The Invisible Living World: Beyond Our Naked Eye | Class 8 Science Notes

How Are We Connected to Microbes?

Microorganisms are present everywhere—in water, soil, air, and on food items. They can cause food to rot, as seen when fruits or vegetables develop powdery or cotton-like growths due to microbial infection. However, some foods like pickles and murabbas resist spoilage because they contain preservatives such as salt or sugar, which inhibit microbial growth. Microorganisms also live on plant surfaces and in extreme environments like hot springs and cold zones. Many microbes live inside our bodies, especially in the gut, aiding digestion. Microorganisms play a crucial role in cleaning the environment by decomposing plant and animal waste into nutrient-rich manure, a process called decomposition. Gardeners collect plant waste to make natural manure, which enriches soil fertility. Microbes also help recycle nutrients, maintaining ecological balance. Some bacteria, like Rhizobium in root nodules of legumes, fix nitrogen from the air, enhancing soil fertility naturally. Microorganisms also produce biogas by decomposing waste in oxygen-free environments, providing a renewable energy source. Scientists like Ananda Mohan Chakrabarty have harnessed microbes to solve environmental problems such as oil spill degradation. Microorganisms are also vital in food preparation processes like fermentation, used in making bread, curd, idli, and dosa.

📊 Diagram: Figure 2.9 shows a fruit with microbial growth causing spoilage. Figure 2.10 illustrates the process of decomposition and manure formation. Figure 2.11 shows dough rising due to yeast fermentation. Figure 2.12 shows root nodules of cowpea containing Rhizobium bacteria.

🧪 Activity: Activity 2.7: Composting fruit and vegetable peels to observe manure formation. Activity 2.8: Preparing dough with and without yeast to observe fermentation. Activity 2.9: Preparing curd from milk under different temperature conditions.

🔗 Connection: This section connects microbial life to environmental and human health, leading to understanding microorganisms' diversity and their role in food and environment.