Importance of air for survival of plants and animals
Plants require energy for their growth and
hence respiration also occurs in plants. During respiration, plants take in
oxygen and release carbonâ€“diâ€“oxide, just as animals do. Gaseous exchange with
air in atmosphere takes place in plants with the help of tiny holes called
stomata present on their leaves.
Plants manufacture food
by a process called photosynthesis. During photosynthesis, Carbon-di-oxide from
the air and water from the soil react in the presence of sunlight to produce
food. Most plants possess a green pigment called chlorophyll and it is also
used-up in the process of photosynthesis. The word equation given below
explains the process of photosynthesis.
+water --- Sunlight Chlorophyllâ†’ Food + Oxygen Chlorophyll
Plants release oxygen during photosynthesis which is much more than the oxygen consumed by the plants, during respiration.
When we breathe in air, the oxygen present in the air reacts chemically with digested food within the body to produce carbon-di-oxide gas, water vapour and energy.
This energy is required to carry out many
processes in the body such as movement, growth and repair. This process by
which oxygen reacts with digested food to form carbon-di-oxide, water vapour
and energy is called respiration. The process can be represented by a word
equation as given below :-
Food + Oxygen â†’ Carbon-di-oxide +
water + Energy
formed during respiration dissolves in the blood and is exhaled out of the body
through the lungs. The inhaled and exhaled air thus contain the same substances
but in different proportion, except nitrogen which is present in the same
amount. Inhaled air contains more oxygen while the exhaled air contains more
Let us have a look
at the following table to compare the composition of air in inhaled and exhaled
Respiration of plants and animals in water
The water of ponds,
lakes, rivers and seas have some amount of dissolved air containing oxygen in
it. The plants and animals that live in water use the oxygen dissolved in water
for breathing. For example, frogs respire through their skin, fish respire
using their gills.
carbon-di-oxide is cooled to -570 C, it directly becomes a solid, without
changing to its liquid state. It is called dry ice and is a good refrigerating agent.
Dry ice is used in trucks or freight cars for refrigerating perishable items
such as meat and fish while transporting them.