All living things are made of carbon. Carbon is also a part of the ocean, air, and even rocks. Because the Earth is
a dynamic place, carbon does not stay still.
In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide. Plants use
carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant.
Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions
of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as
carbon dioxide.
oxygen cycle
Oxygen is an important element to life on Earth. It is the most common element of the human body.
It makes up about 65% of the mass of the human body. Most of this is in the form of water (H2O).
Oxygen also makes up about 30% of the Earth and 20% of the atmospher
Oxygen is constantly being used and created by different processes on planet Earth. All of these processes together make up the oxygen cycle. The oxygen cycle
is interconnected with the carbon cycle. In the simple example of the oxygen cycle, the oxygen is used and cycled by plants and animals. Plants are the main
creators of oxygen in the atmosphere through the process of photosynthesis. Here the tree uses sunlight and carbon dioxide to produce energy and releases
oxygen. The giraffe breathes in the oxygen and then breathes out carbon dioxide. The plant can then use this carbon dioxide and the cycle is complete. Simple
diagram of the oxygen cycle
Nitrogen is one of the primary nutrients critical for the survival of all living organisms. Although
nitrogen is very abundant in the atmosphere, it is largely inaccessible in this form to most organisms.
This article explores how nitrogen becomes available to organisms and what changes in nitrogen
levels as a result of human activity means to local and global ecosystems.
Nitrogen is one of the primary nutrients critical for the survival of all living organisms. It is a
necessary component of many biomolecules, including proteins, DNA, and chlorophyll. Although
nitrogen is very abundant in the atmosphere as dinitrogen gas (N2), it is largely inaccessible in this
form to most organisms, making nitrogen a scarce resource and often limiting primary productivity
in many ecosystems. Only when nitrogen is converted from dinitrogen gas into ammonia (NH3) does
it become available to primary producers, such as plants. In addition to N2 and NH3, nitrogen exists
in many different forms, including both inorganic (e.g., ammonia, nitrate) and organic (e.g., amino
and nucleic acids) forms. Thus, nitrogen undergoes many different transformations in the
ecosystem, changing from one form to another as organisms use it for growth and, in some cases,
energy. The major transformations of nitrogen are nitrogen fixation, nitrification, denitrification,
anammox, and ammonific