Energy Transfer And Productivity Flashcards
What percent of the suns energy do plants convert into organic matter
Between 1% and 3%
Why is most of the suns energy not converted to organic matter by photosynthesis
Over 90% of the suns energy is reflected back into space by clouds and the dust or absorbed by the atmosphere
Not all wavelengths of light can be absorbed and used for photosynthesis
Lights may not fall on a chlorophyll molecule
A factor, Such as low carbon dioxide levels, may limit the rate of photosynthesis
What is the gross primary production (GPP)
It is the total quantity of the chemical energy store in Plant biomass, in a given area or volume, in a given time
What’s the formula for net primary production
Net primary production= gross primary production - respiratory losses
NPP=GPP-R
What percent do plants use of this energy in respiration
20% to 50%
What is the net primary production available for
Plants growth and reproduction
What percent of the net primary production in plants can be used by primary consumers for growth
10%
What percent can secondary and tertiary consumers transfer of the energy available from their prey into their own bodies
20%
The low percentage of energy transferred at each stage is the result of what
Some of the organism is not consumed
Some parts are consumed but cannot be digested and are therefore lost in faeces
Some of the energy is lost in excretory materials, such as urine
Some energy losses occur as heat from respiration and lost their environment. These losses are high in mammals and birds because of the high body temperature. Much energy is needed to maintain the body temperature when heat is constantly being lost to the environment
How can the net production of consumers be calculated
N=I-(F+R)
Where:
N represents the net production
I represents the chemical energy store of ingested food
F represents the energy lost in the faeces and urine
R represents the energy lost in respiration
What does the relative inefficiency of energy transfer between trophic levels explain
Most food chains have only four or five trophic levels because insufficient energy is available to support a large enough breeding population at trophic levels higher than these
The total mass of organisms in a particular place (biomass) is less at higher trophic levels
The total amount of energy available is less at each level as one moves up a food chain
How do we calculate the percentage efficiency
Energy available after the transfer/energy available before the transfer x 100
How can energy conversion be made more efficient
By ensuring that as much energy from respiration as possible goes into growth rather than other activities or other organisms
This is achieved by keeping animals in confined spaces e.g. small enclosures, barns, cages
How does keeping animals in confined spaces increase the energy conversion rate
Movement is restricted and So less energy is used in muscle contraction
Environment can be kept warm in order to reduce heat loss from the body
Feeding can be controlled so that the animals receive the optimum amount and type of food for maximum growth with no wastage
Predators are excluded so that there is no loss to other organisms in the food web
Pesticides are used to increase productivity. Suggest how they use might sometimes reduce productivity
Simplify the food web
Balance the cost of pest control with the benefits it brings
Need to balance the farmer who has to satisfy our Demand for cheap food while still making a living and the conservation of natural resources
