Unit A: Energy and Matter Exchange in the Biosphere Chapter 3 Section 3.2 The Carbon and Oxygen Cycle

Unit A: Energy and Matter Exchange in the Biosphere The Carbon Cycle Carbon is the key element for living things. Carbon can be found in the atmosphere and dissolved in the oceans as part of the inorganic carbon dioxide (CO2) molecule. Each year 50 to 70 million tonnes of carbon dioxide are cycled into more complex organic substances. This is done through photosynthesis. Some of the organic carbon is released back to the atmosphere through cellular respiration.

Carbon dioxide  Glucose  Carbon dioxide Because photosynthesis and cellular respiration are complementary processes, and because the carbon that they use is repeatedly cycled through both processes, this is known as the carbon cycle. The carbon cycle – is the cycle of matter in which carbon atoms move from an inorganic form to organic and then back to inorganic. Carbon dioxide  Glucose  Carbon dioxide Carbon is released from living beings through body waste and decomposition. Carbon is released from fossil fuels through combustion, the chemical reaction of carbon molecules with water to form carbon dioxide and water.

Reservoirs for Inorganic Carbon Inorganic carbon can be found in 3 main reservoirs or storages areas: Atmosphere Oceans Earth’s crust

Reservoirs for Organic Carbon Unit A: Energy and Matter Exchange in the Biosphere Reservoirs for Organic Carbon Organic carbon is stored in 2 main sources: Living things 2. Bogs - bogs contain very little oxygen, so decomposition is very slow - therefore carbon can remain in dead plant matter for many years - occasionally these deposits are overlaid with sediment and eventually the carbon will be trapped in-between layers of rock - the result is the carbon containing fossil fuel coal - the same process happens at the bottom of the ocean to form oil

Unit A: Energy and Matter Exchange in the Biosphere The Carbon Cycle

Unit A: Energy and Matter Exchange in the Biosphere The Oxygen Cycle The oxygen cycle consists of the movement of oxygen gas (O2), from living things into the atmosphere through photosynthesis, and then back into living things through cellular respiration. Oxygen atoms are also present in carbon dioxide, water, glucose, and other substances which contribute to the cycle as well.

Unit A: Energy and Matter Exchange in the Biosphere The Oxygen Cycle

Human Impact on the Carbon Cycle Unit A: Energy and Matter Exchange in the Biosphere Human Impact on the Carbon Cycle Our major impact on the carbon cycle is through the burning of fossil fuels. The excess carbon dioxide contributes to the greenhouse effect and therefore to global warming.

Unit A: Energy and Matter Exchange in the Biosphere

Unit A: Energy and Matter Exchange in the Biosphere The Albedo Effect If global warming continues to increase, much of our permanent ice and snow cover will melt. As radiation from the Sun reaches Earth, it is reflected back by Earth’s surface. Some surfaces reflect radiation better than others. The term albedo is used to describe the extent to which a surface can reflect radiation. The higher the albedo, the greater the ability to reflect. The lower the albedo, the greater the ability to absorb.

Unit A: Energy and Matter Exchange in the Biosphere Surfaces like snow and ice have very a high albedo. In the winter the Sun’s energy reflects off the snow and ice keeping temperatures low. Global warming affects the amount of snow and ice Earth has. If the climate warms, there will be less snow and more energy will be absorbed instead of reflected, further increasing global warming. This is called the snow-temperature feedback cycle.

Snow – Temperature Feedback Cycle Unit A: Energy and Matter Exchange in the Biosphere Snow – Temperature Feedback Cycle Climate Warms Earth’s surface has lower albedo, more energy is absorbed Less snow, shorter winters