Chapter 13 - Energy and ecosystems Flashcards
(22 cards)
What is biomass
Biomass is the total mass of living material, in a given area or volume, at a given time
How do we measure biomass
Dry out mass as water content of organisms varies
Mass of carbon (dry mass of tissue) per given area per given time
e.g. g m-2 (area) or g m-3 (volume)
grams per meters squared or cubed
Volume = aquatic organisms Area = terrestrial organisms
units of biomass
g m-2 in terrestrial organisms
g m-3 in aquatic organisms
Steps in calorimetry
Energy in dry biomass = kJ kg-1
1. Weigh dry sample
2. Burn sample in pure oxygen in sealed container (bomb)
3. Bomb is surrounded by water
4. Heat from combustion raises the temperature of the water
5. This increase in temperature allows us to calculate energy content as we know how much energy it takes to raise the temperature of 1g of water by 1°C
labelled colorimetry setup
why is only a small amount of sun’s energy converted to organic matter by photosnthesis
- 90% is reflected back into space
- Some is the wrong wavelength for the pigments
- Some may not fall on chlorophyll, so will pass through the leaf
- Other factors may limit the rate of photosynthesis
What does GPP stand for and what is GPP
GPP - gross primary product
Total chemical energy stored in plant biomass, in a given area or volume, in a given time
GPP of an ecosystem will be affected by both abiotic and biotic factors as these will affect rate of photosynthesis
What does NPP stand for and what is NPP
Chemical energy stored in plant biomass after respiratory losses to the environment have been taken into account
formula relating GPP and NPP
NPP = GPP - R
R - respiratory losses
units for chemical energy in biology
KJ per hectare per year
KJ - energy
ha - standardised area
y - takes into account seasonal variations for comparison of ecosystems
What is the net production in conumers
N = I - (F+R)
I = chemical energy ingested
F = chemical energy in faeces and urine
R = respiratory losses
What are decomposers and the two types
decomposers - gain energy from dead organic matter
Detrivores - do this internally e.g woodlice and worms
Sabrobionts - do this externally by excreting enzymes e.g bacteria and fungi
why are there only 4 or 5 trophic levels
Food chains usually only have 4 or 5 trophic levels because there is not enough energy available to support a large enough breeding population in another level
What is a trophic level
stages of a food chain
What is percentage efficiency and its equation
energy available after transfer
———————————————– x 100
energy available before transfer
why are mycorrhizae important in nutrient cycles
- mycorrhizae are a mutualistic relationship between fungi and plant roots
- mycorrhizae provide extensions to the plants roots to increase surface area and uptake of water and mineral ions from the soil
- the fungi gain carbohydrates and amino acids from the plant in return
generalised nutrient cycle
What is the nitrogen cycle for
*Used to produce amino acids/proteins, nucleic acids and ATP
* Generally absorbed as nitrates from the soil by active transport
nitrogen cycle
what is the phosphorus cycle for
Organisms use phosphorus for:
ATP
Phospholipids
Nucleic acids
Main reservoirs of carbon and nitrogen are the atmosphere, but phosphorus is mineral form in sedimentary rocks (no gaseous form in the P cycle)
Phosphate ions is the main form of phosphorus
Weathering and erosion releases phosphate ions from rocks to become dissolved in water
