Flashcards
Ecology p2
Flashcards do conjunto (28)
- 1Nitrogen cycleFlow 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
- 2Nitrogen cycle- how it worksPlants/ 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
- 3Bacteria process 1- AmmonificationPutting ammonium ions back in the soil- detritivores consume dead organisms and animal waste and saprotrophic bacteria and fungi (collectively=decomposers)- secrete enzymes decayes remains-
- 4Ammonification-enzymesProteases 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 - 5NitrificationThe 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
- 6What type of reaction is nitrificationNitrogen atom in ammonium= progressively losing hydrogen atoms and gains oxygen atoms- reactions= oxidations- Nitrosomonas and Nitrobacter therefore require aerobic conditions
- 7DenitrificationDenitrification= 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 - 8Nitrogen fixationThe 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
- 9AzotobacterFree living nitrogen fixing bacterium in the soil- accounts for most biological nitrogen fixation-
- 10RhizobiumMany 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
- 11Last one on nitrogen fixation I promiseAmmonium 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 - 12Plants without mutualistic nitrogen fixing bacteria...Take up nitrates/ ammonium ions via active transport and facillitated diffusion
- 13Nevermind I lied- more nitrogen fixationradicles 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-
- 14Nevermind I lied- more nitrogen fixation p2nodules 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
- 15Non 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 - 16Human impact on nitrogen cycleHuman 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
- 17PloughingImproves 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
- 18Draining land/ artificial nitrogen fixationDL- 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 - 19Large amounts of animal wastewaste 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
- 20Slurry/ biosolidsLiquid 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 - 21Fields of legumeseg alfalfa or clover- enhances nitrogen fixation- when crop dies it is ploughed back into the soil as 'green manure' value is high nitrogen content
- 22Effects of fertilisers on habitatsUpland 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
- 23Problems caused by excess nitrates in soilsOn agricultural land- increased fertiliser has reduced species diversity on grassland- fertilisers increase growth of grasses and plants eg nettles- shade out smaller plants
- 24Problems 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
- 25Fertiliser leaching P2Nitrate= 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-
- 26Fertilising leaching p3general 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
- 27To avoid high nitrate concsFarmers 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 - 28To avoid high nitrate concs- P2Drainage 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