Chapter 16: Environmental Issues

Over the years, the exponential rise in population has led to increased demand in the supply of food, water, shelter, electricity, clothing, automobiles, and many such commodities. These demands exert immense pressure on natural resources which contribute to pollution of the air, water, soil, the environmental pollution ultimately. Hence it has become very essential to check the degradation and depletion of our valuable natural resources without hindering the process of development. Through this chapter, we understand the importance of our natural resources, the numerous issues persisting in the environment in which we reside and the counter-active measures we can adapt in the direction of a healthy environment.

Very Short Answer Type Questions

Q.1. Why is lead-free petrol or diesel recommended to reduce pollutants emitted by automobiles?

A.1. Diesel and petrol are added with lead in the form of Pb(CH3)4b and Pb(C2H5)4 as an antiknock agent.

Q.2. To include noise as air pollution, in which year was the Air Prevention and Control of Pollution Act amended?

A.2. 1987
Q.3. Which city in India has all the public road transport running on CNG?

A.3. Delhi
Q.4. What is a possible source of silt that gets accumulated in water tanks?

A.4. Soil particles that are carried out with water from rivers and deep borewells etc.

Q.5. Define cultural eutrophication.

A.5. It is a phenomenon wherein effluents from homes and industries fuel the cultural and natural ageing process of water bodies which otherwise takes thousands of years.

Q.6. Write two severe effects of particulate matter on human health.

A.6. Inflammation. Damage to the lungs and premature death.

Q.7. Name the raw material for polyblend.

A.7. They are made by a mixture of two or multiple polymers, mainly plastic waste products.

Read More: Effects Of Plastics

Q.8. Why does the road life factor increase by a factor of three upon addition of blends of bitumen and poly blend?

A.8. Plastic increases the melting point of bitumen that prevents its melting given India’s hot climatic conditions, where temperature frequently crosses 50℃. Because of the plastic blend, rainwater will not be able to penetrate.

Q.9. List two examples of plants that are used in agricultural fields as windbreakers.

A.9. The Calotropis and Vetia act as windbreakers.

Q.10. Write the name of an industry which can cause – eutrophication, thermal and air pollution.

A.10. Thermal power plants, chemical fertilizer units, smelting, refineries, metallurgical processing units, steel mills cause these pollutions. It may result in eutrophication is chemical is released from these industries.

Q.11. Define algal bloom.

A.11. Presence of organic matter in water acts as a food source resulting is extensive growth of planktonic algae in water bodies and is called an algal bloom.

Q.12. What is biomagnification?

A.12. Increase in the concentration of toxic substances at consecutive trophic levels in the food chain is referred to as biomagnification.

Q.13. List the three major impurities found in domestic wastewater.

A.13. Biodegradable organic matter, Pathogenic microbes, dissolved salts such as nitrates and phosphates.

Q.14. Define reforestation.
A.14. It is the process of restoring a forest which existed once but was removed at some point in the past.

Q.15. How can electronic wastes be treated in the most efficient way?

A.15. Recycling. It has two advantages:

  • It blocks the entrance of toxic substances into the fragile environment and groundwater through a landfill.

  • It lowers the utility and mining of primary raw materials.

Short Answer Type Questions

Q.1. Can curtains and carpets positioned on the floor or surfaces of walls reduce the noise level? Justify your answer.

A.1. Yes, it can. They act as muffling devices and absorb sounds of moderate level.

Q.2. With advantages and suitable examples, explain hybrid vehicle technology.

A.2. It is a technology used to run vehicles on dual modes like compressed natural gas or petrol. CNG is a green and clean fuel so it is useful to decrease environmental pollution and also conserve petrol fossil fuel.

Q.3. Will water turn septic if dissolved oxygen level drops to zero? Which factor could lower the dissolved content of oxygen of an aquatic body.

A.3. Yes, it can turn septic. Fertilizers in aquatic bodies are responsible for lowering the level of dissolved oxygen.

Q.4. Listing a greenhouse gas, write its possible source of production on a larger scale. What are its harmful effects?

A.4. Some common greenhouse gases are carbon dioxide, methane, an oxide of nitrogen, water vapour, etc. Due to large scale deforestation, unlimited burning of fossil fuels causes the level of carbon dioxide to increase thus leading to global warming. Incomplete decomposition by anaerobic methanogens, garbage dump, flooded paddy field and marshy land is few of the sources leading to an increase in the levels of methane. Rice fields of Asia, release about 90% of methane.

Further Reading: Putrefaction

Q.5. Is planting trees and shrubs near boundary walls of buildings a common practice? Write about its usage.

A.5. Yes, it is. It acts as a boundary for sound and checks noise pollution. It also keeps a check on primary air pollutants such as dust, fly ash, etc.

Q.6. Why is it recommended to have a larger forest cover for hills than plains by the National Forest Commission of India?

A.6. It is because, large forest areas of hills check soil erosion, percolation and recharges groundwater. It monitors landslides and other such natural calamities and also promotes maintenance of original flora and fauna of the hills.

Q.7. Can burn and slash become eco-friendly? How?

A.7. Yes they can be, if:

  • Crop rotation is practised to reduce soil fertility
  • By shortening the cropping period and keeping fallow period for longer
  • Small widely scattered plots are used for cultivation

Q.8. What is Snow-blindness?

A.8. It is the excessive absorption of ultraviolet-B-radiations that cause inflammation of the cornea.

Q.9. How is the bird population affected by DDT?

A.9. Calcium metabolism in birds is influenced by high concentrations of DDT that cause thinning of the eggshell and hence their premature breaking, gradually causing declination in the bird population.

Q.10. Answer the following questions based on figure A and B.

a) True or False – The power generation is non-polluting with these two methods as given in the above figure.

b) Write two applications of solar energy

c) Define a photovoltaic cell.


a) True. Figure A is a solar energy panel and figure B is a windmill device.

b) Solar hot water system (geyser) and solar lamp (lantern) are two applications.

c) It is a form of a photoelectric cell that converts light into electrical energy and is a solar cell.

Long Answer Type Questions

Q.1. Write notes on electronic wastes. Write about the various sources of e-wastes and issues associated with its disposal.

A.1. Solid wastes can be recyclable, biodegradable, non-biodegradable and can be categorized as municipal wastes – the sewage, hospital and nursing wastes, industrial wastes and electronic wastes. Mobiles, irreparable computers, and other such electronic goods are known as e-waste or electronic wastes. Some of their sources are:

  • Many developing countries like India, China import irreparable electronic goods for their precious metals like nickel, gold, copper.

  • E-wastes should be disposed of in landfills or incinerated

  • Manual extraction of metals from e-wastes takes place in developing countries. Hence working with them can expose one to toxic substances present in it, leading to skin diseases

  • Recycling is the only solution for e-waste treatment.

Q.2. Explain organic farming. In a developing nation like India, discuss its benefits as a viable practice.

A.2. In an eco-friendly and pollution-free environment, organic farming mainly aims at sustainable production. Cultivation on land happens through techniques such as green manure, crop rotation, composting and biological pesticides along with beneficial microbes instead of pesticides and chemical fertilizers. Few of its benefits are:

  • Regulates diseases and pests without causing harm to the environment

  • Maintains long-term soil fertility

  • Assures that water remains safe and clean.

  • To make it economic, use resources which already exists with the farmer

  • Produces high-quality crops and nutritious food.

Use of organic farming techniques in developing nations makes much more sense. Modern agricultural practices make use of expensive herbicides and chemical fertilizers which ooze out from the soil and contaminate water bodies damaging the fertility of the soil.

Q.3. What are the causes and severe effects of soil salinity and waterlogging in the green revolution?

A.3. Soil salinity and waterlogging are caused by huge irrigation without suitable drainage of water. The constant presence of water trails salt to the soil surface, which accumulates as a thin crust on the surface of the land or begins to collect at the plant roots. Severe effects:

  • High salt content exploits the growth of crop plants

  • Cells of the roots get damaged with saline water saturation

  • Plants tend to die

  • The yield of crops is affected

  • Farmers procure financial loss

Economic costs of management of soil-water systems to check the salination and water logging issues are very high.

Q.4. Define multipurpose trees. Write the botanical and local names of any two multipurpose trees along with their uses.

A.4. Upon plantation, trees that fulfil a number of purposes are called as multipurpose trees. These purposes can be providing shade, wood, fruit, food, soil improvement, etc. They serve a wide variety of services and functions for human needs. Azardicta, Indica – Neem, is well-known for its medicinal benefits. Its leaves, wood, fruit and the oil extracted from wood is mostly used in ayurvedic medicines.

Due to chemical azadirachtin, its wood is pest resistant. Coconut palm is another important tree, with the botanical name – Cocos Nucifera belongs to the family – Palmae and provides a variety of functions such as wood, oil, food fibre, etc and has medicinal, fibre and commercial importance. Another multipurpose tree is the Morinaoleifera and Gliricidia septum which is utilized for fences in Central America. It provides firewood fodder and fixes atmospheric nitrogen. It is commonly used for shade and animal forage and its leaves are edible.

Q.5. Write three basic characteristics of a modern landfill site. What are the reasons they are used?

A.5. Following are the characteristics:

  • Compaction and integument of the waste to prevent it from being blown by the wind

  • Procedures to contain leachates such as lining clay or plastic liners

  • To extract gas to use in the generation of power, landfills gas extraction systems are installed.

The following are the reasons why their use must be promoted:

  • Through recycling and recovery of waste, they trigger the waste prevention

  • A uniform cost for the disposal of waste is created which subsequently will prevent the essential transport of waste.

  • They help in bringing down negative effects on the environment and risk to human health that emerges from the landfilling of wastes.

Q.6. Explain the working of the electrostatic precipitator.

A.6. They can eliminate 99% particulate matter that is found in the exhaust from a particular thermal power plant through these mechanisms:

  • It contains electrodes wires which are constantly maintained at a several thousand volts, which provides a corona releasing electrons.

  • The electrons hence released are attached to dust particles offering them with a net negative charge

  • The plates that collect, are grounded and draws through attraction the dust particles that are charged.

  • The velocity of air is maintained low between the plates to facilitate falling of dust.

Read More: Important Questions for Class 12 Biology – All Chapters

Discover more about environmental issues and other concepts at BYJU’S Biology.

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