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The Invisible Living World: Beyond Our Naked Eye - Key players in cleaning the environment

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Microorganisms as Decomposers: Bacteria and fungi break down dead plant and animal matter into simpler inorganic substances.

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Formation of Manure: The process where organic waste from kitchens (vegetable peels, leftover food) is converted into nutrient-rich humus by microbial action.

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Bioremediation: The use of microorganisms like bacteria to neutralize or remove pollutants from a contaminated site, such as oil spills or heavy metals in soil.

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Sewage Treatment: In Sewage Treatment Plants (STPs), aerobic bacteria are used to digest organic matter in the secondary treatment phase to clean the water before it is released into water bodies.

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Recycling of Nutrients: By decomposing organic matter, microbes return essential elements like Carbon (CC), Nitrogen (NN), and Phosphorus (PP) back to the soil, maintaining the ecological balance.

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Chemical Transformation: Microbes convert complex organic molecules into simpler molecules like CO2CO_2, H2OH_2O, and nitrates (NO3−NO_3^{-}).

📐Formulae

Organic Matter+O2→MicroorganismsCO2+H2O+Minerals+EnergyOrganic\ Matter + O_2 \xrightarrow{Microorganisms} CO_2 + H_2O + Minerals + Energy

N2→Nitrogen Fixing BacteriaNH3 (Ammonia)N_2 \xrightarrow{Nitrogen\ Fixing\ Bacteria} NH_3 \text{ (Ammonia)}

Efficiency of Waste Reduction=Initial Mass−Final MassInitial Mass×100\text{Efficiency of Waste Reduction} = \frac{\text{Initial Mass} - \text{Final Mass}}{\text{Initial Mass}} \times 100

💡Examples

Problem 1:

In a school composting project, the initial weight of the organic waste was 850 kg850\ kg. After three months of microbial decomposition, the final weight of the manure produced was 235 kg235\ kg. Calculate the total mass of the waste that was converted into gases like CO2CO_2 and water vapor during the process.

Solution:

850−235615\begin{array}{r} 850 \\ - 235 \\ \hline 615 \end{array} Therefore, 615 kg615\ kg of waste was converted into gases and water vapor.

Explanation:

According to the law of conservation of mass in a biological system, the initial mass of organic waste is equal to the sum of the final mass of manure and the mass of the substances (like CO2CO_2 and H2OH_2O) released into the atmosphere by microorganisms.

Problem 2:

A specific strain of bacteria can decompose 0.5 g0.5\ g of oil per square meter per hour. If an oil spill covers an area of 100 m2100\ m^2, how much oil (in grams) will be cleaned by the bacteria in 2424 hours?

Solution:

Total Oil Cleaned=Rate×Area×Time\text{Total Oil Cleaned} = \text{Rate} \times \text{Area} \times \text{Time} Total Oil Cleaned=0.5×100×24=1200 g\text{Total Oil Cleaned} = 0.5 \times 100 \times 24 = 1200\ g

Explanation:

Bioremediation efficiency depends on the rate of microbial activity, the surface area of the pollutant, and the duration of the treatment.