1. Mr. Blacher's 7th Grade Biology
CYCLES
The LAW OF CONSERVATION OF MATTER…datz what itz all about YO!
Matter isn’t created…it ain’t destroyed neither.
Hmmmm…whatchoo gonna do with all that matter?
Ooooh I know! Cycle it between the biotic (living) world and the abiotic (non-living) world.
Simple right?
Mr. Blacher's 7th Grade Biology

2. CYCLES
There are some major cycles that are important for biologists to understand.
WATER CYCLE: a continuous process wherein water moves from the Earth’s surface to the atmosphere and back.
There are four basic part to this cycle.

3. 1. WATER CYCLE

4. 1. WATER CYCLE
EVAPORATION: LIQUID water absorbs energy (heats up) and turns into a GAS (Surface to atmos.).
CONDENSATION: Water vapor (GAS) in the atmosphere looses energy (cools) and turns into a liquid (clouds).
PRECIPITATION: occurs when droplets of water that are formed during condensation get bigger and fall back to Earth.
Transpiration: water is absorbed by plants and subsequently released back into the atmosphere through their leaves.

5. 2. CARBON (CO2) CYCLE

6. 2. CARBON (CO2) CYCLE Photosynthesis (in the chloroplasts):
PHOTOSYNTHESIS & CELLULAR RESPIRATION
Producers take in carbon from CO2 and produce oxygen, while consumers take in the oxygen and give off CO2.
Photosynthesis (in the chloroplasts):
6CO2 + 6H2O O2 + C6H12O6
Cellular Respiration (in the mitochondria):
6O2 + C6H12O6 6CO2 + 6H2O + ATP (Energy)
Sunlight

7. The Essence! Carbon is cycled (converted) from Inorganic Carbon is to Organic Carbon…and the other way around.
Photosynthesis: Plants make FOOD from ENERGY Cellular Respiration: Organisms make ENERGY from FOOD.

8. The NITROGEN CYCLE

9. The NITROGEN CYCLE
Nitrogen is another important element for living things.
Most organisms cannot get it directly from the atmosphere.
Nitrogen by itself in the atmosphere is called FREE nitrogen. Nitrogen that is attached to other elements is called FIXED nitrogen…that’s the kind we need.

10. Organisms require nitrogen-compounds, (proteins and nucleic acids).
Air is about 78% nitrogen gas (N2). That’s where most of the nitrogen hangs out.
Most organisms can’t use atmospheric (free) nitrogen as is. They need it changed into nitrogen compounds.
Plants need their nitrogen "fixed", which means as part of compounds such as:
ammonia and ammonium (NH3 & NH4+)
urea (NH2)2CO
nitrate ions (NO3−) and nitrate ions (NO2-)

11. NITROGEN FIXATION
This is the process that changes free nitrogen into the usable fixed kind.
Bacteria in the soil, plant root nodules, and in water change the nitrogen into compounds called nitrites /NO2- (nitrosomonas) and then to nitrates /NO3-(nitrobacter).
These can be used by the plants to make proteins and other needed compounds.
Animals eat the plants…other animals eat those animals, and the nitrogen gets used by them too.
Lightning and industrial processes also fix free nitrogen.

12. When an organism dies, the nitrogen compounds return to the ecosystem and are reused.
Eventually they are broken down completely (denitrification) and return to the atmosphere…and the cycle begins again…that’s why its called a cycle!

13. Here’s the Upshot…in 4 Steps
Free N2-in the air…can’t use it
Nitrogen Fixation-Bacteria in soil, water, and plants chemically change N2 into usable Nitrogen compounds.
Decay-stuff dies and decomposes
Denitrification-other bacteria turn the N back into N2 aka Free Nitrogen.
That’s it!

14. FYI…if you’re gonna take biology in college…
There are four sub-processes involved in the Nitrogen Cycle. You don’t have to know this now, but…someday…
Nitrogen Fixation: breaks N2 apart so it can form compounds.
Decay: waste from life processes (ammonification).
Nitrification: bacteria converting ammonia to nitrites and then to nitrates (which what plants can assimilate).
Denitrification: bacteria converting nitrates to nitrogen gas again.

15. 4. The Phosphorus Cycle

16. 4. The Phosphorus Cycle
Phosphorus is a super-important element that is a key part of ATP, DNA molecules (more on DNA later…a lot more!), bone, shells…n’ other stuff too. Ya know how NITROGEN is from the atmosphere? Of course you do…we just talked about it. Well…Phosphorous (most of it) is in the Earth’s soil and rocks in compounds called phosphates (PO43-).

17. Most Phosphorus is stored in the crust as the mineral Apatite aka…Calcium Phosphate aka Ca5(PO4)3
The extrusive igneous rock…granite, is where you can find apatite, but it is also found in metamorphic and sedimentary rocks too.
  Some Phosphorus is dissolved in fresh and ocean water, or is stored in soil or in organic matter.
Plants can take phosphates from the soil sorta like they do with NITROGEN. No special bacteria for this one.

18. Too much phosphate (or nitrogen) ain’t a good thing and can lead to problems such as lake eutrophication (nutrient buildup) leading to algal and bacterial blooms. These guys use up the oxygen and BLAMMO!…dead fish everywhere! NOT COOL