TOPIC 4.3 CARBON CYCLING

Transcription

1 TOPIC 4.3 CARBON CYCLING

2 INTRO IB BIO 4.3 The carbon cycle is made up of the series of processes that convert 2 and move carbon in ecosystems.

3 IB BIO U1: Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds. Autotrophs are organisms that use photosynthesis to form carbon compounds from carbon dioxide. Since CO 2 is removed from the air, photosynthesis decreases overall atmospheric CO 2 levels. The average CO 2 levels are currently 0.039%, or 390 micromoles per mol. Levels are lower where there are more plants and vice versa.

4 IB BIO In addition to the atmosphere, CO 2 can also be stored in water. It U2: In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions. can either be stored as a dissolved gas or combine with water to form carbonate ions (H + and HCO 3- ). Dissolved CO 2 Hydrogen Carbonate Ions

5 IB BIO The consumption of CO 2 by autotrophs during photosynthesis U3: Carbon dioxide diffuses from the atmosphere or water into autotrophs. decreases internal concentrations. The resulting concentration gradient causes CO 2 to diffuse into autotrophic cells from water/air. Key Term

6 IB BIO U4: Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere. Inversely, aerobic cell respiration produces CO 2 in tissues which increases internal concentration. As a result, CO 2 diffuses out of organisms into the surrounding water or air. This diffusion can occur in many cells, including: Non-photosynthetic cells in plants Animal cells Saprotrophs

7 IB BIO Methanogens are microbes that produce methane gas from organic matter through methanogenesis. Three groups involved include: U5: Methane is produced from organic matter in anaerobic conditions by methanogens and some diffuses into the atmosphere or accumulates in the ground. Methanogenesis Bacteria that convert organic matter to acids & alcohol Bacteria that convert acids & alcohol to acetate, CO 2 & H 2. Methanogenic archaeans that produce methane from acetate, CO 2 & H 2.

8 IB BIO U5: Methane is produced from organic matter in anaerobic conditions by methanogens and some diffuses into the atmosphere or accumulates in the ground. Methanogenic archaeans can carry out methanogenesis in many anaerobic environments. Areas include: Mud along shores and in beds of lakes Swamps, mangroves and other wetlands Landfill sites Methanogenic Archaeans The methane they produced can diffuse into the atmosphere or accumulate in the ground.

9 IB BIO U6: Methane is oxidized to carbon dioxide and water in the atmosphere. Once in the atmosphere, methane can be naturally oxidized into water and carbon dioxide. On average, methane molecules persist in the stratosphere for 12 years.

10 IB BIO U7: Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils. Saprotrophs are unable to thrive in anaerobic, waterlogged soils. As a result, dead organic matter here cannot be fully decomposed. Peat Over time, this matter becomes compressed to form a dark brown, acidic material called peat. It covers ~3% of Earth s land surface.

11 IB BIO U7: Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils. Because peat contains organic matter, it is often used in gardening and also as a fuel source to produce heat. Peat

12 IB BIO U8: Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks. Carbon and its compounds are very stable and so can remain unchanged in rocks for long periods of time. There are large desposits from past geological eras found in the Earth. Coal forms when peat deposits are buried under sediments. Over time it is heated and compressed causing chemical changes. Coal

13 IB BIO U8: Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks. Oil and natural gas formed at the bottom of seas and lakes where decomposition is often not completed. Over time, sediments caused the organic matter to be compressed and heated Oil & Natural Gas Chemical changes resulted in mixtures of liquid carbon compounds and gas that accumulated in porous rocks where they were stored.

14 IB BIO U9: Carbon dioxide is produced by the combustion of biomass and fossilized organic matter. When organic matter is heated in the presence of oxygen, it can ignite and burn. The reactions that occurs are called combustion. Combustion The products of complete combustion are carbon dioxide, water, and large amounts of heat energy.

15 IB BIO Coal, oil and natural gas are U9: Carbon dioxide is produced by the combustion of biomass and fossilized organic matter. forms of fossilized organic matter that can be burned as fuels. When they are combusted, large amounts of CO 2 are released into the atmosphere. Combustion This is believed to be the primary cause of climate change that is being observed worldwide.

16 IB BIO Some animals have hard body parts composed of CaCO 3, including: The hard shell of molluscs The exoskeletons of hard corals U10: Animals such as reefbuilding corals and mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone. Limestone When these animals die, their hard parts can be deposited onto the sea bed. Over time, this forms limestone, which makes up ~10% of the Earths sedimentary rock.

17 IB BIO All of the processes mentioned so far are components of the carbon Skills S1: Construct a diagram of the carbon cycle. cycle. A drawn diagram can resemble the one shown here. Carbon Cycle

18 IB BIO Applications A1: Estimation of carbon fluxes due to processes in the carbon cycle. Scientists are able to estimate the quantities of carbon moved by processes in the carbon cycle. The rate of exchange of carbon between sources/reservoirs is referred to as carbon flux. Carbon Fluxes

19 IB BIO Applications A2: Analysis of data from air monitoring stations to explain annual fluctuations. Monitoring stations from around the world allow any person to analyze atmospheric CO 2 data. The graph shown here was obtaind from the Mauna Loa station in Hawaii, USA.

20 IB BIO Applications A2: Analysis of data from air monitoring stations to explain annual fluctuations. The annual fluctuations in CO 2 levels are caused by changes in rates of photosynthesis. During winter months, rates decrease which causes the atmospheric levels to increase and vice versa in summer.

21 REVIEW IB BIO Describe the effect of photosynthesis on atmospheric CO 2 21 levels. 2. Outline how carbon can be stored in aquatic bodies. 3. Outline how CO 2 can diffuse in and out of organisms. 4. Define methanogenesis and list areas where it can take place. 5. Outline the formation of peat. 6. Outline the storage of carbon in coal and oil. 7. Describe the process of combustion. 8. Outline the formation of limestone. 9. Draw a diagram of the carbon cycle. 10. Define carbon flux.