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Ecology and Environment - Environmental Issues

Grade 12ICSEBiology

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

🔑Concepts

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Air Pollution: Presence of materials in air in concentrations harmful to humans and environment. Major pollutants include CO2CO_2, SO2SO_2, NOxNO_x, and particulate matter (PM2.5PM_{2.5} and PM10PM_{10}).

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Electrostatic Precipitator (ESP): A device used to remove over 99%99\% of particulate matter from industrial exhaust. It uses electrode wires at high voltages to produce a corona that releases electrons, giving dust particles a negative charge.

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Catalytic Converters: Fitted in automobiles to reduce emission of poisonous gases. They use expensive metals like platinum-palladium and rhodium as catalysts to convert unburnt hydrocarbons into CO2CO_2 and H2OH_2O, and COCO and nitric oxide into CO2CO_2 and N2N_2 gas.

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Biochemical Oxygen Demand (BODBOD): The amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample. High BODBOD indicates high water pollution.

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Biomagnification: The increase in concentration of a toxicant (like DDTDDT or Mercury) at successive trophic levels. This happens because a toxic substance accumulated by an organism cannot be metabolized or excreted.

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Eutrophication: Natural aging of a lake by biological enrichment of its water. 'Cultural Eutrophication' is accelerated aging due to human activities like sewage and agricultural runoff providing excess nitrogen (NN) and phosphorus (PP).

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Greenhouse Effect: A natural phenomenon where gases like CO2CO_2 (60%60\%), CH4CH_4 (20%20\%), CFCsCFCs (14%14\%), and N2ON_2O (6%6\%) trap heat in the Earth's atmosphere, leading to Global Warming.

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Ozone Depletion: Degradation of the ozone layer in the stratosphere primarily due to Chlorofluorocarbons (CFCsCFCs). The thickness of ozone is measured in Dobson Units (DUDU).

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Solid Waste Management: Categorized into bio-degradable, recyclable, and non-biodegradable. Includes E-waste (electronic waste) which is buried in landfills or incinerated.

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Deforestation: Conversion of forested areas to non-forested ones. Concepts include 'Jhum cultivation' (Slash and burn) and the 'Chipko Movement' for forest conservation.

📐Formulae

BOD∝Organic matter in waterBOD \propto \text{Organic matter in water}

BOD∝1Dissolved Oxygen (DO)BOD \propto \frac{1}{\text{Dissolved Oxygen (DO)}}

CFCl3+UV→CFCl2+Cl∙CFCl_3 + UV \rightarrow CFCl_2 + Cl^{\bullet}

Cl∙+O3→ClO+O2Cl^{\bullet} + O_3 \rightarrow ClO + O_2

ClO+O→Cl∙+O2ClO + O \rightarrow Cl^{\bullet} + O_2

💡Examples

Problem 1:

Explain the biomagnification of DDTDDT in an aquatic food chain starting from water with 0.0030.003 ppb.

Solution:

The concentration of DDTDDT increases at each trophic level: Water (0.0030.003 ppb) →\rightarrow Zooplankton (0.040.04 ppm) →\rightarrow Small fish (0.50.5 ppm) →\rightarrow Large fish (22 ppm) →\rightarrow Fish-eating birds (2525 ppm).

Explanation:

Because DDTDDT is lipophilic and not easily metabolized, its concentration increases nearly 10710^7 times from water to the top predator, interfering with calcium metabolism in birds and causing eggshell thinning.

Problem 2:

In a water body, the BODBOD is found to be 400400 mg/L. What does this indicate about the water quality and the level of Dissolved Oxygen (DODO)?

Solution:

A BODBOD of 400400 mg/L indicates highly polluted water (likely raw sewage) and very low levels of Dissolved Oxygen (DODO).

Explanation:

There is an inverse relationship: as sewage/organic matter increases, BODBOD increases because microbes consume O2O_2 to decompose the waste, leading to a sharp decline in DODO, which often causes the death of fish and other aquatic creatures.