<p>My teacher insists that one of the essays will be on Ecology/Global Warming/Polution.
What do you guys think?</p>
<p>my teacher said that she heard something from collegeboard bout the nitrogen cycle and btw do u think if ii got a 5 on the sparknotes tesst is that a good indicator or is it easier ?? should i be expectin a 4 or 5 ?</p>
<p>My teacher gave us a list of possible topics..I dont remember all of it. She said one of the exam writers is a fungi expert. who knows. :O</p>
<p>Jwalsh1316,
I got a very very very high 5 on sparknotes practice tests (like 95% right), but I got 4's on all the released exams.</p>
<p>and jwalsh1316,
I've heard that rumor, too. I guess it's time to go review the nitrogen cycle.
Here, I have an essay + outline:</p>
<p>Nitrogen Cycle.
Nitrogen enters ecosystems via two natural pathways. The first is atmospheric deposition: NH4+ and NO3-, the two forms available to plants, are added to the soil by being dissolved in the rain or by settling as part of fine dust. The other natural pathway is nitrogen fixation. Only certain prokaryotes can fix nitrogenthat is, convert N2 to minerals that can be used to synthesize nitrogenous organic compounds such as amino acids. Nitrogen is fixed in terrestrial ecosystems by free-living soil bacteria and some symbiotic bacteria (Rhizobium) in the root nodules of legumes. Some cyanobacteria fix nitrogen in aquatic environments. In addition to these natural sources of usable nitrogen, industrial fixation of nitrogen for fertilizer now makes a major contribution to the pool of nitrogenous minerals.
The direct product of nitrogen fixation is ammonia (NH3). However, most soils are at least slightly acidic, and NH3 released into the soil picks up a hydrogen ion to form ammonium, NH4+, which can be used directly by plants. Most of the ammonium in soil is used by certain aerobic bacteria as an energy source; their activity oxidizes ammonium to nitrite NO2- and nitrate NO3-, a process called nitrification. Some bacteria can obtain the oxygen they need for metabolism from nitrate rather than from O2, under anaerobic conditions. As a result of this denitrification, some nitrate is converted back to N2, returning to the atmosphere. The decomposition of organic nitrogen back to ammonium, a process called ammonification, is carried out mainly by bacterial and fungal decomposers. </p>
<p>Outline:
Nitrogen is required to make amino and nucleic acids.
Reservoirs: atmosphere (N2), soil (NH4+ or ammonium, NH3 or ammonia, NO2- or nitrite, NO3- or nitrate)
Assimilation: plants absorb nitrogen as either NO3-/NH4+; animals obtain nitrogen by eating plants, or other animals.
Nitrogen fixation: N2 to NH4+ by prokaryotes. N2 to NO3- by lightning and UV radiation.
Nitrification: NH4+ to NO2- and NO2- to NO3- by various nitrifying bacteria. NH4+ or NO3- to organic compounds by plant metabolism.
Release:
Denitrification: NO3- to N2 by denitrifying bacteria.
Ammonification: Organic compounds to NH4+ by detrivorous bacteria.
Animals excrete NH4+ (or NH3), urea, uric acid</p>
<p>my teacher also said nitrogen cycle/greenhouse effect but he really doesnt know.</p>
<p>Based on what my AP bio teacher has told us, an essay as nitpicky as the nitrogen cycles seems unlikely. I would expect, based on what I've looked at, more an essay on cycles in general than an entire free response on one little cycle.</p>
<p>thats a good outline grayday
thanks</p>
<p>disolved oxygen</p>
<p>AHH i hate this! X_X</p>
<p>I would doubt nitrogen cycle or greenhouse effect; these are topics covered by AP Environmental Science, and I doubt that the CB would want to have redundancy in course coverage like that. </p>
<p>Any lab is fair game to me. Just because it was covered recently doesn't mean it won't come up again, because they are all fundamentally important to biology.</p>
<p>My teacher says she thinks evolution will come up; it hasn't been covered recently, and it is certainly topical.</p>