nutrient cycles Flashcards
what is the simple sequence of a nutrient cycle
nutrients taken up by producer as inorganic ions —> producer incorporates nutrients into complex organic molecules—> producer eaten and nutrients passed to consumer and along food chain —> when producers/consumers die complex molecules are broken down by saprobiotic microorganisms —> inorganic ions released
what is the role of saprobionts in recycling chemical elements
feed on the remains of dead plants and animals and their waste products and break down the organic molecules
by secreting enzymes for extra cellular digestion
what is the role of mycorrhizae in recycling chemical elements
symbiotic relationship between fungi and roots of plants
fungi act as an extension of the plant roots
- increase surface area to increase rate of absorption of water and nutrients
mutualistic relationship - plants provide fungi with carbohydrates
draw the nitrogen cycle
describe the process of ammonification
nitrogen containing compounds eg. amino acids from dead organisms and animal waste are broken down
converted to ammonia which goes on to form ammonium ions in the soil
by saprobionts
by secreting enzymes for extracellular digestion
describe the process of nitrification
ammonium ions in the soil turn to nitrites then nitrates
at a two stage oxidation reaction
by nitrifying bacteria
who need oxygen (aerobic)
nitrates can be absorbed by plant root hair cells by active transport
what do farmers do to their soil relating to the nitrogen cycle
aerate their soil to increase oxygen to allow number of nitrifying bacteria to increase and denitrifying bacteria to decrease
describe the process of denitrification
nitrates in the soil turn into nitrogen gas
by denitrifying bacteria (anaerobically respire)
when low oxygen conc. in soil eg. waterlogged
describe the process of nitrogen fixation
nitrogen gas converted to nitrogen containing compounds eg. ammonia
by nitrogen fixing bacteria
- can be free loving in soil
- or mutualistic ( live in nodules in roots of plants eg. legumes)
what is the importance of the nitrogen cycle
nitrogen gas is i reactive and not easily converted into other compounds
most plants can only take up nitrogen in the form of nitrate
used by plants and animals to make proteins and nucleic acids for growth
draw the phosphorus cycle
describe the stages of the phosphorus cycle
- phosphate ions in rocks released to soil by erosion and weathering
- phosphate ions taken into plants by roots and incorporated into biomass
- DNA RNA and phospholipids
- rate of absorption increased by mycorrhizae - phosphate ions transferred through food chain
- some phosphate ions lost from animals in waste products and plants and animals that die
- decomposed by saprobionts - release enzymes for extracellular digestion releasing phosphate ions into soil
what is the need for fertilisers
replaces nutrients lost when crops are harvested and livestock is removed
nutrients removed form soil and incorporated into their biomass cant be released back into soil through decomposition by saprobionts
fertilisers improve efficiency of energy transfer
- nutrient could no longer be a limiting factor
- increase productivity of agricultural land
what is the difference between natural and artificial fertilisers
artificial
- inorganic
- contain pure chemicals eg. ammonium nitrate as powders/ pellets
- inorganic substances more water soluble so larger quantities washed away impacting environment
nature
- organic
- eg. manure, compost, sewage
- cheaper/ feee but exact nutrients cannot be controlled
what are the environmental issues with fertilisers
leaching
- rain/ irrigation systems wash water soluble compounds out of soil into waterways
- worse when more fertiliser asses to field than used
eutrophication
- rapid growth of algae in ponds and rivers
- algae blocks light preventing it from reaching plants below
- death of plants so they cannot photosynthesise
- aerobically respiring saprobionts decompose the dead plants reducing oxygen conc. in water
- leading to death of aquatic organisms
leaching less likely with natural fertilisers
- nitrogen/ phosphorus contained in organic molecules
- organic molecules less soluble in water so need to be decomposed by saprobionts before nitrogen and phosphorus are released
can also reduce species diversity
- - favour faster growing plants -> slower growing plants lose out -> less organisms who feed off them
