Energy Transfer & Nutrient Cycle Flashcards
Describe the energy transfer from sun to producer
- some of light energy is reflected
- some light energy may be absorbed by gases in the atmosphere
- some of light energy is wrong wavelength
- some light energy does not strike chlorophyll
Describe the energy transfer from producer to primary consumer
- large amounts of plant may be indigestible and lost from animal as faeces
- not all of plant may be eaten
- some energy is lost in excretion such as energy lost in urine
- energy lost in respiration and as heat to the environment
Describe the energy transfer from primary consumer to secondary consumer
- large amounts of the animal may be indigestible
- not all of the animal may be eaten
- some energy is lost in excretion such as energy lost in urine
- energy lost in respiration and as heat to environment
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 100oc
- weigh and heat until no further change in mass
what is the advantage of using dry mass and not fresh mass to compare the yield of plants
- water content is variable
- will not affect dry mass
Define Biomass
- Mass of carbon
- Dry mass of tissue per given area
Suggest what you should do to ensure all water is removed from a tissue / sample
- regularly weigh and heat (less than 100oc)
- until mass is constant
The percentage of the light energy trapped by the producers is very low. Give two reasons why.
- reflected by water vapour
- reflected from producers
- passes between plants
In natural ecosystems, most of the light falling on producers is not used in photosynthesis.
Suggest two reasons why.
- light is reflected
- light is wrong wavelength
- light misses chlorophyll
The biomass of primary consumers is less than the biomass of producers.
Explain why.
- loss of energy
- in respiration
- in excretion
- indigestible parts to decomposers
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer
- some light energy is reflected
- efficiency of photosynthesis in plants is low
- respiratory loss
- loss as heat
- efficiency of transfer to consumer greater than transfer to producers
- efficiency lower in older animals
- carnivores use more of their food than herbivores
Explain how the intensive rearing of domestic livestock increases net productivity
- slaughtered before maturity so more energy transferred to biomass
- fed on concrete so higher proportion of digested food
- movement is restricted so less respiratory loss
- kept inside so no heat loss
- genetically selected for higher productivity
Describe the need for plants to both photosynthesise AND respire
- in dark no ATP production in photosynthesis
- some tissues unable to photosynthesise
- ATP cannot be moved from cell to cell
- plant uses more ATP than produced in photosynthesis
- ATP for active transport
- ATP for synthesis (of named substance)
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use you knowledge of photosynthesis to describe the changes and explain why they occur.
- high concentration of CO2 linked with darkness
- no photosynthesis in dark
- in dark plants respire
- in light net uptake of CO2 by plants
- decrease in CO2 conc with height
- at ground level less photosynthesising tissue
Describe the nitrogen cycle
- plants take up nitrogen from soil in the form of nitrate ions (NO3-) which are absorbed by active transport through the root hair cells
- plants use nitrogen to synthesise amino acids & proteins and other N containing compounds like DNA & RNA, this allows plants to grow and reproduce
- consumers eat plants and hydrolyse proteins into amino acids, these are absorbed and assimilated into new tissue in consumer
- primary consumers may be eaten by secondary consumers and nitrogen passes through trophic levels this way
- both plants and animal die
- animals also excrete nitrogenous waste
- decomposers secrete extra cellular enzymes through exocytosis
- this is to hydrolyse N containing polymers into monomers which can be absorbed and release ammonia into soil (ammonification)
- ammonia oxidised into nitrites then nitrates by nitrifying bacteria (nitrification)
- nitrates can be converted to N2 gas by denitrifying bacteria (denitrification)
- nitrogen fixing bacteria & fungi found in root nodules of some leguminous plants & can reduce N2 gas to ammonium which plants can then use in a process called nitrogen fixation.
