TOPIC OF THE DAY

Environment and Ecosystem

The Water-Cycle

• The whole process in which water evaporates and falls on the land as rain and water flows back into the sea via rivers is known as the water-cycle,
• As water flows through or over rocks containing soluble minerals, some of them get dissolved in the Water.
• Thus rivers carry many nutrients from the land to the sea, and these are used by the marine organisms.

The Nitrogen-Cycle

• Nitrogen gas makes up 78% of our atmosphere and nitrogen is also a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins found in other biologically important compounds such as alkaloids and urea to the nitrogen-fixing bacteria are found in the roots of legumes (generally the plants which give us pulses) in special structures called root nodules.
• Other than these bacteria, the only other manner in which the nitrogen molecule is converted to nitrates and nitrites is by a physical process.
• During lightning, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen.
• These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain.
• Plants generally take up nitrates and nitrites and convert them into amino acids which are used to make proteins
• Once the animal or the plant dies, other bacteria in the soil convert the various compounds of nitrogen back into nitrates and a different type of bacteria converts the nitrates and nitrites into elemental nitrogen.

The Carbon-Cycle

• It occurs in the elemental form as diamonds and graphite
• it is found as carbon dioxide in the atmosphere, as carbonate and hydrogen carbonate salts in various minerals,
• While all life-forms are based on carbon-containing molecules like proteins, carbohydrates, fats, nucleic acids and vitamins.
• The endoskeletons and exoskeletons of various animals are also formed from carbonate salts. Carbon is incorporated into life-forms through the basic process of photosynthesis which is performed in the presence of Sunlight by all life-forms that contain chlorophyll.
• This process converts carbon dioxide from the atmosphere or dissolved in water into glucose molecules

The Oxygen-Cycle

• In the crust, it is found as the oxides of most metals and silicon, and also as carbonate, sulphate, nitrate and other minerals.
• It is also an essential component of most biological molecules like carbohydrates, proteins, nucleic acids and fats (or lipids).
• Oxygen from the atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen.