ecosystems Flashcards
Ecosystem
includes all organisms living in a particular area as well as the abiotic factors of that particular environment
the distribution and abundance of organisms in a habitat is controlled by both biotic and abiotic factors
Succession
- change of one community of organisms into the other
Primary succession
an area of bare rock or previously devoid of life, is colonised by communities of organisms
the area is first colonised by pioneer species e.g. lichens, which are adapted to survive in such harsh conditions
as organisms die, they are decomposed by microorganisms forming humus which leads to soil making the environment more suitable for more complex organisms
overtime, the soil becomes richer enabling plants e.g. shrubs to survive
Climax community
it’s a self-sustaining and stable community which is established in the final seral stage of succession
Secondary succession
occurs in previously colonised areas in which an existing community has been cleared. E.g after forest fires. soil layer is already present, succession begins at a later stage
Biomass and trophic levels
biomass is lost between successive trophic levels because…
- not all of the organism is eaten (e.g bones)
- not all of the eaten material is digested (excretion)
- energy used in respiration
- some energy lost in urine and urea
- energy lost for movement and heat
Efficiency of energy transfer
(energy or biomass post transfer/ energy or biomass before transfer) x 100
Efficiency at producer levels
producers only convert 1-3% of sunlight to chemical energy
the total amount of solar energy converted to organic matter is the GROSS PRODUCTION
energy is used in respiration, the remaining = biomass
the energy available to next trophic Lebel is the NET PRODUCTION
*net production = gross production - respiratory losses
Efficiency at consumer levels
10% of biomass in their food becomes their own
Carbon cycle
- carbon is a component of all organic molecules
- it is recycles by photosynthesis, feeding, respiration and decomposition
Nitrogen
essential component of metabolism, required for the synthesis of proteins and nucleic acids
nitrogen can not be used in its gas form so must be fixed in the form of ammonium ions or nitrates to be of any use to plants
Nitrogen cycle
- N is fixed by bacteria such as Rhizobium (in root nodules of leguminous plants) because of symbiotic mutualistic relationship with the plant
- N gas is reduced to ammonium ions in ammonification
- ammonium ions are released by bacteria
- Nitrosomonas oxidise ammonium ions to nitrites (NO2-)
- Nitrobacter oxidised nitrites to nitrates (NO3-)
- plants absorb nitrates from soil
- denitrifying bacteria convert nitrates back to oxygen, nitrogen gas for respiration
Limiting factors for carrying capacity
competition takes place when there is limited supply of…
- food
- water
- light
- oxygen
- nesting sites
- shelter
- parasites and predators
- carbon dioxide
- mates
Predator-prey relationships
- give rise to fluctuating population size
predator population grows more prey consumed prey decreases too little prey fewer predators prey increases predator growth
Conservation
- maintain or increase the biodiversity within a particular habitat (sustainably)
