Unit 2: The atmosphere                                                       1   2   3   4   5

5. The importance of the atmosphere

The atmosphere has some characteristics that provide Earth with the right environment for life.

The air contains some of the raw materials necessary for life and protects the Earth against harmful radiations and the impact of meteorites:

- Carbon dioxide is necessary for photosynthesis.

- Oxygen is necessary for respiration.

- Carbon dioxide maintains the optimal temperature conditions for life

  to develop, thanks to the greenhouse effect.

- The ozone layer protects living things from harmful ultraviolet radiation

  from the sun.

- Water vapour condenses and forms clouds, which provide water through

  rainfall.

- Rocky bodies from the outer space are disintegrated by friction

  with the atmospheric gases.

Changes in the composition of the atmosphere have serious consequences for living beings.

a) Atmospheric pollution      

     Human activities cause atmospheric pollution: the release of harmful

     substances called pollutants into the atmosphere. They can be:

             - Gases: sulphur dioxide, carbon dioxide and nitrogen oxide.

               They are produced by combustion from motor vehicles,

               by burning fossil fuels, and from industrial activities.

             - Liquid and solid molecules: ash from forest fires, black smoke,

               dust and soot.

     Pollutants in the air can cause health problems: respiratory system

     irritation, eye irritation, increase in asthmatic processes, headaches.

b) Acid rain

     Some pollutants such as sulphur dioxide and nitrogen oxide, form acids

     when mixed with water vapour of the air.

     When it rains, these acids fall down mixed with water. This damages plants,

     and pollutes rivers and lakes destroying aquatic life. Acid rain also

     damages the monuments.

c) The destruction of the ozone layer

   CFCs are gases often used in fridges, air conditioning units, aerosols, etc.

   These gases interact with ozone and destroy it. Without the ozone layer,

   ultraviolet radiation can arrive to Earth’s surface and provoke mutations

   in living beings.

   The destruction of the ozone layer mainly affects Antarctica, where we can

   find ozone hole.

d) An increase in the greenhouse effect  

The increase in the greenhouse effect has two main causes:

       - Contamination: increase the amount of CO₂ in the atmosphere.

       - Deforestation: the destruction of forest, which could have consumed

         this excess of CO₂ through photosynthesis

The direct consequence of an increase of greenhouse effect is

global warming: an increase in the global temperature of the planet.

Global warming could have many other consequences:

- The melting of ice masses at the Poles will raise sea levels and many coastal

   areas will disappear

- It will increase evaporation, and the global pattern of rain and winds

  will change.

- Desertification will increase in many areas, while in others there will be

  torrential rains.

- Many animals and plants would disappear.

- The higher temperatures will provoke the spread of many tropical diseases

   to temperate areas.

Animación: Efectos de la contaminación atmosférica (SM)

5.1. Why is the atmosphere so important for living beings?

5.2. Listen and relate each sentence with the role of the atmosphere as:

5.3. What is atmospheric pollution?

5.4. Answer the questions:

       a. What pollutant is responsible for the destruction of the ozone layer?

           Where do they come from?

       b. What pollutant is responsible for the increase of the greenhouse effect?

           Where do they come from?

       c. What pollutant is responsible for the acid rain?

           Where do they come from?

5.5. Identify the consequences of the global warming among the sentences:

a. The melting of ice masses at the Poles

b. The increase of mutations

c. The raising of sea levels

d. The alteration of global climate

e. The increase of the size of the ozone hole

f. The acid rain

g. The increment of tropical diseases

h. The extinction of many species

i. The increment of the greenhouse effect

j. The disappearance of lands near the coasts

5.6. Listen and identify what environmental problem is described: