3.5.3 - Energy and Ecosystems Flashcards
In an ecosystem, what are plants?
Plants are the producers in a food web as they produce their carbs using CO2 or water
What happens to energy between trophic levels ?
Energy is lost due to respiration and excretion
The remaining is used to form biomass
What is biomass?
The mass of carbon of tissue per given area within the organism
What is the productivity of an ecosystem dependent on ?
How is this quantified?
The abiotic and biotic factors
Using GPP and NPP
What is GPP?
Gross primary production
- Chemical energy store in plant bimass in a given area/volume
Total energy resulting from photosynth.
What is NPP?
The chemical energy store in plant biomass, taking into account the energy lost due to R (respiration)
Equation linking NPP, GPP and R
NPP=GPP - R
How to work out the net production of consumers ?
N= I - (F+R)
I = chemical energy in ingested food
F = Chemical energy lost (faeces and urine)
R = respiratory losses
what is rate of productivity measured in ?
kj/hectare/year
Why are there 3 parts to the units for productivity rate ?
- KJ = energy
- per unit area to standardise results to compare environments
- per year to take into account the impact of the seasons - affect photosynthesis
Why is the nitrogen cycle important?
- Nitrogen is in proteins, ATP and nucleic acids - essential
- Nitrogen has a triple bond - we cant get it through gas exchange.
What steps make up the nitrogen cycle?
- saprobiotic nutririon and microbes
1. Ammonification
2. Nitrification
3. Nitrogen Fixation
4. Denitrification
What is saprobiotic nutrition ?
When microbes are feeding on dead plant matter or waste
What is nitrogen fixation?
- Biological - N2(g) from atmosphere is converted into ammonia or NH4+ by nitrogen-fixing bacteria i.e Rhizobium or by free-living bacteria such as Azotobacter
- Insutrially - the Haber process synthesizes ammonia from N and H
step 2 - Ammonification
Following organism death or excretion, organic Nitrogen = broken down
Produces NH3 or NH4+ form nitrogen compounds
What is Nitrification ?
- Oxidation of ammonium to nitrates by bacteria such as Nitrosomonas
- Oxidation of Nitrates to nitrates (NO2- to NO3-) by bacteria like Nitrobacter
what is assimilation ?
When plants absorb nitrates through roots.
These NO3- form AAs, proteins and nucleic acids - passed through the food chain
What is denitrification ?
Denitrifying bacteria i.e Pseudomonas and Clostridium convert nitrates into N2 gas
Typically occurs in anaerobic conditions and reduce nitrogen available in soil
Why is phosphorous important?
Because it is used for phosphate groups of : DNA,RNA,ATP and phospholipid bilayer
How is the phosphorous cycle different ?
Phosphorous isn’t found as a gas and isn’t in the atmosphere
It is found as a P ion in mineral form in rocks
What are mycorhhizae ?
Fungal associations that occur between plant roots and beneficial fungi
Why are micorrhizae beneficial for growth ?
- They increase SA for mineral absorption
- They act like a sponge, holding water and minerals at roots
^ This makes plants more drought resistant and able to take ^ more inorganic ions
This is a mutualistic relationship
What do plants do for the fungus?
- through photosynthesis make carbohydrates which can be supplied to the fungus
- Thus they have a mutualistic relationship
Phosphate ions are found where ?
In oceans or soil, plants absorb through their root hair cells
How do they get into animals ?
They consume and eating the plants - absorb the materials and get phosphate ions
How is phosphorous released back into the ocean or soil
By excretion of animals
- Excretion
- erosion
- erosion and fertilisers
How else can phosphate ions be released ?
Animals with bones or shells contain phosphate ions, these can be eroded, releasing the ions
What is guano
It is from bird faeces - a type of excrement very rich in phosphate ions
What is deposition
Is when we get phosphate ions building up to create rocks
What is sedimentation - how phosphate ions go back into ocean/soil
Over time from high pressure phosphate ions within soil will compact through sedimentation to form sedimentary rocks
These can be eroded to release phosphate ions back into the soil or oceans
What are fertilisers
They are added to soil, to replace the nitrate and phosphate ions lost when plants are harvested and removed
- eventually, you’d end up with plants and soil which are mineral deficient
Fertilisers can either be
Natural - manure
Artificial - inorganic chemicals - contain the exact proportion and quantities of mineral ions required
Pros and cons of natural fertiliser
- cheaper
- doesn’t contain the exact proportion of minerals needed - cannot be controlled
Artificial fertilisers pros and cons
- they contain the exact proportions of the minerals needed
- inorganic substances used = very soluble - can dissolve in water and leach
- they contain the exact proportions of the minerals needed
What is leaching
When water soluble compounds are washed away into rivers or ponds
- causes eutrophication
What is eutrophication
Nitrates stimulate the growth of algae in a pond or river
- more likely in a pond
- creates a blanket of algae on top of water
- blocks the light
- plants can’t photosynthesise - they die
- bacteria feeds and respires - uses up oxygen
- eventually not enough for the animals in the water for O2 for respiration
