3.5 Energy Transfers Flashcards
What is the role of producers and how is it limited?
Plants photosynthesise and form biological molecules to form biomass
Limited:
•not enough light hitting the chlorophyll
•light can be reflected off
•different wavelengths of light
How can biomass be measured?
•mass of carbon
•dry mass of tissue per given area, where its chemical energy is measured using calorimetry
How is energy lost between trophic levels?
•lost by respiration
•excretion where energy contained in faeces and urine is transferred to decomposers
•not all parts are digested = egestion
(Cannot sustain many trophic levels)
What is Gross and Net primary production? (+equation)
GPP= The chemical energy store in plant biomass, in a given area or volume, resulting from photosynthesis
NPP= The chemical energy store in the plant biomass, taking into account the energy lost due to respiration. (Represents dry mass of C)
NPP=GPP-R
What is the equation for net production of consumers?
N= I - (F + R)
I:chemical energy store in ingested food
F:chemical energy lost to environment in faeces/urine
R:respiratory losses
Why is rate of production measured in KJ ha-1 year-1?
•per unit area to standardise, allowing environments to be compared as it takes into account different environments will vary in size
•per year to take into account the impact of seasons on weather, providing an annual average to allow fair comparison between environments
What methods are used in intensive farming?
•temperature controlled so less respiration to maintain body temp.
•limited space so restricted movement so less respiration
•controlled nutrients/high protein
(Less biomass is wasted in respiration)
What are the disadvantages of intensive farming?
•infectious diseases can spread quickly so lots of antibiotics used which increases risk of antibiotic resistant bacteria
•unethical as animals get stressed
Why is the biomass of the primary consumer higher than the producer (sometimes in a pyramid)?
Producers are reproducing slower than they are being consumed
Why is intensive farming produce cheaper?
•faster rate of growth
•high survival rate so more plentiful food supply
Why does higher biodiversity compared to monoculture cause higher food yields?
•pests tend to be specific so will not destroy all crops
•different species have different root length so less competition for e.g water/mineral nutrients
Why does crop rotation lead to high crop yields?
•soils can regain mineral nutrients by e.g planting legumes (N-fixing bacteria)
•different crops have different pests/disease
•different plants use different minerals so continued growth
What is nitrogen fixing?
Nitrogen fixing bacteria e.g in legumes root nodules will convert N2 gas into ammonia = ammonium ions converted into nitrites and then nitrates
What is nitrification?
Nitrifying bacteria will turn ammonium into nitrites and then nitrates (aerobic conditions)
What is the role of saprobiotic bacteria in the nitrogen cycle?
They will do extracellular digestion to hydrolyse proteins (faeces/urea), forming ammonium (ammonification)
What is denitrification and what conditions does it need?
•Denitrifying bacteria converts nitrates into N2 gas
•waterlogged/poorly aerated (e.g no ploughing) so less O2 = anaerobic conditions
What is mycorrhizae?
•Mutualistic relationship= fungal association between plant roots and beneficial fungi
1.fungi increases SA for water/mineral absorption
2.mycorrhizae holds water/minerals around roots
3.plants is more drought resistant and able to take up more inorganic ions
What is the phosphorus cycle?
•sedimentary rocks are weathered/eroded to release PO4 3- into soils/water
•taken up by producers/consumers
•saprobionts will decompose dead matter/excretions to release into soil/oceans or to form sediment
Why are fertilisers used?
To replace nitrates and phosphate ions in soil, lost when plants are harvested + removed from nutrients cycles as crop
What are the advantages/disadvantages of natural fertilisers?
Ad:•cheaper/free as manure
•less soluble so less risk of leaching
Dis:•exact mineral proportion cannot be controlled
•smells
•unwanted material e.g fungal spores
What are the advantages/disadvantages of artificial fertilisers?
Ad:•control exact proportion of mineral nutrients
Dis: •more water soluble so higher risk of leaching
•expensive
What is eutrophication?
1.nitrogen fertiliser leaches into water
2.nitrates increase growth of algae and make a blanket on surface of water that blocks light
•plants below cannot photosynthesise and will die
•bacteria does microbial respiration as it decomposes dead matter
•decreases O2 content in water so organisms cannot respire and will die
Why do natural fertilisers cause less leaching?
1.made of organic matter
2.which needs to be broken down by microorganisms in soil before
3.it means the release of mineral nutrients is more controlled and it is less likely to be leached into ponds/rivers
What is the light dependent reaction and where does it occur?
In the thylakoid membrane
1.photoionisation=chlorophyll absorbs light energy and an e- is excited, lost and passed onto an e-acceptor
2.the e- will be transferred across an e-transport chain and will release energy in a series of redox reactions in the thylakoid membrane
3.energy is used to actively transport H+ from the stroma to the membrane which produces an electrochemical gradient
4.H+ will diffuse back to the stroma via ATP synthase that will catalyse ADP + Pi = ATP
5.NADPH forms when NADP picks up H+ and an e-