Summary
OCR A-Level Biology Ecosystems Summary
Handwritten Summary by an Oxford Medical Student which covers all content necessary for an A* in Ecosystems at OCR Biology A-Level.
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Biotic factors foodLiving factors that affect an ecosystem space competition breeding partners
:
, ,
,
Abiotic factors Non-living factors that offect an ecosystem
:
↳
Light temperature water/oxygen availibility edaphic factors
, , ,
Biomass mass of
living
material present
:
↳ Biomass at a no
trophic level biomass present =
x .
organisms
measuring biomass Water must be discounted :
so
dry samples (dead) are often uses
Efficiency of biomass transfer Only:
a small proportion of food is converted to biomass
↳ Producers Not used for photosynthesis energy lost
au solar
energy is in reactions,
limiting factors
:
,
↳ Consumers Not all :
biomass (bones) is eaten , metabolic waste in heat and excretions
Ecological Efficiency :
Biomass available after transfer/biomass availible before transfer
Nitrogen Fixation Nitrogen fixing bacteria ie
:
· .
aztobacter and Rhizobium convert Ne-NH3
·
Nitrification :
Nitrifying bacteria is .
Nitrosomonas
and Nitrobacter Convert NHz-NO ? -
NO
·
Denitrification :
Anaerobic conditions NO ?-N2 :
·
Ammonification Decomposers :
convert
nitrogen
rich molecules into ammonium compounds
Photosynthesis Converts CO2 to molecules
:
·
containing carbon in plants
Respiration Releases CO2 gas to the atmosphere
·
:
feeding Carbon molecules transferred from producers
·
:
are
to consumers
·
Decomposition :
CO2 is released
fluctuations in CO2 No :
photosynthesis at
night and
increased human activity causes CO2 levels to fluctuate
Primary succession Bare
newly formed rock
Secondary succession Soil but no
organisms
:
or
:
Pioneer Arrives seeds ie lichen
Community or
Algae
as
spores or
:
.Reproduce
↳ nitrogen withstand harsh conditions , can fix
quickly photosynthesise , ,
Intermediate community Species that thrive on the rich soil produced by decomposed pioneer species
:
Climax Community Stable community displaying little change over time
:
Plagiodimax Artificially deflected :
succession is by human activity
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