Microorganisms

Microorganisms: friends and foes

Q1) What are microorganisms?

Ans:

Tiny organisms that can’t be seen with naked eyes.

Q2) what is an unicellular organisms?

Ans:

Organisms made up of one cell.

Q3) name any three types of microorganisms.

Ans:

Bacteria, viruses, unicellular algae.

Q4) name the first living thing on the earth.

Ans:

Cyanobacteria

Q5) What are chemosynthetic bacteria?

Ans:

Some bacteria obtain energy from  chemical reaction of inorganic substances. Such bacteria are said to be chemosynthetic bacteria. They are capable of living in complete darkness .

Q6) What are phytoplanktons?

Ans:

Phytoplanktons are plant-like floating microorganisms. Since they require light to photosynthesis, they live near the surface of the water. they live in ponds, lakes,  rivers and oceans.

Q7) what are protozoa?

Ans:

Protozoa are unicellular animal-like organisms. Paramecium and amoeba are protozoa. They are found in stagnant water, ponds, soil, oceans and animal faeces. They depend on other organisms for food. Some feed on other protozoa and bacteria.

Q8) name a disease caused by a protozoa.

Ans:

Malaria

Q9) what are antibodies?

Ans:

Vaccines contain dead or weakened microbes which on entering the human body, induce the body to produce antibodies. Antibodies fight against the disease causing microorganisms.

The antibodies remain in the body and prevent the occurrence of the disease.

Q10) who discovered the process of pasteurisation?

Ans:

Louis Pasture

Q11) Differentiate between aerobic and anaerobic.

Ans:

Aerobic bacteria require oxygen for respiration.

Anaerobic bacteria do not need oxygen. They respire in the absence of oxygen.

Q12) Algae are plant-like while protozoa are animal-like microorganisms. Explain.

Ans:

Protozoa are unicellular animal- like organisms. Paramecium and amoeba are protozoa, they are found in stagnant water, ponds, soil, oceans, and in animal faeces. They depend on other organisms for food. Some feed on other protozoa and bacteria. Some parasites.    

Q13) Microscopic algae sustain life on earth. How?

Ans:

Microscopic algae contribute in sustaining life on the earth. They produce food and add huge amount of oxygen into the atmosphere.

Q14) phytoplanktons live near the surface of water. Why?

Ans:

Phytoplanktons are plant-like floating microorganisms. Since they require light to photosynthesis, they live near the surface of water. They live in ponds, lakes, rivers and oceans.

Q15) why do dry food items like biscuits not spoil easily?

Ans:

There is no moisture content for survival of microorganisms.

Q16) Pasteurisation involves heating. Why?

Ans:

Pasteurisation is a technique of processing food especially milk. It involves heating milk to a temperature between 72 and 75 C for a period of 30 seconds and then cooling it immediately.

Q17) Describe the different types of bacteria.

Ans:

Bacteria are rod-like, spherical or spiral in shape. Some bacteria are heterotrophic. They depend on other living things for food. Some bacteria are autotrophic, that is they make their own food. Autotrophic bacteria contain chlorophyll and make food through the process of photosynthesis. They are called photosynthetic bacteria. Cyanobacteria are also photosynthetic.

Q18) describe the nitrogen cycle with the help of a well labelled diagram.

Ans:

Remains of plants and animals waste contain nitrogen in the form of nitrogen compounds. When such organic matter mixes with the soil, it decomposes. The soil fungi and bacteria decompose the organic matter and convert it to nitrates. This process is called nitrification.

Nitrates are soluble in water and are absorbed by the roots along with the water. certain kinds of bacteria living in the wet soil convert nitrates into nitrogen gas or nitrates oxide ( N₂O) gas which is returned to the atmosphere. This process is known as denitrification .

Atmospheric nitrogen is also fixed in the soil by the action of lighting.

  

Q19) list three diseases caused by microorganisms. Explain the symptoms of any one disease.

Ans:

Diseases like Polio, chicken pox and Malaria Are caused by microorganisms.

Malaria is caused by a protozoa parasites called plasmodium vivax. It lives in the female Anopheles mosquito. When the female anopheles mosquito carrying plasmodium vivax bites a human being, the parasites are introduced into the human’s blood. If the parasites multiply, they destroy the red blood cells in large numbers and the person suffer from Malaria.

Q20) Explain Pasteurisation .

Ans:

It is a technique of preserving food especially milk. It involves heating milk to a temperature between 72 and 75 c for a period of 30 seconds and then cooling it immediately .

This process kills approximately 99.5% of all microorganisms in the milk. Pasteurised milk can be stored for five to six days in a refrigerator. Pasteurisation is also used for preserving fruit juices, wine and diary products.

Q21) write a short note on food preservation.

Ans:

Salts, sugar, oil and vinegar are food preservatives that prevent food spoilage. These edible products do not allow microbes to grow and thus preserve food. Chemical like Sodium benzoate and Sodium metabisulphite are also used to preserve pickle jams fruit juices.

  

Question 22:

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 _________.

Answer:

(a) Microorganisms can be seen with the help of a _ microscope _.

(b) Blue green algae fix __ nitrogen _ directly from air to enhance fertility of soil.

(c) Alcohol is produced with the help of _ yeast _.

(d) Cholera is caused by _ bacteria _.

Question 23:

Tick the correct answer:

(a) Yeast is used in the production of

(i) sugar                                    (ii) alcohol           

(iii) hydrochloric acid                     (iv) oxygen

(b) The following is an antibiotic

(i) Sodium bicarbonate                  (ii) Streptomycin

(iii) Alcohol                              (iv) Yeast

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito         (ii) cockroach

(iii) housefly                           (iv) butterfly

(d) The most common carrier of communicable diseases is

(i) ant                                   (ii) housefly

(iii) dragonfly                           (iv) spider

(e) The bread or idli dough rises because of

(i) heat                                   (ii) grinding

(iii) growth of yeast cells                 (iv) kneading

(f) The process of conversion of sugar into alcohol is called

(i) nitrogen fixation                   (ii) moulding

(iii) fermentation                     (iv) infection

Answer:

(a) Yeast is used in the production of

(i) sugar                                  (ii) alcohol

(iii) hydrochloric acid                    (iv) oxygen

(b) The following is an antibiotic

(i) sodium bicarbonate             (ii) streptomycin 

(iii) alcohol                         (iv) yeast

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito         (ii) cockroach

(iii) housefly                            (iv) butterfly

(d)The most common carrier of communicable diseases is

(i) ant                                  (ii) housefly

(iii) dragonfly                          (iv) spider

(e)The bread or idli dough rises because of

(i) heat                               (ii) grinding

(iii) growth of yeast cells            (iv) kneading

(f) The process of conversion of sugar into alcohol is called

(i) nitrogen fixation                 (ii) moulding

(iii) fermentation                   (iv) infection

Question 24:

Match the organisms in Column I with their action in Column II.

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

  

       

Answer:

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

Question 25:

Can microorganisms be seen with the naked eye? If not, how can they be seen?

Answer:

Micro-organisms are too small to be seen through naked eyes. They can be seen with the help of a magnifying glass or microscope.

For example, fungus that grows on bread is so small that it can be seen only with the help of a magnifying glass or microscope.

Question 26:

What are the major groups of microorganisms?

Answer:

There are five major groups of micro-organisms:

(i) Bacteria − They are single celled disease-causing micro-organisms. They can be spiral or rod- shaped.

(ii) Fungi − They are mostly multicellular disease-causing microbes. Bread moulds are common examples of fungi.

(iii) Protozoa − They mainly include organisms such as Amoeba, Plasmodium,etc.

They can be unicellular or multicellular.

(iv) Virus −Viruses are disease-causing microbes that reproduce only inside the host organism.

(v) Algae − They include multicellular, photosynthetic organisms such as Spirogyra, Chlamydomonas, etc.

Question 27:

Name the microorganisms which can fix atmospheric nitrogen in the soil.

Answer:

Bacteria such as Rhizobium and certain blue-green algae present in the soil can fix atmospheric nitrogen and convert it into usable nitrogenous compounds. These nitrogenous compounds can be easily utilized by plants for the synthesis of plant proteins and other compounds.

Question 28:

Write 10 lines on the usefulness of microorganisms in our lives.

Answer:

Micro-organisms are too small to be seen through naked eyes. However, they are vital to plants and the environment.

Importance of micro-organisms:

They are used in wine making, baking, pickling, and other food making processes.

Alcoholic fermentation by yeast is widely used in the preparation of wine and bread.

A bacterium Lactobacillus, promotes the formation of curd.

Microbes are used to reduce pollution. For example, decomposers such as bacteria and fungi break down dead bodies and excreta to form inorganic compounds, which can be absorbed by plants.

They are used to increase the soil fertility by fixing the atmospheric nitrogen with the help of bacterium Rhizobium and some other blue-green algae.

Microbes also play an important role in the preparation of medicines. Antibiotics are chemicals produced by micro-organisms to kill bacteria. Streptomycin, for example, is an antibiotic.

Certain microbes are also used in the biological treatment of sewage and industrial effluents.

Question 29:

Write a short paragraph on the harms caused by microorganisms.

Answer:

Harmful effects of micro-organisms:

Micro-organisms cause diseases in animals. For example, in humans, bacteria cause diseases such as tuberculosis, cholera, typhoid, etc. In cattle, the foot and mouth disease is caused by a virus. Also, several microbes cause diseases in plants. For example, the productivity of wheat, orange, apple, etc. is reduced due to microbial diseases in plants. Certain microbes, on entering into our body, produce toxic substances. This leads to food poisoning. Some micro-organisms such as fungus spoil our food. For example, bread when left unused under moist conditions gets spoilt by fungus, producing a white cotton-like growth on the bread.

Question 30:

What are antibiotics? What precautions must be taken while taking antibiotics?

Answer:

Antibiotics are medicines produced by certain micro-organisms to kill other disease causing micro-organisms. These medicines are commonly obtained from bacteria and fungi. Streptomycin, tetracycline, penicillin, etc. are common antibiotics.

Precautions to be taken while using antibiotics:

(i) Antibiotics should be taken under the supervision of a well qualified doctor.

(ii) Course (intake) of antibiotics should be completed as per the prescription given by the doctor.

(iii) Antibiotics should be taken in the right amount and at the right time. A wrong dose of antibiotics makes the drug ineffective. Also, excessive consumption of drugs may kill the useful bacteria present in our body.