IMO Practice Test — Microbes in Human Welfare
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
Curd is more nutritious than milk partly because lactic acid bacteria:
Add vitamins and improve nutrition
Remove all nutrients
Add antibiotics
Make it sterile
Explanation: LAB increase vitamin content and improve the nutritional value of curd over plain milk.
Question 2 of 6
Releasing untreated sewage into a river is harmful because the organic matter lets microbes multiply and:
Use up the water's oxygen, harming fish
Add oxygen
Purify it instantly
Make biogas in the river
Explanation: Decomposing waste depletes dissolved oxygen, suffocating aquatic life — why treatment is needed first.
Question 3 of 6
Biogas plants are especially valuable in villages because they turn cattle dung into:
Clean cooking fuel and useful manure
Antibiotics
Curd
Drinking water
Explanation: They provide a renewable fuel and leave a nutrient-rich slurry, using waste productively.
Question 4 of 6
Biofertilisers are preferred over chemical fertilisers because they:
Enrich soil without polluting it
Cost the most
Kill all crops
Add carcinogens
Explanation: Living biofertilisers add nutrients naturally and sustainably, avoiding chemical pollution.
Question 5 of 6
Using ladybird beetles to control aphids is an example of biocontrol because it relies on a:
Natural predator instead of a chemical pesticide
Stronger poison
New antibiotic
Vaccine
Explanation: Letting a natural enemy reduce the pest avoids toxic chemicals — the essence of biocontrol.
Question 6 of 6
Bt is considered safer than chemical insecticides mainly because it:
Targets specific insect larvae and spares other animals
Kills everything it touches
Pollutes water heavily
Cannot kill any insect
Explanation: Its selective action on certain larvae, while harmless to others, makes Bt environmentally safer.