Ecosystems Flashcards
Succession
Progressive change in a community or organism over time
-directional change
Primary Succession
Development of a community from bare ground
- sand dunes
Pioneer community
Species that begins the process of succession, often colonizing an area as the first living things there
-opportunist/grow quickly/short-lived
-don’t need many nutrients
-marram/moss and lichen
-microhabitat for invertebrates i.e. spiders and mites
Climax community
The final stable community that exists after the process of succession has occurred
i.e. UK Woodland communities
- when reached succession will not go any further but does not mean there won’t be any further change
Secondary Succession
Takes place on a previously colonised but disturbed or damaged habitat
What is each stage called in succession
Sere
- each new community is better adapted to the changed environment which has been provided by the previous community
Process of succession on sand dunes
1) Pioneer Species (Sea rocket/ Sandwort) colonize above water mark - tolerate salty water and unstable sand
2) Winds blow and sand build up around base of plants/ plants die and decay nutrients accumulate/ sea sandwort and Sea couch grass - underground stems helps to stabilize
3) More nutrients and stability (sea spurge and marram)
4) More plants colonize - many are leguminous (hare foot clover and birds foot trefoil) convert nitrogen to nitrate
5) Nitrate available more species colonize (sand fescue and vipers bugloss)
Why are more nutrients accumulated in the soil
Plants decay and organic matter goes back into the soil enabling other plants to grow
Deflected Succession
happens when succession is stopped or interfered with i.e. grazing/ lawn mowed
- sub climax community that results is a plagioclimax
What are problems with deflected succession
makes it hard for preservationists and conservationists to decide which habitats warrant conservation/ preservation
ecosystem
A community of biotic and abiotic factors interacting with an environment
Habitat / Population / Community / Niche
Habitat = a place where an organism lives
Population = one species, living at the same time and breeding
Community = Lots of species interacting with each other in one place
Niche = a role of a species within an ecosystem
Biotic factors
Dependant on the niche the Living things in an ecosystem can affect one another:
- Competition (resources)
- Disease
-Predatation
( Parasitism, Producers, Consumers)
Abiotic Factors
Non Living components that affect an ecosystem:
- Sunlight
-Wind speed
- Humidity
- Soil structure - measure with a penetrometer
- soil pH
- Temperature
Can vary in space and time, also could be disturbance i.e. storms, biotic components i.e. the canopy in a rainforest affects temp and humidity
What happens at extremes of abiotic factors
Can affect an organisms performance and may even cause death
Ecosystems are dynamic - what does this mean and what are the types of change
Subject to change:
- Cyclic - repeat in a rhythm i.e. movement of tides/ changes in the day
- Directional - one direction and last for long periods of time i.e. coastal erosion / deposition of silt in an estuary
- Unpredictable/ erratic - No rhythm and no constant direction i.e. the effects of hurricanes or lightening
Biomass transfer
Transfer of biomass from one trophic level to another
Trophic level
The level at which an organism feeds on a food chain
What happens to energy at each trophic level of a food chain
Only 10% of energy is transferred from one trophic level to the next - this means we have a limit to our food chain
Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition
How is biomass lost in a food chain
- life processes respiration which releases energy from glucose and some of this energy is converted to heat and materials lost in CO2 and H20
- Dead organisms and waste material = only available to decomposers including bones / hair that cannot be eaten by consumers
What does the pyramid of numbers represent
Representation of organisms at each level of the food chain, area of each bar in the pyramid is proportional to the number of individuals at that trophic level
- counting number of individuals does not always provide an accurate picture of how much biomass exists at each level
Pyramid of biomass
Representation of biomass at different trophic levels of a food chain; the area of each bar is proportional to the dry mass of all the individuals at that trophic level
1) Collect all individuals and put them in oven at 80 degrees until all the water has evaporated
2) Check periodically by checking mass of organisms
3) Once mass plateaus = all water has evaporated
Damaging to ecosystem so measure wet mass and calculate dry mass on previously est. data
Ecological efficiency
(Biomass at higher Tropic level / lower) x100
Why is the gross primary productivity low at the start of a food chain and entry of biomass
- Photosynthesis produces glucose so biomass transfer inefficient
- in optimal conditions only 40% of light energy from the sun enters the reaction of photosynthesis:
- sunlight bounces off of leaves/ chloroplasts absorb only within a certain spectrum
and only half of this is involved in glucose production - 2/3 glucose used for starch and cellulose etc. for growth - rest respired
Only 1-8% of sun remains to enter the food chain: Net primary productivity is 8%
Gross primary productivity
The rate at which plants convert light energy into chemical energy through photosynthesis
Net productivity
The proportion of energy from the sun available to enter the food chain
1-8%
Why does net primary productivity vary
-Solar input
-Temperature
-Moisture levels
-CO2 levels
-Nutrient availability
-Community interaction (i.e. grazing by herbivores)
Productivity
The rate of production of new biomass from producers
Primary productivity
Rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances
Secondary productivity
Rate at which consumers convert the chemical energy of their own biomass
How do humans manipulate primary productivity
1) Planting pants earlier in the year to provide a larger growing season as the plants will harness more light and perform more photosynthesis
2) Irrigating crops and producing drought resistant strain crops
3) Growing plants in greenhouses provides warmer temperatures increasing the rate of photosynthesis and production of biomass
4) Crop rotation stops the reduction in soil levels of inorganic materials and stops the rate of biomass slowing through photosynthesises
5) Pesticides stops pests removing biomass from the foo chains and reducing the yield
6) Fungicides stops fungal disease from reducing biomass
7) Herbicides stops competition for light
How have humans improved secondary productivity
1) Harvesting animals before adulthood minimises loss of energy
2) Selected breeding - improved animal breeds
3) Antibiotics to avoid loss of energy from parasites and pathogens
4) Zero grazing maximises energy allocated to muscle by stopping animals from moving and keeping environment constant
Decomposers
Organisms that feed on dead waste and organic material releasing the nutrients and energy
What organisms recycle organic material within eco-systems
Decomposers i.e. bacteria and fungi that feed saprotrophically, Saprotrophs
How do saprotrophs work
1) Saprotrophs secrete enzymes onto dead waste and material
2) Enzymes digest the material into small molecules, absorbed into the saprotrophs body
3) Once absorbed, molecules are stored/ respired to release energy
What would happen if there were no decomposers
Valuable nutrients would stay trapped within the dead organism
- digesting dead/waste material, micro-organisms obtain a supply energy to stay alive and the trapped nutrients are recycled
What is Nitrogen used for
Living things need to make proteins and nucleic acids
In the Nitrogen cycle what are the processes
Ammonification; Nitrogen fixation ; Nitrification ; Denitrification
Why can’t plants use nitrogen in the air
very unreactive and hard for plants to use directly
- Plants need a supply of ‘fixed’ nitrogen i.e. ammonium ions (NH4+) / Nitrate ions (NO3-)
What do nitrogen fixation do
Convert atmospheric nitrogen to ammonia
How does nitrogen fixation work in the soil
Azobacter supplies 90% of the nitrogen fixation
- Lives in the soil and fixes nitrogen gas, within the air in the soil, using it to manufacture amino acids/ nucleotide bases
How is nitrogen fixation different with bean plants
Rhizobium lives inside the root nodules of beans/clover etc.
- mutualistic relationship, provide plant with fixed nitrogen and receive carbon compounds i.e. glucose in return
How do the bacteria ‘fix’ the nitrogen
- Proteins (leghaemoglobin) in the nodules absorb O2 keeping conditions anaerobic.
- Bacteria then uses enzyme nitrogen reductase, to reduce nitrogen gas to ammonium ions that can be used by host plants
- this can then be absorbed into the plant / nitrification
Ammonification
Ammonium ions released by bacteria involved in putrefaction (decay) of proteins found in dead waste/organic matter
Nitrification - how bacteria get their energy
- After ammonification the ammonium ions that are not absorbed back into the plant are released and converted to nitrite then nitrite to nitrate
- Rather than obtaining energy by sunlight, some chemotrophic bacteria obtain by oxidising ammonium ions to nitrites
/ others obtain by oxidizing nitrites to nitrates
What happens to the nitrates after nitrification
Absorbed from the soil by plants and used to make nucleotide bases and amino acids
- by active transport/ diffusion
What does oxidation need the soil to be
Oxidation requires oxygen therefore process can only happen in well aerated soils
Denitrification
other bacteria convert nitrates back to nitrogen gas which then combines with hydrogen and then can be converted back to ammonium ions (nitrogen fixation)
Nitrogen fixation definition
Conversion of atmospheric nitrogen into nitrate or ammonium
Nitrification definition
Oxidation of ammonium ions to to nitrite and nitrite to nitrate
Denitrification
Conversion of nitrates to nitrogen gas
Haber process
N2 from lightening converted in Haber process to fertilisers which produce nitrates
How are the conditions in the soil kept anaerobic (denitrification)
Waterlogged soil will have water filling up its air spaces, hence very low oxygen levels within
There is no light on the ocean bed, what producers are within this ecosystem, and how do they convert their energy
Producers are thermophilic bacteria and use chemical energy
Why is pyramid of biomass more effective then pyramid of numbers
P of N - does not reflect varying sizes of individuals
P of B - More accurate rep. of how much biomass is available at each trophic level
Why is there no quintenary trophic level
Not enough energy or material in the fifth level to sustain a viable population
How is carbon used
CO2 from the atmosphere is taken up by photosynthetic organisms and used to make organic molecules
Slow geological processes: formation of sedimentary rocks; fossil fuels - contribute to the carbon cycle over long decades
Carbon cycle - biotic
-CO2 in air, dissolves and reacts with water to form HO3-
-Photosynthesis coverts CO2/HO3- to organic molecules
- Passed through food chains and cellular respiration coverts organic carbon back to CO2
Carbon cycle - decomposers
Release CO2 also back into atmosphere when breaking down dead organisms
Carbon cycle - geological
-Long term storage of organic carbon occurs when matter from living organisms is buried deep underground/sinks and forms sedimentary rock at the bottom of oceans
- eventually = limestone = biggest carbon store
How do volcanoes release carbon back into the atmosphere
Eruption of volcanoes - tectonic plates/ subduction
What does fertiliser run off cause
Eutrophication
Causes growth of algae which limits O2 availability at night
bacteria names in nitrogen cycle
Nitrogen fixing - azobacter/ rhizobium
Nitrification - Nitrosomnas/ Nitrobacter
How to calculate the dry mass of grass
calorimeter/ dry mass calculated as material burnt in oxygen
How do leguminous plants return nitrate back to the soil
decomposition
