Understanding: Skills: 4.3 Carbon cycle - Construct a diagram of the carbon cycle Understanding: Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds In aquatic habitats carbon dioxide is present as a dissolved gas and hydrogen carbonate ions Carbon dioxide diffuses from atmosphere or water in autotrophs Carbon dioxide is produced by respiration and diffuses out of organisms in water or atmosphere Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere Methane is oxidised to carbon dioxide and water in the atmosphere Peat forms when organic matter is not fully decomposed because of anaerobic conditions in water logged soils. Partially decomposed organic matter from past geological eras was converted into oil and gas in porous rocks or into coal Carbon dioxide is produced by the combustion of biomass and fozzilised organic matter Animals such as reef building corals and molluscs have hard parts that are composed of calcium carbonate and can become fossilised in limestone Nature of science: Making accurate, quantitative measurements: it is important to obtain reliable data on the concentration of carbon dioxide and methane in the atmosphere Applications Estimation of carbon flues due to processes in the carbon cycle Analysis of data from atmosphere monitoring stations showing annual fluctuations

C Cycle WB

The carbon cycle Terms: Pool = reserve of the element Carbon dioxide in atmosphere Biomass of producers in ecosystem Flux = transfer of the element from one pool to another Absorption of carbon dioxide from the atmosphere by plants, contributing to plant biomass through photosynthesis

Carbon fluxes Process Flux/gigatonnes a year Photosynthesis 120 Cell respiration 119.6 Ocean uptake 92.8 Ocean loss 90 Deforestation and land use changes 1.6 Burial in marine sediments 0.2 Combustion of fossil fuels 6.4

Use page 220 - 225 to add details to your carbon cycle Add methanogenesis and oxidation of methane to your cycle 221 Add peat formation to your cycle 224/225 Use page 220 - 225 to add details to your carbon cycle

Carbon Fixation Autotrophs absorb carbon dioxide from the atmosphere Convert into carbon compounds they require (glucose, AA, Lipids)

Carbon Dioxide Carbon dioxide is soluble in water. Either dissolves in water, or combine with water to form carbonic acid. Carbonic acid then splits to form hydrogen and hydrogen carbonate ions. Decrease in pH (problems?) Both carbon dioxide and hydrogen carbonate ions absorbed by autotrophs in the water by diffusion.

Methanogenesis Methanogenic archaeans (single celled like bacteria) Methane (CH4) is produced in anaerobic conditions as a waste product. Mud in beds of lakes Swamps (or other areas where soil is waterlogged) Guts of cattle and sheep Landfill sites.

Methane in the atmosphere Methane is oxidised to carbon dioxide and water in the atmosphere. CH4 + O2 H2O + CO2 *methane is a greenhouse gas though!

Peat formation Waterlogged environments (water unable to drain out = anaerobic conditions) Saprotrophs cannot survive here - no oxygen – not all dead matter is broken down Large quantities of partially decomposed matter accumulates in ecosystem – compresses to form peat. Peat is also used as a fuel which releases carbon dioxide back into the atmosphere

Fossilisation Incomplete decomposition of organic matter which has been buried, compressed and heated underground from past geological eras. Most commonly under the sea – anaerobic conditions Forms: Crude oil Natural gas Coal

Limestone Some animals have hard body parts composed of calcium carbonate Mollusc shells Hard corals Soft parts decompose. Hard calcium carbonate deposited on sea bed – creating limestone rock 10% of all sedimentary rock is limestone 12% mass of calcium carbonate is carbon Huge amounts of carbon locked up in limestone rock on earth

Building a carbon cycle Notes for the team leader: You need to make a carbon cycle with the materials provided (big whiteboards, small whiteboards, rulers/string, arrow heads, pens etc) Each pool and fluxes needs to be labelled and explained: Carbon fixation in photosynthesis Carbon dioxide in solution in the ocean Aquatic autotrophs absorbing carbon dioxide Respiration Methanogenesis and oxidation of methane Peat formation Fossilisation Limestone as a pool of carbon Combustion of fossil fuels (peat is also used as a fuel) Allocate jobs to your team 25 minutes Go

Building a carbon cycle Notes for the team leader: You need to make a carbon cycle with the materials provided (big whiteboards, small whiteboards, rulers/string, arrow heads, pens etc) Each pool and fluxes needs to be labelled and explained: Carbon fixation in photosynthesis Carbon dioxide in solution in the ocean Aquatic autotrophs absorbing carbon dioxide Respiration Methanogenesis and oxidation of methane Peat formation Fossilisation Limestone as a pool of carbon Combustion of fossil fuels (peat is also used as a fuel) Allocate jobs to your team 25 minutes Go

Speaking and listening Get into pairs. One person in the pair faces the board (speaker) The other person faces away so they cannot see the board (listener) Speaker describes what they see on the board to the listener – with neither turning around. We will swap to complete the second half of the diagram.