AP 8th Class Biology 2nd Lesson Questions and Answers Microorganisms: Friend and Foe

AP State Board new syllabus 8th Class Biology Guide 2nd Lesson Microorganisms: Friend and Foe Textbook Exercise Questions and Answers.

AP 8th Class Biology 2nd Lesson Questions and Answers Microorganisms: Friend and Foe

8th Class Biology 2nd Lesson Microorganisms: Friend and Foe Questions and Answers (Exercise)

Question 1.
Fill in the blanks :

a) Microorganisms can be seen with the help of a ……………
Answer: microscope.

b) Blue green algae fix …………… directly from air and enhance fertility of soil.
Answer: nitrogen.

c) Alcohol is produced with the help of ……………
Answer: yeast.

d) Cholera is caused by ……………
Answer: bacteria.

Question 2.
Tick the correct answer:

a) Yeast is used in the production of
i) sugar
ii) alcohol
iii) hydrochloric acid
iv) oxygen
Answer:
(ii) alcohol.

b) The following is an antibiotic
i) sodium bicarbonate
ii) streptomycin
iii) alcohol
iv) yeast
Answer:
(ii) streptomycin.

c) Carrier of malaria causing protozoan is
i) female anopheles mosquito
ii) cockroach
iii) housefly
iv) butterfly
Answer:
(i) female anopheles mosquito.

d) The most common carrier of communicable diseases is
i) ant
ii) housefly
iii) dragonfly
iv) spider
Answer:
(ii) housefly.

e) The bread or idli dough rises because of
i) heat
ii) grinding
iii) growth of yeast cells
iv) kneading
Answer:
(iii) growth of yeast cells.

(f) The process of eonversion of sugar into alcohol is called
i) nitrogen fixation
ii) moulding
iii) fermentation
iv) infection
Answer:
(iii) fermentation.

Question 3.
Match the organisms in column A with their action in column B.

Column-A	Column-B
i) Bacteria	a) Fixing nitrogen
ii) Rhizobium	b) Setting of curd
iii) Lactobacillus	c) Baking of bread
iv) Yeast	d) Causing malaria
v) A protozoan	e) Causing cholera
vi) A virus	f) Causing AIDS
	g) Producing antibodies

Answer:

Column-A	Column-B
i) Bacteria	e) Causing cholera
ii) Rhizobium	a) Fixing nitrogen
iii) Lactobacillus	b) Setting of curd
iv) Yeast	c) Baking of bread
v) A protozoan	d) Causing malaria
vi) A virus	f) Causing AIDS

Question 4.
Can microorganisms be seen with the naked eye ? If not, how can they be seen ?
Answer:

• No, it is not possible to see microorganisms with our naked eye because they are very small in size.
• But, bread mould (Rhizopus), a fungus can be seen with a magnifying glass.
• We can observe the microorganisms by using a microscope.
• Even very minute microbes can be seen by using electron microscope.

Question 5.
What are the major groups of microorganisms ?
Answer:
1) Microorganisms are classified into four major groups based on their size.
2) These are

• Bacteria
• Fungi
• Protozoa
• Some algae

3) Viruses are also microscopic but are different from the above microorganisms.

Question 6.
Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer:
Rhizobium, Azatobactor and clostridium are the microorganisms that can fix the atmospheric nitrogen in the soil.

Question 7.
Write 10 lines on the usefulness of microorganisms in our lives.
Answer:
Uses of microorganisms in our daily life :

• Lactobacillus convert milk into curd.
• Yeast is used in the preparation of bread, cakes and pastries.
• Yeast is also used in the large scale production of alcohol and wine through fermentation.
• Decomposing bacteria are useful in cleaning up of the environment. The organic wastes, remains of plant and animal bodies are broken down into harmless and usable substances.
• Some bacteria are used in the preparation of medicines.
• In agriculture, some bacteria are useful to increase the soil fertility.
• Bacteria are used in the making of cheese, pickles and many other food items.
• Bacteria and yeast are also helpful for fermentation of rice, idlis and dosa batter.
• Microorganisms are very useful for the large scale preparation of acetic acid (vinegar)
• Microorganisms are used in the preparation of antibiotics.

Question 8.
Write a short paragraph on the harmful effects of micro organisms.
Answer:

• Some microorganisms are harmful in many ways, they cause diseases in human beings, plants and animals.
• These disease causing microbes are called pathogens.
• Some microorganism spoil food, clothing and leather.
• Pathogens enter our body through air water and food. They can also get transmitted by direct contact with an infected person or carried by an animal (carrier).
• Microbial diseases that can be spread from an infected person to a healthy person through air, water, food or physical contact are called “Communicable diseases”.
• Bacteria cause diseases like T.B., typhoid and cholera in human beings. In plants citrus canker disease is caused by bacteria.
• Virus causes diseases like measles, polio, chicken pox and AIDS in human beings. In plants it causes yellow vein mosaic of bhindi (okra)
• Fungus causes ring worm in human beings and in plants, it causes rust of wheat.
• Protozoans cause some serious diseases like malaria and dysentery in human beings.

Question 9.
What are antibiotics ? What precautions must be taken while taking antibiotics ?
Answer:

• Antiblotics are the medicines which kill or stop the growth of the disease causing microorganisms.
• A number of antibiotics are being produced from bacteria and fungi.
  Ex: Streptomycin, Tetracycline and Erythromycin etc.

Precautions while using antibiotics :

• Antibiotics should be taken only on the advice of a qualified doctor.
• You must complete the course prescribed by the doctor.
• If you take antibiotics when not needed, you help bacteria in your body to develop resistance to them. When you fall ill and need these antibiotics, they would be less effective.
• Antibiotics taken unnecessarily may kill the beneficial bacteria in the body.
• We should not use antibiotics against viral diseases like flu and cold, because they are not effective against viruses.

Question 10.
I saw that my mother added a little curd to warm milk, to set curd for the next day. I wonder why?
Answer:

• Curd contains several microorganisms.
• Especially, Lactobacillus bacterium promotes the formation of curd.

Question 11.
Why are children / infants given vaccination?
Answer:

• By giving vaccination, we can prevent the diseases like cholera, tuberculosis, small pox, polio, hepatitis etc., in children.
• Children and infants have been given vaccination to protect them against several diseases.
• It is essential to protect all children in our country against these diseases.

Question 12.
How do you prevent the spread of communicable diseases ?
Answer:

• We should keep a handkerchief on the nose and mouth while sneezing.
• It is better to keep a distance from infected person.

Question 13.
Why does the teacher keep telling us not to let water collect anywhere in the neighbourhood?
Answer:

• Mosquitoes are the carriers of malaria, dengue and chikungunya causing pathogens.
• All mosquitoes breed in water.
• Hence, one should not let water collect anywhere, in coolers, tyres, flower pot etc.,

Extended Learning – Activities And Projects

Question 1.
Pull out a gram or bean plant from the field. Observe its roots. You will find round structures called root nodules on the roots. Draw a diagram of the root and show the root nodules.

Question 2.
Collect the labels from the bottles of jams and jellies. Write down the list of contents printed on the labels.
Answer:
I) Jams
1) Gemini Strawberry Jam
Ingredients : Strawberry pulp, sugar, thickener 470, acidity regulator – 330, preservative – 211, 223, contains added flavour – artificial strawberry flavouring, class – II preservative.

2) Varun Venella Jam
Ingredients : Sugar, apple fruit pulp, thickner, acidity regulator, preservative flavour and colour.

II) Jelly :
Lion Fruity Jelly
Ingredients : Sugar, liquid glucose, fruit pulp, pectin and citric acid, synthetic colour, preservative and flavouring agent.

Question 3.
Visit a doctor. Find out why antibiotics should not be overused. Prepare a short report.
Answer:

• Antibiotics are the medicines which kill or stop the growth of the disease causing micro organisms.
• A number of antibiotics are being produced from bacteria and fungi. Ex : Streptomycin, Tetracycline and Erythromycin etc.

Precautions while using antibiotics:

• Antibiotics should be taken only on the advice of a qualified doctor.
• You must complete the course prescribed by the doctor.
• If you take antibiotics when not needed, you help bacteria in your body to develop resistance to them. When you fall ill and need these antibiotics, they would be less effective.
• Antibiotics taken unnecessarily may kill the beneficial bacteria in the body.
• We should not use antibiotics against viral diseases like flu and cold, because they are not effective against viruses.

Question 4.
Project : Requirements – 2 test tubes, marker pen, sugar, yeast powder, 2 balloons and lime water. Take two test tubes and mark them A and B. Clamp these tubes in a stand and fill them with water leaving some space at the top. Put two spoonfuls of sugar in each of the test tubes. Add a spoonful of yeast in test tube B. Inflate the two balloons incompletely. Now tie the balloons on the mouths of each test tube. Keep them in a warm place, away from sunlight. Watch the setup every day for next 3-4 days. Record your observations and think of an explanation.
Now take another test tube filled 1/4 with lime water. Remove the balloon from test tube B in such a manner that gas inside the balloon does not escape. Fit the balloon on the test tube and shake well. Observe and explain.
Answer:

Observations :

• Balloon fitted in test tube-B inflates completely. The reason for this is the formation of CO₂ gas in the process of fermentation by yeast cells.
• Lime water in the third test tube turns milky. This is because of the reaction of carbondioxide filled in the balloon with the lime water.

8th Class Biology 2nd Lesson Questions and Answers (Lab Activities)

Activity-1

How do you observe microorganisms present in moist soil ?
Answer:

• Collect some moist soil from the field in a beaker and add water to it.
• After some time, the soil particles will settle down.
• Now, take a drop of water from the beaker with the help of a dropper on to a slide.
• Observe it under microscope.

Observations : Some minute organisms are moving in the water drop.
Inference: Soil contains microorganisms in it.

Activity-2

How do you observe microorganisms present in pond water ?
Answer:

• Collect some water in a beaker from a near by pond.
• Take a drop of water on a slide and observe it under microscope.

Observation: We can observe many minute microbes like blue green algae, chlamydomonas, paramoecium etc. in the water.
Inference: Water contains many microorganisms in it.

Activity-3

Write the procedure to observe the action of yeast in atta or maida mixed with sugar.
Answer:

• Take 1/2kg flour (atta or maida). Add some sugar and mix it with warm water.
• Add a small amount of yeast powder and knead to make a soft dough. Left it for 2 hours.

Observations :

• Yeast reproduces rapidly and produces carbondioxide during respiration.
• Bubbles of the gas fill the dough and increase it’s volume.

Activity-4

Write the procedure to observe fermentation process in your school lab.
Answer:

• Take a 500 ml beaker filled upto 3/4th with water.
• Dissolve 2-3 teaspoons of sugar in it.
• Add 1/2 a spoon of yeast powder to the sugar solution.
• Keep it covered in a warm place for 4-5 hours. Now smell the solution.

Observations : We can observe that the alcoholic smell is evolving from the solution, as sugar has been converted into alcohol by yeast.

Activity-5

Write an activity to show that organic and vegetable wastes can be converted into organic manure.
Answer:

• Take two pots and fill each pot half with the soil.
• Mark them A and B.
• Put plant wastes in Pot – A.
• Put things like polythene bags, empty glass bottles and broken plastic toys in pot – B.
• Put the pots aside. Observe them after 3-4 weeks.

Observations :

• Plant waste in pot – A has been decomposed.
• The plant ‘waste has been converted into manure by the action of microbes.
• The nutrients released in the process can be used by the plants again.
• The polythene bags, empty glasses, bottles and broken toy parts did not undergo any change. Because microbes could not ‘act’ on them and convert them into manure.