Energy And Ecosystems Flashcards
How do plants use the sugars from photosynthesis?
- as respiratory substrates
- to synthesise other biological molecules
What is biomass?
Total dry mass of tissue or mass of carbon measure over a given time in a specific area
What are the units for biomass?
- when an area is being sampled : gm-2
- when a volume is being sampled : gm-3
How can the chemical energy store in dry mass be estimated?
- using calorimetry
- energy released = specific heat capacity of water x volume of water (cm3) x temperature increase of water
Why is bomb calorimetry preferable to simple calorimetry?
Reduces heat loss to surroundings
How could a student ensure that all water had been removed from a sample before weighing?
Heat the sample and reweigh it until the mass reading is constant
Define gross primary production (GPP)
Total chemical energy in plant biomass within a given volume or area
Define net primary productivity (NPP)
Total chemical energy available for plant growth, reproduction and energy transfer to other trophic levels after respiratory losses
What is the mathematical relationship between GPP and NPP?
NPP = GPP - R
Why is most of the sun’s energy not converted to organic matter?
- most solar energy is absorbed by atmosphere or reflected by clouds
- photosynthetic pigments cannot absorb some wavelengths of light
- not all light falls directly on a chlorophyll molecule
- energy lost as heat during respiration / photosynthesis
How can the net production of consumers be calculated?
N = I - (F+R)
I: chemical energy from ingested food
F: energy lost as faeces and urine
R: respiratory losses
Why does biomass decrease along a food chain
- energy lost in nitrogenous waste and faeces
- some of the organism is not consumed
- energy lost to surroundings as heat
Outline some common farming practices used to increase the efficiency of energy transfer
- exclusion of predators
- artificial heating
- restriction of movement
- feeding is controlled at optimum
Give a general equation for % efficiency
Energy converted to a useful form (J) x 100 / total energy supplied (J)
Explain why the length of food chains is limited
- energy is lost at each trophic level
- insufficient energy to support a higher trophic level
What is a pyramid of biomass?
Diagram that shows the biomass at each trophic level
Why is a pyramid of biomass preferable to a pyramid of numbers?
Shape of pyramid of numbers may be skewed since a small number of producers can support many consumers
What is the mass of carbon?
- the measure of the mass of carbon an organism has
- about half the dry mass
What is secondary/consumer production useful for?
Allows us to study how much energy consumers store in their biomass
