Energy Transfers And Productivity Flashcards
What do ecosystems contain
All the living components (i.e. biotic factors such as organisms and their interactions)
All the non-living components (i.e. abiotic factors such as temperature and rainfall)
What are primary producers
Transfer light energy from the sun to synthesise organic molecules eg glucose in photosynthesis
They then use respiration to transfer energy from glucose into ATP
This acts as an immediate source of energy for living organisms
The rest of the glucose is used to make other biological molecules that the plant requires
How does the producer play a key role in the food chain
The chemical energy in these biological molecules can then be used by other organisms within the community known as consumers (i.e. the organisms in higher trophic levels)
How many tropic levels are there
Primary consumers (herbivores or omnivores) feed on producers
Secondary consumers (carnivores or omnivores) feed on primary consumers
Tertiary consumers (carnivores or omnivores) feed on secondary consumers
Can be more but oftener limited by insufficient energy
What are decomposers
Organisms tha break down dead and decaying material of organisms from all trophic levels
What are the 2 types of decomposers
Saprobionts - bacteria and fungi - carry out extra-cellular digestion, secrete enzymes onto dead/decaying matter which then break it down into a food source
Detritivores- earthworms,woodlice, millipedes and centipedes - feed on dead/decaying material whilst directly breaking down material - they also increase the SA for bacteria and fungi to act upon
What are food webs
These show all the different interactions that exist within a community
However not as accurate as don’t show actual energy
What is biomass
The total mass of living material in a specific area at a given time
- use the dry mass
-or the amount of carbon an organism contains
It is measured in grams per square metre or grams per cubic metre in an aquatic system
How does biomass change overtime
For example, the biomass of deciduous trees decreases over autumn and winter as they lose their leaves
This means that biomass is sometimes given with units of time as well
This shows the average biomass of an organism within a given area over that time period
For example, if the average biomass of a group of oaks trees over the course of a year is found to be 13,000 kg, the biomass may be given as 13,000 kg y⁻¹ (this means 13,000 kg per year)
If the average biomass of 1 m² of a grass field over the course of a year is found to be 0.15 kg m⁻², the biomass may be given as 0.15 kg m⁻² yr⁻¹ (this means 0.15 kg per square metre per year)
How is calorimetry used to estimate chemical energy stored in biomass
This involves burning the sample of dry biomass in a piece of equipment known as a calorimeter
The burning sample heats a known volume of water
The change in temperature of the water provides an estimate of the chemical energy the sample contains
What are the limitations of calorimetry
It can take a long time to fully dehydrate (dry out) a plant sample to find its dry mass
This is partly because the sample has to be heated at a relatively low temperature to ensure it doesn’t burn
Depending on the size of the sample, the drying process could take several days
Precise equipment is needed, which may not be available
A very precise digital balance should be used to measure the mass of the plant sample as it is drying (to detect even extremely small changes in mass)
It is preferable to use a very precise digital thermometer when measuring the temperature change of the water in the calorimeter (again, to detect even very small temperature changes)
The more simple and basic the calorimeter, the less accurate the estimate will be for the chemical energy contained within the plant sample
This is due to heat energy from the burning sample being lost and not being transferred efficiently to the water
A bomb calorimeter ensures that almost all the heat energy from the burning sample is transferred to the water, giving a highly accurate estimate
What is the method for carrying out calorimetry
Weigh the crucible (heat-proof container) without the sample first
Place the sample in the crucible
Place the crucible in the oven
Set the oven to a low temperature (if the temperature is too high the sample may burn, which would cause it to lose biomass)
Remove and weigh the crucible (containing the sample) at regular intervals during the drying process
Once the mass of the crucible (and sample) stops decreasing and becomes constant, the sample is fully dehydrated (all the water has been removed)
From this final constant mass, subtract the original mass of the crucible (without the sample in it) to find the dry mass of the sample
Why is only some of the suns light available to be used
Over 90% is reflected back
Not all wavelengths of light can be absorbed and used for photosynthesis
Light may pass straight through the leaf and not fall on a chlorophyll molecule
May be other limiting factors
What is gross primary productivity
The total quantity of the chemical energy stored in plant biomass in a given area or volume
Easily comparable as is in an area/ volume
What are the units of GPP
Gross primary productivity is expressed using units of energy/mass per unit area per unit time
Time must be included as it is a rate
For example
Mj m–2 y-1 (megajoules per square metre per year)
kg km-2y-1 (kilograms per square kilometre per year)
What is net primary productivity
Energy stored after respiratory losses
NPP = GPP - respiratory losses
Why is so little energy passed up the food chain
-not all part of plants or animal will be eaten eg bones hair
-of the parts eaten not all is digested and would be lost in faeces
-some energy is lost in excretory materials
-some is lost in heat energy from respiration
How is net productivity calculated for animals
N = I - (F + R)
I = chemical energy store of ingested food
F = energy lost in faeces or urine
R = energy lost in respiration
How is the efficiency of energy transfer calculated
Energy available after transfer/ energy available before X 100
What are ecological pyramids
Representation of the numbers of organisms at each tropic level
There will be greater numbers at lower levels and less at higher levels
What are the problems of ecological pyramids
Size isn’t taken into account
What are biomass pyramids
Used to overcome number pyramids
Dry biomass is measured
Greater biomass at bottom - usually
What are pyramids of energy
Total energy that flows through each trophic level - always get an upright pryamid
Measured in kJm-2 year -1
why do nitrogen,carbon and phosphorus have to be recycled
there is a limited source of nutirent ions in a useable form
how are nutrients taken up by plants
-as inorganic molecules
-they are then incorporated into complex moeucles and then passed on in the consumer chain when they are eaten
-they are then demopressed by saprobionts - decomposers
how is nitrogen taken up by plants and why can it not be used in natural form
-in nitrate ions as they cant be used directly form in the air
-mostly in the form od ntirate ions by roots taken up in the process of acitve transport
-the nitrogen is used in amino acids and nitrogenous bases in DNA
what are the four main processes in the nitrogen cycle
-ammonification
-nitrification
-nitrogen fixation
-denitification
what is ammonification
-when organisms die the nitrogen-containing substajces they contain are digested by saprobiotic bavcteria
-nitrogen from consumers is also made avaliable to saprohiotic bacteria through nitrogen-containing excretory products
-these relases ammonium ions - NH4+ -
what are saprobiotic microrganisms
-feed on these materials releasing ammonia which forms ammonium ions in the soil
-they do thus by removing the amino gorups from amino acids converting them into ammonia or ammonium ions
what is nitrification
-another group of bacteria, the nitrifying bacteria, oxdise the ammonium ions into nitrites (NO2-)
-and then futher oxidise into (NO3-)
-this process is an oxidation process it is very improtant that the soil contains air spaces - so argiculture this requires good soil management
what is the process of nitrogen fixation
nitrogen gas is coverted to nitrogen-containing compounds - this carrried out by two different types of micro-organsims
-free-living nitrogen fixing bacteria - nitrogen gas is converted to ammonia and ammonium ions, they are then used to make amino acids and proteins and other nitrogen-containing compounds - these will be rleasead into the soil into the soil when they decay
-mutualisitic nitrogen-fixing bacteria - these live in the root nodules of legumes - it is a mutaulaistic reltaionship as both partners gain - the bacteria use carbs from th eplabt and the plant gains amino-acids from the bacteria
how can the nitrogen be fixed naturally and atrifically
-artificially - the haber process
-naturally - when lightning passes throught the atmosphere and fixes the nitrogen from the air
what is the process of denitrification
-anaerobic process and often in waterlogged soilds
-fewer aerobic nitrifying and nitrogen-fixing bacteria bacteria are found and there is an increase in an aerobc denitrifying bacteria
-nitrates are coverted into nitrogen gas
what happen to nitrogen fixing if the soil is waterlogged
-less/no oxygen present
-active transport and nitification
-therefore it is very important in agriculture as it rould negatively affect productivity
what are mycorrhizal fungi
-evolved symbiotic/mutualistic relationship with plants
-comosed of long, thin filamnets known as hyphae whic interact with the roots of plants
-these hyphae greatly increase the surface area of the root systems of the plants increasing the amount of water and mineral ions that can be absrobed by the plant roots
-in return the fungi recieve organic comound such ad carbs
where is phosphorus used for
-important bio molecule
-found in DNA,RNA and ATP and phospholipid bilayer
-found in bones and teeth
what is phosphorus found as
-phosphate ions which are located in water,soil and sediments
why does the phosphorus cycle not involve the atmosphere
it is not found in gaseous form
what is the main source of phosphorous and how is it taken up by plants
-sedimentary rock
-phospte ions rleased by chemical weathering and washed into the soils by rain
-the phospahte ions then are avaliable for uptake by plants and icorportated into their biomass
-can then be passed on from conusumer to consumer in a food chain
what is another way in whihc phsopate ions can be taken up
-when organisms produce faeces or die the phosphorus containing substances in their tissues or feaces are digested by saprobiotic bacteria releasig the phosphate ions which can then be taken up by plants
-animal urine and brid guano are rich in phospate ions
-can also be realesed in bones or the shells of animals but are very slow to break down
how is the phosphate returened to sedimentary rock
the algae is eaten and when organism and aqauatic life die they fall to the bottem of the ocean and are incorportated into ocean sediments - possibly forming mroe sedimentary rock over the years
why does farming disrupt the natural uptake of mineral ions
in a natural ecosytem the deomposers would break down the dead remains of plants but in crop harvesting this is not possible
what are the 2 main types of fertiliser
artiifcial inorganic fertiliser
natural organic fertiliser
what are artificial inorganic fertiliser
-come in the from of pellets, granules or liquids that contian a mix of inorganic nutrients
-these are expensive but quick-acting and reliable
what are the problems with artificial inorganic fertiliser
-they may damage the soil but the biggest [roblem is that they are very soluble and easily lesached into aqautic environments
-this can lead to eutrophication which resukts in the deoxygenation of the water and death of aquatic organisms
what are natural organic fertiliser
-these are dead and ecaying remains of plants and animals such as manure and sewage sludge
-they promtoe humus formation and can improve soil textrure - however they are undpredictable as the composition is unkown
fertilisers consqeuneces
-used in the correct amounts fertilisers can greatly increase crop yeild but above a certain level the increase in crop yeild for each unit of fertilser gets less
-they can reduce crop yeild and damage the environment if used in excess
