p2: energy transfers Flashcards
producers
- autotrophic
- build up organic compunds (eg: DNA, proteins) from simple molecules (eg: glucose, nitrates and phsophates)
consumers
- heterotrophic: rely on source of organic compounds
- eat producers
saprobionts
heterotrophic/saprotrophic
- break down complex organic compounds in dead organisms
- bacteria and fungi
biomass
total mass of carbon in
dry mass of tissue per given area
fresh mass (wet)
- living
- easy to access
- variable water content
- unreliable
- variable food indigested
dry mass (mass of carbon)
- dead
- difficult to access
- small sample size, may not be representative
- unreliable as unethical to collect large samples
- situational: may fluctuate
how woud you calculate the energy stored in biomass?
- calorimetry
- dry mas combusted in a sealed container
why do plants not absorb a large amount of sun energy?
- some energy refleted
- some light energy absorbed by water vapour in the atmosphere
- some light energy the wrong wavelength
- some light energy doesnt strike the chlorophyll
gross primary production
- chemical energy store in biomass, in a given area or volume
light energy converted into organic molecules
- eg: glucose, cellulose, starch
- photosynthesis
net primary production equation
- NPP: energy stored as biomass after respiratory losses accounted
- NPP= GPP- R
- NPP available for new plant growth and reproduction
- kJ/ ha/ year
suggest what you should do to ensure that all the water is removed from a tissue
- regularly weigh and heat
- until mass is constant
the percentage of light energy trapped by producers is very low. explain three reasons why.
- reflected/absorbed by water vapour
- wrong wavelength
- passes between chlorophylls
in natural ecosystems, most of the light falling producers is not used in photosynthesis. explain why.
- light is reflected
- light is wrong wavelength
- light misses chlorphull
- co2 conc or temperature is limitng factor
the biomass of primary consumers is less than the biomass of producers. explain why.
- large amounts may be indigestible and lost by animal as faeces
- not all plant may be eaten (eg: roots)
- some energy lost as excretion and urine
- energy lost in respiration
- energy lost as heat to the environment
describe how and explain why the efficiency of energy transfer is different at different stages of the transfer.
- some light energy fials to strike the chlorophyll
- some light energy may not be the correct wavelength
- efficiency of photosynthesis in plants is low/ 2%
- energy lost in excretion and respiration
- lost as heat
- efficiency lower in older animals
- carnivores use more of their food thank herbivores
equation to calculate the net production of consumers
N = I - (F +R)
N = net production
I= energy store of ingested food
f= energy lost in faeces
R= energy lost in respiration
efficiency equation
energy after transfer / energy before transfer
x100
yield can be determined by measuring the dry mass of plants. suggest how you could determine the dry mass of a sample of plant material.
- heat at 100 degrees to evaporate water
- weigh and heat until mass is constant
what is the advantage of using dry mass and not fresh mass to compare the yields of plants?
- water content is variable
- will not affect dry/fresh mass
explain how the intensive rearing of domestic livestock increases net productivity
- restricting movement so less respiratory loss due to less muscle contraction
- keeping animals indoors and warm to reduce heat loss
- slaughtered when still growing so more energy transferred to biomass
- controlled diets so less loss in faeces
- genetically selectred for high productivity
monoculture
- one crop grown over large area
- easy for disease to spread and insects travel
- reduces biodiversity (via less niches, less food sources)
describe the need for plants to PS and respire
- in the dark no ATP production in PS
- some tissues unable to PS
- ATP cant be moved from cell to cell
- plants use more ATP than produced in PS
- ATP for active transport
- ATP for synthesis of (eg: DNA)
the concentrations of CO2 in the air at different heights above the ground in a forest changes within 24 hours. use your knowledge of PS to desxcribe why these changes occur and explain them.
- high C2 cnc in night
- no PS in dark
- in dark, plants RP
- light of PS > rate of RP in light
- co2 higher with height
- ground level, less leaves
