Global Systems
- Recycling in Nature

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The biosphere

This is the part of the Earth’s surface and atmosphere where all living things exist .  Three parts

1. Lithosphere – the land
2. Hydrosphere – water
3. Atmosphere – the air

All the living things interact and part of this interaction involves recycling enabling the ecosystem to be self-sustaining
Sustainable ecosystems – those ecosystems that are diverse and provide for the needs of the organisms in them.

Carbon Cycle

The Carbon Cycle

 

Carbon is essential for life. It is cycled through the Earth sometimes taking minutes and at other time taking 1000s of years or more.

Animals produce carbon dioxide , which is needed for photosynthesis in plants.  Photosynthesis produces food (containing carbon) for animals and the cycle begins again.  Also, sometimes carbon is trapped in plants and animals for long times such as in coal and oil deposits ( fossil fuels ).  In recent history man has released this carbon by taking it out of the ground and burning it to produce more carbon dioxide Other trapped carbon in plants and animals occurs when they die and then the carbon is released by decomposing organisms. Carbon is also stored in an inorganic substance called calcium carbonate (limestone – made from the shells of marine animals).

Nitrogen Cycle

This is much more complicated than the carbon cycle. Nitrogen is an important part of proteins . Plants get nitrogen from the soil and animals get nitrogen from plants . The air contains 78% nitrogen.

Bacteria and Nitrogen

Bacteria in the soil

Organisms die and bacteria causes nitrogen to be released as ammonia into the ground. Other bacteria convert this ammonia to water soluble nitrates . Plants can take up both ammonia and nitrates.

Nitrogen-fixing bacteria

Can capture nitrogen from the air, trapped in the soil, and convert it to ammonia and nitrates.

Some plants, called legumes , have a place for these bacteria to live.  In return they supply the plants with nitrates. Examples are

• Beans
• Peas
• Wattle
• Clover

Denitrifying bacteria

Release energy from nitrates and convert them back into nitrogen .

Lightning and fertiliser

• lightning can also convert nitrogen to nitrates and is washed to earth in the rain
• Farmers add nitrates to their soil by way of fertilizer and this places nitrogen into the cycleThe Water Cycle

The Water Cycle

Water is necessary for all living organisms on Earth. The water cycle is relatively simple.

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