Cycles Of Matter
The cycles of matter are summarized as the hydrologic cycle, the carbon cycle, and the nitrogen cycle.
The Hydrologic Cycle
The hydrologic cycle begins with the evaporation of water from the surface of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation. Once the water reaches the ground some of the water may evaporate back into the atmosphere or the water may penetrate the surface and become groundwater. Groundwater either seeps its way to into the oceans, rivers, and streams, or is released back into the atmosphere through transpiration. The balance of water that remains on the earth's surface is runoff, which empties into bodies of water and is carried back to the ocean, where the cycle begins again.
The Carbon Cycle
The CO2 in the air is taken in by green plants for photosynthesis. The green plants die eventually and is decomposed; decomposition return carbon to the atmosphere. Animals respire and return carbon dioxide to the atmosphere. Decomposers respire as well. Green plants can be used to make fuels, which combust to return carbon dioxide to the air.
The Nitrogen Cycle
In order for plants and animals to be able to use nitrogen, N2 gas must first be converted to more a chemically available form such as ammonium (NH4+), nitrate (NO3-), or organic nitrogen (e.g. urea - (NH2)2CO). The inert nature of N2 means that biologically available nitrogen is often in short supply in natural ecosystems, limiting plant growth. Microorganisms, particularly bacteria, play major roles in all of the principal nitrogen transformations. Because these processes are microbially mediated, or controlled by microorganisms, these nitrogen transformations tend to occur faster than geological processes like plate motion, a very slow, purely physical process that is a part of the carbon cycle. Instead, rates are affected by environmental factors that influence microbial activity, such as temperature, moisture, and resource availability.
Nitrogen Fixation- Nitrogen fixation is the process wherein N2 is converted to ammonium, or NH4+. This is the only way that organisms can attain nitrogen directly from the atmosphere; the few that can do this are called nitrogen fixing organisms. They take the nitrogen from the atmosphere and it becomes available to plants through the soil.