Ecosystems 2 Flashcards
Ecosystem
All the living organisms that interact with one another in a defined area
Factors affecting ecosystems
Biotic and abiotic factors
Biotic factors
Interactions between organisms
Competition for food territory and breeding partners
Abiotic factors
Light
Temperature - effect enzymes in metabolic reactions can trigger migration
Water availability- lack of water leads to death
Oxygen availability- in aquatic ecosystems require fast flowing cold water containing O2
Soil factors
Trophies levels
Each stage in the food chain
First tropic level= producer - light energy into chemical energy
Trophies levels after are all consumers
Rare to have more that quaternary consumer
Biomass
Mass of living material present in particular place or particular organisms can be equated to energy content
To calculate biomass multiply dry mass by total number of organisms at that level g per square metre
Efficiency of biomass and energy transfer
Biomass is nearly always less than tropic level below
When animals eat tropic level below only transfer small proportion into making new tissues - only this part of the biomass the next level can eat
Energy available measures in kJ per m^2 per yr
Ecological efficiency
Efficiency with which biomass is transferred from one tropic level to the next
Net production = gross production- respiratory losses
Ecological eff. = energy after transfer/ energy before transfer x 100
Consumer efficiency
Convert 10% of biomass to tissue because
- not all biomass is eaten leaving bones and roots
- some energy transferred to environment
-some parts are not edible sheared into faeces
- some energy is lost via urine
Human manipulation of biomass
Plants and animals provided with abiotic factors required to thrive
Competition is removed and predators
Farming animals 3 tropic levels more biomass to consume
Crops only 2 tropic levels
Minimum energy is lost max biomass eaten
Ammonification
Sabriobonts to undergo extra cellular digestion of nitrogen containing matter
Decomposing
Nitrification
NH4- released into soil
Bacteria in the soil converts ammonia to nitrates
nitrifying bacteria (nitrosomas) oxidise ammonia to nitrites
Nitrobacter oxidise nitrites to nitrates for plants
Denitrification
Bacteria in soil break down nitrates and release nitrogen into the atmosphere
Only anaerobic conditions
Nitrogen fixing
Atmospheric nitrogen converted to ammonia using nitrogen fixing bacteria
Rhizobium
Using nitrogenase
Nitrogen cycle
Ammonification
Denitrification
Nitrification
Nitrogen fixation
Carbon cycle
Decomposers - break down dead organisms respiring CO2 into atmosphere
Dead organic matter become trapped making fossil fuels
Consumers carbon macromolecules passed from producer respire releasing CO2
Producers take CO2 from atmosphere for photosynthesis release during respiration
Atmospheric CO2
Atmospheric CO2 levels are higher at night and during winter as photosynthesis levels are low
Combustion of fossil fuels once levels of CO2
Deforestation- less CO2 is removed from atmosphere
Temp increasing sea cannot dissolve CO2 as it’s too warm etc
Primary succession
Occurs on areas of land taht has been newly formed eg bare rock no organic matter or soil to begin with
V slow process
Seral stages
Succession steps
Pioneer community - colonisers (lichen)
Intermediate community - secondary colonisers tertiary , scrubland -> climax community dominant species
Climax community
Less hostile conditions
High species diversity
Stable
Eg woodland
Secondary succession
Occurs where soil is present but contains no plant or animal species
Eg bare earth after forest fire
Recolonised -> rapid process
Pioneer species adaptions
Ability to produce large quantities of spores which are blown by wind
Seeds germinate rapidly
Ability to photosynthesise or produce own energy
Tolerance to extreme conditions
Ability to fix nitrogen from atmosphere
Animal succession
Primary consumers first to colonise area- much slower than plant succession
Secondary consumers arrive once suitable food source established
Larger animals then colonise the area
Deflected succession
Activities which prevent ecosystems reaching climax community - stopped artificially (plagioclimax)
Grazing of animals or mowing grass clearing field for crops forest clearance to promote biodiversity
Measuring abundance of plants
Estimated number in population= number of individuals in sample /area of sample
Measuring abundance of animals
Mark release recapture
Lincoln index = No in first x No in 2nd/ number of recaptured
