Class 12 Biology - Chapter Environmental Issues NCERT Solutions | Why ozone hole forms over Antarctica? Ho
Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?
The ozone hole is more prominent over the region of
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.
More Questions From Class 12 Biology - Chapter Environmental Issues
- Q:- Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
- Q:- Discuss briefly the following:
(a) Radioactive wastes
(b) Defunct ships and e-wastes
(c) Municipal solid wastes - Q:- Write critical notes on the following:
(a) Eutrophication
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment - Q:- What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
- Q:- Discuss the role of women and communities in protection and conservation of forests.
- Q:- What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
- Q:- 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?
- Q:- Discuss briefly the following:
(a) Greenhouse gases
(b) Catalytic converter
(c) Ultraviolet B - Q:- What measures, as an individual, you would take to reduce environmental pollution?
- Q:- 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
Popular Questions of Class 12 Biology
- Q:- Why is reproduction essential for organisms? Answer
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- Q:-
Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
(b) Humans are__________. (oviparous/viviparous/ovoviviparous)
(c) Fertilization is __________ in humans. (external/internal)
(d) Male and female gametes are __________. (diploid/haploid)
(e) Zygote is __________. (diploid/haploid)
(f) The process of release of the ovum from a mature follicle is called__________.
(g) Ovulation is induced by a hormone called the __________.
(h) The fusion of male and female gametes is called _____________.
(i) Fertilisation takes place in _____________.
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between fetus and uterus is called ____________. - Q:- What do you think is the significance of reproductive health in a society?
- Q:- Mention the advantages of selecting pea plant for experiment by Mendel.
- Q:- Group the following as nitrogenous bases and nucleosides:
Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine. - Q:- Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
- Q:- What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q:- Explain in brief the role of animal husbandry in human welfare.
- Q:- Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
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2 Comment(s) on this Question
Suraj singh really
ok you are right there is high concentration of chlorine in atmosphere of antartica but the reason of this high conc. are stratospheric clouds which formed during colder weather in antartica these clouds enhance the catalytic role of Chloride in stratosphere.
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