Ecology p2

Frage	Antworten
Nitrogen cycle	Flow of nitrogen atoms between inorganic nitrogen compounds and atmospheric nitrogen gas in an ecosystem- living organisms need nitrogen to make amino acids, proteins, chlorophyll and nucleic acids
Nitrogen cycle- how it works	Plants/ animals= unable to use nitrogen gas- so plants absorb nitrates into their roots- organic nitrogen compounds produced by plants are transferred through the food chain- primary consumers eat plant- decomposers of plants/ animals after death/ excreted and egested products of animals releases minerals back to soil- bacteria are key in cycle
Bacteria process 1- Ammonification	Putting ammonium ions back in the soil- detritivores consume dead organisms and animal waste and saprotrophic bacteria and fungi (collectively=decomposers)- secrete enzymes decayes remains-
Ammonification-enzymes	Proteases digest proteins into amino acids Deaminases remove (-NH2) groups from amino acids- reduce to ammonium ions- (NH4+) Digestion products are absorbed by decomposers- used by other organisms
Nitrification	The addition of nitrogen to the soil, most commonly as nitrite (NO2-) and nitrate (NO3-) ions- ammonium ions formed in decomposition are converted to nitrites then nitrates- various bacteria involved eg Nitrosomonas converts ammonia to nitrite and Nitrobacter converts nitrite to nitrate
What type of reaction is nitrification	Nitrogen atom in ammonium= progressively losing hydrogen atoms and gains oxygen atoms- reactions= oxidations- Nitrosomonas and Nitrobacter therefore require aerobic conditions
Denitrification	Denitrification= loss of nitrate from the soil- anaerobic bacteria eg Pseudomonas converts nitrate ions to nitrogen NO-3 -----> N2 Reduction reaction as O2 is lost- so favours anaerobic conditions - enhanced in waterlogged soils
Nitrogen fixation	The reduction of nitrogen atoms in nitrogen molecules to ammonium ions by prokaryotic organisms- although 79% of atmosphere is nitrogen very few organisms can use it as they don't have enzymes to break triple bond in nitrogen molecules- geological processes releasing nitrates/ ammonium ions= very slow- biosphere therefore relies on ptokaryotes to reduce nitrogen molecules to ammonium ions
Azotobacter	Free living nitrogen fixing bacterium in the soil- accounts for most biological nitrogen fixation-
Rhizobium	Many symbiotic nitrogen fixing bacteria in angiosperm families- Rhizobium found in root nodules of plants can be in legumes- gas diffused into root nodule nitrogenase catalyses reduction reactions using ATP- so nitrogen fixing organisms= aerobic-but nitrogen fixation (reduction)=poisoned by oxidising reactions in root nodules genes of host plant code for a type of haemoglobin that binds molecular O2 in nodules- protects reactions from oxidation- turns nodules pink
Last one on nitrogen fixation I promise	Ammonium ions= converted to organic acids then to amino acids for incorporation into bacterial proteins N2----> NH4+---> organic acids--->amino acids reduction by nitrogenase for first conversion Some amonnium ions are diverted into the vascular strand connecting root nodule to plant- this way plant obtains nitrogen for its own metabolism
Plants without mutualistic nitrogen fixing bacteria...	Take up nitrates/ ammonium ions via active transport and facillitated diffusion
Nevermind I lied- more nitrogen fixation	radicles of newly germinated legumes do not contain rhizobium-newly emerged radicle and rhizobium both secrete chemo attractants- radical grows toward rhizobium cells and the rhizobium cells use their flagella to move the cortex of the radicle- invade- large no. produced when they replicate causes swelling in root nodule-
Nevermind I lied- more nitrogen fixation p2	nodules and the bacteria they contain enable legumious to grow successfully even when soil nitrates are scarce- when plant dies both plants and rhizobium from nodules = decomposed into ammonium compounds- released to soil- goes to nitrites to nitrates
Non biological processes that impact the nitrogen cycle	-application of agricultural fertilisers- adds nitrogen to soil - Lightning adds a small amount of nitrogen to the soil - Leaching of minerals removes nitrogen from soil
Human impact on nitrogen cycle	Human pop increases- need to produce more food- plant breeding/ genetic modification contribute as well as pesticides- treating soil and maintaining its structure is vital for efficient food production
Ploughing	Improves soil aeration- favours: aerobic organisms eg free living nitrogen fixers, enhancing formation of ammonium ions in the soil, Nitrifying bacteria and so enhances the conversion of ammonium into nitrites and nitrates, Mineral uptake as plants respire aerobically and generate ATP needed for active transport
Draining land/ artificial nitrogen fixation	DL- allows air to enter soil = reduces anaerobic conditions which favour denitrifying bacteria- loss of nitrates= reduced ANF- eg Haber process- converts nitrogen to ammonia for fertilisers- largely compounds contaiining ammonium and/ or nitrate ions- essential for food production
Large amounts of animal waste	waste from stock rearing= used as brown manure- nitrogen and other nutrients it contains= essential for plant growth- improves soil structure- holds more water/ nutrients/ more fertile- encourages microbial activity- improves mineral supply- manure releases nitrogen componds to the soil gradually
Slurry/ biosolids	Liquid made from manure and water- ptoduced by more intensive rearing systems - concrete slats are used instead of straw bedding- usually stored in tank or lagoon before use- slurries from intensive pig farm has very unpleasant smell- usually injected into soil- herbivore manure= smells milder- less protein unlike omivore pig Treated sewage sludge 'biosolids' is sustainable alternative to fertilisers
Fields of legumes	eg alfalfa or clover- enhances nitrogen fixation- when crop dies it is ploughed back into the soil as 'green manure' value is high nitrogen content
Effects of fertilisers on habitats	Upland streams are oligotrophic- very few minerals dissolved- as water flows over rocks dissolves minerals- water becomes enriched w/minerals= described as eutrophic- when mineral conc is so high organisms die- described as dystrophic- eutrophication=artificial enrichment of aquatic habitats by excess nutrients- often caused by run off fertilisers
Problems caused by excess nitrates in soils	On agricultural land- increased fertiliser has reduced species diversity on grassland- fertilisers increase growth of grasses and plants eg nettles- shade out smaller plants
Problems caused by nitrates leaching into rivers-	Leaching of nitrates and phosphates from surrounding lands= slow, natural process during which concs of salts build in water - normally mineral ions accumulate until equilibrium is reached addition to water counterbalanced by rate of removal- but sewage/ fertiliser adds extra minerals- results in eutrophication
Fertiliser leaching P2	Nitrate= highly solule- readily leached from soil and washed into rivers- drains through soil via gravity-as ground water but heavy rainfall increases conc of nitrate in water- nitrate= fertiliser- algae respond- bloom- water becomes green- light unable to penetrate- plants in deeper regions can't photosynthesise- die-
Fertilising leaching p3	general decrease in animal species diversity-rely on food and shelter- short lived algae soon die- decomposed by saprobiontic bacteria- aerobic organisms- use lots of O2- creates biochemical O2 demand- water in all but very uppper areas- exposed to air- becomes deoxygenated- fish and other oxygen requiring species die- anaerobic bacteria in water reduce nitrate to nitrite- flourish some species release gases w/ noticeable smell eg hydrogen sulphide
To avoid high nitrate concs	Farmers must comply w/ strict legislation-reduce quantity of nitrate they release into environment- must: Restrict amount of fertiliser Only apply fertiliser when crops are actively growing- readily- readily used doesn't remain in soil= leached away Leave 10m strip next to watercourses- nitrates don't directly enter soil and whn they do- over long time
To avoid high nitrate concs- P2	Drainage ditches- minerals concentrate in drainage ditches- undergo eutrophication- protects natural watercourses- water flows slowly in ditches- accumulate silt- led to local drop in invertebrate biodiversity and high nitrate conc reduces species diversity in adgacent grassland- but rare species reported in drainage ditches due to unusual conditions

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	Erstellt von Darcey Griffiths vor 15 Tage