Biogeochemical Cycles Flashcards
What six elements do organisms need in high quantitites?
Organisms require six elements in high quantities:
- Hydrogen
- Carbon
- Nitrogen
- Phosphorous
- Sulfur
- Oxygen
Other elements are in smaller amounts and include:
- Fe, Co, I, Na, K, Br, B
What forms of Nitrogen do plants use?
Plants use NH4+ and NO3-
What is atmospheric fixation?
Atmospheric fixation is when lightning splits N2 into N atoms that combine with O2 to form NO3- that dissolves into the atmospheric water and descends to the ground via rain into the soil
- This accounts for about 5-10% of the Nitrogen required by plants
What is nitrogen fixation?
Nitrogen fixation is when bacteria and archae take atmospheric N2 and create NH3.
- This requires ATP
- NH3 becomes NH4+ and is used by the plant
- NH4+ is also used by aerobic bacteria that convert it into NO2- and NO3-.
- Plants love NO3- and will use it to form amino acids and proteins
What is denitrification?
Denitrification:
- Some NO3- is converted back to N2 by denitrifying bacteria.
- These denitrifying bacteria live in the anaerobic mud of lakes, bogs, estuaries, and on the sea floor
- denitrification lowers soil fertility and decreases agricultural productivity
- denitrification bacterial species include psuedomonas and bacillus
- This is always done under anaerobic conditions
Why is denitrification important?
Denitrification is important because without it, our supply of N2 would accumulate in the oceans and life would end.
What is ammonification?
Ammonification is when decomposers like bacteria and fungi decompose dead organic materials and release excess nitrogen as NH3 or NH4+.
- Other bacteria can then take the ammonia and convert it to NO3- for plants or denitrification
What is the nitrogen cycle?
The nitrogen cycle is the cycle of bringing N2 from the atmosphere into the soil for plants to use and then releasing it back into the atmosphere
- Atmosphere fixation brings NO3- directly into the soil
- Nitrogen fixation converts N2 into NH3 via ATP which then converts to NH4+. This can be used by the plant or by other bacteria
- Bacteria eat NH4+ and convert it to NO3- that can be used by the plant or bacteria
- The plant dies and is decomposed by bacteria into NH3
- The NH3 can be used by the plant or bacteria again to be converted to NO3- for the plants to use again
- Anywhere along this cycle, NO3- can be used by anaerobic pseudomonas and anaerobic bacillus to form N2 gas, through denitrification. This releases N2 back into the atmosphere for the cycle to repeat itself again.
- While fertilizers can play a role in this cycle, it’s pretty negligible compared to the bacterial actions
What is the Carbon Cycle?
The Carbon cycle involves CO2 balance
- CO2 comes from cellular respiration, fossil fuel burning, volcanic eruptions, and bacterial decomposers
- Photosynthesis uses this CO2 and makes O2.
- CO2 for photosynthesis comes from two reservoirs
- Atmosphere
- Ocean: The ocean contains 3/4 of the worlds carbon, mostly in the form of HCO3- and CO3(2-) and a small amount in dead organic material and phytoplankton
Where is C incorporated in the ocean?
Carbon is incorporated into the following in the ocean:
- Mostly in the form of HC03- and CO3(2-)
- A small percentage of it is in phytoplankton
- A small percentage of it is in dead organic material. Carbon can be incorporated into the shells of organisms. When they die, their shells sink to the bottom of the ocean and become buried in sediments
What is the phosphorous cycle?
The phosphorous cycle is as follows:
- Phosphorous is not a gas, but rather a solid. Thus this is a sedimentary cycle
- Sedimentary rocks of marine origin are weathered releasing phosphorous in the form of PO4- into the water and soil
- Plants take up some soil PO4- which are then eaten and taken up by animals
- Within the soil bacteria contribute PO4- to plants in a very minor way.
- When plants and animals die, their phosphorous is returned to the soil for the next organism
How do humans disrupt the phosphorous cycle?
Humans disrupt the phosphorous cycle in the following ways:
- Deforestation: nutrients stored in rocks and plants are destroyed
- Over-fertilization: Plants can’t take up all the phosphorous given to them, so its washed into rivers and streams, causing eutrophication of bacteria and algae. The exponential growth of these uses up all the O2 and aquatic life perishes.
What is eutrophication?
Eutrophication occurs when fertilizer runoff enters waterways and causes a proliferation of plants, bacteria, or algae.
- This often results in a loss of O2 to the water killing many aquatic organisms
- Many algae blooms are also toxic, causing further death and destruction
What physical properties does hydrogen bonding give water?
Water’s unique physical properties include:
- Abnormally high boiling point
- Low vapor pressure
- High surface tension
- Solid phase less dense than liquid phase
What is the water cycle?
The water cycle involves the following:
- Water evaporates or is transpired from plants into the atmosphere
- atmospheric water travels around in the atmosphere around the world until it is ready to be released via precipitation.
- Most evaporation occurs over oceans. A lot of the water that falls via precipitation makes its way back into the ocean
- metabolic processes due create water, but its at a negligible level to be included in this cycle
