Energy And Ecosystems Flashcards
(18 cards)
How is biomass formed in plants ?
During photosynthesis plants make carbon compounds from Co2
Most sugars synthesised are used by the plants as respiratory substances
The rest make biological molecules (lipids and proteins) to form biomass
How is biomass measured
Mass of carbon or dry mass of tissue per area
How can dry mass be measured
Samples is dried in a oven at 100oc
Samples weighed and reheated
Until mass reaches 0
Why is dry biomass more representative than wet?
Water will be in wet samples
How can the chemical energy stored in dry biomass be calculated
Using calorimetry:
-known mass of dry biomass is fully combusted (burnt)
-heat energy is released heats a known volumes of water
-increase in temp of water is used to calculate the chemical energy of the biomass
Features of calorimeter
Stirrer - evenly distributes the heat energy
Air/insulation- reduces heat loss and gain from its surrounding
Water-has a high specific heat capacity
What is the gross primary production (GPP)
Chemical energy store in plant biomass(in area/volume per time)
Total energy transferred from light to chemical (photosynthesis)
What is net primary production (NPP)
Chemical energy store in plant biomass after respiratory losses to the environment taken into account
Formula for NPP
NPP=GPP-R
When R= respiratory losses to the environment
Importance of NPP in ecosystems
NPP is Available for plant growth and reproduction
NPP is available to other trophic levels in the ecosystems (herbivores and decomposers)
Units used for primary and secondary productivity
KJha-1year-1
Unit energy per unit area per year
Why are those units used
Unit per area- diffrent environments may vary in size (standardising to enable comparison)
Per year- seasonal variation (representative and enables comparison)
Why is most light that falls on producers not used in photosynthesis
Light is reflected or wrong wavelength
Light misses chrolophyll
Co2 conc or temp is a limiting factor
Formula for net production of consumers (N)
n=I-(F+R)
Where I= chemical energy store in ingested food
F=chemical energy lost to the env in faces and urine
Formula for effiencey of energy transfer
Energy/biomass available after transfer
Divided by
Energy/biomass available before transfer
What energy transfer between trophic levels is inefficient
Heat energy lost via respiration
-energy lost via plants of organisms that aren’t eaten
-energy lost as faces
-energy lost as excretion (urine)
How can crop farming increase energy transferred efficiency
Simplify food webs:
-herbicides kill weeds so less competition
-pesticides kill pests
-fungicides kill fungal infections
-fertilisers provide nutrients
How livestock farming practices increase energy transfer effiency
Reducing respiratory losses:
-restricting movement(less loss from respiration)
-treat with antibiotics (prevent energy loss via pathogens)
