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📘 Study MCQs
Q1. what is the main characteristic of all micro-organisms?
• they can be seen with naked eyes
• they are all harmful
• they are microscopic
• they are only found in water
Answer: they are microscopic
micro-organisms are living organisms that are too small to be seen without the help of a microscope.
Q2. which of these is the smallest micro-organism?
• bacteria
• fungus
• virus
• protozoa
Answer: virus
viruses are the smallest of all micro-organisms. they can only be seen with a very powerful electron microscope.
Q3. the blue-green algae present in the soil fix which gas from the air?
• oxygen
• carbon dioxide
• nitrogen
• hydrogen
Answer: nitrogen
certain blue-green algae, like bacteria, can convert atmospheric nitrogen into usable nitrogen compounds, enriching the soil.
Q4. what do we call the mode of transmission of a disease from an infected person to a healthy person?
• communication
• infection
• vaccination
• preservation
Answer: infection
the spread of a disease-causing microbe from an infected person to a healthy person is called infection.
Q5. which food item is produced with the help of lactobacillus?
• bread
• cheese
• vinegar
• yogurt
Answer: yogurt
yogurt is made by fermenting milk using lactobacillus bacteria, which turns lactose into lactic acid.
Q6. which of these is a fungal disease in humans?
• typhoid
• ringworm
• malaria
• cholera
Answer: ringworm
ringworm is a common skin infection caused by a fungus, not a worm.
Q7. what is the common carrier of diseases like typhoid and cholera?
• mosquito
• housefly
• cockroach
• rat
Answer: housefly
houseflies sit on garbage and sewage, picking up bacteria on their bodies, and then transfer them to food and water.
Q8. what is the shape of the bacterium that causes cholera?
• rod-shaped
• spherical
• comma-shaped
• spiral
Answer: comma-shaped
the bacterium vibrio cholerae, which causes cholera, has a characteristic comma or curved rod shape.
Q9. which of these micro-organisms is considered a connecting link between living and non-living?
• bacteria
• fungus
• virus
• protozoa
Answer: virus
viruses behave like non-living things when outside a host cell but show characteristics of life when inside a living host.
Q10. the process of fixing nitrogen into the soil by lightning is called?
• biological fixation
• atmospheric fixation
• industrial fixation
• electrical fixation
Answer: atmospheric fixation
the high energy of lightning breaks nitrogen molecules, allowing them to combine with oxygen to form nitrogen oxides that dissolve in rain and enter the soil.
Q11. which part of the leguminous plant houses the nitrogen-fixing bacteria?
• leaves
• flowers
• root nodules
• stem
Answer: root nodules
the rhizobium bacteria live in small swollen structures called nodules on the roots of plants like peas and beans.
Q12. a substance that kills or stops the growth of microbes on a wound is called an?
• antibiotic
• vaccine
• antiseptic
• antigen
Answer: antiseptic
antiseptics like dettol or iodine are applied on cuts and wounds to kill any microbes that may have entered.
Q13. which of these diseases is transmitted through the air by droplets from a sneeze or cough?
• tetanus
• cholera
• common cold
• rabies
Answer: common cold
when a person with a cold sneezes or coughs, tiny droplets containing the virus are released into the air, which others may breathe in.
Q14. what are the hair-like structures used by some bacteria for movement called?
• cilia
• flagella
• tentacles
• pseudopodia
Answer: flagella
many bacteria have one or more whip-like structures called flagella that help them swim in liquid environments.
Q15. which preservation method involves removing water from food?
• pasteurization
• refrigeration
• dehydration
• salting
Answer: dehydration
dehydration or drying removes water from food. microbes need water to grow, so dry food does not spoil easily.
Q16. which of these is a plant disease caused by a virus?
• citrus canker
• rust of wheat
• yellow vein mosaic of bhindi
• blight of potato
Answer: yellow vein mosaic of bhindi
yellow vein mosaic is a viral disease that affects the okra (bhindi/ladyfinger) plant.
Q17. what do we call the proteins produced by our body to fight pathogens?
• antigens
• antibiotics
• antibodies
• antiseptics
Answer: antibodies
when a pathogen enters our body, the immune system produces special proteins called antibodies to fight the infection.
Q18. which of these is a communicable animal disease?
• foot and mouth disease
• goiter
• arthritis
• diabetes
Answer: foot and mouth disease
foot and mouth disease is a highly communicable viral disease that spreads among cattle, sheep, and goats.
Q19. what do we call micro-organisms that obtain food from dead and decaying matter?
• autotrophs
• parasites
• saprotrophs
• pathogens
Answer: saprotrophs
saprotrophs, like many fungi and bacteria, feed on and decompose dead organic material.
Q20. which gas is released during the decomposition of organic waste by microbes?
• oxygen
• methane
• nitrogen
• hydrogen
Answer: methane
bacteria that decompose organic matter in the absence of air (anaerobic conditions) produce biogas, which is mainly methane.
Q21. which of these is a beneficial role of fungi?
• causing rust in plants
• causing athlete’s foot
• making antibiotics
• causing food poisoning
Answer: making antibiotics
fungi like penicillium are used to make life-saving antibiotics such as penicillin.
Q22. what is the name of the protozoan that causes amoebic dysentery?
• plasmodium
• paramecium
• entamoeba
• euglena
Answer: entamoeba
entamoeba histolytica is a protozoan parasite that causes amoebic dysentery, often spread through contaminated water.
Q23. preserving fish by covering it with salt is an example of which method?
• chemical method
• refrigeration
• dehydration
• pasteurization
Answer: chemical method
salt acts as a chemical preservative. it draws out moisture and creates an environment where bacteria cannot grow.
Q24. which of these is a way to prevent water-borne diseases?
• using mosquito nets
• drinking boiled water
• washing hands regularly
• both b and c
Answer: both b and c
drinking boiled or purified water kills germs, and washing hands prevents the transfer of microbes to our mouth.
Q25. what is the name of the scientist who developed the process of pasteurization?
• alexander fleming
• robert koch
• louis pasteur
• edward jenner
Answer: louis pasteur
louis pasteur, a french scientist, developed the technique of heating liquids to kill harmful bacteria, now known as pasteurization.
Q26. which of these is a disease caused by a protozoan?
• tuberculosis
• typhoid
• malaria
• influenza
Answer: malaria
malaria is caused by a protozoan parasite of the genus plasmodium, which is transmitted by mosquitoes.
Q27. what is the primary source of most antibiotics?
• viruses
• bacteria and fungi
• protozoa
• algae
Answer: bacteria and fungi
most antibiotics are obtained from bacteria and fungi. for example, streptomycin from bacteria and penicillin from fungus.
Q28. which food preservation method uses smoke?
• salting
• canning
• smoking
• freezing
Answer: smoking
Q29. what do we call the practice of growing two different crops alternately in the same field?
• crop rotation
• mixed cropping
• harvesting
• irrigation
Answer: crop rotation
crop rotation, often with leguminous plants, helps restore soil nitrogen and prevents the buildup of soil-borne diseases.
Q30. which of these micro-organisms is used in the production of vinegar?
• lactobacillus
• yeast
• acetobacter
• rhizobium
Answer: acetobacter
acetobacter bacteria convert ethanol (alcohol) into acetic acid, which is the main component of vinegar.
Q31. the disease that spreads on a large scale in a community at the same time is called an?
• infection
• epidemic
• pandemic
• sporadic
Answer: epidemic
an epidemic is the rapid spread of an infectious disease to a large number of people in a given population within a short period.
Q32. which of these is not a shape of bacteria?
• coccus (spherical)
• bacillus (rod-shaped)
• spiral
• cubical
Answer: cubical
bacteria are mainly classified by their shapes as coccus (round), bacillus (rod), and spirillum (spiral). cubical is not a bacterial shape.
Q33. what is the name of the process by which yeast helps in making idli and dosa batter fluffy?
• fermentation
• nitrogen fixation
• pasteurization
• infection
Answer: fermentation
the yeast or bacteria in the batter produce carbon dioxide gas during fermentation, which makes the batter rise and become fluffy.
Q34. which of these diseases is caused by biting by an infected dog?
• tetanus
• rabies
• polio
• typhoid
Answer: rabies
rabies is a deadly viral disease that spreads to humans from the saliva of infected animals, usually through a bite.
Q35. what is the term for introducing a weak or dead pathogen into the body to develop immunity?
• medication
• vaccination
• antibiotic treatment
• antiseptic application
Answer: vaccination
vaccination involves administering a vaccine (containing a weakened or killed pathogen) to stimulate the body’s immune response.
Q36. which of these is a harmful role of algae?
• producing oxygen
• causing water blooms
• fixing nitrogen
• being a food source
Answer: causing water blooms
when algae grow excessively in water bodies (algal blooms), they deplete oxygen and can release toxins, harming aquatic life.
Q37. what is the common name for the disease caused by the bacterium clostridium tetani?
• lockjaw
• whooping cough
• plague
• diphtheria
Answer: lockjaw
tetanus, often called lockjaw, is caused by clostridium tetani. it affects the nervous system, causing painful muscle stiffness.
Q38. which of these is a micro-organism used in the production of soy sauce and tempeh?
• virus
• fungus (mould)
• protozoa
• nitrogen-fixing bacteria
Answer: fungus (mould)
moulds like aspergillus oryzae are used in fermenting soybeans to produce foods like soy sauce, miso, and tempeh.
Q39. what is the primary reason for adding oil to pickles?
• for taste
• to create an air-tight layer
• to add moisture
• to provide color
Answer: to create an air-tight layer
oil floats on top of the pickle and creates a layer that prevents air (oxygen) from reaching the food, inhibiting microbial growth.
Q40. which of these is a disease where a carrier does not show symptoms but can spread the disease?
• typhoid
• common cold
• chickenpox
• malaria
Answer: typhoid
some people, called carriers, can harbour typhoid bacteria (salmonella typhi) in their body without being sick and can spread it to others.
Q41. what do we call the micro-organisms that live in extreme environments like high salt or acid?
• pathogens
• extremophiles
• saprotrophs
• parasites
Answer: extremophiles
extremophiles are micro-organisms that thrive in physically or geochemically extreme conditions that are harmful to most life.
Q42. which disease is caused by the bite of a female anopheles mosquito?
• dengue
• chikungunya
• malaria
• yellow fever
Answer: malaria
the female anopheles mosquito is the vector that transmits the malaria-causing plasmodium parasite when it bites.
Q43. the process of converting ammonia into nitrates in the soil is called?
• nitrogen fixation
• nitrification
• denitrification
• ammonification
Answer: nitrification
nitrification is the process where certain soil bacteria convert ammonia into nitrites and then into nitrates, which plants can absorb.
Q44. which of these is not a component of oral rehydration solution (ors)?
• salt
• sugar
• water
• lemon juice
Answer: lemon juice
ors is a simple mixture of clean water, salt, and sugar. lemon juice is not a standard component, though it may be added for taste.
Q45. what is the term for a disease that lasts for a very long time?
• acute disease
• chronic disease
• communicable disease
• deficiency disease
Answer: chronic disease
chronic diseases are long-lasting health conditions that often progress slowly. tuberculosis is an example of a chronic bacterial disease.
Q46. which of these micro-organisms is unicellular and can perform photosynthesis?
• mushroom
• amoeba
• chlamydomonas
• penicillium
Answer: chlamydomonas
chlamydomonas is a unicellular green alga. it contains chlorophyll and can make its own food through photosynthesis.
Q47. what is the main purpose of vaccination?
• to cure a disease
• to kill pathogens directly
• to provide temporary relief
• to develop immunity
Answer: to develop immunity
vaccines train the immune system to recognize and fight specific pathogens, providing long-term protection or immunity.
Q48. which of these diseases has been completely eradicated from the world through vaccination?
• polio
• smallpox
• measles
• tuberculosis
Answer: smallpox
smallpox is the only human disease to have been completely eradicated globally, thanks to a worldwide vaccination campaign.
Q49. the fungus that grows on moist bread is usually?
• yeast
• penicillium
• rhizopus (bread mould)
• aspergillus
Answer: rhizopus (bread mould)
the common black bread mould that appears on stale, moist bread is a type of fungus called rhizopus.
Q50. what is the main danger of using antibiotics without a doctor’s advice?
• they become less effective
• they cause immediate allergy
• they are too expensive
• they work only on viruses
Answer: they become less effective
unnecessary or improper use of antibiotics can lead to bacteria developing resistance, making the antibiotics less effective when truly needed.