The Cycles of Matter
Matter on earth is limited, so the matte is used over and over again. Each kind of matter has its own cycle. Ion these
cycles, matter moves between the environment and living things. Can you think of the three natural cycles? They are the
water cycle, carbon cycle and the nitrogen cycle. Let’s talk about the water cycle first.
The Water Cycle
The movement of water, H20, between the rivers, oceans, our atmosphere and living thing is known as the water cycle.
The parts of the water cycler are evaporation, transpiration, condensation, and precipitation. During evaporation, the
sun’s heat causes water to change from liquid into a gas, or vapor; this vapor rises into our atmosphere. In the process
of condensation, the water vapor cools and returns to a liquid state. Condensation forms many different types of clouds.
Water is a very heavy element and once the water falls from the atmosphere to the land and oceans it is called
precipitation. Precipitation can come in many forms: rain, snow, sleet and hail. Most of the precipitation falls into the
oceans since they cover 70% of Earth’s surface. Some of the precipitation that falls on land flows into streams, rivers,
and lakes; it is called runoff. The rest of the water precipitation that falls on land soaks into the ground is known as
groundwater. Groundwater is stored for plants and eventually makes its way to streams, rivers and lakes.
The Carbon Cycle
Besides the water cycle, the most common molecules in living things are organic molecules- or molecules that contain
carbon. The exchange of carbon between the environment and living things is known as the carbon cycle.
Photosynthesis is the basis of the carbon cycle. Think about the photosynthetic process. During photosynthesis, plants
use carbon dioxide from the air to make glucose (sugar). Most animals get the carbon and energy they need by eating
plants. How does the carbon return to the environment? It returns when sugar molecules are broken down to release
energy. This process, called respiration, uses oxygen. Carbon dioxide and water are released as byproducts of
respiration.
The Nitrogen Cycle
Nitrogen is also important to living things. Organisms need nitrogen to build proteins and DNA for new cells. The
movement of nitrogen the environment and living thing is called the nitrogen cycle.
About 78% of earth’s atmosphere is nitrogen gas. Most organisms cannot use nitrogen as a gas directly. However,
bacteria in the soil are able to change nitrogen gas into forms that plants can use. This process ins called nitrogen
fixation. Other organisms may then get the nitrogen they need by eating plants or eating organisms that eat plants.
When that organism dies, decomposers break down the remains. Decomposition releases a form of nitrogen into the
soil that plants can used. Finally, certain types of bacteria in the soil convert nitrogen to a gas, which is returned to the
atmosphere and the cycle continues.
Other forms of matter on earth pass through cycles. Many of the minerals that living cells need, calcium and
phosphorous, are cycled through the environment. When an organism dies, every substance in its body is likely to be
recycled or reused. Many of these cycles are connected. For examples, some forms of nitrogen and carbon are carried
through the environment by water. Many nutrients pass from soil to plant to animals and back again. Living organisms
play a part in each of the cycles.