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Q1. What is the main characteristic of all micro-organisms?
The main characteristic of all micro-organisms is that they are microscopic, meaning they cannot be seen with the naked eye and require a microscope for observation. They can be found in various environments, and not all are harmful—many are beneficial. They exist in air, water, soil, and living organisms.
Q2. Which of these is the smallest micro-organism?
Viruses are the smallest micro-organisms, much smaller than bacteria, fungi, and protozoa. They are so small that they can only be seen with an electron microscope. Viruses are considered on the borderline between living and non-living and are measured in nanometres.
Q3. The blue-green algae present in the soil fix which gas from the air?
Blue-green algae (cyanobacteria) present in the soil can fix atmospheric nitrogen into forms that plants can absorb. This is a type of biological nitrogen fixation. They convert nitrogen gas (N₂) into usable nitrogen compounds like nitrates, enriching the soil.
Q4. What do we call the mode of transmission of a disease from an infected person to a healthy person?
The transmission of a disease from an infected person to a healthy person is called infection. This can happen through air, water, food, physical contact, or vectors like mosquitoes. Vaccination protects from diseases, preservation is food-related, and communication is unrelated.
Q5. Which food item is produced with the help of lactobacillus?
Yogurt (curd) is produced by the action of Lactobacillus bacteria, which ferment milk sugar (lactose) into lactic acid. This acid causes milk to coagulate and gives yogurt its sour taste. Bread is made with yeast, cheese uses other bacteria, and vinegar is produced by Acetobacter.
Q6. Which of these is a fungal disease in humans?
Ringworm is a fungal infection of the skin caused by dermatophytes. It appears as ring-shaped rashes on the skin. Typhoid and cholera are bacterial diseases, and malaria is caused by a protozoan parasite.
Q7. What is the common carrier of diseases like typhoid and cholera?
The housefly is a common carrier of typhoid and cholera. It picks up pathogens from faecal matter and contaminated sources and transfers them to food, leading to waterborne and foodborne diseases. Mosquitoes carry malaria and dengue, cockroaches also contaminate food, and rats spread plague.
Q8. What is the shape of the bacterium that causes cholera?
The bacterium that causes cholera, Vibrio cholerae, is comma-shaped (curved rod). Rod-shaped bacteria are bacilli, spherical are cocci, and spiral are spirilla. The comma shape is characteristic of Vibrio species.
Q9. Which of these micro-organisms is considered a connecting link between living and non-living?
Viruses are considered connecting links between living and non-living because they show characteristics of both. They are non-living outside a host (cannot reproduce or metabolise) but become living inside a host cell, where they multiply and cause infection. Bacteria, fungi, and protozoa are clearly living organisms.
Q10. The process of fixing nitrogen into the soil by lightning is called?
Lightning fixes atmospheric nitrogen into the soil through a process called atmospheric fixation. The high energy of lightning converts nitrogen gas into nitrogen oxides, which dissolve in rainwater and reach the soil as nitrates. Biological fixation is done by bacteria like Rhizobium, and industrial fixation is done in fertiliser factories.
Q11. Which part of the leguminous plant houses the nitrogen-fixing bacteria?
Nitrogen-fixing bacteria, such as Rhizobium, live in the root nodules of leguminous plants (like peas, beans, and groundnuts). These nodules provide a suitable environment for the bacteria to convert atmospheric nitrogen into usable compounds for the plant.
Q12. A substance that kills or stops the growth of microbes on a wound is called an?
Antiseptics are substances applied to wounds or skin to kill or inhibit the growth of microbes. They are safe for external use and prevent infection. Antibiotics are taken internally, vaccines provide immunity, and antigens trigger immune responses.
Q13. Which of these diseases is transmitted through the air by droplets from a sneeze or cough?
The common cold is transmitted through the air when an infected person sneezes or coughs, releasing droplets containing the virus. Tetanus enters through wounds, cholera spreads through contaminated water, and rabies is transmitted through animal bites.
Q14. What are the hair-like structures used by some bacteria for movement called?
Some bacteria use flagella, which are long, whip-like structures, for movement. Cilia are shorter and found in protozoa like Paramecium, pseudopodia are temporary extensions used by Amoeba, and tentacles are found in animals like hydra.
Q15. Which preservation method involves removing water from food?
Dehydration is the removal of water from food to prevent microbial growth. Microorganisms need moisture to survive, so removing water slows spoilage. Pasteurization uses heat, refrigeration uses cold, and salting uses salt to draw out moisture.
Q16. Which of these is a plant disease caused by a virus?
Yellow vein mosaic of bhindi (okra) is caused by a virus. Citrus canker is caused by bacteria, rust of wheat by fungi, and blight of potato by fungi or bacteria. Viral plant diseases are often transmitted by insect vectors.
Q17. What do we call the proteins produced by our body to fight pathogens?
Antibodies are proteins produced by the immune system in response to antigens (foreign substances like pathogens). They bind to pathogens and neutralise them. Antigens trigger antibody production, antibiotics treat infections, and antiseptics are used on wounds.
Q18. Which of these is a communicable animal disease?
Foot and mouth disease is a highly contagious viral disease affecting cattle and other livestock. It is communicable among animals. Goitre, arthritis, and diabetes are non-communicable diseases caused by nutritional deficiencies, metabolism, or lifestyle.
Q19. What do we call micro-organisms that obtain food from dead and decaying matter?
Saprotrophs are organisms that feed on dead and decaying organic matter by secreting digestive enzymes and absorbing nutrients. Fungi and many bacteria are saprotrophs. Autotrophs make their own food, parasites live on living hosts, and pathogens cause diseases.
Q20. Which gas is released during the decomposition of organic waste by microbes?
During the decomposition of organic waste by anaerobic bacteria, methane gas is released. This is part of the process of biogas production. Decomposers also release carbon dioxide, but methane is a key product of anaerobic decomposition.
Q21. Which of these is a beneficial role of fungi?
Fungi like Penicillium are used to produce antibiotics (e.g., penicillin). This is a beneficial role. Causing rust and athlete’s foot are harmful roles, and food poisoning is usually caused by bacteria, not fungi.
Q22. What is the name of the protozoan that causes amoebic dysentery?
Amoebic dysentery is caused by the protozoan Entamoeba histolytica. It spreads through contaminated food and water. Plasmodium causes malaria, Paramecium and Euglena are harmless protozoa.
Q23. Preserving fish by covering it with salt is an example of which method?
Salting is a chemical method of preservation. The salt draws out moisture and creates an environment where microorganisms cannot grow. Dehydration is the removal of water, but salting is specifically a chemical preservation method.
Q24. Which of these is a way to prevent water-borne diseases?
Water-borne diseases can be prevented by drinking boiled water (kills pathogens) and washing hands regularly (prevents contamination). Mosquito nets prevent mosquito-borne diseases like malaria, not water-borne ones.
Q25. What is the name of the scientist who developed the process of pasteurization?
Louis Pasteur developed the process of pasteurization, which involves heating milk and other liquids to kill harmful microbes. Alexander Fleming discovered penicillin, Robert Koch identified disease-causing bacteria, and Edward Jenner created the smallpox vaccine.
Q26. Which of these is a disease caused by a protozoan?
Malaria is caused by the protozoan Plasmodium. Tuberculosis and typhoid are caused by bacteria, and influenza is caused by a virus. Malaria is a protozoan disease transmitted by mosquitoes.
Q27. What is the primary source of most antibiotics?
Most antibiotics are derived from bacteria and fungi. For example, penicillin comes from the fungus Penicillium, and streptomycin comes from bacteria (Streptomyces). These organisms produce antibiotics to kill competing microbes.
Q28. Which food preservation method uses smoke?
Smoking is a method of preserving food (especially fish and meat) by exposing it to smoke from burning wood. The smoke contains chemicals that preserve the food and also enhances flavour. It is a traditional preservation technique.
Q29. What do we call the practice of growing two different crops alternately in the same field?
Crop rotation is the practice of growing different crops in the same field in a sequential order. It helps maintain soil fertility, reduce pest and disease buildup, and improve crop yield. Mixed cropping is growing multiple crops at the same time, harvesting is reaping, and irrigation is watering.
Q30. Which of these micro-organisms is used in the production of vinegar?
Acetobacter is a bacterium used in the production of vinegar. It oxidises alcohol (from fermentation) into acetic acid. Lactobacillus makes curd, yeast is used for fermentation to produce alcohol, and Rhizobium fixes nitrogen.
Q31. The disease that spreads on a large scale in a community at the same time is called an?
An epidemic is the widespread occurrence of a disease in a community at a particular time. A pandemic is a global epidemic. Infection is the entry of pathogens, sporadic occurs occasionally. Cholera and dengue outbreaks are examples of epidemics.
Q32. Which of these is not a shape of bacteria?
Cubical is not a shape of bacteria. Bacteria are classified into spherical (coccus), rod-shaped (bacillus), comma-shaped (vibrio), and spiral (spirillum). 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?
Yeast ferments the sugars in idli and dosa batter, producing carbon dioxide gas, which makes the batter rise and become fluffy. This is fermentation, the same process used in making bread. Nitrogen fixation, pasteurization, and infection are unrelated.
Q34. Which of these diseases is caused by biting by an infected dog?
Rabies is caused by a virus transmitted through the bite of an infected animal, most commonly a dog. It affects the nervous system and is fatal if untreated. Tetanus enters through wounds, polio is waterborne, and typhoid is food/waterborne.
Q35. What is the term for introducing a weak or dead pathogen into the body to develop immunity?
Vaccination is the introduction of a weakened or dead pathogen (or its parts) into the body to stimulate the immune system to produce antibodies and develop immunity against that disease. Medication treats disease, antibiotics kill bacteria, and antiseptics are used on wounds.
Q36. Which of these is a harmful role of algae?
Excessive growth of algae in water bodies causes algal blooms, which deplete oxygen, release toxins, and harm aquatic life. This is a harmful role. Producing oxygen, fixing nitrogen, and being a food source are beneficial roles of algae.
Q37. What is the common name for the disease caused by the bacterium clostridium tetani?
Lockjaw is the common name for tetanus, caused by Clostridium tetani. It causes painful muscle spasms, especially in the jaw. Whooping cough is caused by Bordetella pertussis, plague by Yersinia pestis, and diphtheria by Corynebacterium diphtheriae.
Q38. Which of these is a micro-organism used in the production of soy sauce and tempeh?
Soy sauce and tempeh are produced using moulds (fungi). Aspergillus oryzae is used in soy sauce fermentation, and Rhizopus is used for tempeh. These are beneficial applications of fungi in food production.
Q39. What is the primary reason for adding oil to pickles?
Oil is added to pickles to create an air-tight layer on top, which prevents the growth of aerobic microorganisms that cause spoilage. It acts as a barrier and helps preserve the pickle. Taste is secondary, and oil does not add moisture or color primarily.
Q40. Which of these is a disease where a carrier does not show symptoms but can spread the disease?
Typhoid can be spread by a carrier who shows no symptoms (asymptomatic carrier). Such carriers can shed the bacteria and infect others. Common cold and chickenpox typically show symptoms, and malaria is mosquito-transmitted, not through carriers without symptoms.
Q41. What do we call the micro-organisms that live in extreme environments like high salt or acid?
Extremophiles are micro-organisms that thrive in extreme environments like high salt (halophiles), high acidity (acidophiles), high temperature (thermophiles), or high pressure. Pathogens cause diseases, saprotrophs feed on dead matter, and parasites live on hosts.
Q42. Which disease is caused by the bite of a female anopheles mosquito?
Malaria is caused by the bite of an infected female Anopheles mosquito. Dengue and chikungunya are transmitted by Aedes mosquitoes, and yellow fever by Aedes or Haemagogus mosquitoes. The Anopheles mosquito is the vector for the malaria parasite, Plasmodium.
Q43. The process of converting ammonia into nitrates in the soil is called?
Nitrification is the process by which ammonia is converted into nitrates by nitrifying bacteria (like Nitrosomonas and Nitrobacter). This makes nitrogen available for plants. Nitrogen fixation is conversion of N₂ gas, denitrification converts nitrates back to N₂, and ammonification produces ammonia from organic matter.
Q44. Which of these is not a component of oral rehydration solution (ors)?
ORS consists of a mixture of salt, sugar, and water. It is used to rehydrate the body during diarrhoea. Lemon juice is not a required component of ORS. The sugar-salt-water combination helps in the absorption of water and electrolytes in the intestine.
Q45. What is the term for a disease that lasts for a very long time?
A chronic disease is one that lasts for a long time (months or years), such as diabetes or arthritis. An acute disease is short-term, communicable diseases spread easily, and deficiency diseases are caused by a lack of nutrients.
Q46. Which of these micro-organisms is unicellular and can perform photosynthesis?
Chlamydomonas is a unicellular green alga that performs photosynthesis due to the presence of chlorophyll. Mushroom and Penicillium are fungi (multicellular, not photosynthetic), and Amoeba is a protozoan that does not photosynthesise.
Q47. What is the main purpose of vaccination?
The main purpose of vaccination is to develop immunity against a disease. Vaccines stimulate the immune system to produce antibodies without causing the disease itself. They do not cure diseases or kill pathogens directly—they prevent them.
Q48. Which of these diseases has been completely eradicated from the world through vaccination?
Smallpox has been completely eradicated from the world through a global vaccination program led by the WHO. The last natural case occurred in 1977. Polio is nearly eradicated but still exists in some countries, and measles and TB are not eradicated.
Q49. The fungus that grows on moist bread is usually?
Bread mould, commonly seen on moist bread, is usually Rhizopus. It is a black or greyish fungus that grows on bread and other organic matter. Yeast is unicellular, Penicillium is greenish mould, and Aspergillus is another type of mould.
Q50. What is the main danger of using antibiotics without a doctor’s advice?
The main danger of using antibiotics without a doctor’s advice is the development of antibiotic resistance. Bacteria can mutate and become resistant, making the antibiotics less effective. This is a serious public health concern. Overuse or misuse of antibiotics should be avoided.