Haryana State Board HBSE 8th Class Science Solutions Chapter 2 Micro Orgmisms: Friends and Foe Textbook Exercise Questions and Answers.
Haryana Board 8th Class Science Solutions Chapter 2 Micro Orgmisms: Friends and Foe
HBSE 8th Class Science Micro Orgmisms: Friends and Foe Textbook Questions and Answers
Fill in the blanks:
(a) Microorganisms can be seen with the help of a ……….. .
(b) Blue green algae fix ………….. directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help of ………….. .
(d) Cholera is caused by ……………… .
(b) atmospheric nitrogen
Tick the correct answer:
(a) Yeast is used in the production of:
(iii) hydrochloric acid
(b) The following is an antibiotic:
(i) Sodium bicarbonate
(c) Carrier of malaria-causiiig protozoan is:
(i) female Anopheles mosquito
(i) female Anopheles mosquito
(d) The most common carrier of communicable diseases is:
(e) The bread or idli dough rises because of:
(iii) growth of yeast cells
(iii) growth of yeast cells
(f) The process of conversion of sugar into alcohol is called:
(i) nitrogen fixation
Match the organisms in Column I with their action in Column II.
|Column I||Column II|
|(i) Bacteria||(a) Nitrogen fixation|
|(ii) Rhizobium||(b) Setting of curd|
|(iii) Lactobacillus||(c) Baking of bread|
|(iv) Yeast||(d) Causes Malaria|
|(v) A protozoan||(e) Causing Cholera|
|(vi) A Virus||(f) Causing AIDS|
|(g) Producing antibodies|
|Column I||Column II|
|(i) Bacteria||(e) Causing Cholera|
|(ii) Rhizobium||(a) Nitrogen fixation|
|(iii) Lactobacillus||(b) Setting of curd|
|(iv) Yeast||(c) Baking of bread|
|(v) A protozoan||(d) Causes Malaria|
|(vi) A Virus||(f) Causing AIDS|
Can microorganisms be seen with the naked eye? If not, how can they be seen?
Some organisms are very small in size. They are so small that they cannot be seen with naked eyes. A microscope has to be used to see these organisms. Therefore, they are called microorganisms.
What are the major groups of microorganisms?
Microorganisms can mainly be divided into five groups:
Name the microorganisms which can fix atmospheric nitrogen in the soil.
Bacteria like Rhizobium, Azotobacter, Blue green algae like Anabaena and Nostoc can fix atmospheric nitrogen in soil.
Write 10 lines on the usefulness of microorganisms in our lives.
Microorganisms are very useful to us.
They help us in following ways:
(i) Microorganisms help us in food sector. They are used for curdling of milk, preparation of bread, cake, etc.
(ii) Microorganisms are used to produce alcohol at large scale.
(iii) They are also used to produce wine.
(iv) Yeast is used to prepare vinegar.
(v) They are also used as preservatives for food items.
(vi) Used to make different medicines, especially the antibiotics.
(vii) Microorganisms are used to prepare vaccines for various disease.
(viii) Useful for agriculture sector, as they enhance the fertility of soil by fixing the biological nitrogen.
(ix) They work as natural cleansers, as they decompose the dead bodies of plants and animals.
(x) Microorganisms prepare manures by decomposing dead bodies of plants and animals.
Write a short paragraph on the harms caused by microorganisms.
Microorganisms can prove very harmful to us, as they cause a number of human and animal diseases. Diseases in humans like common cold, tuberculosis, measles, chiken pox, Polio, Cholera, Typhoid, Hepatitis B, Malaria, etc. are caused by microorganisms. Some serious deseases like Anthrax is also caused in animals by the microbes. Microbes grow on food products and render them unfit for consumption.
Consumption of such food causes food poisoning. Microbes also spoil clothings and leather products. Microbes also cause diseases of plants like blights in potatoes, sugarcanes, oranges etc. They also reduce the yield.
What are antibiotics? What precautions must be taken while taking antibiotics?
Medicines taken to kill or stop the growth of harmful or disease causing microbes in human body are called antibiotics. Antibiotics are very useful as only antibiotics can save us from many microbial infections and diseases. Antibiotics are made from fungi and bacteria. Alexander Fleming discovered the first antibiotic called Penicillin in 1929. Now-a-days a number of antibiotics are used to cure a variety of human and animal diseases. Streptomycin, Tetracycline, Erythromycin etc. are some commonly used antibiotics.
Antibiotics should only be taken when adviced by a qualified physician. Antibiotics should only be taken when needed otherwise, they become less effective for future use.
Extended Learning – Activities And Projects
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.
Do it yourself.
2. Collect the labels from the bottles of jams and jellies. Write down the list of contents printed on the labels.
Ingredients: Sugar, Mixed fruit pulp, Gelling Agent (E440), And acidity regulator (E330). Permitted synthetic food colour (E122) and added artificial flavours. Contains permitted class-II Preservatives (E211, E224).
3. Visit a doctor. Find out why antibiotics should not be overused. Preapare a short report.
Antibiotics should not be overused because they reduce of power of immunity.
(i) Regular or frequent use make the drug ineffective when needed in future.
(ii) They kill beneficial bacteria in our body.
So, antibiotics should only be consumed when prescribed by doctore only.
Requirement – 2 text tubes, marker pen, sugar, yeast powder, 2 ballons and lime water.
Take two test tubes and mark them A and B. Champ 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 to 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 you observations and think of an explanation.
Now take another test tube filled V4 with lime water. Remove the balloon from test tube B in such a manner that gas inside the balloon does not escape. Fill the balloon on the test tube and shake well. Observe and explain.
The balloon in test tube B will get inflated because process of fermentation has taken place in test tube B due to yeast bacteria and carbondioxide gas produce during this process has inflated the balloon. Now the balloon will get a little deflated as gas in consumed by the lime water and the lime water will turn milky.
5. For more information, visit the following websites.
- www.biology4kids.com/files/micro_main html
HBSE 8th Class Science Microorganisms: Friend and Foe Important Questions and Answers
Very Short Answer Type Questions
Very small organisms around us which cannot be seen with naked eyes are called microorganisms.
Where are microorganisms found?
Microorganisms are found everywhere. In air, water and in the body of other organisms.
Name the groups in which microorganisms can be divided.
Bacteria, fungi, protozoa, some algae and viruses.
Which common diseases do viruses cause?
Viruses cause diseases like common cold, flu and most of the coughs.
Which serious diseases are caused by viruses?
Diseases like polio and chicken pox.
Name diseases caused by protozoans.
Dysentery and malaria are caused by protozoans.
Name any two algae.
Chlamydomonas and spirogyra.
Name any two protozoa.
Amoeba and paramecium.
Name any two fungi.
Rhizopus and Aspergillus.
Name unicellular microbes.
Bacteria and protozoa.
Name multicellular microbes.
Algae and fungi.
Which bacteria is responsible for the curdling of milk?
Which bacteria is used to produce alcohol?
What do you mean by fermentation?
Conversion of sugar into alcohol using yeast is palled fermentation.
Who discovered the process of fermentation?
What are antibiotics?
Medicines used to kill or stop the growth of diseases causing microorganisms inside human body are called antibiotics.
Who discovered the first antibiotic?
Which antibiotic did Alexander Fleming discover?
Which microorganism is not affected by antibiotics?
Name certain diseases which can be prevented by vaccination.
Cholera, tuberculosis, small pox, hepatitis, polio, etc.
Name microorganisms which can fix atmospheric nitrogen.
Bacteria and blue green algae.
Name one free living bacteria and one blue green algae who fix nitrogen using oxygen from atmosphere.
What are pathogens?
Disease causing microorganisms are called pathogens.
What are communicable diseases?
Diseases which spread with physical contacts are called communicable diseases.
Name an insect which is a common carrier of microbial diseases.
Name the carrier of dengue virus.
Female Aedes mosquito.
Where do mosquitoes breed?
Mosquitoes breed in stagnant water and damp places.
Short Answer Type Questions
What are the major group of the microorganisms?
Major groups of microorganisms are:
(i) Bacteria: They are non-green single celled microorganisms.
(ii) Fungi: They are long thread like unicellular as well as multicellular microorganisms.
(iii) Algae: Aquatic* photosynthetic organisms commonly called sea weeds.
(iv) Protozoan: They are unicellular organisms.
(v) Virus: They are non-cellular microbes which only get active inside a living cell.
Describe various types of bacteria with examples.
On the basis of their shape, the bacteria are divided into three types:
(i) Bacillus or rod shaped: Long rod shaped bacteria like Bacillus, Pseudomonas, Lactobacillus.
(ii) Cocus or round shaped: Streptococus, Sarcinaltc. are round shaped bacteria.
(iii) Spirillum or spiral: Comma shaped bacteria, they can also be spiral rods e.g. Camphilovector, Triponema.
State some beneficial effects of bacteria.
Bacteria are very useful to us. Some of the beneficial effects of bacteria are as follows:
(i) Bacteria is helpful in agriculture as it fixes the atmospheric nitrogen in soil.
(ii) Products like vinegar, alcohol, curd etc. are obtained.
(iii) It decomposes the dead bodies of plants and animals.
(iv) Valuable medicines like antibiotics are obtained by bacteria.
Mention important uses of fungi,
(i) Some fungi are eaten raw as food such as mushrooms.
(ii) Yeast being rich in amino acids and proteins are an important source of food for man and his farm animals.
(iii) Yeast is also used in the preparation of products like wine and bears from fruit juices or barley. It brings about fermentation of sugars into alcohols and carbondioxide.
Write the harmful effects of Bacteria.
Bacteria cause a number of diseases in humans and animals. Diseases like cholera, pneumonia, tuberculosis are caused by bacteria. It also causes food poisoning as it makes the food unfit to consume. It spoils leather and clothings.
Write the harmful effects of fungi and algae.
Some fungi causes damages or diseases. Smuts and rusts are fungi that damage the crops. Ring-warm and atheletes food diseases are caused by fungi. Amanite mushrooms contain poisonous substance. Algae are great nuisance as they spoil the drinking water. Excess growth of algae also blocks the movement of water in channels.
Write the diseases caused by protozoa.
Several protozoa cause diseases in man and other animals. Antaemoeba Histolytica causes amoebic dysentry in man. Dangerous plasmodium causes malaria and dengue. Trypanosoma, causes sleeping sickness in man, cattle, pigs and horses.
Describe the main characteristics of viruses in brief.
(i) They do not possess any cell wall or cell membrane.
(ii) They can only multiply in the bodies of living beings.
(iii) They cause many diseases.
(iv) Antibiotics do not have any affect on viruses.
What are vaccines?
A vaccine consists of antigens of mild strains of pathogens of a particular disease. Vaccine when injected into the blood stream stimulates white blood cells to produce antibodies. These antibodies act against the antigens and neutralise their toxins or destroy them.
How does microorganisms enter into our body?
Microorganisms enter into our body:
(i) through the air we breathe.
(ii) through the water we drink.
(iii) through direct contact with infected person.
(iv) by the use of polluted water or food.
What are viruses?
Viruses are microscopic organisms. These are the smallest organisms. They may be rod-shaped, polygonal, spherical or even cubical. There are four types of viruses: Plant viruses, Insect viruses, Bacterial viruses and mammalian viruses.
Long Answer Type Questions
What do you understand by microorganisms? Describe their different forms.
Different living organisms present around us which cannot be seen with naked eyes are called microorganisms. They are present in soil, water and air. Microorganisms can be divided into five groups:
(i) Bacteria are the non-green single celled microscopic organisms. They have a rigid cell wall. It has a nuclear material. They are the simple most common form of life on earth. They have different shapes and sizes.
(ii) Algae are aquatic, photosynthetic organisms. In simple terms they are called sea weeds. They range in size, colour. Algae are of green, blue, red and blue^green colours.
(iii) Fungi are plants not having chloroplast but a cell wall. They are both unicellular and multicellular. Moulds, mushrooms etc. are fungi.
(iv) Protozoa are one celled living things. They range from 2 to 200 microns. Amoeba, Paramecium, Euglena and Plasmodium etc. are protozoas.
(v) Viruses are the non-cellular microbes. They are smaller than bacteria and multiply only inside a living cell.
Write a short note on Bacteria.
Answer:Bacteria are non-green single celled microscopic organisms. They have a rigid cell wall. They have a nuclear material. They are simple most common form of life on earth. They occur singly but are seen in chain of cells. They are of different shapes such as rod shaped, spiral, cork screw and comma shaped.
Bacteria are harmful for us, but some bacteria are quite useful. The most disadvantageous aspect of bacteria is their disease causing tendency. Various serious diseases like Tuberculosis, cholera, typhoid etc. are caused by bacteria. Bacteria are useftd as they are used to prepare vaccines and antibiotics. They decompose waste material and fix the atmospheric nitrogen into soil to enhance its fertility. Bacteria are also used to manufacture vinegar, acetic-acid, curd and cheese etc.
What are fungi? How are they useful or harmful to us?
Fungi are microorganisms which exist in unicellular as well as multicellular forms. Some of the fungus like mushroom, yeast etc. can be seen with naked eyes. They have long thread like structures called hyphae. Fungus can reproduce sexually as well as asexually. Fungi are both harmful and useful. Smuts, crusts and ringworm etc. cause many diseases in humans as well as in animals and plants.
They are useful as they are used as food in many parts of world. Mushrooms are the mostly used food around the word. Yeast is used to make alcohol, breads, bhathuras, idlis, dosas etc. Penicillium is used to make penicillin an antibiotics.
What do you know about Protozoa?
Protozoa are single celled living things. The size ranges from 2 microns to 200 microns.
Amoeba, Paramesium, Euglena, Plasmodium etc. are examples of Protozoa. Protozoa are the part of animal kingdom because they do not have chlorophyll.
They are oval, elongated and spherical in shape. Protozoa cause diseases like malaria and dengue. Protozoa like Entamoeba Histolytica causes amoebic dysentery in man. Trypanosoma causes sleeping sickness in man and cattle. Protozoa are useful as they form an important link in acquatic food chain. They decompose organic matters to convert them in useful soil nutrients.
What are food preservatives? Explain some common preservatives.
Chemicals used to check or stop the growth of harmful microorganisms in food are called preservatives. These preservatives keep the edibles protected from the invasion of microorganisms which can spoil the food.
Some commonly found preservatives are:
Salt: Common salt is used to preserve meat, fish, amla, raw mangoes, tamarind, etc.
Sugar preserves jam, jellies, squashes and other sweet drinks. Sugar reduces the moisture and checks the growth of microorganisms.
Oil: Edible oils are used as preservatives in vegetables and pickles. Oil does not allow the moisture to surface thus preventing the growth of harmful bacteria.
Vinegar preserves vegetables, fruits, fish, meat and pickles.
Other processes like pasteurization etc. also preserve the milk and other liquids.
How can we detect the spoilage in food?
Following indications help us an detecting the spoilage in food:
When food gives out smell, it is the indication that the bacteria has spoiled the food. Food gives out repulsive smell when bacteria breaks the proteins found in food. This is called Putrefaction.
Growth of microbes on food results in discolouration of food black. Moulds on breads, blue green moulds on citrus fruits and cheese cause the change in the original colour of the food. Any small discolouration indicates that the food has been spoiled and is unfit for consumption.
Sometimes the cooked food starts tasting sour. It is due to the production of acids by the action of certain bacteria. Milk starts tasting sour if not preserved properly, same is the case with curries and gravies of some vegetables.
Sometimes the food became slimy. It is also due to action of certain bacteria thread like slimes are also caused due to moulds.
(e) Gas formation:
Due to action of bacteria gases like carbondioxide are produced. They also spoil the food by making it swell or become spongy.
Microorganisms: Friend and Foe Class 8 HBSE Notes
1. Many living organisms exist around us in water, soil and air. They are so small that they cannot be seen with naked eyes. These tiny organisms are called microorganisms or microbes.
2. Microorganism can live in any kind of extreme environment like hot, cold, humid, icecold, saline water, desert or hot soil.
3. Microorganisms have wide variety of structural forms. They can be from unicellular to multicellular organisms.
4. Microorganisms are classified as bacteria, fungi, protozoa, algae and viruses.
5. Viruses are different from other microorganisms, yet referred to as the microorganism.
6. These microorganisms are helpful economically. They are also used to make many medicines.
7. These microorganisms can be very harmful too as they cause many diseases. Such microbes are called pathogens.
8. Microorganisms are used to enhance the fertility of the soil as they trap the biological nitrogen and fix them in the soil, which in turn is used by plants.
9. Microorganisms work on the dead bodies of the plants and animals to decompose them. They, thus, work as the natural cleansers of the environment.
10. Some microorganisms destroy our food by growing on it. The food infected by these microorganisms become unfit to consume. If consumed it can cause food poisoning.
11. Some special microbes reside in the nodules of the leguminous plants which fix the biological nitrogen from air into soil. The nitrates and nitrites present in soil are further converted into nitrogen gas and released in atmosphere. This whole cycle is called the nitrogen cycle.