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
