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