Role of Biology in Transferring Energy and Mass Through the
Earth System
RememberConservation of Energy
& Conservation of Mass
3 Basic Steps in Photosynthesis
• Light reactions- energy capture: chemiosmosis generation of ATP from harvested sunlight
• Dark reactions- fixation of carbon: enzyme catalyzed reactions using the ATP formed in the light reactions to “fix” CO2 into sugars
• Pigment regeneration- electron replacement from the splitting of H2O in oxygenic photosynthesis
Light Reactions:A very specific energy is required for photochemistry since only photons of a certainwavelength can dislodge electrons from an object
Most common range of wavelengthfrom the sun is the most sensitiverange for photosynthesis
Carbon enters water leaves the plant through the same pore; thus theexchange of the two substances is linked. This processes is known as
transpiration.Stoma
The Essential Elements Necessary for Plant Growth: 1. the bulk mass (95%)
Element Available from Present in Essential Role in Plants
Carbon, C CO2 Air, water All organic molecules
Hydrogen, H H2O Air, water All organic molecules
Oxygen, O CO2, H2O Air, water Most organic molecules
Nitrogen, N NO3-, NH4
+ Soil, water All proteins and
nucleic acids
N2 (only by
nitrogen fixation)
Air
Sulfur, S SO42- Soil, water Most proteins
Phosphorous, P PO43- Soil, water Nucleic acids and
energy transfer
The Essential Elements Necessary for Plant Growth: 2. minor constituents
available from soil minerals or dissolved in water
Element Role in Plants
Potassium, K Water balance, essential for certain enzymes
Calcium, Ca Membrane function, essential of cell walls of most plants
Magnesium, Mg Essential in chlorophyll
Iron, Fe Photosynthesis, energy release reactions
Mn, B, Z, Cu, Mo, Co Essential for function of certain enzymes
Chlorine, Cl Essential for photosynthesis
Source: SeaWiFS Project of the NASA Goddard Space Flight Center
Data aquired between Noverber 1978 and June 1986
Biological Controls on Climate
Albedo
Interception of rainfall
Cloud formation
Surface roughness
Greenhouse gasses
Long-term atmospheric change
Albedos for Various Terrestrial Biomes
• Equatorial forest 0.18
• Savannah 0.18-0.24
• Mid-latitude forest 0.14-0.46
• Tundra 0.18-0.80
• Desert 0.35
(In general vegetated surfaces reflect less than bare soil and rock.Tall vegetation prevents snow from making surface completely white)
Aerosols are cloud condensation nuclei
Increased terrestrial vegetation leads to decrease dust (aerosol)Ocean plankton release a sulfur compound (aerosol)
Surface Roughness
• Vegetation roughens the surface of the earth, causing air to flow less smoothly.
• This increase in turbulence near the surface increases the efficiency of mixing of heat and moisture between the surface and rest of troposphere
• Additionally, the rough surface causes surface winds to blow in a different direction from winds at high levels.
Long-term Atmospheric Change
The CO2 Content of the atmosphere is critical to maintianing the earth’s mean surface temperture. The CO2 content is controled by the biosphere. It has not
always been as it is today.