energy flow Flashcards
biomass
the dry mass of organic molecules
productivity
rate of biomass accumulation
units if productivity
kg/km2/year
net productivity of consumers
NP = I - (E+R)
net productivity = ingested - (egestion + respiratory losses)
net productivity of producers
NPP = GPP - R
net primary productivity = rate of photosynthesis - respiratory losses
% of light energy which becomes chemical energy in producers
2%
% chemical energy in producers which becomes chemical energy in primary consumers
10%
% chemical energy in primary consumers which becomes chemical energy in secondary consumers
20%
why is percentage of chemical energy lost between trophic levels so high
- not all of previous trophic level is consumed or didgested
- energy lost in undigestible food (eg. feaces)
- respiratory losses of energy
- excretion - CO2/urea
- some of organism cannot be consumed
why is percentage of chemical energy lost between sun and producers so high
- not all wavelengths of light are absorbed by pigments - some reflected
- some light reflected by clouds
- not all light hits chlorophyll
- limiting factors affect rate of photosynthesis
how to increase productivity of producers (5)
- sewing density
- controlling pests
- fertilisers
- genetically modifying / selected breeding
- control limiting factors eg. temp, light + CO2
how to increase productivity of consumers (non-producers) (8)
- restricting movement - limiting respiratory losses
- keep warm - limit heat lost to environment
- vaccination - reduce disease
- more digestible food
- selective breeding
- hormones/steroids
- more nutrient rich food
- early slaughter - when feed:gain ratio is at its highest
percentage efficiency
energy available after transfer / energy available before transfer x 100
advantages of artificial fertilisers
- faster response
- specific to a crop
disadvantages of artificial fertilisers
- expensive (although less machinery needed)
- soluble - lead to leaching
advantages of natural fertilisers
- free/cheap - eg. manure
- increases soil stability
- organic
- increases drainage - decrease water-logging
disadvantages of natural fertilisers
- slower acting - as decomposition needed
environmental consequences of overuse of fertilisers (2)
- loss of biodiversity - extra N spreads to neighbouring environments, favouring fast-growing plants ie. weeds which outcompete other species
- eutrophication
detritus
dead organic matter
saprobiotic bacteria
decomposers
ammonification
converting nitrogen ion in detritus to ammonium ions in the soil
nitrification
taking ammonium ions and
producers
photosynthetic organisms which make organic substances using light energy, H2O and CO2 + mineral ions
consumers
organisms which obtain energy by feeding on other organisms (p. s. t. )
food chain
feeding relationship where producers are eaten by consumers - each stage is a TROPHIC LEVEL
- diagram shows energy flow through ecosystem
how to estimate energy store in dry mass
- method
- units of results
CALORIMETRY -
bomb calorimetry - sample of dry material weighed and burnt in exc. O2 in sealed chamber - energy given out heats water and temp rises
- calculate energy change in kJ/Kg
d. Gross primary product (GPP)
total quantity of chemical energy in plant biomass in a given area/volume
Net primary productivity (NPP)
chemical energy store after taking respiratory losses into account
summary of nitrogen cycle:
1) AMMONIFICATION - saprobiotic bacteria make ammonia from dead organisms and waste -> ions into soil
2) NITRIFICATION - nitrifying bacteria make NO3- ions by oxidation reactions of ammonium ions -> nitrite ions -> nitrate ions
3) NITROGEN FIXATION - nitrogen gas - > nitrogen containing compounds - by: 1 - free living nitrogen fixing bacteria (make ammonia and release nitrogen rich compounds when they die and decay)
2 - mutualistic nitrogen fixing bacteria in nodules of plant roots - obtain carbs from plants and releases amino acids to plants
4) DENITRIFICATION - [less O2 = less aerobic nitrifying and nitrogen-fixing bacteria. more anaerobic denitrifying bacteria] - convert nitrates to gaseous N2 gas
how to combat denitrification
keep soils well aerated and drained
stores of phosphorus
mineral rock
stores of nitrogen
gases in atmosphere
eutrophication process
- lakes and rivers, [N] = limiting factors
- [N] ↑ = algae +plant pop. ↑
- algal bloom at surface, reducing light intensities for plants at lower depths (= limiting factor)
- plants die - broken down by saprobiotic bacteria - releasing CO2 by aerobic respiration
- [O] ↓ = limiting reactant
- fish and aerobic organisms die (broken down)
- anaerobic pop ↑ more dead material to break down - releasing products such as nitrates and Hydrogen sulfates, making water putrid
effects of nitrogen (neg.)
- leaching - down by rainwater out of reach of plants and into groundwater supplies - leading to health effects eg stomach cancers
- reduced species diversity as high [N] favours fast growing plants - increased interspecific competition
uses of phosphorus (3)
- ATP
- Phospholipids
- DNA
uses of nitrogen (2)
- nucleic acid synthesis
- ATP
- amino acids
