Important Questions: The Invisible Living World: Beyond Our Naked Eye | Science Curiosity Class 8 - New NCERT PDF Download

Q1: Explain the role of microorganisms in the nitrogen cycle. How do they contribute to the availability of nitrogen for plants?
Ans: Microorganisms, particularly certain bacteria, play a crucial role in the nitrogen cycle by fixing atmospheric nitrogen into compounds that plants can use. These bacteria live in the soil and root nodules of leguminous plants, converting nitrogen gas into nitrogenous compounds that enhance soil fertility. Additionally, other bacteria decompose nitrogenous wastes, facilitating the recycling of nitrogen in the ecosystem.

Q2: Describe the process of pasteurization and its significance in ensuring the safety of milk consumption.
Ans: Pasteurization involves heating milk to about 70°C for a short duration and then rapidly cooling it. This process kills harmful microorganisms present in the milk, ensuring its safety for consumption. It was discovered by Louis Pasteur and is crucial in preventing the spread of diseases through milk consumption.

Q3: How do antibiotics work, and why is it important to complete the prescribed course of antibiotics?
Ans: Antibiotics are medicines that kill or inhibit the growth of disease-causing microorganisms. It's essential to complete the prescribed course to ensure all the pathogens are eliminated. Incomplete courses may lead to the development of antibiotic-resistant strains and make future infections more challenging to treat.

Q4: Discuss the role of microorganisms in the production of alcohol and wine. How is yeast involved in this process?
Ans: Microorganisms, specifically yeast, are used in the production of alcohol and wine through a process called fermentation. Yeast metabolizes sugars present in fruits or grains, converting them into alcohol and carbon dioxide. This process is widely employed in the brewing and winemaking industries.

Q5: Explain the symbiotic relationship between Rhizobium bacteria and leguminous plants. How does this relationship contribute to the nitrogen cycle?
Ans: Rhizobium bacteria form a symbiotic relationship with leguminous plants, residing in the root nodules. In return for shelter and nutrients, these bacteria fix atmospheric nitrogen into forms that plants can use. This process enriches the soil with nitrogen, benefiting both the bacteria and the plants.

Q6: How do microbes contribute to the preservation of food? Discuss the various methods of food preservation involving microorganisms.
Ans: Microbes contribute to food preservation through methods like salting, sugaring, pickling, and fermenting. These processes inhibit the growth of spoilage-causing microorganisms, increasing the shelf life of the food.

Q7: Discuss the harmful effects of microorganisms on food. How can these effects be minimized?
Ans: Microorganisms can spoil food by producing toxic substances. To minimize these effects, proper food preservation methods, such as refrigeration, can be employed. Additionally, maintaining cleanliness and hygiene in food handling and storage areas is crucial.

Q8: Explain the role of microorganisms in cleaning up the environment. Provide examples of their contributions.
Ans: Certain microorganisms play a vital role in decomposing organic waste, contributing to environmental cleanup. Bacteria and fungi break down dead plants and animals, converting them into simple substances that can be reused by other organisms.

Q9: How does the process of fermentation contribute to the production of bread and alcoholic beverages? Discuss the role of yeast in this process.
Ans: Fermentation is a metabolic process where microorganisms, particularly yeast, convert sugars into alcohol and carbon dioxide. In bread-making, yeast causes dough to rise, while in alcohol production, yeast ferments sugars present in fruits or grains, producing alcohol.

Q10: Explain the concept of biological nitrogen fixation. How do certain bacteria contribute to increasing soil fertility?
Ans: Biological nitrogen fixation involves certain bacteria converting atmospheric nitrogen into forms usable by plants. These bacteria, known as biological nitrogen fixers, enhance soil fertility by providing plants with essential nitrogen compounds.

Q11: Describe the role of antibiotics in controlling microbial infections. Why is it crucial to use antibiotics responsibly?
Ans: Antibiotics control microbial infections by killing or inhibiting the growth of bacteria. Using antibiotics responsibly is crucial to prevent the development of antibiotic-resistant strains and to avoid harming beneficial bacteria in the body.

Q12: How do microorganisms contribute to the production of curd, cheese, and other dairy products? Explain the microbial processes involved.
Ans: Microorganisms, especially bacteria like Lactobacillus, play a crucial role in the production of dairy products. Lactobacillus promotes the formation of curd, while other bacteria contribute to the fermentation processes involved in making cheese and other dairy items.

Q13: Discuss the role of microorganisms in the decomposition of plant waste and its conversion into manure. How does this process benefit the environment?
Ans: Certain microorganisms decompose plant waste, converting it into manure. This benefits the environment by recycling nutrients, making them available for plants again. It also reduces the accumulation of organic waste, contributing to a cleaner environment.