Q1.
Now, think what would have happened if microorganisms did not exist on Earth?
Answer
Life as we know it could not continue. The most serious loss would be that nothing would decay — nutrients would be locked up in dead bodies for ever.
| What microbes do now | What would happen if they did not exist |
|---|---|
| Decompose fallen leaves, plant waste, dung and dead animals | Dead plants, dead animals and waste would pile up and never break down. Nutrients would never return to the soil, so the soil would lose its fertility and plants would grow poorly. |
| Make manure and compost | No natural manure and no compost pits; farmers would depend entirely on other means. |
| Release biogas from waste in oxygen-free conditions | No biogas for cooking, heating, electricity or vehicles. |
| Rhizobium traps nitrogen from the air in root nodules | Legumes would get no nitrogen from the air, and crop rotation would not enrich the soil. |
| Yeast and Lactobacillus in food | No curd, no idli, no dosa, no bhatura, no bread or cake — all of these depend on fermentation. |
| Gut bacteria help in digestion | Our own digestion would be affected. |
| Microalgae make food using sunlight | More than half of Earth's oxygen supply would be gone, and the aquatic animals that feed on microalgae would lose their food. |
The one gain would be that the microbes which cause disease in plants, animals and humans would also be absent. But weighed against everything above, that gain is very small.
The idea behind it: nature works in cycles. A plant takes nutrients from the soil, an animal eats the plant, and both eventually die. Only the decomposers close that cycle by returning the nutrients to the soil. Remove them and the cycle becomes a one-way street that soon runs out.