IB biology: option C (VI)

what bacteria convert atmospheric nitrogen to ammonia? (NITROGEN FIXATION)

nitrogen-fixing bacteria

what is the catalyst in nitrogen fixation?

nitrogenase, produced by nitrogen-fixing bacteria in soil

azotobacter

nitrgoen fixing bacteria found in soil

rhizobium

nitrogen fixing bacteria that forms nodules within plants routes,

mutualistic relationship as supplies plant with ammonia in exchange for carbohydrates

how does ammonia become ammonium?

ammonia is mixed with water, ammonium can then be used by plants

what is ammonification?

As a plant or animal decays, saprotrophs will decompose organic materials to produce ammonia (and ammonium ions)

what is nitrification?

the conversion of ammonium ions into nitrites (NO2–) and nitrates (NO3–) by nitrifying bacteria in the soil

Nitrosomonas

nitrification - converts ammonium ions into nitrites,

Nitrobacter

nitrification - converts the nitrites (from nitrosomonas) into nitrates

what is denitrificaiton?

a chemical reduction process that converts nitrates (NO3–) into nitrogen gas (N2)

denitrifying bacteria

carry out denitrification in the absence of oxygen, reduced availability of nitrates to plants

what is waterlogging?

when soil becomes inundated with water

what are the effects of waterlogging on nitrogen in soil? (denitrification)

soil will lose nitrates and nitrites due to denitrification;

waterlogging reduced oxygen availability, creating oxygen-poor conditions favoured by denitrifying bacteria, converting available nitrates into nitrgoen gas, reducing soil nitrogen content

what are the effects of waterlogging on nitrogen in soil? (leaching)

soil will lose nitrates and nitrites due to leaching;

as water drains downwards through soil, soluble minerals (e.g nitrites and nitrates) are removed with it

describe venus fly traps in relation to nitrogen

venus fly traps are native to wetlands, with waterlogged soil, meaning a low nitrogen environment,

plants terminal leaves form trapping structure, when insects become trapped plant releases digestive enzymes that allow it to absorb nutrients from insect

what are uses of phosphate in ecosystems?

for organisms to synthesise nucleic acids, membranes and ATP

what is the rate of phosphorus turnover in ecosystems? why?

rate of turnover is slow as there are not gaseous components, phosphorus is cycled through decomposition of organisms and by weathering

how can phosphates be removed from the lithosphere?

through mining and the making of phosphate-based fertilisers

why are global phosphorus reserves becoming low?

The demand for fertiliser in agriculture is very high, however the rate of turnover in the phosphorus cycle is very low - this means that phosphates are being removed from the lithosphere at a much faster rate than they are being replenished

what is eutrophication?

the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.)

what places are eutrophication common? why?

eutrophication is common around agricultural lands where the use of artificial fertilisers are prevalent - leaching form soil by rainfall or released as a part of sewage

what are impacts of eutrophication?

rapid growth of algae increases number of decomposers,

high rate of decomposition increases biochemical oxygen demand (BOD),

deoxygenation of water supply causes stress on marine life, reducing biodiversity within ecosystem

how can we assess the nutrient content of a soil sample?

using soil testing kits to assess; nutrients, soil pH, texture, water content