Carbon is exchanged or cycled among Earth's spheres. Organisms are composed of carbon compounds. Carbon is the fundamental building block of life, and an important component of many biological and chemical processes. Let's take a look at how carbon is cycled through the Earth's spheres. The carbon cycle consists of several storage reservoirs, as well as the processes by which the carbon moves between these reservoirs. The global carbon cycle, one of the major biogeochemical cycles, can be divided into geological and biological components. The geological carbon cycle operates on a timescale of millions of years, while the biological carbon cycle operates on a timescale of days to thousands of years. 00:47: Let's take a look at the biological cycle. Biology plays an important role in the movement of carbon through the process of photosynthesis and respiration. Virtually all multicellular life on Earth depends on the production of sugars from sunlight and carbon dioxide, photosynthesis, and the metabolic breakdown respiration of those sugars to produce the energy needed for movement, growth and reproduction. Plants take in the carbon dioxide from the atmosphere during photosynthesis, and release carbon dioxide back into the atmosphere during cellular respiration. Consumers rely on the plants and other producers for food. Indirectly, they are utilizing the products of photosynthesis and releasing carbon dioxide during cellular respiration as well. Finally, we are all carbon-based life forms, and carbon is recycled during the composition process after death. 01:49: The geological component of the carbon cycle includes the rock cycle and the processes of weathering and dissolution, precipitation of minerals, burial and subduction, and volcanic eruptions. In the atmosphere, carbonic acid forms by a reaction with atmospheric carbon dioxide and water. As this weakly acidic water reaches the surface as rain, it reacts with minerals at the Earth's surface, slowly dissolving them into their component ions through the process of chemical weathering. These ions are carried in streams and rivers, eventually reaching the ocean, where they precipitate out as minerals like calcite. Through continued deposition and burial, this calcite sediment forms a rock called limestone. In the oceans, phytoplankton use carbon to make shells of calcium carbonate. The shells settle to the bottom of the ocean when phytoplankton die and are buried in the sediments. The shells of phytoplankton and other creatures become compressed as they are buried, and eventually transformed into limestone. 02:56: Additionally, under certain geological conditions, organic matter can be buried over time and form deposits of the carbon-containing fuels, coal and oil. It is the non-calcium-containing organic matter that is transformed into fossil fuel. Both limestone formation and fossil fuel formation represent long-term carbon dioxide sinks. 03:21: Scientists have been studying both short and long-term measurements of atmospheric carbon dioxide levels. Data collected at the Mauna Loa observatory in Hawaii has revealed that human activities are significantly altering the natural carbon cycle. Since the onset of the Industrial Revolution about 150 years ago, human activities, such as burning of fossil fuels and deforestation, have accelerated, and both have contributed to a long-term rise in atmospheric carbon dioxide. Burning oil and coal releases carbon into the atmosphere far more rapidly than is being removed, and this imbalance causes atmospheric carbon dioxide concentrations to increase. In addition, by clearing forests, we reduce the ability of photosynthesis to remove carbon dioxide from the atmosphere, also resulting in a net increase. Because of these human activities, atmospheric carbon dioxide concentrations are higher today than they have ever been over the last half million years. 04:22: The carbon cycle is just one of the many biogeochemical cycles used on Earth today.

Question

Carbon is exchanged or cycled among Earth's spheres. Organisms are composed of carbon compounds. Carbon is the fundamental building block of life, and an important component of many biological and chemical processes. Let's take a look at how carbon is cycled through the Earth's spheres. The carbon cycle consists of several storage reservoirs, as well as the processes by which the carbon moves between these reservoirs. The global carbon cycle, one of the major biogeochemical cycles, can be divided into geological and biological components. The geological carbon cycle operates on a timescale of millions of years, while the biological carbon cycle operates on a timescale of days to thousands of years. 00:47: Let's take a look at the biological cycle. Biology plays an important role in the movement of carbon through the process of photosynthesis and respiration. Virtually all multicellular life on Earth depends on the production of sugars from sunlight and carbon dioxide, photosynthesis, and the metabolic breakdown respiration of those sugars to produce the energy needed for movement, growth and reproduction. Plants take in the carbon dioxide from the atmosphere during photosynthesis, and release carbon dioxide back into the atmosphere during cellular respiration. Consumers rely on the plants and other producers for food. Indirectly, they are utilizing the products of photosynthesis and releasing carbon dioxide during cellular respiration as well. Finally, we are all carbon-based life forms, and carbon is recycled during the composition process after death. 01:49: The geological component of the carbon cycle includes the rock cycle and the processes of weathering and dissolution, precipitation of minerals, burial and subduction, and volcanic eruptions. In the atmosphere, carbonic acid forms by a reaction with atmospheric carbon dioxide and water. As this weakly acidic water reaches the surface as rain, it reacts with minerals at the Earth's surface, slowly dissolving them into their component ions through the process of chemical weathering. These ions are carried in streams and rivers, eventually reaching the ocean, where they precipitate out as minerals like calcite. Through continued deposition and burial, this calcite sediment forms a rock called limestone. In the oceans, phytoplankton use carbon to make shells of calcium carbonate. The shells settle to the bottom of the ocean when phytoplankton die and are buried in the sediments. The shells of phytoplankton and other creatures become compressed as they are buried, and eventually transformed into limestone. 02:56: Additionally, under certain geological conditions, organic matter can be buried over time and form deposits of the carbon-containing fuels, coal and oil. It is the non-calcium-containing organic matter that is transformed into fossil fuel. Both limestone formation and fossil fuel formation represent long-term carbon dioxide sinks. 03:21: Scientists have been studying both short and long-term measurements of atmospheric carbon dioxide levels. Data collected at the Mauna Loa observatory in Hawaii has revealed that human activities are significantly altering the natural carbon cycle. Since the onset of the Industrial Revolution about 150 years ago, human activities, such as burning of fossil fuels and deforestation, have accelerated, and both have contributed to a long-term rise in atmospheric carbon dioxide. Burning oil and coal releases carbon into the atmosphere far more rapidly than is being removed, and this imbalance causes atmospheric carbon dioxide concentrations to increase. In addition, by clearing forests, we reduce the ability of photosynthesis to remove carbon dioxide from the atmosphere, also resulting in a net increase. Because of these human activities, atmospheric carbon dioxide concentrations are higher today than they have ever been over the last half million years. 04:22: The carbon cycle is just one of the many biogeochemical cycles used on Earth today.

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Question 1
Biological carbon acts on a timescale of ______________ of years.
Responses
A hundredshundreds
B thousandsthousands
C millionsmillions
Question 2
Plants, algae and phytoplankton are the main components of the _________ carbon cycle.
Responses
A fastfast
B slowslow
Question 3
What two recurring events in Earth’s history have an impact on the carbon cycle?
Responses
A Earth’s orbit and climate changeEarth’s orbit and climate change
B Solar events and eclipsesSolar events and eclipses

Answer 1

C Volcanic eruptions and meteorite impactsVolcanic eruptions and meteorite impacts