Carbon/Water Cycle

Where does the water come from that is needed by your cells? Or the carbon and nitrogen that is needed to make your organic molecules? Unlike energy, matter is not lost as it passes through an ecosystem. Instead, matter is recycled. This recycling involves specific interactions between the biotic and abiotic factors in an ecosystem.

Biogeochemical Cycles

The chemical elements and water that are needed by organisms continuously recycle in ecosystems. They pass through biotic and abiotic components of the biosphere. That’s why their cycles are called biogeochemical cycles. For example, a chemical might move from organisms (bio) to the atmosphere or ocean (geo) and back to organisms again. Elements or water may be held for various periods of time in different parts of a cycle. ”

“Water on Earth is billions of years old. However, individual water molecules keep moving through the water cycle. The water cycle is a global cycle. It takes place on, above, and below Earth’s surface, as shown in Interactive 11.1.

During the water cycle, water occurs in three different states: gas (water vapor), liquid (water), and solid (ice). Many processes are involved as water changes state in the water cycle. ”

“Water changes to a gas by three different processes:

Evaporation occurs when water on the surface changes to water vapor. The sun heats the water and gives water molecules enough energy to escape into the atmosphere.

Sublimation occurs when ice and snow change directly to water vapor. This also happens because of heat from the sun.

Transpiration occurs when plants release water vapor through leaf pores called stomata (see The water is a product of photosynthesis.

Condensation and Precipitation

Rising air currents carry water vapor into the atmosphere. As the water vapor rises in the atmosphere, it cools and condenses. Condensation is the process in which water vapor changes to tiny droplets of liquid water. The water droplets may form clouds. If the droplets get big enough, they fall as precipitation—rain, snow, sleet, hail, or freezing rain. Most precipitation falls into the ocean. Eventually, this water evaporates again and repeats the water cycle. Some frozen precipitation becomes part of ice caps and glaciers. These masses of ice can store frozen water for hundreds of years or longer. ”

“Precipitation that falls on land may flow over the surface of the ground. This water is called runoff. It may eventually flow into a body of water. Some precipitation that falls on land may soak into the ground, becoming groundwater. Groundwater may seep out of the ground at a spring o or into a body of water such as the ocean. Some groundwater may be taken up by plant roots. Some may flow deeper underground to an aquifer. This is an underground layer of rock that stores water, sometimes for thousands of year”

“Flowing water can slowly dissolve carbon in sedimentary rock. Most of this carbon ends up in the ocean. The deep ocean can store carbon for thousands of years or more. Sedimentary rock and the ocean are major reservoirs of stored carbon. Carbon is also stored for varying lengths of time in the atmosphere, in living organisms, and as fossil fuel deposits. These are all parts of the carbon cycle, which is shown in Figure 11.9.

As it travels through the environment, these five steps of the carbon cycle ensure a healthy, equal distribution of this life-sustaining element: 

1. Carbon enters the atmosphere via carbon dioxide.

Through breathing and other metabolic processes, humans and animals release carbon atoms into the atmosphere as carbon dioxide. Carbon atoms are also released through other human activities, such as burning fuels and composting.

2. Carbon dioxide is absorbed and used as energy.

Plants make use of airborne carbon atoms, absorbing them via photosynthesis. These atmospheric carbon compounds generate energy necessary for plants and other producer organisms to thrive.

3. Carbon compounds enter the food chain.

When carbon-containing plants are consumed, carbon atoms are absorbed by the humans and animals that eat them. As these atoms travel through the food chain, carnivorous and omnivorous animals get carbon from the animals they consume.

2. Carbon dioxide is absorbed and used as energy.

Plants make use of airborne carbon atoms, absorbing them via photosynthesis. These atmospheric carbon compounds generate energy necessary for plants and other producer organisms to thrive.

3. Carbon compounds enter the food chain.

When carbon-containing plants are consumed, carbon atoms are absorbed by the humans and animals that eat them. As these atoms travel through the food chain, carnivorous and omnivorous animals get carbon from the animals they consume.

4. Carbon reenters the atmosphere via decomposition.

Now that carbon atoms are available again for organic absorption, the particles can travel through the air, into plants, and through the steps of the cycle indefinitely. 

5. The carbon cycle repeats.

When plants and animals die, decomposition prompts the release of carbon into the air. Carbon atoms can also enter the planet’s bodies of water, soil reserves, and mineral deposits. 

What Two Processes Fuel the Carbon Cycle?

Ultimately, the carbon cycle relies heavily on two natural mechanisms: photosynthesis and cellular respiration (also referred to as metabolism). 

1. Photosynthesis

With photosynthesis, plants intake carbon dioxide to produce energy and maintain growth, emitting oxygen in the process. 

2. Cellular Respiration

During cellular respiration, organisms use oxygen to convert food and water into energy, producing carbon dioxide as a result. 

These two processes work in tandem to keep the natural carbon cycle going—and global reservoirs in balance.