3.5.4 Nutrient cycles Flashcards
role of saprobionts in recycling chemical elements
decompose organic compounds in dead matter by secreting enzymes for extracellular digestion. They then absorb soluble needed nutrients and release mineral iona (eg phosphate ions)
explain the role of mycorrhizae
fungi act as an extension of plant roots to increase surface area of root system which will increase rate of uptake/absorption of water and inorganic ions
in return, fungi receive organic compounds
examples of biological molecules that contain nitrogen
amino acids, proteins or enzymes, urea, DNA or RNA, chlorophyll, ATP or ADP. NAD or NADP
key stages in nitrogen cycle
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- Nitrogen fixation (nitrogen fixing bacteria) nitrogen in gas to ammonia in legume root modules
- Ammonification (saprobionts ) urea and proteins broken into nitrogen containing molecules. Nitrogen gass into ammonia by bacteria /Ammonium
3.) Nitrification (nitrifying bacteria ) Ammonia to nitrites, nitrites to nitrates, assimitation
4.) Denitrification ( denitrifying bacteria )
Describe the role of bacteria in nitrogen fixation
Nitrogen Gas converted into ammonia which forms ammonium ions in soil by nitrogen fixing bacteria (may be found in rootu nodules)
Describe the role of bacteria in ammonification
Nitrogen containing compounds (eg proteins/urea) are decomposed by saprobionts and converted to ammonia which forms ammonium ions in soil
Describe the role of bacteria in nitrification
ammonium ions in soil converted into nitrites then nitrates via a two step oxidation reaction (for uptake by plant root hair cells by active active transport)
by nitrifying bacteria in aerobic conditions
describe the role of bacteria in denitrification
Nitrates in soil converted into nitrogen gas by denitrifying bacteria in anaerobic respiration
suggests why ploughing soil increases its fertility
aerates soil
therefore more ammonium converted into nitrite and nitrate (more nitrification) as more nitrifying bacteria as it is an aerobic process
less denitrification so less nitrate converted into gas as anaerobic process
examples of biological molecules that contain phosphorus
Phospholipids/ DNA or RNA/ ATP or ADP/ TP or GP/ RuBP
Describe phosphorus cycle , starting with phosphorus in rocks
1.) Phosphate ions in rocks released into soils by erosion or weathering
2.)phosphate ions taken up by producers and incorporated into their biomass (mycorrhizae increases rate of absorption)
3.)phosphate ions travel through food chains
4.)some phosphate ions lost through waste products
5.) Saprobionts decompose organic compounds releasing phosphate ions
benifits of fertilisers
to replace nitrates/ phosphates lost when plants are harvested and livestock are removed
those removed cannot be incorporated into biomass as arent released back into soil through decomposition by saprobionts
so improve efficiency of energy transfer
therefore increase productivity / yield
environmental issues arising from fertilisers
Phosphate/ nitrates dissolve in water, leading to leaching of nutrients into lakes, rivers or oceans
this leads to eutrophication
describe eutrophication
Rapid growth of algae (algae bloom) so light blocked
submerged plants die as they cannot photosynthesise
saprobionts decompose dead plant matter, using oxygen in aerobic respiration
less oxygen for fish to aerobically respire
dead fish
describe the difference between artificial and natural fertilisers
natural- organic (manure, compost, sewage)
ions are released during decomposition by saprobionts
artificial- contain inorganic compounds of nitrogen, phosphorus and potassium
key advantage of natural fertiliser over artificial
less water soluble so less leaching therfore eutrophication less likely
organic molecules require breaking down by saprobionts, slower release of nitrate or phosphate
