Natural Resources Test - 19

• The presence of the layer of ozone (trioxygen) prevents the UV rays from reaching the surface of the earth.
• The reactions that occurs to form ozone from oxygen are shown below:

The ozone layer absorbs the harmful ultraviolet (UV) rays from the Sun. The ozone layer depletion causes an increase in surface UV-B levels, which makes direct contact with the skin. This could lead to serious damage to the skin, and can also result in skin cancer.

The roots of plants and trees hold the soil together. Soil surface that is bare or lacks vegetation is subjected to removal very quickly. The detachment of soil particles of the top layer of soil by raindrops and their removal down the slope with the flow of water is often referred to as topsoil erosion. This is mainly observed in hilly areas. Heavy rains tend to wash the top layer of soil easily down the hilly terrain.

• The various greenhouse gases are carbon dioxide, methane, chlorofluorocarbons (CFCs), and nitrogen oxide. 
• Other minor contributors are water vapours and ozone. 
• The rise in carbon dioxide concentration is due to large scale deforestation (for grazing land, cropping land or urban settlements), change in land use pattern and large scale combustion of fossil fuels. 
• Methane is produced by incomplete biomass combustion, incomplete decomposition mostly by anaerobic methanogens. 
• CFCs are inert propellants used in aerosol cans and jet fuel, refrigerants in air conditioner and refrigerators. 
• Thus, the correct answer is option D. 

Crop rotations help organic systems to protect our environment. They involve changing the type of crop grown in one area on a regular basis. Organic farmers, plant alternate groups of plants (roots, cereals, brassicas, legumes etc.) to add fertility and prevent pests and diseases from building up.

• The major source of $$O_2$$ liberation is photosynthesis and about 90% of total photosynthesis is done by phytoplankton (floating plants)

Protein is present inside the body of plant and animals. The protein degrade and the decaying biomass undergoes ammonification. In nitrogen cycle, the nitrogen is converted into its various chemical forms and ammonification takes place. 

 

The fertility of the soil is not only determined by its ability to hold water or organic materials or its capacity to retain nutrients. It is determined by all of its characteristics combined and how well it can support life. It is considered to be very fertile soil when plants thrive in abundance, microorganisms thrive in abundance, and adequate resources are available.

So. the correct answer is option D.