Q3. Give the contributions of the following:

  A. Louis Pasteur

  B. Alexander Fleming

  C. Robert Koch

Give two uses of microorganisms in the following areas:
i) Food Industry            ii) Medicinal Use               iii) Environment related

. List few differences between Antibiotics and Antibodies?

8. List some harmful effects of microorganism?

9. How can we control the spread of diseases caused by mosquitoes?

10. Why milk in polypacks does not get spoiled?

11.Why does sugar solution with yeast powder become alcoholic in taste? 

12. Megha, a class VIII student was asked to submit a project report on mosquito transmitted  diseases. She visited a nearby hospital where her aunt was staffed as a nurse. Her aunt took her to  a patient suffering from malaria. Megha talked to the patient and asked him about his health and  also took some flowers for him. 
(a) Name the mosquito that spreads malaria. 
(b) What is the name given to such organisms that transmit the diseases from infected to healthy  persons? 
(c) How can we control the spread of diseases by mosquitoes? 
(d) Identify two important values as shown by Megha. 
 
13. Kushal's family is happy as he became a proud father to a baby girl. Upon a routine visit to the hospital, the doctor advised him not to skip the vaccination schedule. While discussing the  same at home, one of the family members suggested that vaccination is not necessary for a girl  child. Kushal opposed this suggestion. 
(a) What is vaccination? 
(b) Name the scientist who prepared the first vaccine? 
(c) Critically comment upon Kushal's viewpoint. 

1.       What are microorganisms? What is its classification?

The organisms which are so small in size and cannot be seen with the unaided eye are called microorganisms or microbes. They are classified into- bacteria, fungi, protozoa and some algae.

2.       Name some common diseases caused by protozoa, bacteria and virus in human.

Protozoa- dysentery, malaria

Bacteria- typhoid, tuberculosis, tetanus, cholera, plague.

Virus- common cold, influenza(flu),polio, chicken pox, dengue fever, chikungunya,

3.       What are viruses?

Viruses are microscopic infectious agent which can reproduce only inside the cells of host organism like a bacterium, plant or animal.

4.       Where do microorganisms live?

a)       Microorganisms can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.

b)       They are also found inside the bodies of animals including humans.

c)       Some microorganisms grow on other organisms while others exist freely.

d)       Microorganism like amoeba can live alone, while fungi and bacteria may live in colonies.

5.       What are the uses of microorganisms?

a.       They are used in preparation of curd, bread, cake, cheese, pickles, etc.

b.       They are used in large scale production of alcohol, wine and acetic acid (vinegar).

c.       They are used in cleaning up of the environment (decomposition)

d.       Bacteria are used in preparation of medicines (antibiotics).

e.       Biological nitrogen fixers (rhizobium bacteria) help in increasing soil fertility by fixing nitrogen.

6.       How can we change milk into curd at home?

To change milk into curd, we need to add a little curd to warm milk and set aside for few hours. Curd contains several microorganisms. Of these, the bacterium Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd.

7.       Why is yeast used in baking industry?

Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume. This is the basis of the use of yeast in the baking industry for making breads, pastries and cakes.

8.       How is yeast used in beverage industry?

Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice, crushed fruit juices etc and converts them into alcohol by the process of fermentation.

9.       What are antibiotics?

The medicines used to kill or stop the growth of disease causing microorganisms are called antibiotics. They are produced from bacteria and fungi.Eg. Streptomycin, Tetracycline, Erythromycin.

10.    How does a vaccine work?

When a disease - carrying microbe enters our body, the body produces antibodies to fight the invader. The body remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies remain in the body and we are protected from the disease- causing microbes. This is how a vaccine works.

11.    How are microorganisms harmful to us?

a)       Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens.

b)       Some microorganisms spoil food, clothing and leather.

12.    What are communicable diseases?

Microbial diseases that can spread from an infected person to healthy person through air, water, food or physical contact are called communicable diseases. Eg. Cholera, Common cold, chicken pox and tuberculosis.

13.    How do communicable diseases spread? How can we prevent the spread of communicable diseases?

When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses are spread in the air. The virus may enter the body of a healthy person while breathing and make him sick. We can prevent it

a)       By keeping a handkerchief / a tissue on the nose and mouth while sneezing.

b)       By isolating the infected persons.

Some insects and animals act as carriers of disease causing microbes. Insects like housefly, female Anopheles mosquito (malaria), Female Aedes mosquito (dengue fever) are carriers of diseases. We can prevent them

a)       By not letting water collect anywhere in our surrounding and prevent mosquitoes from breeding.

b)       By keeping the surrounding clean and dry.

14.    What is food poisoning?

Food poisoning is the condition caused due to the consumption of food spoilt by some microorganisms. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death.

15.    List the methods of food preservation.

a)       Preservation using chemical method by adding preservatives.

b)       Preservation by adding common salt.

c)       Preservation by adding sugar.

d)       Preservation by adding oil and vinegar.

e)       By heat and cold treatment

f)         By proper storage and packing.

16.    What is pasteurisation?

The process of preserving milk by heating it to about 70⁰C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurisation.