Microorganisms: Friend and Foe

Q58. How do pathogens enter our body?

Ans. Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried through an animal.

Q59. Why should we keep our food covered?

Ans. Flies sit on uncovered food and they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick. So, it is advisable to always keep food covered.

Q60. Why should we not let water collect anywhere in the neighbourhood?

Ans. All mosquitoes breed in water. Hence, one should not let water collect anywhere, in coolers, tyres, flower pot etc. By keeping the surroundings clean and dry we can prevent mosquitoes from breeding.

Q61. Name the bacterium found in the roots of pea plant. How is this bacterium useful?

Ans. Rhizobium lives in the root nodules of leguminous plants such as beans and peas. It is involved in the fixation of nitrogen in leguminous plants (pulses).

Q62. Why are viruses considered to be on the borderline between living organisms and non-living things?

Ans. Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal.

Q63. What will happen if we take antibiotics when not needed?

Ans. If we take antibiotics when not needed or in wrong doses, it may make the drug less effective when we might need it in future. Also antibiotics taken unnecessarily may kill the beneficial bacteria in the body.

Q64. What are carriers of disease causing microbes? Give examples.

Ans. There are some insects and animals which act as carriers of disease causing microbes. Housefly is one such carrier. Another example of a carrier is the female Anopheles mosquito, which carries the parasite of malaria.

Q65. What happens when yeast powder is added to sugar solution and kept for 4-5 hours?

Ans. When yeast powder is added to sugar solution and kept for 4-5 hours, fermentation takes place. Sugar has been converted into alcohol by yeast. This process of conversion of sugar into alcohol is known as fermentation.

Q66. Write some common uses of yeast.

Ans. Common uses of yeast are:

                         i.        It is used in the baking industry for making breads, pastries and cakes.

                        ii.        It is used for commercial production of alcohol and wine.

Q67. Why is yeast used in baking industry?

Ans. 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.

Q68. How do houseflies spread disease?

Ans. Housefly is one such carrier. The flies sit on the garbage and animal excreta. Pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick.

Q69. Write a short paragraph on the harms caused by microorganisms.

Ans. Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather.

Q70. What is called pasteurization?

Ans. It is a process in which milk is heated 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 pasteurization.