The Invisible Living World Beyond Our Naked Eye Class 8 Long Question Answer

The Invisible Living World Beyond Our Naked Eye Class 8 Long Question Answer

The Invisible Living World Beyond Our Naked Eye Class 8 Long Question Answer

Question 1.

Why did the farmer growing bean crops choose not to add nitrogen fertiliser?

Answer:

The farmer growing bean crops likely chose not to add nitrogen fertiliser because beans, like other legumes, have a symbiotic relationship with nitrogen-fixing bacteria called Rhizobium. These bacteria live in root nodules of the bean plants and can convert atmospheric nitrogen into a form that the plants can use for growth. This natural process enriches the soil with nitrogen, reducing the need for chemical fertilisers and promoting healthier soil for future crops.

Question 2.

What is the significance of the experiment Snehal conducted with pits A and B?

Answer:

Snehal's experiment with pits A and B aims to test the effect of mixing organic waste with dried leaves on the decomposition process. In pit A the mixture of fruit and vegetable peels with dried leaves provides a balanced carbon-to-nitrogen ratio, which can enhance microbial activity and speed up decomposition. In contrast, pit B, which lacks dried leaves, may decompose more slowly due to an imbalance in nutrients, allowing Snehal to observe the differences in decomposition rates and the role of carbon sources in composting.

Question 3.

What happens to bread slices placed in different environments after three days?

Answer:

When one slice of bread is placed near the sink and the other in the refrigerator, the slice near the sink is likely to show mould growth after three days, while the refrigerated slice may remain relatively unchanged. The warmer, moist environment near the sink provides optimal conditions for mould spores to germinate and grow, while the cold temperature and reduced moisture in the refrigerator inhibit microbial growth. This observation highlights the importance of temperature and moisture in the growth of microorganisms.

Question 4.

Why does curd become sour when left out for a day?

Answer:

Curd becomes sour when left out for a day due to the activity of lactic acid bacteria, primarily Lactobacillus, present in the curd. These bacteria ferment lactose, the sugar found in milk, producing lactic acid as a byproduct. The accumulation of lactic acid lowers the pH of the curd, making it sour. This process is facilitated by warm temperatures, which promote bacterial growth and fermentation, explaining why curd left at room temperature becomes sour more quickly than when refrigerated.

Examples from daily life

Question 1.

Fermentation in Food Production

Answer:

Microorganisms play a crucial role in the fermentation process, which is used in the production of various foods. For instance:

1. Bread Making: Yeast, a type of fungus, is used in baking bread. When yeast ferments the sugars present in the dough, it produces carbon dioxide gas and alcohol. The carbondioxide gas forms bubbles in the dough, causing it to rise and become fluffy, while the alcohol contributes to the flavour. This process is evident when you observe the dough rising after adding yeast, as mentioned in the textbook.
2. Dairy Products: Bacteria such as Lactobacillus are essential in making yogurt and cheese. When these bacteria ferment lactose (the sugar in milk), they produce lactic acid, which thickens the milk and gives yogurt its tangy flavour. This is a great example of how microorganisms are utilised in food processing.

Question 2.

Decomposition and Nutrient Recycling

Answer:

Microorganisms are vital for the decomposition of organic matter, which helps recycle nutrients back into the soil. For example:

1. Composting: When fruit and vegetable peels, along with garden waste, are left to decompose, microorganisms such as bacteria and fungi break down this organic material into nutrient-rich manure. This process enriches the soil, making it more fertile for plant growth. As described in the textbook, this is a natural way of recycling nutrients in the ecosystem.

Question 3. Microorganisms in Our Gut

Answer:

The human body hosts a variety of microorganisms, particularly in the gut, which are essential for digestion:

1. Gut Flora: The bacteria present in our intestines help break down complex carbohydrates and synthesise vitamins, such as vitamin K and some B vitamins. This symbiotic relationship is crucial for our health, as these microorganisms aid in digestion and contribute to our immune system. The textbook mentions that these bacteria are beneficial and play a significant role in our daily life.

Question 4.

Bioremediation

Answer:

Microorganisms are also employed in environmental cleanup processes:

1. Pollution Cleanup: Certain bacteria can degrade pollutants in the environment, such as oil spills or heavy metals. This process, known as bioremediation, utilises the natural abilities of microorganisms to break down harmful substances into less toxic forms. For example, specific strains of bacteria can be introduced to contaminated soil or water to help clean it up, demonstrating the beneficial role of microorganisms in maintaining ecological balance.