Chapter 6 Nutrient Cycles

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6.1 The Carbon Cycle

Saprobiotic organisms break down dead organisms by secreting enzymes, absorbing the products

Dead matter can be compressed into fossil fuels - carbon is released through combustion

Variations in CO2 and O2 are due to changes in photosynthesis and respiration

Combustion of fossil fuels has increased the atmospheric amount of CO2

Deforestation has removed photosynthesising biomass

CO2 is contributing to global warming

Oceans contain 50x more carbon than the atmosphere - constant levels

Phytoplankton use CO2 to form their bodily macromolecules

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6.2 The Greenhouse effect and Global Warming

Greenhouse effect keeps global temperatures constant

Solar radiation warms the Earth but some is reflected

CO2 traps heat for a longer time than Methane

Concentration of CO2 is rising due to human activities - Causing environmental concerns

Global warming is changing: temp. rain, seasons and extreme events

Melting of polar ice caps - rising sea levels

Rising sea levels - flooding of low lying land

Spread of tropical diseases due to increased temp.

Age of fossils - radioactive decay of an isotope of carbon

CO2 concentration - air bubbles within ancient ice

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6.3 The Nitrogen Cycle

Nitrogen fixing - nitrogen gas is converted into nitrogen containing compounds

Saprobiotic digestion - digestion of proteins to amino acids by decomposers

Ammonification - Amino acids are converted into ammonium compounds

Nitrification - ammonia compounds are converted to nitrites then nitrates

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6.4 Use of Natural and Artificial Fertilisers

Natural - Organic / Artificial - Inorganic

Food production is intensive on land which is repeatedly used

Maximum yields can be produced

Mineral ions are removed from the recycling system and need to be replaced

Minerals are returned by being broken down by decomposers

Mineral ions could become a limiting factor - decreased plant growth and productivity

Combination of fertilisers increases productivity

Needed for DNA and proteins = growth

Plants develop earlier and taller

Increased rate of photosythesis and crop production

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6.5 Environmental consequences of using nitrogen f

Reduced species diversity

Leaching

Eutrophication

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