Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

(1) Use of sterilize equipment is necessary in the hospital.
Ans. By sterilizing the equipment, bacteria etc. get removed due to which there is no possibility of infection.
(2) The fertility of the field, where plants of leguminous family are grown, remains intact.
Ans. The roots of the plant of Leguminous family are are nodular. These nodules contain bacteria called Rhizobium leguminosarum which increase the fertility of the soil by fixing N2 .
(3) Fresh and unboiled milk has more possibilities of turning sour.
Ans. Some bacteria ferment the lactose sugar present in the milk into lactic acid, as a result the milk turn sour e.g. Streptococcus lactis, Lactobacillus casei, L. acidophiles etc. On boiling the milk, those bacteria are destroyed and the milk can be prevented by turning sour.
(4) Alcohol turns sour, if kept for a long time.
Ans. If alcohol kept for a long time, bacteria attack on it and it turns sour.
(5) The temperature of rotten thing is higher while rotting.
Ans. These are saprophytic bacteria, the temperature increases due to the release of energy from the oxidation and metabolic processes of organic substances.