What is biomass? the mass of living material
or the chemical energy stored in the plant
How can biomass be measured? mass of carbon that an organism contains
or dry mass of its tissue per area
Describe how we can determine the biomass. -sample of organism is dried
- in an oven set to a low temp
- weighed at regular intervals
- once mass is constant you will know all the water has been removed
- result from the sample can be scaled to give total population or area
Whats a typical unit for dry mass? kg m⁻²
The mass of carbon... is generally taken to be 50% of the dry mass
Whats the GPP? Gross primary production:
total amount of chemical energy converted from light energy by plants in a given area
Whats R? Respiratory loss:
50% of GPP is lost to the environment as heat when plants respire.
Whats the remaining chemical energy called? NPP: Net primary production
Energy available to the plant for growth and reproduction
Also energy available to organisms at the next stage in the food chain
How do we calculate NPP? NPP = GPP - R
How is the NPP stored? As biomass
How can primary production be expressed? as rate - primary productivity
What are the typical units for this? kJ ha⁻¹ year⁻¹
How do consumer store their chemical energy? in their biomass
Around how much energy is lost? 90%
How? not all the food is eaten (bones and roots)
some parts are indigestible so egested as faeces
some energy is lost as respiration or urine
What happens to the energy that's left? Stored as the consumers biomass
Is the consumers net production
Whats the calculation for net production of consumers? N=I-(F+R)
N = Net production
I = Chemical energy ingested in food
F = Chemical energy lost in faeces and urine
R = Energy lost through respiration
What can the net production of consumers be called? Secondary production or
secondary productivity
What do food chains and webs show? How energy is transferred through an ecosystem
What are food chains? simple lines of energy transfer
Each of the stages is called a trophic level
What are food webs? Show lots of interconnected food chains
What are decomposers? Break down dead or undigested material allowing nutrients to
be recycled.
Also apart of food webs
What do most farming practices aim to do? Increase the amount of energy that is available
for human consumption
What two ways do they do this? reducing the energy lost to other organisms
reducing the energy lost through respiration
How can they reduce the energy lost to other organisms? (Mainly for plants):
- reduce the number of pests using chemical pesticides
,insecticides and herbicides
- using biological agents
parasites and pathogenic bacteria and viruses
Farmers can use integrated systems that combine both
Combined effect reduce pest numbers even more so NPP is increased more
How can they reduce respiratory loss? ( Mainly for animals )
Control the conditions they live in:
- movement increases respiration so they restrict movement by keeping them in small pens
which are often indoor and kept warm so less energy is wasted by generating body heat
What are the other benefits of this? more food can be produced in a shorter space of time
often at a lower cost
What are the issues of this? Ethical issues
the conditions they are kept in cause animals to be in pain / distress or restrict their natural
behaviour so it should not be done
What do fungi form with the roots of plants? Form symbiotic relationships
What are these relationships known as? mycorrhizae
Describe the relatioship? - fungi have hyphae: long thin strands
- hyphae connect to plant roots
- increases surface area helping plant to absorb ions rom soil which are usually scarce
- hyphae also increases uptake of water
- fungi in return obtain organic compounds like glucose from plant
What is the nitrogen cycle? Shows how nitrogen is converted into a usable form and then
passed between different living organism and the non living environment.
Why do plants and animals need nitrogen? To make proteins and nucleic acids
Describe the process of the nitrogen cycle? Nitrogen fixation:
- N₂ to NH₄⁺ (ammonium ions)
- carried out by nitrogen fixing bacteria
- Bacteria use nitrogen gas, water and many ATP to make ammonium ions
- ammonia is a usable form of nitrogen ∴ these bacteria can make DNA, amino acids etc.
Ammonification:
- detritus to (NH₄⁺) ammonium ions
- carried out by saprobients
- secrete proteases onto protein in detritus to absorb amino acids
- some amino acids are deaminated and waste ammonium ions are excreted
Nitrification
- NH₄⁺ to NO₂⁻ (nitrite) to NO₃⁻ (nitrate)
- carried out by nitrifying bacteria / chemoautotrophs
- one class of bacteria oxidise ammonium ions into nitrite ions
- another class of bacteria oxidise nitrite into nitrate
- oxidation provides energy to fix CO₂ into organic product
Denitrification
- NO₃⁻ (nitrate) to N₂
- carried out by denitrifying bacteria
- use nitrate ions as their terminal electron acceptor
- so can perform a form of aerobic respiration
- bacteria removes nitrates from soil
, - farmers discourage these by drainage / ploughing which makes soil aerobic
What is the phosphorous cycle? Shows how phosphorous is passed through an
ecosystem
Why is phosphorous needed? to make biological molecules like phospholipids, DNA and
ATP
Describe the phosphorous cycle? 1) Phosphorus ions in rocks are released into the soil by
weathering
2) Phosphorous ions are taken into the plants through roots
Mycorrhizae increase the rate at which phosphorous is assimilated
3) Phosphorous ions are transferred through the food chain as animals eat the plants and are
eaten by other animals
4) Phosphate ions are lost through animals in waste products
5) When plants and animals die saprobionts break down the organic compounds and release
phosphate ions into the soil for assimilation by plants
Also release phosphate ions from urine and faeces
6) weathering of rocks releases phosphate ions into seas, lakes and rivers.
Taken up by aquatic producers such as algae and passed along the food chain to birds
7) waste products by sea birds is guano and contains a high proportion of phosphate ions.
guano returns a lot of phosphate ions to soils
used as a natural fertiliser
What happens when crops are harvested? nutrients are lost and are not replaced
What do we do to replace the lost nutrients? add fertilisers
What are the two types of fertilisers? natural and artificial
What are natural fertilisers? organic matter
include manure, composted vegetables, crop residues and sewage sludge
What are artificial fertilisers? inorganic
contain pure chemicals as powders or pellets
e.g ammonium nitrate
How does using fertlisers raise environmental issues? - sometimes more fertiliser is
applied than the plants need or are able to use
- lead to fertilisers leaching into waterways
- leaching is when water soluble water compounds in the soil are washed away
- can lead to eutrophication
When is leaching more likely to happen? if fertiliser is applied before heavy rainfall
How do artificial fertlisers impact leaching? contain inorganic ions which are relatively
soluble
excess minerals that are not used immediately are more likely to leach into waterways
How do natural fertilisers impact leaching? nitrogen and phosphorous are still contained in
organic molecules
need to be decomposed by microorganisms before absorbed by plants
leaching less likely as their release into soil for uptake by plants is more controlled
Is leaching less likely for phosphates or nitrates? phosphates as they are less soluble
How else can fertlisers have an impact? change the balance of nutrients in the soils - too
much of a particular nutrient can cause crops and other plants to die
What cuases eutrophication? Excess nutrients
Describe its process. - mineral ions are leached from fertilised fields
- causes raid growth of algae
- large amounts of algae blocks light from reaching plants below
- eventually plants die as they can not photosynthesis enough
- bacteria feed on dead plant matter
or the chemical energy stored in the plant
How can biomass be measured? mass of carbon that an organism contains
or dry mass of its tissue per area
Describe how we can determine the biomass. -sample of organism is dried
- in an oven set to a low temp
- weighed at regular intervals
- once mass is constant you will know all the water has been removed
- result from the sample can be scaled to give total population or area
Whats a typical unit for dry mass? kg m⁻²
The mass of carbon... is generally taken to be 50% of the dry mass
Whats the GPP? Gross primary production:
total amount of chemical energy converted from light energy by plants in a given area
Whats R? Respiratory loss:
50% of GPP is lost to the environment as heat when plants respire.
Whats the remaining chemical energy called? NPP: Net primary production
Energy available to the plant for growth and reproduction
Also energy available to organisms at the next stage in the food chain
How do we calculate NPP? NPP = GPP - R
How is the NPP stored? As biomass
How can primary production be expressed? as rate - primary productivity
What are the typical units for this? kJ ha⁻¹ year⁻¹
How do consumer store their chemical energy? in their biomass
Around how much energy is lost? 90%
How? not all the food is eaten (bones and roots)
some parts are indigestible so egested as faeces
some energy is lost as respiration or urine
What happens to the energy that's left? Stored as the consumers biomass
Is the consumers net production
Whats the calculation for net production of consumers? N=I-(F+R)
N = Net production
I = Chemical energy ingested in food
F = Chemical energy lost in faeces and urine
R = Energy lost through respiration
What can the net production of consumers be called? Secondary production or
secondary productivity
What do food chains and webs show? How energy is transferred through an ecosystem
What are food chains? simple lines of energy transfer
Each of the stages is called a trophic level
What are food webs? Show lots of interconnected food chains
What are decomposers? Break down dead or undigested material allowing nutrients to
be recycled.
Also apart of food webs
What do most farming practices aim to do? Increase the amount of energy that is available
for human consumption
What two ways do they do this? reducing the energy lost to other organisms
reducing the energy lost through respiration
How can they reduce the energy lost to other organisms? (Mainly for plants):
- reduce the number of pests using chemical pesticides
,insecticides and herbicides
- using biological agents
parasites and pathogenic bacteria and viruses
Farmers can use integrated systems that combine both
Combined effect reduce pest numbers even more so NPP is increased more
How can they reduce respiratory loss? ( Mainly for animals )
Control the conditions they live in:
- movement increases respiration so they restrict movement by keeping them in small pens
which are often indoor and kept warm so less energy is wasted by generating body heat
What are the other benefits of this? more food can be produced in a shorter space of time
often at a lower cost
What are the issues of this? Ethical issues
the conditions they are kept in cause animals to be in pain / distress or restrict their natural
behaviour so it should not be done
What do fungi form with the roots of plants? Form symbiotic relationships
What are these relationships known as? mycorrhizae
Describe the relatioship? - fungi have hyphae: long thin strands
- hyphae connect to plant roots
- increases surface area helping plant to absorb ions rom soil which are usually scarce
- hyphae also increases uptake of water
- fungi in return obtain organic compounds like glucose from plant
What is the nitrogen cycle? Shows how nitrogen is converted into a usable form and then
passed between different living organism and the non living environment.
Why do plants and animals need nitrogen? To make proteins and nucleic acids
Describe the process of the nitrogen cycle? Nitrogen fixation:
- N₂ to NH₄⁺ (ammonium ions)
- carried out by nitrogen fixing bacteria
- Bacteria use nitrogen gas, water and many ATP to make ammonium ions
- ammonia is a usable form of nitrogen ∴ these bacteria can make DNA, amino acids etc.
Ammonification:
- detritus to (NH₄⁺) ammonium ions
- carried out by saprobients
- secrete proteases onto protein in detritus to absorb amino acids
- some amino acids are deaminated and waste ammonium ions are excreted
Nitrification
- NH₄⁺ to NO₂⁻ (nitrite) to NO₃⁻ (nitrate)
- carried out by nitrifying bacteria / chemoautotrophs
- one class of bacteria oxidise ammonium ions into nitrite ions
- another class of bacteria oxidise nitrite into nitrate
- oxidation provides energy to fix CO₂ into organic product
Denitrification
- NO₃⁻ (nitrate) to N₂
- carried out by denitrifying bacteria
- use nitrate ions as their terminal electron acceptor
- so can perform a form of aerobic respiration
- bacteria removes nitrates from soil
, - farmers discourage these by drainage / ploughing which makes soil aerobic
What is the phosphorous cycle? Shows how phosphorous is passed through an
ecosystem
Why is phosphorous needed? to make biological molecules like phospholipids, DNA and
ATP
Describe the phosphorous cycle? 1) Phosphorus ions in rocks are released into the soil by
weathering
2) Phosphorous ions are taken into the plants through roots
Mycorrhizae increase the rate at which phosphorous is assimilated
3) Phosphorous ions are transferred through the food chain as animals eat the plants and are
eaten by other animals
4) Phosphate ions are lost through animals in waste products
5) When plants and animals die saprobionts break down the organic compounds and release
phosphate ions into the soil for assimilation by plants
Also release phosphate ions from urine and faeces
6) weathering of rocks releases phosphate ions into seas, lakes and rivers.
Taken up by aquatic producers such as algae and passed along the food chain to birds
7) waste products by sea birds is guano and contains a high proportion of phosphate ions.
guano returns a lot of phosphate ions to soils
used as a natural fertiliser
What happens when crops are harvested? nutrients are lost and are not replaced
What do we do to replace the lost nutrients? add fertilisers
What are the two types of fertilisers? natural and artificial
What are natural fertilisers? organic matter
include manure, composted vegetables, crop residues and sewage sludge
What are artificial fertilisers? inorganic
contain pure chemicals as powders or pellets
e.g ammonium nitrate
How does using fertlisers raise environmental issues? - sometimes more fertiliser is
applied than the plants need or are able to use
- lead to fertilisers leaching into waterways
- leaching is when water soluble water compounds in the soil are washed away
- can lead to eutrophication
When is leaching more likely to happen? if fertiliser is applied before heavy rainfall
How do artificial fertlisers impact leaching? contain inorganic ions which are relatively
soluble
excess minerals that are not used immediately are more likely to leach into waterways
How do natural fertilisers impact leaching? nitrogen and phosphorous are still contained in
organic molecules
need to be decomposed by microorganisms before absorbed by plants
leaching less likely as their release into soil for uptake by plants is more controlled
Is leaching less likely for phosphates or nitrates? phosphates as they are less soluble
How else can fertlisers have an impact? change the balance of nutrients in the soils - too
much of a particular nutrient can cause crops and other plants to die
What cuases eutrophication? Excess nutrients
Describe its process. - mineral ions are leached from fertilised fields
- causes raid growth of algae
- large amounts of algae blocks light from reaching plants below
- eventually plants die as they can not photosynthesis enough
- bacteria feed on dead plant matter
