The Carbon Cycle

Описание: Transcript:
Because the earth is finite, matter has to be reused and recycled over and over again. So, the atoms that are in you, were once in the air, in soil, in water, and in rocks. These atoms have also been used by countless other living things, from dinosaurs, to broccoli plants, to Abraham Lincoln. And after they leave you, they will become part of other living things or of the environment. This recycling of matter is known as a nutrient cycle and there are several different nutrient cycles for different elements. Today, we will focus on the carbon cycle, the process by which the element carbon moves around in ecosystems.
The carbon cycle is crucial for all life on earth because carbon is needed to make every single organic molecule needed by all living things! This includes carbohydrates, lipids, proteins, and nucleic acids! Because carbon is so necessary, we often say that life on earth is carbon-based! Without carbon, there would be, literally, no life as we know it. So, the carbon cycle is a really important cycle. Let’s get into it!
Carbon Dioxide (CO2) is a gas that makes up a small percentage of our atmosphere. Nevertheless, it is extremely important because plants take in CO2 during photosynthesis and use it to make sugars (like glucose), and other organic compounds. This is how plants grow and make the food that supports life in ecosystems. Notice that plants remove carbon dioxide from the atmosphere during photosynthesis, using the carbon to build carbon-rich molecules like glucose.
These carbon compounds can be broken down by the plant to produce ATP (a key energy molecule used by living things), in a process called cell respiration. Respiration produces CO2 that is released back to the atmosphere. You may have noticed that we have already completed a cycle since the carbon atoms have ended up back where they started.
But this is not the only path that carbon atoms can take. Some of the carbon atoms are stored long-term in plants, and others make their way into animals and other consumers. Anytime an organism eats another organism, carbon moves into the eater. This carbon is used to build the organic molecules that make up the bodies of living things. It can also be used in respiration, to make the ATP energy that animals need to function. Respiration from animals also produces CO2 that the animals breathe back out, returning it to the atmosphere (or water if you’re aquatic).
When organisms die or produce wastes, decomposers like bacteria and fungi break down the carbon compounds that are present in the dead bodies or wastes. This also returns carbon dioxide to the atmosphere since decomposers are doing respiration with much of the material that they are decomposing.
Sometimes, dead organisms and wastes don’t get completely decomposed. Instead, they get buried deep in the earth and are subjected to intense heat and pressure for many, many years, eventually becoming fossil fuels like coal, oil, and natural gas. These fossil fuels store carbon compounds for very long periods of time. Since these carbon compounds have a lot of stored energy in them, people mine and drill for them in order to use them as energy sources to power our technologies, like factories, vehicles, and power plants. Burning fossil fuels also releases CO2 to the atmosphere. This process of burning things is called combustion. Notice that burning fossil fuels adds CO2 to the atmosphere that had been removed from the cycle for a very long time, causing an increase above typical levels for our geologic time period. Since CO2 is a greenhouse gas, this extra CO2 can impact earth’s climate.
So, there you have some of the most important aspects of the carbon cycle. Notice that carbon moves from the atmosphere to living things through photosynthesis, and that carbon gets returned to the atmosphere by respiration, decomposition, and combustion. Carbon can also be stored long-term as fossil fuels deep in the earth, but people can extract these stored carbon compounds and burn them, returning more CO2 to the atmosphere. And don’t forget, living things are made of carbon compounds, so carbon also moves through food chains and food webs as living things consume one another.
If you would like to practice doing the carbon cycle yourself, please try the interactive game at biomanbio.com