Ecosystems Flashcards
Ecosystem
-group of living and non living things and the interrelationship between them
Components of an ecosystem
1.habitat- where an organism lives
2.population- all of the organisms of the same species that live in the same place at the same time
3.community- all of the populations of different species that live in the same place at the same time
Niche
-role of each species in the ecosystem
-difficult to fully define as each organism interacts with living and non living parts
Biotic factors effecting ecosystems
-producers eg.plants that supply chemical energy
-consumers eg. primary, secondary, tertiary
-decomposers eg. fungi that feeds on waste material
Abiotic factors affecting ecosystems
-pH
-humidity
temperature
-concentration of pollutants
-at extreme values, species may perform better or worse or may die
Types of changes in ecosystems that affect population size
-cyclic- repeating rhythm eg. predator and prey fluctuations
-directional- not cyclic, one direction eg. erosion
-unpredictable/erratic- no rhythm and no constant direction eg. effects of hurricanes
Biomass
-organic (glucose) and inorganic (mineral ions) components of a plant
Trophic level
-level at which an organism feeds in a food chain
Biomass transfers
-each trophic level, some biomass is lost (either through respiration and heat or dead organisms and waste material)
-biomass is less at higher levels of the food chain
-represented as a pyramid of numbers
-producers at bottom with biggest bar, consumers above, bars smaller
Calculating efficiency of biomass transfer
=biomass at higher trophic level/ biomass at lower trophic level x100
or
=biomass of primary consumer/ biomass of producer x100
Productivity
rate of production of new biomass by producers
Gross primary productivity
rate which plants convert light energy into chemical energy through photosynthesis
Net primary productivity
proportion of energy from the sun available to enter the food chain
How farmers increase primary productivity (plants)
-plant crops early in the season so they get a lot of light
-breed drought resistant strains
-greenhouse so plants kept warm
-crop rotation which stops reduction in soil level of in organic materials
-pesticides, fungicides, herbicides
How farmers increase secondary productivity (livestock)
-harvest animals just before adulthood to minimise loss of energy
-selective breeding, animals with faster growth rates
-antibiotics to reduce loss of energy fighting pathogens
-stopping grazing which prevents loss of energy
Steps in saprophytic decomposition
-secrete enzymes onto waste material
-digest the material into small molecules and the absorb them into their body
-molecules are then stored or respired
Nitrogen cycle
-nitrogen fixation
-ammonification
-nitrification
-denitrification
Nitrogen fixation
-plants can’t use N2 directly due to triple bond
-has to be fixed by lightning, haber process or nitrogen fixing bacteria
-bacteria live in root nodules and have mutualistic relationship- supplies plant with fixed nitrogen in exchange for glucose
-proteins in nodules absorb O2, making conditions anaerobic which is optimum for nitrogen reductase
Ammonification
-NH4+ is released from ammonification by bacteria involved in putrefaction of proteins found in waste matter
Nitrification
-oxidising NH4+ to NO2-
or
-oxidising NO2- to NO3-
Denitrification
-some bacteria convert NO3- to N2 gas
-they do this in anaerobic conditions as they use NO3- as a source of O2
Carbon cycle
-driven by photosynthesis and respiration
-animals and plants respire producing CO2
-plants use CO2 in photosynthesis
-carbon is exchanged between air and water, forming carbonic acid when dissolved in water or hydrogen carbonate
Succession
progressive change in a community of organisms over time
Primary succession
development of a community from bare ground
Secondary succession
take solace in a previously colonised but disturbed or damaged habitat
How primary succession occurs
-algae and lichens live on bare rock= pioneer community
-erosion of rock and build up of waste material creates enough soil for larger plants to grow
-larger plants succeed the smaller plants until a stable community is reached= climax community
Succession on sand dunes
-pioneer species eg sea rocket colonise sand just above high water mark
-sand builds up around plants due to wind. Plants die and decay, nutrients accumulate so larger plants can colonise it
-with more stability and nutrients, plants like marram grass start to grow
-as nutrients build up other plants colonise the sand
Deflected succession
-when succession is stopped or interfered with eg. cutting the grass, using herbicide/fertiliser
2 types of data quadrants can collect
-Distribution- presence or absence of each species
-Abundance- number of individuals of each species
Where to place a quadrat
(sampling)
Random sampling- use random numbers and plot coordinates
Systematic sampling- take samples at regular distances
Population size of species=
mean no. individuals of species in each quadrant/ fraction of total habitat area covered by single quadrat
2 types transects
-Line- regular intervals, count the species touching the tape
-Belt- regular intervals, place quadrat next to the line
Using pilot study to determine how many samples to take
-take random samples across the habitat and create a cumulative frequency table
-plot cumulative frequency against quadrat number
-where the curve levels off is how many quadrats to use
