NCERT Solutions for Class 12 Biology Chapter 16 Environmental Issues to Study Online as well as download in PDF form. Download Offline Apps following NCERT Solutions for other subjects also. Come to the world of knowledge and Share Your Thoughts.
|Chapter 16:||Environmental Issues|
NCERT Solutions for class 12 Biology Chapter 16
Go back to Class 12 Biology main Page
Solutions for 12 Biology Chapter 16
- View Online NCERT Sols
- Download NCERT Solutions
- NCERT Book Chapter 16
- Revision Notes with Practice Questions for 2019-20 Exams
- NCERT Exemplar Problems for Class 12 Biology
Class 12 Biology Chapter 16 Question Answers
Important Notes on 12 Biology Chapter 16
- Pollutants: Agents which cause pollution.
- Pollution: Undesirable physical/chemical/biological characteristics of air/water/land which cause damage to the animals/plants/humans and architectural structures.
- Reforestation: Process of restoring a forest that was removed at some point of time in the past.
- Effluents: Something flowing over a large body of water (may be sewage or industrial effluents).
- JFM (Joint Forest Management): Introduced by the Government of India in 1980s to work closely with local communities for protecting and managing forests.
- It refers to increase in concentration of toxic substances at successive trophic levels.
- Harmful Effect of DDT: High concentration of DDT disturbs calcium metabolism in birds, which causes thinning of egg shell and their premature breaking, causing decline in birds population.
- Global Warming: Increase in the level of greenhouse gases is mainly responsible for global warming, (increase in mean global temperature due to trapping of infrared radiation). Carbon dioxide, Methane, CFCs, N2O are the main gases that causes greenhouse effect.
Measures to Control Global Warming
- Minimize the use of fossil fuel.
- Improving efficiency of energy usage.
- Reducing deforestation.
- Planting trees.
- Eutrophication: It is the process of nutrient enrichment of water and subsequent loss of species diversity like fishes. Excess nutrients causes algal bloom which may cover the whole surface of water body and release toxins. It causes oxygen deficiency in water that leads to the death of aquatic animals like fishes.
- Ozone Hole: Large area of thinned ozone layer over Antarctica.
Steps leading to ozone depletion
- UV-rays split CFCs and release atomic chlorine (Cl)
- UV-rays also split ozone into oxygen.
- Chlorine atoms trap oxygen atoms and ozone is not formed again from oxygen. This leads to depletion of ozone in the stratosphere.
- Electronic Wastes (e-waste): e-wastes are irreparable computer and other electronic goods.
Disposal of e-wastes
- Burned in landfills
List all the wastes that you generate, at home, school or during your Trips to other places, could you very easily reduce? Which would be Difficult or rather impossible to reduce?
Wastes generated at schools include waste paper, plastics, vegetable and fruit peels, food wrappings, sewage etc.
Wastes generated at trips or picnics include plastic, paper, vegetable and fruit peels, disposable cups, plates, spoons etc.
Yes, wastes can be easily reduced by the judicious use of the above materials. Wastage of paper can be minimized by writing on both sides of the paper and by using recycled paper. Plastic and glass waste can also be reduced by recycling and re-using. Also, substituting plastics bags with biodegradable jute bags can reduce wastes generated at home, school, or during trips. Domestic sewage can be reduced by optimizing the use of water while bathing, cooking, and other household activities.
Non- biodegradable wastes such as plastic, metal, broken glass, etc. are difficult to decompose because micro-organisms do not have the ability to decompose them.
What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
Write critical notes on Eutrophication.
Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?
Chlorine is mainly released from chlorofluorocarbons (CFC’s) widely used as refrigerants. The CFC’s magnate from the troposphere to the stratosphere, where they release chlorine atoms by the action of UV rays on them. The release of Chlorine atoms causes the conversion of ozone into molecular oxygen. One atom of chlorine can destroy around 10,000 molecules of ozone and causes ozone depletion.
The formation of the ozone hole will result in an increased concentration of UV – B radiations on the Earth’s surface. UV −B damages DNA and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of UV −B cause corneal cataract in human beings.
Discuss briefly the Greenhouse gases.
What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
Various steps have been taken to improve the quality of air in Delhi.
Introduction of CNG (Compressed Natural Gas): By the order of the supreme court of India, CNG-powered vehicles were introduced at the end of year 2006 to reduce the levels of pollution in Delhi. CNG is a clean fuel that produces very little unburnt particles.
Phasing out of old vehicles
Use of unleaded petrol
Use of low-sulphur petrol and diesel
Use of catalytic converters
Application of stringent pollution-level norms for vehicles
Implementation of Bharat stage I, which is equivalent to euro II norms in vehicles of major Indian cities.
The introduction of CNG-powered vehicles has improved Delhi’s air quality, which has led to a substantial fall in the level of CO2 and SO2. However, the problem of suspended particulate matter (SPM) and respiratory suspended particulate matter (RSPM) still persists.