5.3 and 5.4 Flashcards
Describe how biomass is formed in plants:
During photosynthesis, plants make organic compounds from atmospheric or aquatic CO2
Most sugars synthesised are used by plant as respiratory substrates
Rest used to make other biological molecules (e.g carbs, lipids, proteins) to form biomass
How can biomass be measured?
Mass of carbon or dry mass of tissue per given area
Describe how dry mass of tissue can be measured:
Sample dried in an oven e.g at 100ºC
Sample weighed and reheated at regular intervals
Until mass remains constant
Explain why dry mass is more representative that fresh (wet) mass
Water volume in wet samples will vary but will not affect dry mass
Describe how chemical energy stored in dry biomass can be estimated:
Using calorimetry:
Known mass of dry biomass is fully combusted
Heat energy released heats a known volume of water
Increases in temperature of water is used to calculate chemical energy of biomass
Explain how features of a calorimeter enable valid measurement of heat energy released:
Stirrer- evenly distributes heat energy
Air/insulation- reduces heat loss/gain to/from surroundings
Water- has high specific heat capacity
What is gross primary production?
Chemical energy store in plant biomass, in a given area/volume in a given time
What is net primary production?
Chemical energy store in plant biomass after respiratory losses to environment
State the formula for NPP
NPP=GPP-R
Explain the importance of NPP in ecosytems:
NPP is available for plant growth and reproduction
NPP is also available to other trophic levels in the ecosystem (e.g herbivores and decomposers)
What is primary or secondary productivity and what units are used?
The rate of primary/secondary production
kJ ha-1 year-1 (energy, per unit area, per year)
Why do we use these units for primary/secondary production?
Per unit area takes into account that different environments vary in size
- standardises results to enable comparison between environments
Per year takes into account effect of seasonal variation on biomass
- more representative and enables comparison between environments
Explain why most light falling on producers is not used in photosynthesis:
Light is reflected/wrong wavelength
Light misses chlorophyll
Co2 conc or temp is a limiting factor
State the formula for net production of consumers?
N = I - (F+R)
State the formula for efficiency of energy transfer
Energy/biomass available after transfer ÷ energy/biomass available before transfer
Why is energy transfer between trophic levels inefficient?
Heat energy is lost via respiration
Energy lost via parts of organism that aren’t eaten
Energy lost via food not digested - lost as faeces
Energy lost via excretion - e.g urea in urine
How do crop farming practices increase energy transfer efficience?
SImplifying forrd webs to reduce energy/biomass losses to non-human food chains
- herbicides kill weed (less competition so more energy to create biomass)
- pesticides kill insects (reduce loss of biomass from crops)
- fungicides reduce fungal infections (more energy to create biomass)
Fertilisers (e.g nitrates) to prevent poor growth due to lack of nutrients
Explain how livestock farming practices increase energy transfer efficiency:
Reducing respiratory losses within a human food chain
- restrict movement and keep warm ( less energy lost as heat from respiration)
- slaughter animals whilst still growing (most of their energy used for growth)
- Treated with antibiotics (prevent loss of energy due to pathogens)
- Selective breeding to produce breeds with higher growth rates
Explain the role of saprobionts in recycling chemical elements:
Decompose organic compounds (e.g proteins/urea/DNA in dead matter/organic waste)
By secreting enzymes for extracellular digestion
Absorb soluble needed nutrients and release mineral ions
Explain the role of mycorrhizae:
Symbiotic association between fungi and plant roots
Fungi act as an extension of plant roots to increases surface are of root system
To increase rate of uptake/absorption of water and inorganic ions
In return, fungi receive organic compounds (carbs)
Which biological molecules contain nitrogen?
Amino acids/proteins or enzymes/urea/DNA or RNA/chlorophyll/ATP or ADP/NAD or NADP
Describe the role of bacteria in nitrogen fixation:
Nitrogen gas converted into ammonia which forms ammonium ions in soil
By nitrogen fixing bacteria
- some free living in soil, others found in root nodules of leguminous plants
Describe the role of bacteria in ammonification:
Nitrogen containing compounds e.g proteins/urea from dead organisms/waste are broken down/decomposed
Converted to ammonia which forms ammonium ions in the soil
By saprobionts (secrete enzymes for extracellular digestion)
Describe the role of bacteria in nitrification:
Ammonium ions in soil converted into nitrites then nitrates via a two step oxidation reaction by nitrifying bacteria in aerobic conditions
