The Greenhouse Effect

The ozone layer is a layer of ozone gas (O3) that absorbs harmful radiations (ultraviolet rays) from the sun, and prevents them reaching the earth. Large amount of ultraviolet rays is harmful to life on earth. Excess ultraviolet ray contribute to global warming and can causes skin cancer. The ozone layer absorbs most of the ultraviolet rays from the sun to reduce their levels on the earth’s surface. Now depletion of the ozone layer is the decline of the levels of the ozone layer in the atmosphere. The decline is due to reaction between chlorofluorocarbon and ozone to form oxygen molecules. This results in the creation of holes in ozone layer. The consequence of the depletion is increases levels of ultraviolet radiations reaching the earth, which contributes to warming of the earth. Greenhouse effect is a phenomenon whereby there is excessive warming of the earth (global warming) as a result of increase in average temperature near the earth. Global warming is caused by the build of carbon dioxide levels in the atmosphere, which insulates the atmosphere against the escape of heat reflected from the earth into space. Plants fix carbon as carbon dioxide in carbohydrates and other organic compounds through photosynthesis. Autotrophic bacteria also fix carbon as carbon dioxide into complex organic molecule through chemosynthesis. Animals depend directly or indirectly on plants for their carbohydrate requirement. This carbon is incorporated into their bodies. Dead plant and animal matter is decomposed by saprophytic bacteria and fungi to release carbon dioxide into the atmosphere. Carbon dioxide is also released into the atmosphere through respiration and combustion (burning) of fuels (petrol, wood, coal etc).