Energy And Ecosystems, Nutrient Cycles, Succession Flashcards
Producers
Plants and algae photosynthesise
Synthesis a glucose molecule from water and carbon dioxide
Light energy is needed
Light energy is ultimately stored in the bonds of the glucose molecule as chemical potential energy
Bio mass definition
All the biological molecules made by the plant and are not immediately used for respiration
Includes cellulose, starch, proteins, lipids etc
Represents the growth of the plant
How is biomass measured
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Mass of carbon
Dry mass
Energy value
Practical estimation of dry mass
1 heat in a low temperature oven to evaporate water in the tissues
2 until there is no further change in mass
3 calculate dry biomass
4 carbon content estimated as 50% of dry mass
Calculating energy in dry biomass
Dried biomass from a known area is placed in a calorimeter
Dry biomass is then burnt (combusted)
Energy released is used to heat water
Change in water temperature is used to calculate energy released
Energy per square metre per year is calculated
Gross primary production
The total amount of light energy captured in photosynthesis and stored in molecules as chemical potential energy
Respiration
The amount of energy lost from the plant in respiration. This returns to the environment as waste heat
Net primary production
This is the remaining amount of chemical potential energy stored in the biomass of the plant. This can be used for growth and reproduction
Reason for only 1-5% of light energy being captured
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Some light is reflected
Only certain wavelengths are absorbed
Light may not strike chlorophyll and pass straight through the leaf
May be other limiting factors
Some may be transferred into thermal energy
Why is NPP important
This is the energy in the new biomass made by the plant
Can be used to make new cells and tissues for growth and reproduction
It is also the part of the light energy captured by the plant that, through plant tissues being eaten; can be transferred to consumers
Net production in consumers
Consumers get their energy by ingesting biomass
Some of this is used for respiration by the consumer and is lost eventually as heat to the atmosphere
Some is indigestible so is lost as faeces and some is excreted as Urine
The rest is used to make consumer biomass ie growth
Only the energy in the net production can be passed on to the next consumer
Net production equation
N= I - (F+R)
N= net production I= chemical energy in ingested food R= respiratory losses F= chemical energy lost to the environment as gardes
Trophic level
The feeding position of an organism in a food web
Each layer of pyramid represents the net production at that level
Keep food chains short
To maximise food production from an area of land food chains should be kept short
This will reduce energy loses due to respiration and faeces and urine
More food is produced from an area of land if it is used for crop production rather than raising livestock
Reduce energy losses by animals in the food chain
Eg if humans intend to eat a cow, to maximise production it is important to ensure as much as possible of food eaten by cow is used for production
Farmers try to minimise the amount of food used by the cow for respiration or that is lost as faeces or urine
Reducing respiration in farming
Reduce movement of farming eg battery farming so less energy is wasted in movement and more of their food used in growth
Keep in heated habitats: reduces the amount of food used to keep itself warm
Slaughter the animal once it has completed this growth. Food used after this time will be wasted in maintenance of the animal
Simplifying food webs
Pesticides: remove insects and other animal pests that eat the crop
Herbicides: kill weeds which are competitors of the crop plant and so reduce yields
How ecosystems work
For organisms to live and grow they need supplies of both energy and matter
In most ecosystems energy ultimately comes from the sun and matter from soil or air
Principles of nutrient recycling
3 key processes
Uptake
Feeding.
Decomposition
Saprobionta
Micro organisms involved in decomposition
Include bacteria and fungi
Which decompose dead material and faeces
They secret digestive enzymes and absorb the products of digestion
Mycorrhizae
Fungi that live in close association with plant roots
Provide a very large surface area for uptake of minerals from the soil
In return for their minerals, the plant provides carbohydrates
An example of mutualism- a relationship between two organism where both benefit
Nitrogen cycle
(4 stages)
And why it is needed
Nitrogen fixation
Ammonification
Nitrification
Denitrification
Nitrogen is used to make amino acids and nucleic acids
It has a triple covalent bond which is too strong for nitrogen to be used directly
Nitrogen fixation
Nitrogen fixing bacteria covert convert nitrogen from the atmosphere into ammonia which can then be used to make amino acids, proteins and nucleic acids
Animals then use the proteins and nucleic acids
Where do nitrogen fixing bacteria live
Some live in the soil but many live in root nodules
In return for providing ammonia, the bacteria receive carbohydrates- mutualism
Only some plants have nitrogen fixing bacteria- legumes
Often these are grown to improve soils as they fix nitrogen which can be used again after the plants are ploughed and decomposed
Ammonification
Nitrogen containing compounds in plants and animals and in faeces are used by saprobiont bacteria in the soil
They digest proteins using secreted enzymes and absorb amino acids in which they can use
They then excrete ammonia and ammonium as waste products
Nitrification
Ammonia and ammonium compounds are absorbed and used by nitrifying bacteria living in the soil
These release nitrites and then nitrates as a waste product
Denitrification
In waterlogged soils there are bacteria that get their energy from absorbing nitrates and converting this into nitrogen gas which is released into the atmosphere
This can only happen in the absence of oxygen
They reduce the amount of soil nitrate and are bad for agriculture
Soil nitrates
Soil nitrates are essential for the growth of all plants that do not posses nitrogen fixing bacteria
Ways of increasing soil nitrates concentration
Activity of nitrifying bacteria
Lightning: N2 -> NO3-
Artificial fertilisers: NO3- and NH4+ ions
Natural fertilisers: manure-> saprobionts->NO3- ions
Ploughing in plants with nitrogen fixing bacteria -> decomposition-> NO3- ions
Land drainage: reduces activity of denitrifying bacteria
Ways of decreasing soil nitrate concentration
Waterlogged soils: denitrification
Harvesting of crops: prevents decomposition and return of nitrates to soil
Phosphorus
Needed to make DNA, RNA, ATP and phospholipids
Found in soil in the form phosphate ions
They come from the rocks through weathering processes
Phosphate cycle process
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- Weathering (from rain on rocks) into the soil
- Uptake by roots with help of microrrhizae
- Plants make ATP, DNA, phospholipids etc, eaten by animals
- Lost in animal waste products
- Saprobionts decompose detritus and faeces, release phosphate
- Weathering + carried into water and taken up by algae etc. Sedimentation also occurs in which phosphates become part of the sedimentary rocks on the sea floor
- Bird guano contains high concentrations of phosphate ions which are often used as fertilisers
Eutrophication
Learn
Natural cycles
Minerals taken up from soil by plants-> used to make biological molecules-> bacteria and fungi decompose biological mmolecules-> minerals taken up from soil by plants
Agricultural cycles
Fertilisers added-> minerals taken up from soils by plants-> used to make biological molecules -> crops and livestock harvested and taken away
No decomposition
Fertiliser
Natural or artificial
Artificial: inorganic chemicals, come in powders, pellets and liquid form, water soluble
Natural: manure/ slurry of compost, they decompose slowly to release minerals and are not soluble until decomposed
Leaching
Artificial fertilisers are washed off the land when it rain and dissolved ions end up in
This leads to eutrophication
Causes of eutrophication (3)
Artificial fertilisers leaching
Phosphates in washing powder in waste domestic water
Raw sewage
Succession
The process by which an ecosystem changes over time
Different communities of plants that replace each other in a predictable way
Each community changes the habitat in ways that make it less hostile for the next community of plants
We call each plant community a sere
Each plant community will have its associated community of animal
Climax community
Final
Stable and very long lasting
Often a forest
How does a primary succession start
Initial condition governed by abiotic variables
Often hostile and subject to large variations
No soil
Few minerals
High light intensity as no shade form plants
Extreme temperatures
Windy
Pioneers
Any plants able to cope with hostile conditions
Colonise the habitat
Pioneer community
On bare rock- lichens, can survive with little water or nutrient providing soil, they anchor themselves in cracks and can dissolve bare rock to get minerals . Also withstand long periods of drought
On sand dunes- marram grass
When lichens die
Decompose to become organic matter
This is the begging of a thin soil able to retain some moisture and to slowly release nutrients through decomposition
Condition become less hostile
Moss sere
Mosses and some grasses can now germinate and grow using moisture held by the thin soil
As the mosses and grasses die, decomposition adds to the developing soil
Herbaceous sere
In less hostile conditions, plants require more water and can now germinate and grow
Include small herbaceous(non woody) plants, ferns and grasses
They have good seed dispersal, producing large numbers of small wind dispersed seeds and germinate rapidly in thin soil
Out compete the mosses and pioneers for light and space
Tall plants reduce wind speed and light intensity
Helps soil to retain moisture and seeds germinate
Shrub sere
Soil has changed significantly
Deeper and contain more humus(decaying matter)
Has a PH closer to neutral
Water availability, light intensity and wind speed improves
Larger shrub plants now grow
Sub climax community forms
Grow fast and out compete lower plants
Tree sere
Woody trees grow slowly but become established
Diverse set of niches to supports a large variety of insects and other animals
Complex food web established
Climax community
Succession order
Pioneer sere Moss sere Herbaceous plant sere Shrub, small tree sere Woodland climax sere
Secondary succession
When a climax community is removed by humans or destroyed by natural disaster, community of plants may be lost
Pioneers and possibly other plants from later in the primary succession will re establish and succession starts again
Secondary succession is usually much quicker as there is already well developed soil which may contain lots of seeds
Plagioclimax
Human activity often deliberately stops or reserves a primary succession to maintain an earlier stage eg grassland
Often use animal to stop the succession such as by grazing
Conservation methods
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Managing succession
Seed banks
Captive breeding
Protected areas
Fishing quotas
Conservation methods
Managing succession
Eg animals grazing
Too many sheep then grassland is reduced so have to have the right number
Seed banks
Conservation methods
store of seeds from crop plants and from wild plants is kept in controlled condition- very cold and dry
Preserved so that if a species becomes extinct they can be revived
Captive breeding
Breeding of endangered species in a controlled environment
Protected areas
conservation methods
National parks and conservation areas
Fishing quotas
Conservation methods
Limits placed on number of fish caught to sustain populations
