Exercise Solutions

Q1: Complete the statements by choosing the correct option.

1. The process of conversion of milk into curd is called fermentation.
2. The process of converting sugar into alcohol is called fermentation.
3. The microscopic organisms that cause diseases are called pathogens.
4. The antibiotic Penicillin is obtained from the fungus Penicillium.
5. Malaria is caused by the protozoan Plasmodium.

Q2: Match the pairs.

Q3: Give reasons.

1. Fungi are important decomposers.
   Answer: Fungi are important decomposers because most of them are saprophytic, meaning they obtain nutrients by breaking down dead organic matter (plants and animals). They secrete digestive enzymes externally, which break down complex organic compounds into simpler substances. This process recycles essential nutrients like carbon, nitrogen, and phosphorus back into the environment, making them available for other organisms and maintaining ecosystem balance. Without decomposers, dead organic material would accumulate, and nutrient cycles would halt.
2. Antibiotics should be taken only under medical supervision.
   Answer: Antibiotics should be taken only under medical supervision because:
   1. Resistance: Misuse or overuse can lead to antibiotic resistance, where bacteria evolve to become immune to the drug, making infections harder to treat.
   2. Side Effects: Antibiotics can have side effects (e.g., nausea, diarrhea, allergic reactions).
   3. Killing Beneficial Bacteria: They can kill beneficial bacteria in the gut, disrupting normal body functions.
   4. Specific Action: Different antibiotics target different types of bacteria. A doctor ensures the correct antibiotic is prescribed for the specific infection.
   5. Dosage and Duration: Proper dosage and duration are crucial for effectiveness and preventing resistance.
3. Microorganisms are useful for making food items like yogurt and bread.
   Answer: Microorganisms are useful for making food items like yogurt and bread through the process of fermentation. In yogurt production, bacteria (e.g., Lactobacillus) ferment lactose in milk into lactic acid, which coagulates milk proteins. In bread making, yeast (Saccharomyces cerevisiae) ferments sugars in dough, producing carbon dioxide gas that causes the dough to rise and become soft. These microbial actions contribute to the unique texture, flavor, and preservation of these food products.
4. Microorganisms are important for the environment.
   Answer: Microorganisms are vital for the environment due to their roles in:
   1. Decomposition: Breaking down dead organic matter, recycling nutrients.
   2. Nutrient Cycling: Participating in cycles like nitrogen, carbon, and phosphorus, making essential elements available.
   3. Bioremediation: Cleaning up pollutants (e.g., oil spills).
   4. Oxygen Production: Photosynthetic algae produce a significant portion of Earth's oxygen.
   5. Symbiotic Relationships: Forming beneficial associations with plants (e.g., mycorrhizae) and animals (e.g., gut flora).

Q4: Write answers to the following questions in your own words.

1. What is the role of microorganisms in the nitrogen cycle?
   Answer: Microorganisms play several crucial roles in the nitrogen cycle, which is the process by which nitrogen is converted into various chemical forms as it circulates between the atmosphere, terrestrial, and marine ecosystems. Key roles include:
   • Nitrogen Fixation: Certain bacteria (e.g., Rhizobium, Azotobacter) convert atmospheric nitrogen gas (N₂) into ammonia (NH₃), which plants can absorb.
   • Nitrification: Nitrifying bacteria convert ammonia into nitrites (NO₂⁻) and then nitrates (NO₃⁻), which are readily absorbed by plants.
   • Ammonification: Decomposing bacteria and fungi break down dead organic matter and waste products, releasing ammonia.
   • Denitrification: Denitrifying bacteria convert nitrates back into nitrogen gas, returning it to the atmosphere.
   These processes ensure a continuous supply of usable nitrogen for living organisms.
2. Explain the importance of microorganisms in the food industry.
   Answer: Microorganisms are indispensable in the food industry for various processes:
   • Fermentation: Used to produce fermented foods like yogurt (Lactobacillus), cheese (various bacteria and fungi), bread (yeast), idli/dosa batter (bacteria and yeast), vinegar (acetic acid bacteria), and alcoholic beverages (yeast). This process enhances flavor, texture, and extends shelf life.
   • Probiotics: Live beneficial microbes are added to food products (e.g., yogurt) to improve gut health.
   • Food Preservation: Fermentation can inhibit the growth of spoilage-causing microbes.
   • Enzyme Production: Microbes produce enzymes used in food processing (e.g., rennet for cheese).
3. Which precautions are necessary while using antibiotics?
   Answer: Precautions necessary while using antibiotics include:
   1. Always take antibiotics only when prescribed by a qualified doctor.
   2. Complete the full course of antibiotics as prescribed, even if symptoms improve, to ensure all bacteria are killed and prevent resistance.
   3. Do not share antibiotics with others or use leftover prescriptions.
   4. Do not self-medicate with antibiotics for viral infections (e.g., common cold, flu), as they are ineffective against viruses.
   5. Inform your doctor about any allergies or other medications you are taking.
   6. Store antibiotics properly as per instructions.
4. Explain the role of microorganisms in sewage treatment.
   Answer: Microorganisms play a critical role in sewage treatment, primarily in the secondary treatment stage. Sewage contains a large amount of organic waste. Various aerobic and anaerobic bacteria and fungi break down this complex organic matter into simpler, less harmful substances like carbon dioxide, water, and inorganic compounds. This biological degradation reduces the biochemical oxygen demand (BOD) of the wastewater, making it safer to discharge into the environment or for further purification. Activated sludge processes, for instance, rely heavily on microbial activity to purify wastewater.

Q5: Give scientific reasons.

1. Spores are important for fungi.
   Answer: Spores are crucial for fungi because they are the primary means of reproduction and dispersal for most fungal species. Spores are lightweight and can be carried by wind or water over long distances, allowing fungi to colonize new environments. They are also often resistant to unfavorable conditions (like drought or extreme temperatures), enabling the fungi to survive until conditions become suitable for growth. This efficient dispersal mechanism ensures the widespread distribution and survival of fungal populations.
2. Viruses are considered to be on the border of living and non-living.
   Answer: Viruses are considered to be on the border of living and non-living because they exhibit characteristics of both. They are non-living outside a host cell, where they exist as inert, crystalline structures and cannot carry out metabolic activities or reproduce independently. However, once they infect a living host cell, they hijack the host's cellular machinery to replicate, multiply, and produce new viral particles, thus exhibiting living characteristics. They lack cellular organization, which is a fundamental property of all other living organisms.
3. Microorganisms are essential for decomposition.
   Answer: Microorganisms, particularly saprophytic bacteria and fungi, are essential for decomposition because they break down complex organic compounds from dead plants, animals, and waste products into simpler inorganic substances. This process is vital for recycling nutrients (like carbon, nitrogen, and phosphorus) back into the soil and atmosphere. Without decomposition, essential elements would remain locked in dead organic matter, depleting the nutrient supply for new life and disrupting ecosystems. They act as nature's recyclers.

Q6: Make a table showing the types of microorganisms and their characteristics.

Q7: Draw neat and labeled diagrams.

1. Various shapes of bacteria
   Sketch: (Imagine simple diagrams showing:
   • A few spherical cells labeled 'Cocci'
   • A few rod-shaped cells labeled 'Bacilli'
   • A spiral-shaped cell labeled 'Spirillum'
   • A comma-shaped cell labeled 'Vibrio'
   Each shape should be distinct.)
2. Yeast (Saccharomyces) with budding
   Sketch: (Imagine a diagram of a single oval-shaped yeast cell with a small outgrowth (bud) forming on its surface, representing asexual reproduction.)