Chapter 14: NATURAL RESOURCES

1.       The utilization of glucose to provide energy to living things involves the process of respiration in which oxygen may or may not be used to convert glucose back into carbon dioxide.

2.       This carbon dioxide then goes back into the atmosphere.

3.       Another process that adds to the carbon dioxide in the atmosphere is the process of combustion where fuels are burnt to provide energy for various needs like heating, cooking, transportation and industrial processes.

4.       In fact, the percentage of carbon dioxide in the atmosphere is said to have doubled since the industrial revolution when human beings started burning fossil fuels on a very large scale.

5.       Carbon, like water, is thus cycled repeatedly through different forms by the various physical and biological activities.

THE OXYGEN-CYCLE

Occurrence of Oxygen:

1.       Oxygen is a very abundant element on our Earth.

2.       It is found in the elemental form in the atmosphere to the extent of 21%.

3.       It also occurs extensively in the combined form in the Earth’s crust as well as also in the air in the form of carbon dioxide.

4.       In the crust, it is found as the oxides of most metals and silicon, and also as carbonate, sulphate, nitrate and other minerals.

5.       It is also an essential component of most biological molecules like carbohydrates, proteins, nucleic acids and fats (or lipids).

Oxygen cycle:

1.       The oxygen-cycle is the cycle that maintains the levels of oxygen in the atmosphere.

2.       Oxygen from the atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen.

3.       Oxygen is returned to the atmosphere in only one major process, that is, photosynthesis.

4.       And this forms the broad outline of the oxygen-cycle in nature.

5.       Though we usually think of oxygen as being necessary to life in the process of respiration, it might be of interest to you to learn that some forms of life, especially bacteria, are poisoned by elemental oxygen.

6.       In fact, even the process of nitrogen-fixing by bacteria does not take place in the presence of oxygen.

Ozone Layer:

What is Ozone? How does it forms in Nature? What is its role?

1.       Elemental oxygen is normally found in the form of a diatomic molecule. However, in the upper reaches of the atmosphere, a molecule containing three atoms of oxygen is found.

2.       This would mean a formula of O3 and this is called ozone. Unlike the normal diatomic molecule of oxygen, ozone is poisonous and we are lucky that it is not stable nearer to the Earth’s surface.

3.       But it performs an essential function where it is found. It absorbs harmful radiations from the Sun.

4.       This prevents those harmful radiations from reaching the surface of the Earth where they may damage many forms of life.

5.       Recently it was discovered that this ozone layer was getting depleted.

6.       Various man-made compounds like CFCs (carbon compounds having both fluorine and chlorine which are very stable and not degraded by any biological process) were found to persist in the atmosphere.

7.       Once they reached the ozone layer, they would react with the ozone molecules.

8.       This resulted in a reduction of the ozone layer and recently they have discovered a hole in the ozone layer above the Antartica.

9.       It is difficult to imagine the consequences for life on Earth if the ozone layer dwindles further, but many people think that it would be better not to take chances.

10.   These people advocate working towards stopping all further damage to the ozone layer.

THE GREENHOUSE EFFECT

1.       If glass house (or polythene house) is observed during the sunny days, heat is trapped by glass, and hence the temperature inside a glass (or polythene) enclosure will be much higher than the surroundings.

2.       This phenomenon was used to create an enclosure where tropical plants could be kept warm during the winters in colder climates.

3.       Such enclosures are called greenhouses.

4.       Greenhouses have also lent their name to an atmospheric phenomenon.

5.       Atmosphere of Earth contains many gases.

6.       Some gases like carbon dioxide, methane, H2S,  prevent the escape of heat from the Earth.

7.       An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase worldwide and this is called the greenhouse effect.

8.       Carbon dioxide is one of the greenhouse gases. An increase in the carbon dioxide content in the atmosphere would cause more heat to be retained by the atmosphere and lead to global warming.

9.       Increase in Carbon dioxide contents is due to emissions through vehicles, industries and other human activities.