Energy Transfer Flashcards
Definition of trophic level
The position an organism occurs within an energy transfer
Producers
Auto trophic- build up organic compounds (DNA/polypeptides) from simple molecules (glucose/nitrates) needed for growth
Consumers
Heterotrophic- rely on an external source of organic compounds i.e. they have to take in organic compounds
Saprobionts/Decomposers
Heterotrophic- break down complex organic compounds in dead organisms (fungi/bacteria)
How many trophic levels are in a food chain?
- No more than 4/5
- energy lost at each trophic level = inefficient
- so not enough energy to support breeding population at higher trophic level
Food webs
- food chains do not occur in isolation
- in habitats, many food chains linked together to form a food web
Effect of complex food webs
- higher diversity
- more complex food web interactions
- closer to climax community
- any one change within web will have less effect on individual species
Definition of biomass
total mass of organic material (carbon) in a specific area at a given time
Fresh mass
- living
- easy to assess
- variable H2O content
- unreliable
- variable food indigested
(wet)
Dry mass
- dead
- difficult to assess
- small sample size
- unreliable
- situational
(mass of carbon)
Calculating energy stored in biomass
- bomb calorimeter
- chemical energy in biomass estimated using calorimetry
- sample of dry biomass combusted with a sealed chamber
- chamber surrounded by water bath, heat energy released causes temperature rise in water
Bomb calorimetry features
Stirrer= distributes heat energy
water= high specific heat capacity
air= insoluble, reduces heat loss
Respirometer Question
The student found that the coloured liquid moved 1.5 cm in 24 hours. The diameter of the lumen (hole) of the capillary tubing was 1 mm.
The volume of a capillary tubing is given by πr2l, where π is 3.14 and l = length.
Calculate the volume of gas produced in cm3 hour–1.
Answer = ____________________ cm3 hour–1
- Correct answer in range of
4.9 × 10–4 to 4.91 × 10–4 = 2 marks;;
Accept any equivalent mathematical representation of this answer
- Incorrect but shows division by 24 = 1 mark
OR
1175 to 1178 = 1 mark;
OR
49 = 1 mark;
Suggest what you should do to ensure all water is removed from a tissue / sample.
Regularly weigh and Heat (less than 100 °C)
Until mass is constant
Advantage of using dry mass not fresh to compare yield
- water content present will vary in fresh mass
- this issue will not affect dry
Energy losses from the sun to the producer
- some light energy is reflected
- some light energy absorbed by gases/ water vapour in atmosphere
- some light energy is the wrong wavelength
- some light energy does not strike chlorophyll
Define Gross Primary Productivity
Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
Define Net Primary Production
- Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
- NPP is available for new plant growth and reproduction
- kJ km–2 year–1
NPP equation
NPP= GPP - R
(R= respiratory losses)
Energy losses from the producer to the primary consumer
- large amounts of plant may be indigestible
- not all of the plant may be eaten (roots)
- some energy lost in excretion such as energy lost in urine
- energy lost in respiration and as heat to the environment
Energy losses from the primary consumer to the secondary consumer
- large amounts of animal may be indigestible
- not all of animal may be eaten (bones)
- some energy lost in excretion such as energy lost in urine
- energy lost in respiration and as heat lost to the environment
Net production of consumer equation
N = I - ( F + R )
N=net production
I=chemical energy store of ingested food
F=energy lost in faeces/urine
R=energy lost in respiration
Calculating efficiency of energy transfer
% efficiency = energy available after transfer/energy available before x100
Calculations up/down trophic levels
producer -> consumer
[energy x %/100 x %/100]
