Energy transfers and nutrient cycles Paper 2 Flashcards
Define biomass and give examples of fresh mass and dry mass
the mass of carbon or dry mass of tissue per given.
Examples of fresh mass: living, easy to access, variable water content, unreliable due to varying water content, variable food ingested
examples of dry mass: dead, difficult to assess, small sample size. may not be representative, unreliable as unethical to collect large samples, measured as gm-2 or gm-3, situational, only valid at that moment in time. standing crop may fluctuate
Calculating energy stored in biomass
estimated using calorimetry.
Sample of dry biomass is combusted within a sealed chamber. The chamber is surrounded by a water bath and the heat energy released causes a temperature rise in the water. using the known specific heat capacity of water, and the volume of water and the temperature rise we can calculate the energy released from the mass of burnt biomass in kjkg-1
energy transferred from sun to producer
- some of the light is reflected by ozone layer
- some light may not be absorbed by gases and vapour in the atmosphere
- some of the light energy is the wrong wavelength
- some light energy does not strike chlorophyll
chemical energy and its equation
light energy is converted to chemical energy in the form of organic molecules (glucose amino acids dna etc)
GPP- chemical energy store in plant biomass in a given area or volume (rate of conversion of light energy into chemical energy of organic molecules by photosynthesis
NPP- chemical energy store in plant biomass after reparatory losses to the environment
NPP= GPP-R
available for plant growth, plant reproduction, other trophic levels
producer to primary consumer
- large amounts of the plant may be indigestible and lost from the animal in egested faeces
- not all the plant may be eaten
- some energy lost in excretion such as urine
- energy lost in respiration and as heat to the envrionment
photosynthetic efficiency equation
total light energy falling on the plant x 100
How to calculate net production of consumers
N= I-(F+R)
I= chemical energy store of ingested food
F= the energy lost in faeces and urine
R= the energy lost in respiration
primary to second consumer
- large amounts of animal may be indigestible
- not all of animal can be eaten
- some energy lost in excretion
- energy lost in respiration and and heat to environment
- only energy that is stored as new biomass is available to the next trophic level
percentage efficiency
energy available before transfer x 100
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 to evaporate water
weigh and reheat 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
how can energy conversion rate be increased
restricting movement so less respiratory loss due to less muscle contraction
keeping animals indoors and warm to reduce heat loss from body
feeding nutritious- optimum type for growth eg with macro-nutrients
food source easier to absorb reducing energy lost in egestion
selective breeding- some varieties of breeds are more efficient at converting energy into new tissue
slaughtered before reaching adulthood so more energy transferred to biomass
Process of the nitrogen cycle and the microorganisms it contains
Nitrification: Nitrifying bacteria. Ammonia to nitrates, nitrites to nitrates
Denitrification- denitrifying bacteria. Nitrates to nitrogen gas, also nitrates back to nitrites
nitrogen fixation: nitrogen fixing bacteria- nitrogen gas to ammonia
decomposition/ ammonification- nitrogen containing compound to ammonia by saprobiants.
What molecules is nitrogen molecules
Amino acids, proteins, nucleic acids , ADP, ATP, NADP, NAD and FAD
Nitrogen cycle
- plants take up nitrogen from the soil in the form of NO3- which are absorbed by active transport through root hair cells
- plant uses nitrogen to synthesise amino acids and proteins
- consumers then eat plants and hydrolyse proteins into amino acids, these are absorbed and assimilated into new tissue
- primary consumers may be eaten by secondary consumers and nitrogen passes up through trophic levels.
- both plants and animals die
- animals also excrete nitrogenous waste
- decomposers, saprobiants, secrete extra cellular enzymes through exocytosis
- this hydrolyses N containing polymers into monomers and release ammonia into soil- ammonification
- ammonia oxidised to nitrites then nitrates by nitrifying bacteria- nitrification
- nitrates converted to N2 gas by denitryfying bacteria- denitrification
- nitrogen fixing bacteria can be found in the root nodules of some leguminous plants and rduce N2 gas to ammonia- nitrogen fixation