier of Malaria plasmodium (Protozoa).
3. Chicken pox is a communicable disease.
Ans: True
4. Citrus canker is transmitted by insects.
Ans: False. Correction statement: Citrus canker is transmitted by air / water
5. Yeast is used in the large scale production of alcohol.
Ans: True
IV. MATCH THE FOLLOWING.
Ans:
V. ANSWER THE FOLLOWING QUESTIONS.
Mark the correct one as:
a. If both assertion and reason are true and reason is the correct explanation of
assertion.
b. If both assertion and reason are true and reason is not the correct explanation of assertion.
c. If assertion is true but reason is false.
d. If both assertion and reason are false.
1. Assertion: Malaria is caused by Protozoa.
Reason: The disease is transmitted by mosquitoes.
Ans: a. If both assertion and reason are true and reason is the correct explanation of assertion.
2. Assertion: Algae are heterotrophic.
Reason: They do not have chlorophyll.
Ans:d. If both assertion and reason are false.
VI. ANSWER VERY BRIEFLY.
1. Write the name of any nitrogen fixing bacteria.
Ans : The names of Nitrogen fixing bacteria are
a. Rhizobium
b. Cyanobacteria
c. Nostoc
2. Name the bacteria used in the production of vinegar.
Ans: Bacteria used in the production of vinegar are Acetobacter.
3. Write the names of any three protozoans.
Ans:
Paramecium
Euglena
Plasmodium
4. Who discovered penicillin?
Ans: Penicillin was discovered by Sir Alexander Fleming in the year of 1928.
5. Which diseases can be prevented by vaccination?
Ans: Vaccine is given for preventing
Measles
Mumps
Rubella.
VII. ANSWER BRIEFLY.
1. Write the four types of bacteria, based on their shape.
Ans: Based on the shape, bacteria are classified into four types. They are
a. Bacilli - Rod shaped bacteria.
b. Spirilla - Spiral shaped bacteria.
c. Cocci - Spherical or ball shaped bacteria.
d. Vibrio - comma shaped bacteria.
2. What are antibiotics?
Ans: The word 'Anti' means 'against'. Antibiotic is a substance produced by living organisms which is toxic for other organisms.
Examples: Penicillin, Streptomycin.
3. What are pathogens?
Ans:A few microorganisms are harmful to humans, animals and plants. They cause diseases and hence they are called pathogens.
Examples: Bacteria, Virus, Protozoa, Algae, Fungi
4. How disease causing microorganisms enter into human beings?
Ans:Pathogens or Diseases causing microorganisms enter into the body through cuts and wounds in the skin, mouth or nose and cause diseases. Viruses causing 'flu' are spread through air. When the patient sneezes droplets containing viruses spread in air and it gets entered to another person when he breathes.
5. Why microorganisms are essential for agriculture?
Ans : Microorganism are essential for agriculture because, microorganisms are helps plant in various ways.
o They act upon degradable wastes and decompose the wastes
o Rhizobium bacteria live in the root of leguminous plants and helpse soil by fixing the atmospheric nitrogen as nitrates which are essential for the growth of plants.
o They also act as biocontrol agent and protect the crops from pests.
VIII. ANSWER IN DETAIL.
1. Write a short note on bacteria and its structure.
i) Bacteria:
Bacteria are single-celled prokaryotes (cells without nuclei).
They are considered to be the first living organisms on earth.
Bacteria are grouped under the kingdom Monera.
The study of Bacteria is called Bacteriology.
The size of bacteria ranges from 1µm to 5µm(micrometer).
Bacteria are of two types based on respiration
a. Aerobic bacteria (requires oxygen).
b. Anaerobic bacteria (Does not require oxygen).
ii) Cell structure:
A bacterium has an outer covering known as the cell wall.
Nuclear material is represented by a nucleoid without nuclear membrane.
An extra chromosomal DNA called plasmid is present in the cytoplasm.
Protein synthesis is carried out by 70S ribosomes.
2. How microorganisms are useful in the field of medicine?
Ans: We obtain antibiotics and vaccines from microbes.
Antibiotics:
o The word ‘anti’ means ‘against’. Antibiotic is a substance produced by living organisms which is toxic for other organisms.
o Sir Alexander Fleming was the first person to discover the antibiotic penicillin in the year 1928.The antibiotic penicillin was obtained from the fungi Penicillium chrysogenum. It is used to treat diseases such as tetanus and diphtheria.
o The antibiotic, streptomycin is obtained from Streptomyces bacteria to cure various bacterial infections. Eg. Plague.
Vaccines:
o Vaccines are prepared from dead or weakened microbes.
o Edward Jenner was the first person to discover small pox vaccine. He coined the term vaccination.
o When the vaccine is injected to the body of a patient, the body produces antibodies to fight against the germs.
o These antibodies remain inside the body and protect from future invasion of the germs. Therefore, vaccination is otherwise called as immunization.
o Eg:
MMR vaccine is given for preventing Measles, Mumps and Rubella.
BCG (Bacille Calmette Guerin) vaccine is given for preventing Tuberculosis.
3. Write a short note on common human diseases caused by microorganisms.
4. How can we improve the beneficial bacterial count in human beings?
When you lose "good" bacteria in your body, for example after you take antibiotics, probiotics can help replace them.
They can help balance your "good" and "bad" bacteria to keep your body working the way it should.
Probiotics are live food supplements used in yoghurt and other fermented milk products.
Lactobacillus. It is found in yogurt and other fermented foods. Different strains can help with diarrhea and may help people who can't digest lactose, the sugar in milk.
Bifidobacterium. It is found in some dairy products. It may help ease the symptoms of irritable bowel syndrome (IBS).
5. Write a short note on probiotics.
Probiotics are live bacteria and yeasts that are good for us, especially to our digestive system. We usually think of these as germs that cause diseases. But our body is full of bacteria, both good and bad. Probiotics are often called "good" or "helpful" bacteria because they help keep our gut healthy.
We can find probiotics in supplements and some foods, like yogurt. Doctors often suggest them to help with digestive problems.
