Energy and Ecosystems Flashcards
What is biomass?
Total dry mass of tissue or mass of carbon measured over a given time in a specific area
What are the units of biomass?
When an area is being sampled: gm^-2
When a volume is being sampled (e.g. a pond) : gm^-3
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, plant reproduction and energy transfer to other trophic levels after respiratory losses.
State the equation involving GPP and NPP.
NPP = GPP - R
Where R represents respiratory losses
Why is most of the sun’s energy not converted to organic matter?
- Most solar energy is absorbed by the atmosphere or reflected by the clouds
- Photosynthetic pigments cannot absorb some wavelengths of light
- Not all light falls directly on a chlorophyll molecule
- Energy lost as heat during respiration
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 (urine) and faeces
- Some of the organism is not consumed.
- Energy lost to surroundings as heat
Define primary and secondary productivity:
- Rate of primary or secondary production
- Biomass in a specific area of a given time period e.g. kJ ha^-1 year^-1
Explain why the length of food chains is limited
- Energy is lost at each trophic level
- So there is insufficient energy to support a higher trophic level
