SULFUR AND OXYGEN CYCLES
The cycling of
is important for proteins, which have the
- containing amino acids cysteine and cystine. The
cycle is
similar to the phosphorus cycle, as it only contains a brief atmospheric
component.
is mainly found in rocks and soil (coal, oil, and peat)
as sulfate minerals. Weathering (by the
cycle) exposes sulfates in
the rocks, and helps remove them into the soil and aquatic ecosystems.
In both these ecosystems, plants and other photosynthetic organisms
take up and assimilate sulfates into their tissues.
eat the plants and likewise assimilate sulfates into their
tissues. Death and
convert organic sulfates into inorganic sulfates.
Animal
also add sulfates to the soil or water. Sulfates then recycle.
There is one important difference between the sulfur cycle and the
phosphorus cycle, however. The sulfur cycle does contain a small
atmospheric component. Atmospheric hydrogen sulfide sources include
and
emissions from burning fossil fuels which
contain sulfur. In the atmosphere, hydrogen sulfide gas quickly breaks
down into sulfur dioxide, where it combines with water vapor to form
This combines with rain water to form
thereby
returning sulfur to the soil and water ecosystems.
Molecular
is a critical substance for living things. It is a byproduct of
and a reactant in respiration.
is very chemically
reactive. The combination of biology and chemistry help to cycle
oxygen on Earth. When talking about the way that oxygen cycles on
Earth, you will always see it in association with the carbon cycle. They
work hand in hand, cycling these two nutrients in a vital way.
The main supply of
on Earth is the atmosphere, which is
21% this gas. Oxygen cycles between the atmosphere, living organisms,
aquatic ecosystems and Earth’s crust. It can be removed, or added.
Processes responsible for the removal include chemically reacting with
rocks and minerals exposed by weathering. Certain red rocks were
originally composed of
which has reacted with the O2 in the
atmosphere to produce “rust”, or
by producers,
consumers, and decomposers also removes oxygen from the atmosphere.
Oxygen is produced through the process of photosynthesis, when plants
SULFUR AND OXYGEN CYCLES
use CO2 and
in the presence of sunlight, and generate
and
oxygen.
occurs when sunlight breaks down water vapor in
the atmosphere, into hydrogen and oxygen. The hydrogen escapes to
outer space and the oxygen remains. This oxygen can combine with
diatomic molecular oxygen to produce triatomic oxygen, also known as
This gas is a vital part of Earth’s atmosphere, at least where it
belongs, in an area of the
(atmospheric layer), known as the
layer. The formation of triatomic oxygen on Earth MUST have
predated the origin of life, as living cells and more complex tissue could
not survive without its protective value. O3 sits in this layer and absorbs
most of the incoming
radiation, which is destructive to cells.