Abiotic Factors Part 2

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Abiotic FactorsPart 2

• Lecture 4
• Chemical cycles

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This lecture

• Chemical cycles
• Water cycle
• Nutrient cycles
• Carbon
• Nitrogen
• Phosphorus
• Other chemicals

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Chemical cycles

• Chemical cycles are an important aspect of an
  organisms abiotic environment
• The amount of water, Carbon, Nitrogen, etc. on
  the planet is fixed
• Even some elements that are common on the planet
  may be in short supply if they are not in a form
  that can be taken up by organisms (e.g., Nitrogen)

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Water cycle

• Approximately 75 of Earths surface is covered
  by water
• Essential for living organisms
• Water has several unusual chemical properties
• Expands in volume when it freezes
• Transition from solid-liquid-gas occurs over the
  narrow range of pressure and temperature
  encountered on earth

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Drinking water

• Although water covers 75 of the planet most is
  not suitable for drinking water
• About 96.5 of the earths water is salt water
• Only 3.5 is fresh water

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Fresh water (3.5)

• 68.7 of fresh water is locked up in ice caps,
  glaciers and permanent snow
• 30.1 ground water
• Surface water makes up less than 1 of the fresh
  water on the planet

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Water cycle
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Global warming and the water cylcle

• 67 of fresh water is locked up in ice caps and
  glaciers
• They look small in area but they are gt 1000 m
  thick
• They are melting more quickly than predicted by
  most models

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Global warming and the water cylcle

• Expected to result in rising sea levels
• Great Lakes will be lower due to increased
  evaporation
• Weather will be more extreme

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Carbon cycle

• All life is based on Carbon
• Carbon is a major component of biological
  molecules including
• DNA
• RNA

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Carbon cycle

• Carbon is also found in
• The atmosphere as CO2
• Oil deposits
• Rock (dolomite, limestone, chalk)
• Dissolved in oceans

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Carbon sinks (Billions of Tonnes)

• Atmosphere
• 766 (as of 1999)
• 578 (as of 1700)
• Soil organic matter
• 1500 -1600
• Oceans 38 000 to 40 000
• Marine sediments and sedimentary rocks
• 66 000 000 to100 000 000
• Terrestrial plants
• 540 to 610
• Fossil fuel deposits
• 4000

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Carbon cycle
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Nitrogen Cycle

• Nitrogen vital component of
• Amino acids
• Proteins
• Nucleic acids

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Nitrogen Cycle

• Largest store of Nitrogen atmosphere
• Air is approx 70 Nitrogen
• N2
• Plants can only take up N in ionic forms
• ammonium ion NH4
• and nitrate ion NO3-

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Nitrogen Cycle

• Nitrogen gas N2
• Ammonium ion NH4
• Nitrate ion NO3-
• Nitrite ion NO2-

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Nitrogen Cycle

• Ammonium ion NH4 Toxic in large concentrations
• Nitrate ion NO3- Is the form most often used by
  plants

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Nitrogen Cycle

• Usable nitrogen is stored in organic matter
• Decomposers make it available for use
• Soil micro organisms convert ammonia (NH3) to
  ammonium ion (NH4)
• Mineralization

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Nitrogen Cycle

• In the soil the positively charged ammonium ion
  (NH4) may bind to soil particles
• Sometimes called micelle fixation

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Nitrogen Cycle

• When ammonium (NH4) is released it can be
  converted to Nitrite (NO2-)
• Autotrophic bacteria Nitrosomonas
• Nitrite is then converted to Nitrate (NO3-)
• Bacteria in the genus Nitobacter

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Nitrogen Cycle--Nitrification

• (NH4) Nitrite (NO2-) Nitrate (NO3-)

Nitrosomonas
Nitobacter
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Nitrogen cycle

• Nitrate (NO3-) is very soluble and is easily
  leached
• Eutrophication
• Water turns green due to excess algal growth

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Nitrogen cycle

• Nitrate (NO3-) can also be converted to N2 or N2O
• Denitrification
• Heterotrophic bacteria
• Anaerobic soils
• Pseudomonas and Bacillus
• Facultative anaerobic bacteria

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Nitrogen cycle

• Most nitrogen used by plants is originally
  derived from atmospheric nitrogen and fixed by
  micro-organisms
• Bacteria
• Actinomycetes
• Cyanobacteria

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Nitrogen cycle

• These organisms convert N2 to NH4
• e.g. Rhizobium which form associations with
  plants in the legume family
• Root nodules
• Cyanobacteria Heterocysts

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Nitrogen Cycle
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The Phosphorus Cycle
Component
Input to soil
Loss from soil
Atmospheric deposition
Crop harvest
Animal manures and biosolids
Mineral fertilizers
Plant residues
Runoff and erosion
Primary minerals (apatite)

• Organic phosphorus
• Microbial
• Plant residue
• Humus

Mineral surfaces (clays, Fe and Al oxides,
carbonates)
Plant uptake
Weathering
Adsorption
Immobilization
Mineralization
Desorption

• Soil solution
• phosphorus
• HPO4-2
• H2PO4-1

Secondary compounds (CaP, FeP, MnP, AlP)
Dissolution
Leaching (usually minor)
Precipitation
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Phosphorus

• Required by living organisms
• cell membranes
• Nucleic acids
• NADPH
• ATP

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Phosphorus

• Originates from rock weathering
• Taken up by plants
• Animals acquire their P from plants

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Phosphorus

• Human inputs-Phosphorus mining
• Agricultural fertilizer
• Explosives

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Humans have altered turnover times
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Phosphorus

• Plants require
• Nitrogen
• Carbon
• Potassium
• Phosphorus
• Other micro-nutrients
• Phosphorus is most often the limiting nutrient
  for plant growth

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Human inputs of P

• Phosphate containing detergents
• Chemical fertilizer

Eutrophication
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ELA Lake 302