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Our Environment - Biodegradable and non-biodegradable substances

Grade 10CBSE

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

🔑Concepts

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Biodegradable substances: These are materials that can be broken down into simpler, harmless substances by the action of micro-organisms like bacteria and fungi. Examples include domestic sewage, livestock waste, and paper.

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Non-biodegradable substances: These are materials that cannot be broken down by biological processes. They persist in the environment for a long time and may harm the ecosystem. Examples include plastics, DDTDDT (Dichlorodiphenyltrichloroethane), and heavy metals like mercury (HgHg).

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Enzymatic Specificity: Decomposers release specific enzymes to break down organic matter. These enzymes are highly specific, which is why microbes can decompose paper (cellulose) but cannot decompose plastics (synthetic polymers) as they lack the necessary enzymes.

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Ecological Impact: Non-biodegradable substances like pesticides enter the food chain and undergo Biological Magnification, where their concentration increases at each trophic level (T1<T2<T3<T4T_1 < T_2 < T_3 < T_4).

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Decomposition Process: During decomposition, complex organic molecules are converted into inorganic substances like CO2CO_2, H2OH_2O, and nutrients, which are returned to the soil and atmosphere.

📐Formulae

Organic Matter+O2→Micro-organismsCO2+H2O+Minerals+Energy\text{Organic Matter} + O_2 \xrightarrow{\text{Micro-organisms}} CO_2 + H_2O + \text{Minerals} + \text{Energy}

Concentration level: CProducer<CHerbivore<CCarnivore<CApex Predator\text{Concentration level: } C_{\text{Producer}} < C_{\text{Herbivore}} < C_{\text{Carnivore}} < C_{\text{Apex Predator}}

Biodegradability∝1Persistence in Environment\text{Biodegradability} \propto \frac{1}{\text{Persistence in Environment}}

💡Examples

Problem 1:

Why does a piece of paper decompose over time while a plastic bottle remains unchanged for hundreds of years?

Solution:

Paper is made of cellulose, which can be broken down by the enzymes produced by bacteria and fungi. Plastic is a synthetic polymer that decomposers cannot recognize or break down chemically.

Explanation:

Micro-organisms are specialized. They produce specific biocatalysts (enzymes) that break specific chemical bonds. The bonds in synthetic plastics are not recognized by the natural enzymes of SaprophytesSaprophytes.

Problem 2:

If 10 ppm10 \text{ ppm} of DDTDDT is present in a water body, explain its concentration in a hawk (top carnivore) within that ecosystem.

Solution:

The concentration of DDTDDT will be significantly higher in the hawk than 10 ppm10 \text{ ppm} due to the phenomenon of Biological Magnification.

Explanation:

Since DDTDDT is non-biodegradable, it is not excreted or metabolized by organisms. As it moves up the food chain (Water →\rightarrow Plankton →\rightarrow Fish →\rightarrow Hawk), it accumulates, reaching maximum concentration in the top consumer.