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 protozoa 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 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

(a) Yeast is used in the production of alcohol. Oxygen, sugar and hydrochloric acid are not produced by yeast (b) Streptomycin is an antibiotic. Sodium bicarbonate, yeast and alcohol are not antibiotics (c) Cockroach, butterfly and house fly are arthropods. Malaria is caused by a protozoan, Plasmodium, which has two hosts, human and female Anopheles. When female Anopheles bites the infected person, blood and parasite are ingested and are carried to the other person by the bite of the same mosquito. Thus, it acts as a carrier for the malarial parasite. (d) House flies act as carriers of many communicable diseases. Pathogens are collected by the flies when they hover over organic matter such as faeces, garbage and animal corpses.Diseases spread by house flies include typhoid, cholera and dysentery (e) Fermentation is a process that involves the growth and action of microbes like yeast. Sugar is broken down into carbon dioxide and water in presence of oxygen. However, in the absence or scant presence of oxygen, the yeast cells decompose the sugar and produce carbon dioxide and alcohol. While the alcohol gets dissolved in the water, the carbon dioxide gas bubbles out. During this process, the thick consistency batters, like that of idli, swell (f) Yeast is a eukaryotic, unicellular, anaerobic microorganism that anaerobically ferments glucose and produces ethanol and carbon dioxide. This process is known as alcoholic fermentation or anaerobic respiration.