(i) The formation and destruction of ozone is a regular natural process, which never disturbs the equilibrium level of ozone in the stratosphere. Any change in the equilibrium level of ozone in the atmosphere will adversely affect the life in biosphere in the following ways.
(ii) Depletion of ozone layer will allow more UV rays to reach the earth surface an would cause skin cancer and also decreases the immunity level in human beings.
(iii) UV radiations affects plant proteins which lead to harmful mutation in plant cells.
(iv) UV radiations affect the growth of phytoplankton and as a result ocean food chain is disturbed and it even damages the fish productivity.

(i) The three main components of photochemical smog are nitrogen oxide, ozone and oxidised hydrocarbons like HCHO, CH₂ = CH - CHO and PAN.
(ii) Photochemical smog causes irritation to eyes, skin and lungs. It also increases the chance of asthma.
(iii) High concentration of ozone and NO can cause nose and throat irritation, chest pain, difficulty in breathing
(iv) PAN is toxic to plants, attack younger leaves and cause bronzing and glazing of their surfaces.
(v) It causes corrosion of metals, stones, building materials and painted surfaces.

(i) Dust, mist, fumes etc. are air borne particles which are dangerous for human health. Particulate pollutants bigger than 5 microns are likely to settle in the nasal passage whereas particles of about 10 microns enter the lungs easily and causes scaring or fibrosis of lung lining. They irritate the lungs causes cancer and asthma. This disease is called pneumoconiosis. Coal miners may suffer from black lung disease. Textile workers may suffer from white lung disease.
(ii) Lead particulates affect children's brain, interferes with the maturation of RBC's and even causes cancer.
(iii) Particulates in the atmosphere reduces the visibility by scattering and absorption of sunlight. It is dangerous for aircraft and motor vechiles.
(iv) Particulates provide nuclei for cloud formation and increase fog and rain.
(v) Particulates deposit on plant leaves and hinder the intake of CO₂ from the air and affect photosynthesis.

Earth's atmosphere can be divided into different layers with characteristic altitude and temperature. 

Degradation of water quality by the addition of substances like chemical effluents, metal residues, sewage, oil, detergent, etc. is called water pollution.
Water pollution can be controlled by the following methods :
(i) Industrial waste should not be allowed to get mixed in water bodies such as river, lakes, etc.
(ii) Check the pH of water regularly.
(iii) Excersive usage of fertilizers should be controlled.
(iv) Oil spills must be avoided as much as possible.
(v) Avoid the usage of DDT and malathion at home.
(vi) Waste water should be treated properly.
(vii) Avoid the usage of non - biodegradable detergents for cleaning of clother.