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The oxygen cycle is based on the
very basic element called oxygen. It circulates through and around the earth in a biogeochemical cycle. During its cycle,
it travels through the atmosphere, lithosphere and hydrosphere, where it is present as a solid, liquid and gas. Uses for oxygen
include replenishing tired cells in plants and animals with energy, when mixed with acid and hydrogen causes weathering of
rocks and minerals, allows fires and fossil fuels to burn, a safety device in cars in the form of an air bag and
when mixed with hydrogen makes drinking water. Oxygen is one of the most abundant
elements on earth, however never found outside a compound. Common compounds include CO2 (carbon dioxide), H2O (water), O2
(air) and O3 (ozone). Oxygen, nitrogen and carbon support our atmosphere and environment. It is what distinguishes our life-sustainable
planet from all the rest. All living plants and animals require oxygen to survive. In its natural form, it is colorless, odorless
and tasteless. Oxygen makes up approximately 20% of the atmosphere, 50% of the lithosphere and 90% of the hydrosphere. It
is the third most abundant element in the universe and particularly essential in our environment on earth.
Atmospheric oxygen (O2)
is continually being circulated through plants and animals. As animals take in air, in a process called respiration,
it is converted into energy for their metabolism where it is broken down into water and carbon dioxide. The water replenishes
cells and carbon dioxide is released back into the atmosphere. Plants take in the carbon dioxide during photosynthesis
and use the gaseous compound that is now useless for animal metabolisms. Plants break it down where it is used as
an energy source. The used carbon dioxide is disposed of back into the atmosphere as oxygen, and the cycle continues.
Photosynthesis and respiration are the key part in the cycle of oxygen in any environment. In fact, the photosynthesis of
prehistoric plants contributed to the formation of the ozone. Since there weren’t as many or any
animals to consume the oxygen, it became very plentiful and as it surrounded the earth, protected it from harmful ultraviolet
radiation.
Other factors
in the oxygen cycle include the cycle of oxygen through the compound H2O (water) in the water cycle. This
sequence of events carries oxygen to the atmosphere, hydrosphere and lithosphere. In the
hydrosphere, oxygen is present in water (H2O), where respiration and photosynthesis also occur. Dissolved oxygen is taken
in by animals through special openings called gills. It is released as carbon dioxide and dissolves in the water, where it
can be absorbed by plants during photosynthesis and released back into the water. From the water cycle and through gaseous
atmospheric oxygen, the element can become part of different rock solids where it is present for long periods
of time, before weathering releases it to the lithosphere and into the water cycle. Oxygen’s abundance
in the lithosphere also comes from dead and decaying plants and animals and other buried
matter such as soil and rocks. Volcanic activity also returns massive
amounts of oxygen back to the cycle from the lithosphere after a lengthy period of time of being trapped underground.
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