Energy Transfers in and Between Organisms- Energy and Ecosystems and Nutrient cycles ( Year 13 Content ) Flashcards
How do plants use sugars from photosynthesis?
- primarily as respiratory substrates
- to synthesise other biological molecules ( cellulose )
what is biomass?
total dry mass of tissue or mass of carbon measured over a given time in specific areas
suggest the units for biomass
- when an area is being sampled: gm-2
- when a volume is being samples: gm-3
how can the chemical energy store in dry mass be estimated?
using calorimetry
q= m x c x Δt
why is bomb calorimetry preferable to simple calorimetry?
reduces heat loss to surroundings
how could a student ensure that all water had been removed from a sample before weighing?
heat the sample and reweigh it until the mass reading is constant
define gross primary production ( GPP )
total chemical energy stored in a plants biomass within a given volume or area
define net primary productivity ( NPP )
total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses
what equation is used to calculate NPP?
NPP = GPP - R
where R represents respiratory losses
why is most of the sun’s energy not converted to organic matter?
- most solar energy is absorbed by the atmosphere ( ozone layer ) or reflected by clouds
- the chlorophyll cant absorb some wavelengths of light
- some of the light might miss the chlorophyll molecule
- energy lost as heat during respiration/ photosynthesis
how can the net production of consumers be calculated?
N = I - ( F + R )
l: chemical energy from ingested food
F: energy lost as faeces and urine
R: respiratory losses
why does biomass decrease along a food chain?
- energy lost in nitrogenous waste ( urine ) and faeces
- some parts of the organism are not consumed ( cellulose and bones )
- energy lost to the surroundings as heat
outline some common farming practices used to increase efficiency of energy transfer
- exclusion of predators: no energy lost to other organisms in food web
- artificial heating: reduce energy lost to maintain constant body temperature
- restriction of movement
- feeding is controlled at the optimum
give the equation for efficiency
useful energy / total energy x100
explain why the length of food chains is limited
energy lost at each trophic level
so there is insufficient energy to support a higher trophic level
what is a pyramid of biomass?
diagram that shows the biomass at each trophic level
name the general stages in the phosphorus cycle
- weathering
- run off
- assimilation
- decomposition
- uplift
why is the phosphorus cycle a slow process?
- phosphorus has no gas phase, so there is no atmospheric cycle
- most of the phosphorus is stored as PO4 3− in rock s
what happens during weathering and run off?
phosphate compounds from sedimentary rocks leach into surface water and soil
explain the significance of phosphorus to living organism
plants convert inorganic phosphate into biological molecules e.g. DNA,ATP,NADP
what happens during uplift?
sedimentary layers from oceans ( formed from
the bodies of aquatic organisms) are brought up to land over many years
how does mining affect the phosphorus cycle?
speeds up uplift
name the 4 main stages of the nitrogen cycle
1) nitrogen fixation
2) ammonification
3) nitrification
4) denitrification
why cant organisms directly use nitrogen from the atmosphere?
nitrogen is very stable due to the strong covalent triple bond
what happens during atmospheric fixation of nitrogen?
1) high energy of lighting breaks N2 to N
2) N reacts with oxygen to form NO2 - ( nitrite )
3) NO2 - dissolves in water to form NO3 - ( nitrate )
outline the role of bacteria in nitrogen fixation
nitrogen-fixing bacteria in the nodules of legumes use enzyme nitrogenase to reduce gaseous nitrogen into ammonia
outline the role of bacteria in ammonification
1) saprobionts feed on and decompose organic waste containing nitrogen
2) NH3 is released
3) NH3 dissolves in water in soil to form NH4+
outline the role of bacteria in nitrification
2-step oxidation process carried out by saprobionts in aerobic conditions
2NH4+ + 3O2 —> 2NO2- + 2H2O + 4H
2NO2- + O2 —> 2NO3-
outline the role of bacteria in denitrification
anaerobic denitrifying bacteria convert nitrates in soil back into gaseous nitrogen
explain the significance of nitrogen to living organism
plant roots uptake nitrates via active transport and use them to make biological compounds
- amino acids
- nucleic acid
- NAD/NADP
outline the role of mycorrhizae
symbiotic relationship between plant and fungus increases surface area of root system = increases uptake of water and mineral ions
give 3 benefits of planting a different crop on the same field each year
- nitrogen-fixing bacteria make soil more fertile by increasing soil nitrate content
- different crops have different pathogens
- different crops use different proportions of certain ions
name the 2 types of fertilisers and the use of fertilisers
-Organic: decaying organic matter and animal waste
-Artificial/Inorganic: minerals from rocks usually containing nitrogen,phosphorus and potassium
-fertilisers are used to increase crop yield
at a certain point, using more fertiliser no longer increases crop yield. why?
another factor affects the rate of photosynthesis so the rate of growth cannot increase any furher
outline 2 environmental issues caused by the use of fertilisers
1) Leaching: nitrates dissolve in rainwater and runoff into water sources
2) Eutrophication: water sources become putrid as a result of algal bloom
outline the stages of eutrophication
1) aquatic plants grow rapidly due to the high nitrate levels
2) algal bloom on the surface prevents light from reaching the bottom and the plants die
3) oxygen level start to decrease because the number of saprobionts respiring aerobically increases so the fish die
how can the risk of eutrophication be reduced?
- sewage treatment marshes on farms
- pumping nutrient-enriched sediment out of the water
