Cycles
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Transcript of Cycles
Chemical Recycling
Biogeochemical Cycles
• The cycling of nutrients in an ecosystem involves both the biotic and abiotic parts.
Macronutrients
• Elements required in large amounts– Carbon– Hydrogen– Oxygen– Nitrogen – Phosphorous– Calcium– Sulfur– Water
Micronutrients
• Elements needed on small amounts– Zinc– Molybdenum– Iron– Selnium– Iodine
• For enzymes
Reservoirs
• Storage sites of nutrients
The Cycles
• Water• Carbon• Nitrogen• Phosphorous• Calcium
The Water Cycle
Why Water?
• Best natural solvent• Most chemical reactions in body take
place in water• Main transport medium• Stable• Ionise into hydrogen and hydroxyl (pH)• Resists rapid temperature changes
The Cycle
Precipitation
• Movement of water from atmosphere to Earth
Evaporation
• Sun’s energy turns water to vapour
• Vapour rises to the atmosphere
• Greatest amount of evaporation from the sea
Transpiration
• Water stored in plant tissues moves up the plant to the leaves
• Carries nutrients with it to the leaves
• Leaves the plant as water vapour through stomata
Metabolic Water
• Cycled by– Photosynthesis and respiration– Drinking and excretion– Burning fossil fuels– Decay by micro-organisms
Humans
• Deplete surface and ground water
• Wasteful use of water
• Pollution
Carbon Cycle
Carbon
• Key compound in – Carbohydrates– Fats– Proteins
Reservoir
• Limestone (CaCO3)• Atmospheric carbon dioxide• Carbon compounds dissolved in water• Fossil fuels
The Cycle
Humans
• Burn forests– Stop photosynthesis– Increase CO2
released by compustion
• Burn fossil fuels– Coal and wood– Petrol, diesel
Global Warming
• Ozone layer reflects some radiation
• CO2 + water vapour reflect radiation back to Earth
• Causes general warming of Earth
Nitrogen Cycle
Nitrogen
• For proteins– Body structure– Enzymes– Hormones– Haemoglobin
Reservoir
• Air 78% nitrogen but largely unusable• Used as nitrate ion dissolved in soil
water• Must be fixed by
– Lightening– Bacteria in legumes– Free-living bacteria– cyanobacteria
The Cycle
• Nitrate absorbed by plant roots and turnid into proteins
• Animals eat proteins• Leaves body as waste (urine, faeces)• Decomposers turn into ammonia
(aminification)• Ammonia turned into nitrate by nitrifying
bacteria (nitrification)
• Nitrite absorbed by plants
• Nitrogen in air fixed by lightening or Rhizobium
• Rhizobium in mutualistic relationship with legumes
• Denitrifying bacteria break down nitrates to nitrogen
Humans
• Use nitrogenous fertilisers• Add compost or sewage• Plant legumes• Remover plants or animals (remove nitrogen)• Plant removal causes nitrates to be released
(leaching)• Remove oxygen (no nitrification)• Burn fossil fuels (nitrous oxide released)
Phosphorous Cycle
Phosphorous
• For DNA, RNA, ATP, phospholipids, bones, teeth, photosynthesis, respiration
Calcium Cycle
• Similar to phosphorous cycle• Calcium for
– Cell membranes– Enzymes– Bones, teeth, exoskeletons
Humans
• Fertilisers add phosphorous and increase the rate of calcium recycling
• Seabird deposits accumulated over years mined for fertiliser
• Fishing returns calcium from sea to land