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Our Environment - Environmental problems

Grade 10CBSE

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

🔑Concepts

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The Ozone layer is a protective shield around the Earth in the stratosphere that absorbs most of the harmful UVUV (Ultraviolet) radiation from the Sun.

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Ozone (O3O_3) is formed at higher levels of the atmosphere by the action of UVUV radiation on oxygen (O2O_2) molecules. The higher energy UVUV radiations split some molecular oxygen into free oxygen atoms (OO).

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Depletion of the Ozone layer is primarily caused by synthetic chemicals like CFCsCFCs (Chlorofluorocarbons), which are used in refrigerants and fire extinguishers.

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Biological Magnification is the process by which the concentration of non-biodegradable harmful chemicals (like DDTDDT) increases at every successive trophic level in a food chain.

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Biodegradable substances are those that can be broken down into simpler, harmless substances by the action of microorganisms like bacteria and fungi.

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Non-biodegradable substances cannot be broken down by biological processes and persist in the environment for a long time, causing pollution (e.g., plastics, DDTDDT, heavy metals).

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Effective waste management includes methods like Landfills, Incineration, Composting, Sewage treatment, and the 3Rs3Rs (Reduce, Reuse, Recycle).

📐Formulae

O2→UVO+OO_2 \xrightarrow{UV} O + O

O+O2→O3O + O_2 \rightarrow O_3

10% Law: Energy available to next trophic level=10%×Energy of current level10\% \text{ Law: Energy available to next trophic level} = 10\% \times \text{Energy of current level}

Concentration at Level n>Concentration at Level (n−1)\text{Concentration at Level } n > \text{Concentration at Level } (n-1)

💡Examples

Problem 1:

If 20,000 J20,000 \text{ J} of energy is available at the producer level in an ecosystem, calculate the amount of energy available to the tertiary consumer.

Solution:

20 J20 \text{ J}

Explanation:

According to the 10%10\% Law: Energy at Primary Consumer level = 10% of 20,000=2,000 J10\% \text{ of } 20,000 = 2,000 \text{ J}. Energy at Secondary Consumer level = 10% of 2,000=200 J10\% \text{ of } 2,000 = 200 \text{ J}. Energy at Tertiary Consumer level = 10% of 200=20 J10\% \text{ of } 200 = 20 \text{ J}.

Problem 2:

Explain why the concentration of DDTDDT is highest in human beings in a food chain consisting of Grass →\rightarrow Goat →\rightarrow Human.

Solution:

Due to Biological Magnification.

Explanation:

DDTDDT is a non-biodegradable chemical. When it enters the food chain at the producer level (Grass), it cannot be metabolized or excreted. As it moves up the trophic levels, its concentration increases at each step. Since humans occupy the highest trophic level in this chain, the accumulated concentration of DDTDDT is highest in them.

Problem 3:

What was the significance of the UNEPUNEP agreement in 19871987 regarding CFCsCFCs?

Solution:

To freeze CFCCFC production at 19861986 levels.

Explanation:

The United Nations Environment Programme (UNEPUNEP) succeeded in forging an agreement to stop the increase in CFCCFC (Chlorofluorocarbons) production to prevent further depletion of the Ozone (O3O_3) layer.

Environmental problems - Revision Notes & Key Formulas | CBSE Class 10 Science