(a) Why and how must the ozone layer in the stratosphere be protected? Explain.

(b) How do deforestation and green house gases negatively affect our environment? Explain.

OR

Biomagnification and accelerated eutrophication are both caused due to indiscriminate use of chemicals and irresponsible human activities. Do you agree? Support your answer with explanation and an example of each.

a) Ozone layer must be protected because it acts as shield and absorbs ultraviolet radiation from the sun. The UV rays are highly injurious to living organism cause causing skin cancer, accelerated aging, snow blindness and cataract. They even damage the DNA and proteins. Ozone layer can be protected by reducing the use of or the emission of chlorofluorocarbons (CFCs.)

b)

• Deforestation leads to an increase in the carbon dioxide concentration in the atmosphere.

• It causes loss of biodiversity due to habitat destruction and disturbs the hydrological cycle.

• It also causes soil erosion and leads to desertification in extreme cases.

• An increase in the level of green house gases leads to the increase in the Earth’s overall temperature, leading to global warming.

• Deleterious changes in the environment result in odd climatic changes such as the El Nino effect.

• There is an increased melting of polar ice caps, Himalayan snow caps.

• There is also a rise in sea levels due to which the costal areas may get submerged.

OR

• Yes, biomagnifications and accelerated eutrophication are both caused due to indiscriminate use of chemicals and irresponsible human activities.

• Biomagnifications is the increase in concentration of toxic substances at successive trophic levels.

• Example: In the aquatic food chain the concentration of DDT increases at each trophic level. It starts at 0.003 ppb and reaches up to 25 ppm in fish eating birds. This causes thinning of the egg shells, premature breaking of egg shell and as a result, a decline in bird population.

• Accelerated eutrophication is caused due to accumulation of industrial and domestic waste into water bodies.

• Prime contaminants are nitrates and phosphates which act as plant nutrients and over-stimulate the growth of algae causing scum, unpleasant odour and an overall reduction in the dissolved oxygen in water bodies.

• This leads to fish mortality and the death of the lake.