Earth’s resources Living organisms have been using supplies on earth for billions of years – why have they not run out? -Carbon -Nitrogen -Hydrogen -Oxygen -Phosphorous

Earth is a closed system – nothing leaves or enters (apart from rockets/meteorite) Earth’s resources

Chemical elements can be endlessly recycled Organisms absorb elements as inorganic nutrients from the abiotic environment, use them and return them to the environment with the atoms unchanged. -Carbon cycle -Nitrogen cycle Nutrient cycling

Write down your day cycle What do you do in the morning? During the day? At night? Where does it start?

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

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.

The Carbon CycleCycle Plants make carbon compounds from carbon dioxide they take from the air. This happens in photosynthesis.

Animals obtain carbon compounds by eating plants or other animals, or both.

Animals and plants return carbon back to the atmosphere as carbon dioxide when they respire.

When animals and plants die, microbes digest them and obtain carbon compounds from their bodies.

Microbes respire, this releases carbon dioxide into the atmosphere.

Burning of wood and fossil fuels releases large amounts of carbon dioxide into the atmosphere. Man’s activities have caused an imbalance in the natural carbon cycle. There is now more carbon dioxide in the atmosphere than before.

Carbon fluxes The amounts of carbon moving from one pool to another is not shown in diagrams Hard to measure – estimates used Based on many measurements in ecosystems or mesocosms Units = gigatonnes (1 gigatonne = 1 x grams)

Carbon fluxes ProcessFlux/gigatonnes a year Photosynthesis120 Cell respiration119.6 Ocean uptake92.8 Ocean loss90 Deforestation and land use changes 1.6 Burial in marine sediments0.2 Combustion of fossil fuels6.4

The carbon cycle Create your own carbon cycle in your note books Include all fluxes and pools: -Carbon dioxide in atmosphere -Photosynthesis -Respiration of plants -Respiration of animals -Egestion -Death -Respiration of saprotrophs and detritivores -Carbon in dead organic matter -Fossilisation of organic matter -Carbon in organic compounds -Feeding