Carbon (C) is the basis of life on Earth.
Scientists consider 99.9% of all organisms on the planet to be carbon based
life. Those organisms need carbon to survive. Whether the carbon is in the form
of a sugar or carbon dioxide gas, we all need it. Unlike energy, carbon is
continuously cycled and reused. The Earth only has a fixed amount of carbon.
The carbon cycle is the ultimate form of recycling.
Plants
are a good starting point when looking at the carbon cycle on Earth. Plants
have a process called photosynthesis that
enables them to take carbon dioxide out of the atmosphere and combine it with
water. Using the energy of the Sun, plants make sugars and oxygen molecules.
All of the non-photosynthetic creatures on the planet use the oxygen. Every
creature on the planet uses the sugars and starches created by plants.
Animals
are the non-photosynthetic creatures of the planet. They are not able to create
their own food. Instead, they eat plants or other animals. The sugars and
starches they eat are broken down by a process of metabolism. The results are
energy for the creature, water, and carbon dioxide molecules. The carbon
dioxide then returns to the atmosphere where the plants use it again.
There are also decomposers involved
in the carbon cycle. They break down organic material such as dead animals,
poop, or leaves. Decomposers are able to break down the chemical compounds
inside the body. They also release carbon dioxide as well as methane.
Sometimes the decomposers don't break down organic
material. There are great oil fields under the surface that are made of plants
that did not decompose millions of years ago. There are also layers of rock
made of millions of creatures who had shells. One day this carbon will return
to the everyday carbon cycle, but geological processes are much slower than
living processes.