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)
Preservation
- maintain biodiversity levels and habitats by minimising the effects of human activities
Reasons for Conservation
economic, social, ethical
- food
- medicine
- tourism
- water quality
- pollination of crops
- right to survive
- aesthetic reasons
Coppicing
cutting down trees close to the ground to encourage new growth as stumps have good root systems
Selective felling
felling only grown mature trees allowing younger trees to grow
replacing them with seeds
Pollarding
form of coppicing, trees cut further up to prevent deer from eating new shoots
Sustainable fishing
quotas - limits no. of certain species that can be caught in an area
nets with bigger mesh size - allows immature fish to escape so only mature fish are caught
seasonal fishing - protects breeding season
Management of ecosystems
- control no. of tourists
- involve local communities
- educate local communities
- active management of vegetation
- control of introduction of species
Galapagos islands
due to increase in tourism, demand for resources, energy has decreased in the GI
waste and pollution has increased
overfishing too
many non-native species have been introduced which outcompete native species
conservation projects:
- goat culling
- captive breeding
- limiting tourism in specific areas
Equilibrium in succession
stable community
Carrying capacity
maximum population size that an ecosystem an support
Sustainability
using resources in a way that also maintains them for future generations
Human influence on biomass
- increases biomass transfer
favourable conditions e.g. water and temp are maximised increases soil nutrients and pests and weeds are removed
Egestion vs excretion
excretion = waste products egestion = rid of undigested material
Biomass
mass of living material present in a place or organism (dry)
Trophic level
stage/position in food web
