Unit 6 - Ecosystems Flashcards
Ecosystem
All the interactions between the living and non-living components in a defined area
Biome
Large ecosystem
Open ecosystem
When living things can move between ecosystems
Closed ecosystems
When living things cannot easily move between ecosystems e.g. islands
Niche
Role of a particular species
Biotic
Involves other living organisms
Biotic factors affecting ecosystems
Predators Food supply (prey) Disease Cooperation between species Competition between species
Abiotic factors affecting ecosystems
pH Conc of pollutants Temp (climatic) Moisture/ rainfall/ relative humidity O2 level Soil type (edaphic) Light intensities
How does low light intensity affect the ecosystem
Plants develop photosynthetic pigments that require less light
Grow larger leaves
Reproductive systems that only work in optimum light intensities
How does temp affect the ecosystem
Temp has the biggest effect on enzymes in the organisms that live in the ecosystem
May trigger migration/ hibernation
Dormancy/ leaf fall/ flowering in plants
How are ecosystems organised
In trophic levels
Producers in an ecosystem
Lowest trophic level
Involves autotrophs, chemotrophs and photoautotrophs
Autotrophs
Convert energy from environment into complex organic matter, then are used as respiratory substrates or for growth
Chemo/photoautotrophs
Use light/ chemicals to convert small inorganic molecules into complex organic ones
Consumers
Higher/est trophic levels
Feed on complex organic matter made by autotrophs and other organisms and use the products of digestion as respiratory substrates or for growth
1’<2’<3’
Decomposers
Feed on waste or dead organsims to gain energy by digesting and respiring organic matter
Recycling - returns inorganic ions to the air/soil
Why are ecosystems dynamic
Always changing due to many interlaced intearctions that any small change causes several others–> alters flow of biomass
Types of changes in ecosystems
Cyclical - repeated change e.g. seasons, day/night
Directional - in one direction e.g.global warming, erosion
Unpredictable/ erratic - no rhythm or constant direction e.g. volcanic eruption
Trophic level
Level at which an organism feeds
Components of an ecosystem
Habitat
Population
Community
Habitat
Where an organism lives
Population
Where all the members of a species living in some place at a given time
Community
All the populations of diff species who live in some place at a given time, who can interact w/ each other
Why are there fewer consumers at higher levels
Energy (biomass) is lost at each trophic level so unavailable to organism at next trophic level, therefore there’s less energy available to sustain living tissue
How is biomass lost
Cellular respiration - conversion to inorganic molecules such as CO2 and H2O
Excretory materials
Indigestible matter
Not everything is fit for consumption e.g. bones
Transferred at metabolic heat (movement)
Loss of biomass in endotherms vs ectotherms
Ectotherms use less energy in maintaing body heat so there is more biomass availabe
Saprotrophs
Secrete extracellular enzymes onto dead/waste materials
Digest the materials into small molecules which are then absorbed and stored/respired
Why is the producer efficiency v. low
Approx 90% of light is reflected, unusable wavelength and transmitted through leaf
Limiting factors
Energy used for photosynthetic reactions
Succession
Progressive change in the structure and species composition in a community
Affects vegetation first but then brings about corresponding changes in bacteria, fungi, insects, birds and mammals
Climax community
Final, stable community that exists after the process of succession has occurred
Usually woodland communities
Deflected succession
Happens when succession is stopped/interfered w/ e.g. grazing so a plagioclimax develops as the species are stuck in that one stage of succession
Pioneer species
Species that begin the process of succession, often colonising an area as the first living thing there
Primary succession
If a community is developed from bare ground e.g. volcanic eruptions
Pioneer communities start succession —> conditions change (build up or organic material /nutrients) and other species succeed them
Larger plants continuously succeed small plants until a climax community is formed
Secondary succession
Does not start from bare ground
Takes place on a previously colonised but damaged/disturbed habitat
Why are sand dunes helpful in terms of succession
Shows us the stages of succession in order of occurrence whereas usually we only see the current stage
How does succession affect species diversity
Increases it however dominant species may outcompete the smaller species killing whole species off
Weathering
Breakdown or decomposition of rock in situ
How does weathering contribute to succession
Decomposition of rock increases soil depth/ changes soil composition
Favouring new species
Calculating net primary production
Gross primary production = npp - products of respiration
Calculating efficiency of energy transfer
Net production/ food intake x 100
Plagioclimax
Sub-climax community when succession has been deflected
Ways to deflect succession
Mainly agriculture and human activity e.g. Grazing Burning Application of fetilisers Application to herbicide Exposure to excessive amounts of wind
How does succession affect biomass
Increases it due to more organisms in the ecosystem
Why should sub-climax communities be conserved
Higher species diversity than climaxx communities - still contain some sub-climax species and climax species
Results in conserving a much wider range of plants and animals that dont live in the climax community
Pioneer species on sand dunes
Species that can tolerate salty water, lack of fresh water and stable sand e.g. sea rcket
Pioneer species on bare rock
Algae and lichens as they don’t need to be anchored into the soil
Increasing primary productivity
Some crops are planted early Irrigating crops Drought resistant crops Using greenhouses Crop rotation Fertilisers (provides inorganic ions) Pesticides/ pest resistant crops
How does planting some crops early increase primary productivity
Provides a longer growing season to harvest more light
How does irrigating crops increase primary productiviy
Water is readily available for the light dependent stage of photosynthesis even when rainfall is below average
How does growing crops in a greenhouse increases primary productivity
Provides a warmer temp —> increases the rate of photosynthesis
How does crop rotation increase primary productivity
Stops reduction in soil levels of inorganic ions e.g. K^+ or NO3^-
Crop rotation
Growing a diff. crop in each field on a rotational cycle
How does use of pesticides increase primary productibity
Prevents loss of biomass and lowering yield of plant
Why do plants need NH4+
Maintains pH
Why do plants need NO3-
Part of the nitrogen cycle
Function of K+ in plants
Improves growth of leaves
Function of PO4 3- in pants
Improves growth of roots
Increasing secondary productivity
Harvesting animals before adulthood Selctive breeding Animals treated w/ antibiotics Zero grazing Keeping environmental temp constant - prevents energy loss through homeostasis
How does harvesting animals before adulthood increase secondary productivity
Minimises loss of energy as younger animals invest a larger proportion of energy into their growth
How does selective breeding increase secondary productivity
Produces improved animal breeds w/ faster growth, increased egg production and increased milk production
Zero grazing
Bringing food directly to animals
Maximises energy allocated to developing muscle by reducing need to move
Processes in the carbon cycle
Photosynthesis Respiration (animals and plants) Anaerobic respiration (dead organic matter and excreta) Fossilisation Combustion Diffusion and carbonic acid formation Diffusion Decomposition Feeding Sedimentation
Processes adding to atmospheric CO2
Respiration
Combustion
Diffusion frm the sea to the air
Processes removing atmospheric CO2
Photosynthesis
Diffusion and carbonic acid formation in the ocean
Sedimentation
CO2 is used by plankton to produce calcium carbonate shells. When these die, their shells sink to the ocean floor and are buried by sediment
Fossilisation
Organic matter is buried and copressed over millions of years forming gas, coal and oil
Human interferences that affect the carbon cycle
Combustion
Population size (respiration and waste)
Deforestation
Farming
Effects of human interences w/ the carbon cycle
Global warming/enhanced greenhuse effect Ocean acidification from carbonic acid Warmer sea - less CO2 absrbed Removing photosynthesisers Releasing more CO2 through combustion of trees
Processes in the nitrogen cycle
Nitrification Assimilation Denitrification Nitrogen fixation by organic and non-living processes Ammonification
What is nitrogen fixing
Conversion of atmospheric nitrogen (N2) into nitrogen containing compounds
Nitrogen fixing
Carried out by denitrifying bacteria (Azobacter) and mtualistic bacteria (Rhizobium) in plant root nodules. Nitrogenase reduces N2 to NH3 to form amino acids
Atmospheric fixation
Haber process to make chemical fertilisers
Atmospheric fixation
Converting nitrogen gas into nitrates by lightning. The energy from lightning breaks the N2 into atoms which combine w/ oxygen and dissolve in rain
Ammonification
Converting nitrogen containg compounds (e.g. urea from urine) to NH3
Carried out by decomposers
Nitrification
Conversion of ammonium ions to nitrites (by Nitrosomonas) and then into nitrates (by Nitrobacter) by nitrifying bacteria (chemoautotrophs)
Assimilation
Nitrates in the soil are absorbed from the soil by plants and algae. Animals then eat plants and assimilate nitrogen compounds too
Denitrification
Conversion of soil nitrates to atmospheric nitrogen. Carried out by denitrifying bacteria in anaerobic conditions (e.g. waterlogged soil) who use the nitrates as the final e- acceptor in respiration instead of O2
Human activities affecting the nitrogen cycle
Use of fertiliser - neutrification, algae use up all the oxygen
Processes removing atmospheric nitrogen
Nitrogen fixation by bacteria
Atmospheric fixation
Haber process
Processes adding to atmospheric nitrogen
Denitrification
Similarities in nitrogen and carbon cycles
Involves plants and animals
Involves anaerobic respiration (decomposers)
Both cycles involve atmospheric chemicals
Differences in nitrogen and carbon cycles
Involves sea in cc
No fixation of CO2
Only uses organic processes in cc
N is fixed by bacteria vs on plants
Use of transects
Look for changes in vegetation across a habitat
Types of transects
Line
Belt
Line transect
At reg. intervals
Note of which species are touching the tape
Belt transect
At reg. intervals
Place a quadrat next to the line (interrupted belt transect) or move the quadrat along the line (continuous)
Used to sample succession
Estimating pop. size
Mean number of a species in a quadrat/ faction of the total habitat area covered by a single quadrat
Deciding how many samples to take
In a pilot study take random samples looking at species distribution
Plot quadrat number against cumulative frequency
When curve levels off use that number of quadrats
Units to measure primary productivity on land
gm-2 yr-1
Units to measure primaary productivity in water
gm-3 yr-1
Decomposes in the nitrogen cycle
Pass urea to next stage
