Oxygen Likes all Elements
If you have ever tried to hold your breath for a long time, you know that it is not possible to hold it for very long. The cells in your body, especially your brain cells, will die if they donít get oxygen. Your body needs a constant supply of oxygen because it is critical for the process of breaking down glucose for energy. In the process of getting energy from glucose, oxygen is combined with hydrogen to form a water molecule.
photosynthesis (See Story Time), a water molecule is split by sunlight in the
energy-forming step. This releases oxygen into the
atmosphere. Animals consume
oxygen just as fast as plants can provide it, so it seems that the amount
of oxygen in the atmosphere would remain constant.
However, according to fossil records, plants existed on the earth
long before the animals. This
means that an excess amount of oxygen was released to the atmosphere
from the photosynthetic plants with no animals to consume it through respiration. Therefore,
until animals began to evolve on the earth, the oxygen content of air continued to increase.
exchange of oxygen seems simple at first:
Oxygen is present in many other compounds besides water. It gets involved with the recycling of elements discussed below because it reacts with all of them. It forms compounds such as nitrate (NO3), sulfur dioxide (SO2), phosphate (PO4), carbon dioxide (CO2), and water (H2O).
In the lower atmosphere, pollutants such as nitrous oxide and volatile hydrocarbons contribute to the production of ozone. This creates the ugly smog that is present in big cities like New York, Los Angeles, and Houston.
Thinning of the ozone in the stratosphere could cause many problems that include altering DNA, increasing the chance of getting skin cancer, and contributing to a global warming of the earth.