NEET Biology Microbes in Human Welfare MCQs Set 10

Answer: (d) Each antibiotic is effective only against one particular kind of germ

Explanation:
1. Many antibiotics act on a range of bacteria (broad spectrum), so the claim that each works on only one kind of germ is false.
2. So the correct choice is option (d).

Teacher's Note:
1. Fleming found penicillin by chance.
2. Waksman coined the word antibiotic.

Answer: (c) Aspergillus niger

Explanation:
1. Citric acid is made by fermentation using the fungus Aspergillus niger.
2. So the correct choice is option (c).

Teacher's Note:
1. Aspergillus niger: citric acid.
2. Lactobacillus: lactic acid.

Answer: (c) Acetobacter aceti

Explanation:
1. Acetobacter aceti oxidises ethanol to acetic acid, which is vinegar.
2. So the correct choice is option (c).

Teacher's Note:
1. Acetic acid comes from the bacterium Acetobacter aceti.
2. Butyric acid comes from Clostridium.

Answer: (b) carbon dioxide, methane and hydrogen

Explanation:
1. Biogas is mainly methane with carbon dioxide and a little hydrogen (plus traces of nitrogen and hydrogen sulphide). Carbon monoxide and ethane are not its constituents.
2. So the correct choice is option (b).

Teacher's Note:
1. Methane is 50 to 70 percent of biogas.
2. CO2 is about 30 to 40 percent.

Answer: (b) Brazil

Explanation:
1. Brazil was the first country to use alcohol on a large scale as motor fuel.
2. So the correct choice is option (b).

Teacher's Note:
1. Brazil leads in bioethanol fuel.
2. India allows blending of ethanol in petrol.

Answer: (b) Euphorbiaceae

Explanation:
1. Hydrocarbon-rich latex is produced by Euphorbiaceae (for example Jatropha), Asclepiadaceae and Apocynaceae.
2. So the correct choice is option (b).

Teacher's Note:
1. Petrocrops give hydrocarbon-rich latex.
2. Melvin Calvin identified such plants.

Answer: (c) three step process

Explanation:
1. The text treats it as three stages: polymers broken into monomers, monomers turned into organic acids and acetic acid, and acetic acid converted to methane.
2. So the correct choice is option (c).

Teacher's Note:
1. Remember the three stages in order.
2. The last stage is done by methanogens.

Answer: (c) barley

Explanation:
1. Beer is brewed from malted barley (Hordeum vulgare) using yeast.
2. So the correct choice is option (c).

Teacher's Note:
1. Wine: grapes. Rum: molasses.
2. Gin: rye-type cereal.

Answer: (a) Brandy

Explanation:
1. Brandy is distilled wine with about 60 to 70 percent alcohol, higher than gin or rum (about 40 percent) or wine (10 to 20 percent).
2. So the correct choice is option (a).

Teacher's Note:
1. Distilled drinks have more alcohol.
2. Beer has the least, about 3 to 6 percent.

Answer: (a) Propionibacterium

Explanation:
1. Propionibacterium sharmanii releases a large amount of CO2 that makes the large holes of Swiss cheese.
2. So the correct choice is option (a).

Teacher's Note:
1. Large holes in Swiss cheese come from CO2.
2. Roquefort and Camembert use Penicillium.

Answer: (b) cellulose

Explanation:
1. Cellulose digestion is very slow, so it limits the speed of biogas formation.
2. So the correct choice is option (b).

Teacher's Note:
1. Slow cellulose digestion controls the rate.
2. Lignin remains as residue.

Answer: (d) Leguminaceae

Explanation:
1. Euphorbiaceae, Asclepiadaceae and Apocynaceae give hydrocarbon latex; Leguminosae do not.
2. So the correct choice is option (d).

Teacher's Note:
1. Latex-bearing families are petrocrops.
2. Legumes are known for nitrogen fixation.

Answer: (d) All the above

Explanation:
1. Biogas burns in efficient burners, the leftover slurry is a good fertiliser, and treatment reduces pathogens, so all statements hold.
2. So the correct choice is option (d).

Teacher's Note:
1. Slurry is a useful manure.
2. Burning dung cakes wastes a fertiliser.

Answer: (d) Lactobacillus acidophilus

Explanation:
1. Lactic acid bacteria such as Lactobacillus coagulate milk proteins and form curd.
2. So the correct choice is option (d).

Teacher's Note:
1. LAB turn milk into curd.
2. They also raise vitamin B12.

Answer: (a) ethanol

Explanation:
1. Brewer's yeast ferments sugars to ethanol and CO2.
2. So the correct choice is option (a).

Teacher's Note:
1. Same yeast is used for bread and for drinks.
2. Acetic acid comes from Acetobacter.

Answer: (a) cyanobacteria

Explanation:
1. Nitrogen-fixing cyanobacteria are a key biofertiliser in paddy fields.
2. So the correct choice is option (a).

Teacher's Note:
1. Anabaena and Nostoc fix nitrogen.
2. Rhizobium works with legumes.

Answer: (c) Methanogenic bacteria

Explanation:
1. Methanogens such as Methanobacterium produce methane from the dung slurry anaerobically.
2. So the correct choice is option (c).

Teacher's Note:
1. Methanogens live in rumen and sludge.
2. They need oxygen-free conditions.

Answer: (b) Saccharomyces

Explanation:
1. Yeast (Saccharomyces) ferments sugars obtained from starch to ethanol.
2. So the correct choice is option (b).

Teacher's Note:
1. Yeast is the main ethanol producer.
2. Penicillium gives penicillin.

Answer: (a) Azolla and BGA

Explanation:
1. Azolla (with its cyanobacterium) and blue-green algae are both biofertilisers. Salmonella is a pathogen.
2. So the correct choice is option (a).

Teacher's Note:
1. BGA means blue-green algae (cyanobacteria).
2. Rhizobium associates with legumes, not grasses.

Answer: (a) Methanogens

Explanation:
1. Methane is made by methanogenic bacteria.
2. So the correct choice is option (a).

Teacher's Note:
1. Gobar gas is mostly methane.
2. Nitrifiers act in the nitrogen cycle.

Answer: (a) yeast

Explanation:
1. Baker's yeast ferments sugar and releases CO2, which puffs the dough.
2. So the correct choice is option (a).

Teacher's Note:
1. Dosa and idli batter puff up through bacteria.
2. Bread uses yeast.

Answer: (b) Lignin

Explanation:
1. Lignin and inorganic salts are not degraded and remain as residue.
2. So the correct choice is option (b).

Teacher's Note:
1. Lipids, proteins and cellulose are degraded.
2. Lignin remains.

Answer: (c) Selman Waksman

Explanation:
1. Selman Waksman introduced the word in 1942.
2. So the correct choice is option (c).

Teacher's Note:
1. Fleming discovered penicillin.
2. Jenner: smallpox vaccine.

Answer: (a) 5%

Explanation:
1. The source states that 5 percent alcohol is allowed in petrol.
2. So the correct choice is option (a).

Teacher's Note:
1. Bioethanol blends reduce petrol use.
2. Later policy raised the percentage.

Answer: (a) Anabaena

Explanation:
1. Anabaena fixes nitrogen both free living and inside Azolla.
2. So the correct choice is option (a).

Teacher's Note:
1. Azolla-Anabaena is used in paddy.
2. Rhizobium is a bacterium of legume nodules.