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AP Enviro



Unit 1

1.4 The Carbon Cycle

3 min readmay 1, 2020

Sumi Vora

Movement of Matter 

The earth is a closed system; matter can never be removed or created. Instead, matter moves across the earth in cycles called biogeochemical cycles. These basic cycles are essential for supporting life on Earth, but when they are disrupted, it can cause matter to get “stuck” or move too quickly between stages. 

Carbon Cycle 🌋

The carbon cycle is the movement of carbon across the earth. The carbon has two stages: the fast stage, which is associated with living organisms, and the slow stage, which is associated with dead organisms (fossil carbons). However, there are also many mini-cycles within the carbon cycle.

Image Courtesy of Wikimedia Commons

The first mini-cycle occurs on land. When plants carry out photosynthesis, they use CO2 from the atmosphere. Plants release some of that CO2 back into the atmosphere with cellular respiration, but they keep most of it within their plant tissues. Next, the plant will die, or it will be eaten by another organism that will eventually die. The dead matter, which contains carbon, will be processed by decomposers and exist in the soil so that more plants can use it. 
There are two mini-cycles that take place in the ocean. The first process that occurs in the ocean is carbon exchange: the ocean absorbs some CO2 from the atmosphere, and it releases roughly the same amount of CO2 back into the atmosphere. 
The second process that occurs in the ocean is sedimentation. The CO2 combines with calcium ions in the water to form calcium carbonate, which sinks to the bottom of the ocean and accumulates. 
In all of these mini-cycles, carbon either ends up back in the atmosphere, or it slowly accumulates in the ground in the form of fossil fuels. This is the slow part of the carbon cycle. Before humans started extracting fossil fuels, the amount of carbon that would be deposited into the ground was roughly the same as the amount of carbon that had risen back up from the ground or through volcanoes and released back into the atmosphere. 

Human Impacts on the Carbon Cycle 🙌

After we discovered that we can use fossil fuels for industrial processes, we have been extracting them way too fast. The rate at which carbon is being deposited back into the ground through sedimentation is much slower than the rate at which we are extracting fossil fuels. This means that two things will happen: we will eventually run out of fossil fuels, and we are putting way more carbon in the atmosphere than we are supposed to have, which is causing global climate change. 
Another way that humans disrupt the carbon cycle is through deforestation. Since there are fewer plants to absorb the carbon in the atmosphere, there is even more carbon that is stuck in the atmosphere, which further exacerbates global warming
🎥 To learn more about the carbon cycle, watch this stream.


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Unit 2: The Living World: Biodiversity
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