Following are Environmental Issues Notes for Class 12 Biology. These revision notes have been prepared by expert teachers of Class 12 Biology as per the latest NCERT, CBSE, KVS books released for the current academic year. Students should go through Chater 16 Environmental Issues concepts and notes as these will help you to revise all important topics and help you to score more marks. We have provided Class 12 Biology notes for all chapters in your book. You can access it all free and download Pdf.

Chapter 16 Environmental Issues Notes Class 12 Biology

Important Questions Environmental Issues Class 12 Biology

Question. PM2.5 is responsible for causing greatest harm to human health. What is it? How is it harmful?
Answer :  PM2.5 stands for particulate matter of size 2.5 micrometres or less in diameter. It’s responsible for causing greatest harm to human health as it can be inhaled deep into lungs and cause breathing problems.

Question. Why is a scrubber used? Which spray is used on exhaust gases passing through a scrubber?
Answer : To remove gases like sulphur dioxide. Spray of water or lime is used

Question. What is the noise level that can cause permanent impairment of hearing ability of human beings?
Answer : 150 dB or more

Question. Why was the Montreal Protocol signed?
Answer : To control emission of ozone depleting substances

Question. Water logging and salinity are some of the problems that have come in the wake of Green revolution. How does water logging create problems of salinity?
Answer : Water logging draws salt to surface of soil. Salt deposited on land surface as a thin crust or at the roots of the plants

Question. Landfills are not much a solution for getting rid of solid wastes. Why?
Answer : Landfill sites are getting filled very fast due to large amount of garbage generation. Also underground water resources may get polluted due to seepage of chemicals

Question. Electrostatic precipitator can remove over 99% particulate matter present in exhaust from a thermal power plant. How?
Answer : Electrode wire at thousand volts, produce corona to release electrons, electrons attach to dust particulars giving them net negative charge, charged dust particulars attracted/collected by collecting plates which are grounded

Question. Why should the velocity of air between the plates of an electrostatic precipitator below?
Answer : To allow the dust to fall.

Question. What are the contributions of AhmedKhan in Bangalore and Ramesh Chandra Dagar in Sonipat?
Answer : a) Polyblend, a fine powder of recycled modified plastic is mixed with bitumen & used to lay roads. This increases bitumen water repellent properties & increase
road life by a factor of three b) Integrated organic farming is a cyclical, zero waste procedure, where waste from process are cycledinasnutrients for other process. Heincludedbee keeping, dairy management, water harvesting composting and agriculture in a chain of processes.

Question. There is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. Why? What are its adverse effects?
Answer : Following discharge of sewage into river, micro organisms involved in biodegradation of organic matter present in sewage consume more oxygen.
This cause mortality of fish and other aquatic creature.

Question. Catalytic converters use expensive metals as catalysts.
(a) Name the metals generally used.
(b) What precaution should be observed while using catalytic converter?
Answer : (a) Catalysts : platinum – palladium and Rhodium (b) Motor vehicles equipped with catalytic converters should use unleaded petrol as lead inactivates the catalysts.

Question. Jhum cultivation has been in practice from earlier days, but it is considered more problematic these days. Why?
Answer : Enough time gap is not being given for the natural process of recovery of land from the effect of cultivation

Question. What are e-wastes? Why are they creating more problems in developing countries in comparison to developed countries?
Answer : a) Irreparable computers and other electronic wastes.
(b) Recycling in developing countries involves manual participation thus exposing workers to toxic substances. In developed countries its mechanized so less dangerous

Question. Deforestation is creating a lot of problems in the environment. List the consequences of deforestation.
Answer : Enhanced CO2 concentration in atmosphere, Loss of biodiversity , Soil erosion Desertification ,Disturbed hydrological cycles.

Question. A radiation causes ageing of skin, skin cancer, and inflammation of cornea called snow blindness. It also damages DNA. Name the radiation.
Answer : Ultraviolet B rays (UV-B rays)

Question. Enlist four harmful effects caused to the humans living in areas having polluted air. Suggest two measures to reduce air pollution.
Answer : Breathing problems, irritation and inflammation, Damage to lungs, Premature death. Reduce emission from automobile exhaust , Growing more trees.

Question. People have been actively participating in the efforts for the conservation of forests.
(i) Name the award instituted in respect of Amrita Devi to promote such efforts.
(ii) Name the movement launched to protect the trees by hugging them.
(iii) Name the step Government of India has under taken in1980 to work closely with the local communities for protecting and managing forests.
Answer : (i) Amrita Devi Bishnoi Wildlife Protection Award. (ii) Chipko movement
(iii) Joint Forest Management (JFM).

Question. What is the relationship between BOD, micro-organisms and amount of biodegradable matter?
Answer : Increase in amount of biodegradable matter leads to rapid multiplication of micro organisms to degrade it, thereby increasing BOD level of the water body.

Question. Pollutant released due to human activities (like effluents from industries and homes)can radically accelerate the ageing process of the water body.
(a) Explain how this process occurs during natural ageing of lake.
(b) Give the term used for accelerated ageing of water bodies. Also give the term used for the natural ageing of lake.
Answer : a) The phenomenon is eutrophication. More nutrients in water, aquatic life increases organic remains deposited on lake bottom, lake grows shallower and warmer, gradually transforms into land due to deposition of silt and organic debris.
(b) Cultural or Accelerated eutrophication ,Natural ageing is Eutrophication.

Question. Since the use of poly bags has become so rampant in our day-to-day life, it is impossible to go back to non-plastic era. Today, the plastic menace has spread from cities to small towns and village. They are “Garbage Forever”.
i) What are the harmful effects of using poly bags?
ii) In your opinion, what steps should be taken to solve this problem?
Answer : (I) Nondegradable, choke our sewage & drainage system, stray cattle eat sit & choke its digestive system
(II) Using paper, jute, cloth bags. Minimise the use voluntarily. Segregation of biodegradable & non-biodegradable material to safe disposal. Educating people on health risk, production of biodegradable plastic bags by mixing cellulose during their manufacturing.

Question. In Arcata, the town’s people have created an integrated wastewater treatment process within a natural system. A citizen group called FOAM helps in upkeep of this project.
(a) What are the main steps in waste water management done in this way?
(b) Ecosan in Kerala and Sri Lanka is also an initiative for water conservation. How? 
Answer : a) Conventional sedimentation, filtering and chlorine treatment. Absorption and assimilation of pollutants by algae fungi and bacteria.
(b) Ecosan derived from ecological sanitation. Handling human excreta using dry composting toilets. Its practical, hygienic and cost effective method.

Question. Nowadays, we see that people use CDs & DVDs for storing information, movies and songs. Do you think these things create pollution?
Answer : Yes, these contain heavy metals & toxic substances. As the technology is changing these products are replaced by i pods, pen drives. They constitute e-waste.