Tag: the earth and its living world

Weather is the state of the atmosphere which can change on a daily basis. It describes the degree to which it is hot or cold , humid or dry, calm or stormy etc. therefore, it cannot be the seasonal change in the atmosphere as that would mean changing of seasons. It cannot be average variation of atmospheric conditions as that would be climate change. It cannot be all of the above because two options indicate season and climate. So the correct answer is 'Short term properties of atmosphere.'

Carbon dioxide is a colourless gas with a density of about 60% higher than that of dry air. Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms. It occurs naturally in Earth's atmosphere as a trace gas. The current concentration is about 0.04% (410 ppm) by volume, having risen from pre-industrial levels of 280 ppm. Carbon dioxide is odourless at normally encountered concentrations. However, at high concentrations, it has a sharp and acidic odour.

Life is not possible without a stable atmosphere containing the right chemical ingredients for living organisms: hydrogen, oxygen, nitrogen, and carbon. These ingredients must be balanced. Therefore we need carbon dioxide, ozone as well as water vapours. These are present in minute quantities but are essential for life. So the correct answer is ' Carbon dioxide, ozone and water vapours'.

The resources can be divided into 5 types based on the resources of earth. These are Tej, Marut, Ap, Khsiti and Vyom. Tej is a basic resource from sun. Marut is basic resource from wind. Ap is basic resource from water. Khsiti is basic resource of earth. It represents air. Vyom is the basic resource of explorating space.

Temperatures in the mesosphere decrease with altitude. Because there are few gas molecules in the mesosphere to absorb the Sun’s radiation, the heat source is the stratosphere below. The mesosphere is extremely cold, especially at its top, about -90 degree Celsius.  So the correct answer is ' it decreases from -2 to -92 degrees. '

The UV-A radiations are scattered and reach the surface of the earth continually. These are the least harmful radiations. The UV-B and UV-C are the most harmful radiations are capable of burning the human skin within 15 minutes of the exposure. These are absorbed by the ozone layer in the stratosphere. The ozone depletion results in the exposure of the earth surface to the UV-B and UV-C causing immunity problems, skin cancers, chlorophyll bleaching etc.