NCERT Solutions for Class 12 Biology Chapter 16

Environmental Issues Class 12

Chapter 16 Environmental Issues Exercise Solutions

<< Previous Chapter 15 : Biodiversity and Conservation

Exercise : Solutions of Questions on Page Number : 286

Q1 :  

What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.


Answer :


Domestic sewage is the waste originating from the kitchen, toilet, laundry, and other sources. It contains impurities such as suspended solid (sand, salt, clay), colloidal material (fecal matter, bacteria, plastic and cloth fiber), dissolved materials (nitrate, phosphate, calcium, sodium, ammonia), and disease-causing microbes. When organic wastes from the sewage enter the water bodies, it serves as a food source for micro-organisms such as algae and bacteria. As a result, the population of these micro-organisms in the water body increases. Here, they utilize most of the dissolved oxygen for their metabolism. This results in an increase in the levels of Biological oxygen demand (BOD) in river water and results in the death of aquatic organisms. Also, the nutrients in the water lead to the growth of planktonic algal, causing algal bloom. This causes deterioration of water quality and fish mortality.

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Q2 :  

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?


Answer :

Wastes generated at home include plastic bags, paper napkin, toiletries, kitchen wastes (such as peelings of vegetables and fruits, tea leaves), domestic sewage, glass, etc.

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.

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Q3 :  

Discuss the causes and effects of global warming. What measures need to be taken to control global warming?


Answer :

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Q4 :  

Match the items given in column A and B:

Column A

Column B

(a)

Catalytic converter

(i)

Particulate matter

(b)

Electrostatic precipitator

(ii)

Carbon monoxide and nitrogen oxides

(c)

Earmuffs

(iii)

High noise level

(d)

Landfills

(iv)

Solid wastes


Answer :

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Q5 :  

Write critical notes on the following:

(a) Eutrophication

(b) Biological magnification

(c) Groundwater depletion and ways for its replenishment


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Q6 :  

Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?


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Q7 :  

Discuss the role of women and communities in protection and conservation of forests.


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Q8 :  

What measures, as an individual, you would take to reduce environmental pollution?


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Q9 :  

Discuss briefly the following:

(a) Radioactive wastes

(b) Defunct ships and e-wastes

(c) Municipal solid wastes


Answer :

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Q10 :  

What initiatives were taken for reducing vehicular air pollution in Delhi?

Has air quality improved in Delhi?


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Q11 :  

Discuss briefly the following:

(a) Greenhouse gases

(b) Catalytic converter

(c) Ultraviolet B


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<< Previous Chapter 15 : Biodiversity and Conservation

Biology : CBSE NCERT Exercise Solutions for Class 12th for Environmental Issues will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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