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]
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer.
- Some light energy fails to strike/is reflected/not
- Efficiency of photosynthesis in plants is low
- Loss as heat
- Efficiency of transfer to consumers greater than transfer to producers
- Efficiency lower in older animals
- Carnivores use more of their food than herbivores
Domestic livestock ethics
barn hens- closely packed together, increased chance of parasites being transmitted
-restricted movement, growth occurs at faster rate than natural
-antibiotic resistance, linked to intensive agriculture
Explain how the intensive rearing of domestic livestock increases net productivity
- Slaughtered when still growing
- Fed on controlled diet
- Movement restricted so less respiratory loss
- heating so less heat loss
You are given samples of water from three different rivers.
Describe how you would obtain a quantitative measurement of their cloudiness.
- Use of colorimeter;
- Measure the absorbance
- Example of how method can be standardised eg same volume of water, zeroing colorimeter, same wavelength of light
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur
- High concentration of carbon dioxide linked with darkness;
- No photosynthesis in dark
- In dark plants respire;
- In light net uptake of carbon dioxide by plants
- Decrease in carbon dioxide concentration with height;
- At ground level fewer leaves
