EEB 2100 UConn Exam 2 questions
and answers
Most profound nutrients being added to ecosystems by humansNitrogen and
phosphorus
Nitrogen factsmakes up 78% of Earths atmosphere and many enzymes and
proteins that humans need
Nitrogen cycle: FixationFixation of N2 gas is done by micro...
EEB 2100 UConn Exam 2 questions
and answers
Most profound nutrients being added to ecosystems by humans✔✔Nitrogen and
phosphorus
Nitrogen facts✔✔makes up 78% of Earths atmosphere and many enzymes and
proteins that humans need
Nitrogen cycle: Fixation✔✔Fixation of N2 gas is done by microorganisms using
energy to break down the gas into organic NOx compounds(Nitrate and Nitrite)
1/3rd of free-living bacteria(cyanobacteria) conduct fixation
2/3rds of plant-associated bacteria do this as well
Nitrogen cycle: Mineralization✔✔NOx compounds are converted into NH4+
(ammonium)
Organic Nitrogen compounds (NOx) are inaccessible to plants
Process done by fungi and bacteria in the soil
Nitrogen cycle: Nitrification✔✔NH4+ (ammonium) is turn into NOx compounds
performed by bacteria to create energy
byproduct of the process is the creation of N2O which is a greenhouse gas that is
300x more effective at warming the earth than carbon dioxide
Nitrogen cycle: Denitrification✔✔NOx compounds are turned back into nitrogen gas
(N2)
performed by microbes
Anammox Process✔✔NH4 + NO2 --> N2
makes up 30-50% of N2 in oceans
Fertilizer and Nitrogen✔✔The nitrogen necessary for fertilizer used to be harvested
from guano and bird poop
Haber-Bosch process✔✔Iron catalyst, high temperature and pressure used to break
N2 bond to form Ammonia(NH3)
Haber-Bosch effects✔✔Leads to great acceleration as more fertilizer can be created
and used to increase food production.
, Doubles the amount of people fed per hectare of crop land
however, over half of fertilizers used are lost from the land and end up in other
places like ponds and streams
Green revolution✔✔Technologies in 1950s that massively increased global
agricultural productivity
Nitrogen addition by humans✔✔300 megatons total of Nitrogen to land where
around half is done by humans
only 270 MT is removed each year so there is a net gain
Phosphorus cycle✔✔Necessary for ATP in cellular energy
rare and is most often the limiting factor in ecosystems
Phosphorus sources✔✔All natural phosphorus is from the weathering of rocks
uplifted from the ocean
Most phosphorus used by humans comes from mining
Recycled between biota
Phosphorus is limited✔✔Stocks could increase in 2030 with the peak of phosphorus
extraction but then slowly decrease over time
Morocco, China, and USA have 85% of global Phosphorus reserves
Phosphorus became scarce in 2007 and the price went up by 700% resulting in a
food crisis and political unrest
Phosphorus Sinks✔✔Overall movement of P from land to rivers causes P to develop
on the floor of water bodies
Ocean floor is the biggest sink
Phosphorus cycle: Phosphate✔✔Only Phosphate (PO3) is available to plants
Phosphate is assimilated to turn it into organic forms such as ATP
Phosphorus cycle: immobilization✔✔Phosphorous can become immobilized when
bound to rocks and other insolubles
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