Energy Systems Flashcards
What is the main route by which energy enters an eco system
Photosynthesis
Plants synthesise organic compounds such as glucose from atmospheric, aquatic or carbon dioxide
Most of the sugars synthesised by plants are used as respiratory substrates the rest are used to make biomass
What is biomass
Biological molecules which make up the organisms
How can you measure biomass
The dry mass of plant tissue is measured per unit area in a given time
What are the points to consider when measuring biomass
- fresh mass is unreliable as water content varies
- dry mass involves killing organisms and evaporating all the water by hearing at a temp below combustion
- biomass measured only represents the situation at a given point in time and does not consider any changes at different times of the year- units are always given per area per time
- ## biomass pyramids may be inverted- this happens in marine ecosystems where phytoplankton could at any point in time have less biomass than the primary consumers
What is a calorimeter and what does it do
Measures energy released
The chemical energy stored in the dry biomass can be determined by burning it in an oxygen rich environment within a calorimeter
Heat energy is released and absorbed by a container of water within a calorimeter and the change in temp of the water provides a measure of the energy released
Why are pyramids of energy shaped in a pyramid shape
Because energy is lost at each trophic level in a food chain
Why is only 1-3 % of available sunlight energy trapped in photosynthesis and converted to chemical energy
- some of the light is reflected
- some light is absorbed by the atmosphere
- some of the light is the wrong wavelength
- some light does not fall on chloroplasts and misses the chlorphyll
What is gross primary production ( GPP )
The rate energy is converted to organic molecules in an ecosystem, linked to rate of photosynthesis
The plants use some of this energy in respiration losing some as heat in the process
Measured in units per area
What is net primary production ( NPP )
Energy which is stored of forms new biomass
What is the equation for net primary production
NPP = GPP - R
How do you calculate the percentage efficiency of photosynthesis
GPP divided by the amount of light striking the plant, X 100
What is passed onto the next trophic level
NPP
Why are there large energy losses from producer to consumer
- large amount of plant may be indigestible
- not all of the food may be eaten
- some energy is lost in excretion
- energy lost in respiration as heat to the environment
How to calculate net production ( N )
N = I - ( F + R ) where I ingested food, F faeces, R respiratory losses
How do you calculate energy efficiency
Useful energy out divided by total energy in, X 100
Why are trophic levels no more than 4-5
Energy transfer is inefficient and results in large losses at each trophic level
There is not enough energy to support a breeding population at a higher trophic level
What are the units of primary production
kJ m -2 year -1 ( energy in a given area at a given time )
kJ ha-1 year-1
How do farmers increase energy transfers to ensure high growth rates of farm animals
- keep animals warm and limit their movement to reduce energy loss through respiration
- some give antibiotics to reduce respiratory losses through fighting infections
- reduce energy losses via faeces by feeding animal easily digestible food
- simplify food chains by removing predators
