Question

2.
Tick the correct answer.
(a)
Yeast is used in the production of
(1) sugar fins alcohol
(iii) hydrochloric acid (iv) oxygen
(b) The following is an antibiotic
(i) Sodium bicarbonate [li) Streptomycin (iii) Alcohol (iv) Yeast
(c)
Carrier of malaria-causing protozoan is
a female Anopheles mosquito (11) cockroach
(iii) houseſly
(iv) butterfly
(d) The most common carrier of communicable diseases is
(i) ant is housefly (iii) dragonfly (iv) spider
(e) The bread or idli dough rises because of
(i) heat (ii) grinding till growth of yeast cells (lv) kneading
(1) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation (ii) moulding on fermentation (iv) Inſection
alion
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Answer 1

Answer:

(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 host- human and female Anopheles. When female Anopheles bites the infected person, blood and parasite is ingested and is carried to the other person by bite of same mosquito. Thus, it acts as carrier for malaria parasite.

(d) House flies act carriers of many communicable diseases. Pathogens are collected by the flies when they hover over organic matter such as feces, garbage and animal corpses.

Diseases spread by house flies include typhoid, cholera and dysentery.  

(e) Fermentation is a process which involves the growth and action of microbes like yeast. Sugars is broken down into carbon dioxide and water in presence of oxygen. However, in absence or scant presence of oxygen, the yeast cells consume 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 an eukaryotic, unicellular, anaerobic microorganism that anaerobically ferments the glucose and produces ethanol and carbon dioxide. The process is known as alcohol fermentation or anaerobic respiration.