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2.3 FLOWS OF ENERGY & MATTER (Solar Radiation (Most becomes…
2.3 FLOWS OF ENERGY & MATTER
Solar Radiation
Most becomes unavailable, absorbed by inorganic matter or reflected back into the atmosphere
A major source for energy to drive processes on Earth
Both UV and visible light are converted to heat energy
1- 4 % of energy from the Sun is available to plants on the surface of the Earth
Productivity
Gross productivity
Total gain in energy or biomass per unit area per unit time
GPP = total energy uptake = amount of sugar produced
GSP = total food ingested - fecal loss
Net productivity
The gain in energy or biomass per unit area per unit time that remains after deductions due to respiration
NPP = rate of accumulation of dry mass of plants
NSP = total gain in energy - respiration
Carnivores
assimilate 80% of energy, egest less than 20%
only can assimilate energy from digestible parts (flesh)
Herbivores
graze static plants
assimilate 40%, egest 60%
Transfers & Transformations (1.2)
Cycles & Flows
Nutrient cycle
Biomass- nutrients stored in forest vegetation & animal life
Litter- nutrients trapped in fallen leaves and dead organisms
Soil- nutrients in soil humus
Carbon Cycle
Carbon sinks: organisms, ocean, soil, atmosphere
Carbon budget: amount of carbon is finite
Carbon released through: combustion of fossil fuels, biomass
Nitrogen Cycle
Denitrification
denitrifying bacteria (in waterlogged and anaerobic conditions) convert ammonium, nitrate, nitrite ions to nitrogen gas
Assimilation
Protein synthesis turns inorganic nitrogen compounds into more complex amino acids
Nitrification
nitrifying bacteria able to convert ammonium to nitrates
Decomposition
Supplies soil with much more nitrogen than nitrogen fixation
Nitrogen fixation
atmospheric nitrogen is made available to plants through the fixation of atmospheric nitrogen
Industrial Haber processes
By lightning
By cyanobacterai
By nitrogen-fixing bacteria (in soil and root nodules)
Efficiency
Trophic inefficiency
Not everything is eaten
Digestion is inefficient
Heat loss through respiration
Some energy used for other life processes
Cold blooded animals have slower assimilation rates than mammals
Energy budget
Quantities of energy entering, staying within and leaving the animal or population
Energy subsidy
the additional energy that we have to put into the system above that which comes from the Sun's energy
aim to maximise the NPP of the organisms we grow to maximise profit
able to feed more people because food production seems more efficient
Gersmehl's nutrient model
