productivity + cycles Flashcards
outline nitrogen cycle
nitrogen fixation
ammonification
nitrification
denitrification
nitrogen fixation
nitrogen converted to ammonia
by nitrogen fixing bacteria
nitrogen from atmosphere
bacteria found in root nodules of legumes
- mutualistic relationship
- provide plant with compounds, get carbohydrates from plant
ammonification
nitrogen compounds converted to ammonia
by saprobionts (decomposers)
nitrogen compounds from anima waste or dead organisms
nitrification
ammonium ions -> nitrites -> nitrates
by nitrifying bacteria
ammonium from soil
denitrification
nitrates converted to nitrogen gas
by denitrifying bacteria
happens in anaerobic conditions
by respiration of the bacteria
role of saprobionts
decomposers
break down remains of dead plants and animals and waste
allows chemical elements in the remains to be recycled
secrete enzymes and digest matter externally
then absorbs nutrients they need - extracellular digestion
organic molecules broken down into inorganic ions
what is saprobiontic nutrition?
obtaining nutrients from dead organic matter using extra cellular digestion
role of mycorrhizae
a symbiotic relation between fungi and roots of plants
- fungi made of long thin strands, hyphae, which connect to plants roots
- increase surface area of plants roots
- helps plant absorb ions from soil
eg phosphorus - increase uptake of water for plant
- fungi get organic compounds from the plant
eg glucose
outline phosphorus cycle
- phosphate ions in rocks released by weathering
- phosphate ions taken into plants through roots (rate increased by mycorrhizae)
- transferred through food chain
- phosphate ions lost from animals in waste products
- saprobionts release phosphate ions into soil by decomposition
- breaking down dead plants, animals and waste
or
6. weathering also releases phosphate ions into water
7. taken up by aquatic producers, eg algae
8. passed along food chain to sea birds
9. phosphate ions returned to soil through guano
returned to producers or trapped in sediment again
outline eutrophication
- mineral ions leached from fertilised fields
- causes rapid growth of algae
- large amounts block sunlight
- plants die as they cant photosynthesise
- bacteria feed on bead plant matter
- increase in bacteria means less oxygen in water (respire aerobically)
- fish and species die as not enough oxygen
how does farming reduce nutrients in soil?
lost when plants harvested
- removed from area
- don’t die and decompose
- mineral ions not returned to soil
animals taken in phosphates and nitrites eating grass
- animals removed
- nutrients not returned in waste
why are fertilisers used?
to replace nutrients lost from soil
by harvesting and removing livestock
loses phosphates and nitrates
artificial fertilisers
inorganic
pure chemicals - ammonium nitrate
environmental impacts of fertilisers
leaching
eutrophication
natural fertilisers
organic matter
eg manure, composted vegetables, sewage
guano
outline leaching
mineral ions from fertilisers washed away (eg nitrate and phosphate)
happens as more fertiliser applied than a plant can use
- remain in soil water
more likely after heavy rainfall
inorganic ions in artificial more soluble - more likely to be leached
phosphates less soluble = leached less (than nitrates)
what is biomass
the mass of living material
amount of chemical energy stored in an organism
in plants:
made up of biological molecules made from light energy into chemical energy in photosynthesis
(synthesised from CO2)
estimated using calorimetry
gross primary production
chemical energy store in plant biomass in a given area
G primary productivity = given time (rate)
respiratory loss
GPP energy lost as heat energy when plants respire
net primary production
chemical energy store in plant biomass after respiratory losses in a given area
NPP = GPP - R
remaining chemical energy
available for:
- plant growth
- reproduction
- other trophic levels in ecosystem eg higher and decomposers
N primary productivity = per given time (rate)
what is net production
energy stored in the biomass of consumers
get energy by digesting plants or animals that have eaten plants
not all energy transferred, lost by:
- respiration
- urine and faeces
- not all food eaten or digestible, eg bones
secondary productivity
how is net production calculated?
N = I - (F + R)
N = net production
I = chemical energy in ingested food
F = chemical energy lost in faeces and urine
R = respiratory loss
what is primary and secondary productivity measured in?
biomass in a given area in a given time
kJ ha-1 year-1
how do farming practises increase efficiency of energy transfer (2)
simplifying food webs
- reduces energy lost
reducing respiratory losses
- reduces energy lost
both increase energy available for human consumption
simplifying food webs
reduces energy lost to other organisms
getting rid of food chains not involving humans
- increases NPP of plants
- less energy lost to pests
done by pesticides + herbicides
kills weeds and pests to reduce competition
how are respiratory losses reduced?
controlling conditions livestock live in
more energy available for there growth
reduce movement
keep indoors - less energy wasted maintaining temperature
more energy maintained (losses reduced) - more energy available for humans
but unethical for livestock to reduce movement
ways nitrogen is introduced into soils
animal waste
nitrogen fixation (by nitrogen fixing bacteria)
artificial fertilisers
decay of organic matter by saprobionts (ammonification)
ways phosphorus is introduced into soils/water
weathering of sedimentary rock
minerals in fertilisers
decomposition of animal waste
what is a tropic level?
position of an organism in a food chain
net primary production available to those higher in tropic levels
and decomposers in soil
production vs productivity
production = mass per area
productivity = mass per area per TIME
rate of production
calorimetry
used to estimate biomass
burn matter in calorimeter
used to heat known volume of water
temperature change measured
use of nitrogen in organisms
proteins and nucleic acids
use of phosphorus in organisms
phospholipids and nucleic acids
efficiency of energy transfer (%)
I - (F + R) = NP
(NP divided by I) x 100
