3.5.3 Energy and ecosystems Flashcards
What do plants synthesise organic compounds from in ecosystems?
Atmospheric or aquatic carbon dioxide
What is most of the sugar synthesised by plants used for?
Respiratory substrates
What are the remaining sugars synthesised by plants used for?
To make other groups of biological molecules
What do the biological molecules made by plants contribute to?
The biomass of the plants
In what terms can biomass be measured?
Mass of carbon or dry mass of tissue per given area
How can the chemical energy store in dry biomass be estimated?
Using calorimetry
Define gross primary production (GPP)
The chemical energy store in plant biomass in a given area or volume
Define net primary production (NPP)
The chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
What is the equation linking NPP GPP and R?
NPP = GPP - R
What does NPP represent in relation to plant function?
Energy available for plant growth and reproduction
What does NPP provide for other trophic levels?
Energy available to herbivores and decomposers
What does I represent in the net production of consumers equation?
Chemical energy store in ingested food
What does F represent in the net production of consumers equation?
Chemical energy lost to the environment in faeces and urine
What does R represent in the net production of consumers equation?
Respiratory losses to the environment
What is the equation for net production in consumers?
N = I - (F + R)
What is primary productivity?
The rate of primary production measured as biomass in a given area in a given time
What is secondary productivity?
The rate of secondary production measured as biomass in a given area in a given time
What unit is used to measure productivity?
kJ ha–1 year–1
How do farming practices increase energy transfer efficiency?
By simplifying food webs to reduce energy losses to non-human food chains and reducing respiratory losses within a human food chain
