13.2 Energy transfer and productivity Flashcards
What percentage of sunlight do plants convert into organic matter
. Between one and three % of the suns energy available to them is converted to organic matter
Why is most of the suns energy not converted to organic matter
. Over 90 % is reflected back into space by clouds and dust or is absorbed by the atmosphere
. Not all wavelengths of light can be absorbed and used for photosynthesis
. Light may not fall on a chlorophyll molecule
. A limiting factor may be present eg CO2 levels
What is gross primary production
What is net primary productivity
. The total quantity of chemical energy store in plant biomass, in a given area or volume, in a given time
. However plants use 20-50% of this energy in respiration
. The chemical energy store which is left when these losses to respiration have been taken into account is called the
Net primary productivity (NPP)
What is equation for net primary production
Gross primary production (GPP) - respiratory losses (R)
What is net primary production used for
Net primary production is available for plant growth and reproduction
It is also available for all other trophic levels in ecosystem eg consumers and decomposers
What percentage of net primary production in plants can be used by primary consumers for growth
Around 10% is passed onto primary consumers
Secondary and tertiary consumers are slightly more efficient, transferring around 20% of that energy available from prey into their own bodies
Why is only a small percentage of energy transferred at each stage
. Some of the organism isn’t consumed eg bones
. Some parts of organism are consumed but can’t be digested so are lost in faeces
. Some of the energy is lost in excretory materials such as urine
. Some energy losses occur as heat from respiration and are lost to environment
These losses are high in mammals and birds because of their high body temperature
Lots of energy is needed to maintain body temperature as it is constantly being lost to environment
What is the net production of consumers calculated as
N= I - (F+R)
N = net production
I = Chemical energy store of ingested food
F = Energy lost in faeces and urine
R = Energy lost in respiration
Why do food chains only have around 4 or 5 trophic levels
. Insufficient energy is available to support a large enough breeding population at trophic levels higher than these.
As energy transfer is inefficient
Why is the biomass of organisms less at higher trophic levels
Insufficient energy transfer as the total amount of energy is less at each level when moving up the foodchain
