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Tamilnadu Samacheer Kalvi 8th Science Solutions Term 1 Chapter 6 Micro Organisms

Samacheer Kalvi 8th Science Solutions Micro Organisms Text Book Exercises

I. Multiple choice questions

8th Science Microorganisms Book Back Answers Question 1.
Micro organisms are measured in ……………..
(a) cm
(b) mm
(c) micron
(d) meter.
Answer:
(c) micron

8th Science Microorganisms Question Answer Question 2.
Shows both living and non-living characteristics ………………
(a) Protozoa
(b) Virus
(c) Bacteria
(d) Fungi
Answer:
(b) Virus

Samacheer Kalvi Guru 8th Science Question 3.
……………. is a prokaryotic micro organisms.
(a) Virus
(b) Algae
(c) Fungi
(d) Bacteria
Answer:
(d) Bacteria

Samacheer Kalvi Guru 8th Science Solutions Question 4.
Based on shape, the bacteria are classified into …………….. types.
(a) 2
(b) 3
(c) 4
(d) 5
Answer:
(c) 4

Samacheer Kalvi 8th Books Solutions Science Question 5.
The plant body of algae is called as ………………
(a) Stem
(b) Thallus
(c) Leaf
(d) Root
Answer:
(b) Thallus

II. Fill in the blanks

  1. ……………… is prepared from a mould called Penicillium.
  2. ……………… are the infectious protein particles.
  3. The infect virus particle found outside the host cell is ………………
  4. Micro organism can be seen with the help of a ………………
  5. Bacteria, which have a flagellum at one end is classified as ………………

Answer:

  1. Penicillin
  2. Prions
  3. Virion
  4. Microscope
  5. Monotrichous

III. Match the following

Samacheer Kalvi 8th Science Question 1.

1. Nitrogen fixing bacteria (a) Vaccine
2. Tuberculosis (b) Prion
3. Kuru (c) Lactobacillus acidophilus
4. Probiotics (d) Bacteria
5. Edward Jenner (e) Rhizobium

Answer:

  1. e
  2. d
  3. b
  4. c
  5. a

III. True or False

Samacheer Kalvi 8th Standard Science Question 1.
Diseases causing micro organisms are called pathogens.
Answer:
True.

8th Standard Samacheer Kalvi Science Question 2.
Female Anopheles mosquito is a carrier of dengue virus.
Answer:
False.
Correct statement:
Female Anopheles mosquito is a carrier of malaria.

Samacheer Kalvi 8th Science Book Question 3.
Chicken pox is a communicable disease.
Answer:
True.

Class 8 Science Samacheer Kalvi Question 4.
Citrus canker is transmitted by insects.
Answer:
True.
Correct statement:
Citrus canker is transmitted by air and water

Samacheer Kalvi 8th Science Book Answers Question 5.
Yeast is used in the large scale production of alcohol.
Answer:
True.

V. Assertion & Reason

Direction:
In each of the following questions, a statement of Assertion is given and a corresponding statement of Reason is given just below it. Of the four statements, given below, mark one as the correct answer.
(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.

8th Standard Science Samacheer Kalvi Question 1.
Assertion : Malaria is caused by Protozoa.
Reason : The disease is transmitted by mosquito.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Science Book Class 8 Samacheer Kalvi Question 2.
Assertion : Algae are heterotrophic.
Reason : They don’t have chlorophyll.
Answer:
(d) Both Assertion and Reason are false

VI. Very short answer type

8th Samacheer Kalvi Science Question 1.
Write the name of any nitrogen fixing bacteria.
Answer:
Rhizobium.

Samacheer Kalvi Science 8th Standard Question 2.
Name the bacteria used in the production of vinegar.
Answer:
Acetobacter aceti.

Science 8th Samacheer Kalvi Question 3.
Write the names of any three protozoans.
Answer:

  1. Amoeba
  2. Plasmodium
  3. Paramecium.

8th Science Samacheer Kalvi Question 4.
Who discovered penicillin?
Answer:
Alexander Flemming.

Samacheer Kalvi Science 8th Question 5.
Which diseases can be prevented by vaccination?
Answer:
Small pox, polio, measles, mumps, rubella, tuberculosis.

VII. Short answer type

Samacheer Kalvi Guru 8th Standard Science Question 1.
Write the four types of bacteria, based on their shape.
Answer:
Bacteria are described according to the shape of their cells. They are:

  1. Bacilli – Rod shaped bacteria.
  2. Spirilla – Spiral shaped bacteria.
  3. Cocci – Spherical or ball shaped bacteria.
  4. Vibrio – Comma shaped bacteria.

Kalvi Guru 8th Science Question 2.
What are antibiotics?
Answer:
Antibiotic is a substance produced by living organisms which is toxic for other organisms. Example: Penicillin.

Samacheer Kalvi 8th Books Science Question 3.
What are pathogens?
Answer:
Disease causing organisms are called pathogens. Example: The bacterium Mycobacterium tuberculosis causes tuberculosis in human beings.

Samacheerkalvi.Guru 8th Science Question 4.
How diseases causing micro organisms enter into human beings?
Answer:
The disease causing microbes are called pathogens. They enter into the body through –

  1. Cuts and wounds in the skin, mouth or nose.
  2. Some pathogens are found in air and enter into a healthy person by breathing. When a patient sneezes, droplets containing microbes spread in air. Example: Tuberculosis, Flu.
  3. Some pathogens enter into our body through food and water contaminated with the pathogen. Example: Cholera.
  4. Pathogens also enter through blood transfusion from a infected to healthy person. Example: Aids

Samacheer Kalvi.Guru 8th Science Question 5.
Why micro organisms are essential for agriculture?
Answer:
Role of microbes in agriculture:
1. Natural fertilizer:
Microbes like bacteria, fungi act as decomposers and break down the dead and degradable waste of plants and animals. During this process nutrients are released into the soil and the soil becomes fertile. This compost is called natural fertilizer.

2. Nitrogen fixation:
Microbes can fix atmospheric gaseous nitrogen as nitrate salts in the soil. Example: Rhizobium (root nodule bacteria in leguminous plants). Free living bacteria, cyanobacteria (Nostoc).

3. Biocontrol agents:
Microbes act as natural biocontrol agents and protect crops from pests. Example: Baculoviruses attack insects which harm the plants.

VIII. Long answer type

Question 1.
Write a short note on bacteria and its structure.
Answer:
1. Bacteria are single – celled prokaryotes (cells without nuclei).

2. Bacteria are grouped under the kingdom Monera. The study of Bacteria is called Bacteriology.

3. Bacteria are of two types based on respiration

  • Aerobic bacteria (requires oxygen).
  • Anaerobjc bacteria (Does not requires oxygen).

4. A bacterium has an outer covering known as the cell wall. Nuclear material is represented by a nucleoid without nuclear membrane.

5. An extra chromosomal DNA called plasmid is present in the cytoplasm.

6. Protein synthesis is carried out by 70S ribosomes. Other cell organelles (mitochondria, Golgi body endoplasmic reticulum etc.,) are absent. Flagella aids in locomotion.

7. Bacteria are described according to the shape of their cells. They are:

  • Bacilli – Rod shape bacteria
  • Spirilla – Spiral shaped bacteria
  • Cocci – Spherical or ball shaped bacteria
  • Vibrio – Comma shaped bacteria

Bacteria are also classified according to number and arrangement of flagella as follows:

  • Monotrichous – Single flagella at one end. Example: Vibrio cholera
  • Lophotrichous – Tuft of flagella at one end. Example: Pseudomonas.
  • Amphitrichous – Tuft of flagella at both ends. Example:Rhodospirillum rubrum.
  • Peritrichous – Flagella all around. Example: E.coli.
  • Atrichous – Without any flagella. Example: Corynebacterium diptherae.

Question 2.
How micro organisms are useful in the field of medicine?
Answer:
Role of microbes in medicine:
We obtain antibiotics and vaccines from microbes.

1. Antibiotics:
It is a substance produced by living organisms which is toxic to other organisms. The antibiotic penicillin got from the fungus Penicillium chrysogenum is used to treat diseases like tetanus, diphtheria. Streptomycin got from streptomyces bacteria is used to cure bacterial infections like plague.

2. Vaccines:
They are prepared from dead or weakened microbes. When a vaccine is injected into the body of a patient, it produces antibodies to fight the germs. These antibodies protect the body from infections in future. Example: MMR vaccine for measles.

Question 3.
Answer:
8th Science Microorganisms Book Back Answers Samacheer Kalvi Solutions Term 1 Chapter 6
Question 4.
How can we improve the beneficial bacterial count in human beings?
Answer:
We can improve the beneficial bacterial count in human beings by adopting the following methods:

  1. Intake of fibre rich foods.
  2. Intake of seasonal fruits and vegetables.
  3. Intake of plenty of fermented foods with live microbes. Eat more of prebiotic foods.
  4. Intake of whole grains.
  5. Prefer plant based diet.
  6. Avoid artificial sweeteners.

Question 5.
Write a short note on Probiotics.
Answer:
Probiotics:
Probiotics are live food supplements used in yoghurt and other fermented milk products. Example: Lactobacillus acidophilus and Bifidobacterium bifidum. These bacteria improve the microbial spectrum in the gut and thus contribute to the following effects:

  1. Decrease the risk of colon cancer
  2. Decrease cholesterol absorption
  3. Prevent diarrheal diseases by increasing the immunity power.

Samacheer Kalvi 8th Science Solutions Micro Organisms Additional Questions

I. Choose the correct answer

Question 1.
……………. is absent in bacteria.
(a) DNA
(b) RNA
(c) Mitochondria
(d) Cell wall
Answer:
(c) Mitochondria

Question 2.
……………. is not a shape seen in bacteria.
(a) Spiral
(b) Rod shaped
(c) Spherical
(d) Tadpole
Answer:
(d) Tadpole

Question 3.
E.coli is an example of ……………. bacteria.
(a) Peritrichous
(b) Atrichous
(c) Lophotrichous
(d) Monotrichous
Answer:
(a) peritrichous

Question 4.
……………. is not a fungus.
(a) Agaricus
(b) Nostoc
(c) Penicillium
(d) Albugo
Answer:
(b) Nostoc

Question 5
‘Grass of water’ refers to …………….
(a) Fungi
(b) Bacteria
(c) Algae
(d) Bryophytes
Answer:
(c) Algae

Question 6.
……………. is a biocontrol agent.
(a) Mycorrhizae
(b) Rhizobium
(c) Trichoderma
(d) Agaricus
Answer:
(c) Trichoderma

II. Fill in the Blanks

  1. One word virus means …………… in Latin.
  2. …………… are considered to be the first living organisms on earth.
  3. The nuclear material of bacteria is called …………….
  4. The extra chromosomal DNA in bacteria is called ……………
  5. …………… is a unicellular fungus.
  6. The study of fungi is called ……………
  7. Yeast has an enzyme called ……………
  8. The mode of respiration in yeast is ……………

Answer:

  1. Poison
  2. Bacteria
  3. Nucleoid
  4. Plasmid
  5. Yeast
  6. Mycology
  7. Zymase
  8. Anaerobic

III. True or False – if false give the correct statement

Question 1.
Agaricus is a biocontrol agent.
Answer:
False.
Correct statement:
Trichoderma is a biocontrol agents.

Question 2.
Nostoc is used for fixing nitrogen.
Answer:
True.

Question 3.
Phycoerythirin is a blue pigment.
Answer:
False.
Correct statement:
Phycoerythrin is a red pigment.

Question 4.
Mushroom is the part of the fungus which produces spores.
Answer:
True.

Question 5.
Plasmodium is a parasite.
Answer:
True.

IV. Match the following

Question 1.

i Probiotic (a) Kuru
ii Preservation (b) Methanogen
iii Prion (c) Curd
iv Biogas (d) Sugar

Answer:

i. c
ii. d
iii. a
iv. b

Question 2.

i Amoeba (a) Autotrophs
ii Algae (b) Gills
iii Agaricus (c) Biocontrol
iv Bt cotton (d) Sporulation

Answer:

i. d
ii. a
iii. b
iv. c

V. Assertion and Reason

Direction:
In each of the following questions, a statement of Assertion is given and a corresponding statement of Reason is given just below it. Of the four statements, given below, mark one as the correct answer.
(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.

Question 1.
Assertion (A) : Fungi are heterotrophic in nutrition.
Reason (R) : They lack chlorophyll.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Question 2.
Assertion (A) : Boiling milk is a method of preservation.
Reason (R) : Probiotics is a method of preserving milk.
Answer:
(c) Assertion is true but Reason is false

VI. Very short Answers

Question 1.
What is a plasmid?
Answer:
Extra chromosomal DNA present in bacteria is called plasmid.

Question 2.
Why is nuclear content of a bacterial cell called nucleoid?
Answer:
The nuclear content of a bacterial cell lacks nuclear membrane. So it is called nucleoid.

Question 3.
What are chemosynthetic bacteria?
Answer:
Bacteria that live in harsh environment use chemicals (Ammonia, hydrogen sulphide) to produce their food instead of utilizing energy from the sun. This process is called chemosynthesis.

Question 4.
Why does yeast help in fermentation?
Answer:
It respires anaerobically and has an enzyme called zymase to bring about fermentation.

Question 5.
Name the pigments found in algae.
Answer:
Chlorophylls, fucoxanthin (brown), xanthophylls (yellow), phycoerythrin (red) phycocyanin (blue).

Question 6.
What is biocontrol?
Answer:
Use of microbes to protect crops is called biocontrol.
Example : Trichoderma (fungi) protects plant roots from pathogens.

Question 7.
What is pasteurization?
Answer:

  1. Milk is heated up to 70°c to kill the bacteria and it is cooled to 10°c to prevent the growth of remaining bacteria.
  2. Then milk is stored in sterilized bottles in cold places.
  3. It is a method of preserving milk.

VII. Short Answer

Question 1.
Mention two living characteristics of viruses.
Answer:

  1. They respond to heat, chemicals and radiations.
  2. They reproduce inside the host cells and produce copies of themselves.

Question 2.
Mention two non living characteristics of viruses.
Answer:

  1. They are inactive when present freely in the environment.
  2. They can be crystallized and stored for a very long time, like other non – living things.

Question 3.
Draw a diagram of a bacteriophage and label the parts.
Answer:
8th Science Microorganisms Question Answer Samacheer Kalvi Solutions Term 1 Chapter 6
Question 4.
How are protozoans classified?
Answer:

  1. Ciliates – presence of cilia for locomotion (e.g. Paramecium)
  2. Flagellates – presence of flagella for locomotion (e.g. Euglena)
  3. Pseudopods – presence of pseudopodia for locomotion (e.g. Amoeba)
  4. Sporozoans – parasites (e.g. Plasmodium)

Question 5.
What is pseudopodia?
Answer:
In amoeba pseudopodia are the extended part of cell membrane. It helps to catch its prey (algae).

Question 6.
What is retting?
Answer:
Flax plants are tied in bundles and kept in water. Bacteria loosen the supporting fibres of the stem by acting on the stem tissues. This process is known as retting.

Question 7.
Mention the symptoms and preventive measures undertaken for foot and mouth disease in animals.
Answer:

Animal disease Symptoms Preventive measures / Treatment
Foot and mouth disease Fever, blisters in mouth, weight loss, decreased milk production FMD vaccine

Question 8.
Draw a virion and label the parts.
Answer:
Samacheer Kalvi Guru 8th Science Solutions Term 1 Chapter 6 Micro Organisms

VIII. Long Answer

Question 1.
How are microbes useful in industry?
Answer:
1. Sewage Treatment:
Aerobic microbes are allowed to grow in the primary effluent during the secondary stage of waste water treatment. These microbes consume the major part of the organic matter in the effluent example Nitrobacter sps. In the anaerobic treatment of sewage Methanobacterium is used.

2. Production of Biogas:
Human and animal faecal matter and plant wastes are broken down by anaerobic bacteria to produce methane (biogas) along with carbon dioxide and hydrogen. These bacteria are called as methanogens.

3. Production of Alcohol and Wine:
Alcoholic drinks are prepared by fermentation process using yeast. Sugars in grapes are fermented by using yeast. Beer is produced by the fermentation of sugars in rice and barley.

4. Microbes in Retting and Tanning Process:
1. Retting:
Flax plants are tied in bundles and kept in water. Bacteria loosen the supporting fibres of the stem by acting on the stem tissues. This process is known as retting. Linen thread is made from these fibres example Pseudomonas aeruginosa.

2. Tanning:
In Tanning industry bacteria act upon the skin of animals and makes it soft and therefore it becomes pliable.

Question 2.
Describe the structure of chlamydomonas with neat labelled diagram.
Answer:

  1. Chlamydomonas is a simple, unicellular, motile fresh water algae. They are oval, spherical or pyriform in shape.
  2. The cell is surrounded by a thin and firm cell wall made of cellulose.
  3. The cytoplasm is seen in between the cell membrane and the chloroplast.
  4. The cell contains large dark nucleus lying inside the cavity of the cup shaped chloroplast.
  5. The anterior part of the cell bears two flagella which helps in locomotion.
  6. Two contractile vacuoles are seen at the base of each flagellum.
  7. The anterior side of the chloroplast contains a tiny red coloured eyespot.

Samacheer Kalvi Guru 8th Science Solutions Term 1 Chapter 6 Micro Organisms

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