Requirements for life supporting system
- Energy
- source
- sink for degraded energy (heat) - Chemical elements
Energy
- needed to produce organic matter
- photosynthesis by autotrophs requires energy and produced glucose
- called primary production
Primary producers (autotrophs)
- Produce organic matter via photosynthesis
- Use organic matter as fuel for metabolism and respiration (releases energy)
- Store some of the organic matter for future use (net production)
Heterotrophs build body mass by eating
Other organisms (autotrophs or other heterotrophs)
Called secondary production
Food chains
- arrange species in a community into trophic levels
- the trophic level indicates how many feeding steps the species is away from the autotroph level (level 1)
Energy flow
- energy is lost at each step of a food chain
- e.g. respiration converts energy into heat
- represents increase in entropy (2nd law of thermodynamics)
Can a circular food chain work
No
Energy flow #2
At each level of a food chain, energy is used-it cannot be recycled or recovered
- limits number of trophic levels
- biomass decreases from bottom to top of food chain (trophic pyramid)
Food web
More complex ecosystems that have multiple food chains woven into a food web
Macronutrients
Required by all living things in large amounts
C H N O S P
Micronutrients
Required in small amounts by all life, or in moderate amounts by some forms of life
Toxins
Detrimental to living organisms
Nutrients must be available
- at the right time
- right amount
- appropriate relative concentration to each other
- correct chemical structure
If not elements can become a LIMITING factor, preventing growth of organism, population or species
Bioconcentration
Happens when an organism takes in a substance faster than it can use or excrete it
Bioconcentration mechanisms
Bioaccumulation: substance taken in, not excreted at comparable rate, becomes more concentrated in organism with age
Biomagnification: substance is passed from consumer to consumer up the food chain
Biogeochemical cycle
Describes the movement of a chemical element or compound through the biosphere and the rest of the earth system
Cycles may include the biosphere, geosphere, hydrosphere, and atmosphere
Nitrogen cycle
- large component of atmosphere at unreactive N2
- also occurs as oxidized N2O, (NO3)2- and as reduced NH3 and NH4+
Essential to life (proteins and DNA)
Nitrogen fixation
Atmospheric N2 is unreactive and must be converted into biologically useful forms, NH3 and (NO3)2-
- 90%done by nitrogen fixing bacteria
- once converted it is taken up by plants and algae and consumed by animals
Denitrification: bacteria convert dead nitrogen computer dd back into N2 and return it to the atmosphere
Phosphorous cycle
Essential to the biosphere
- forms part of helical framework of DNA
- facilitates life energy transactions
- often a limiting nutrient
Occurs as phosphates in rocks in soils (low concentrations)
Liberated by weathering
Taken up by plants, bacteria, plankton from surface and sea water
Phosphorous cycle (2)
Heterotrophs concentrate phosphorous (important for vertebrate bones)
Fish eating birds excrete phosphorous as guano deposits in arid climates (guano deposits are mined for phosphorous)
Carbon cycle: RESERVOIRS
Atmosphere (CO2 and CH4)
Hydrosphere (carbonic acid, bicarbonate, organic carbon)
Biosphere (land and marine plants and animals, soil microbes)
Geosphere (carbonate rocks, soils, fossil fuels, crustal organic matter, graphite, diamond, other forms in earth’s mantle)
Carbon cycle
- Enters atmosphere via volcanoes, respiration, fires, decay, ocean diffusion
- removed by photosynthesis and dissolution into water
- dissolved carbon (as carbonic acid) is converted to bicarbonate which is used by organisms and buried and stored in sediment
- photosynthesis produces organic carbon compounds in living organisms
- preserved as dead organic matter
- can be transformed into coal, Kerogen, natural gas, oil, graphite or diamond
- can be subducted and recycled into mantle
