1. CYCLES
There are some major cycles that are important for biologists to understand.
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. 1. WATER CYCLE
Mr. Blacher's 7th Grade Biology

3. 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.
Percolation: water filtering through the soil, sand, rock into the groundwater supply.
Iffin’ yer interested…check these out too: Interception, infiltration, runoff, and storage.
Mr. Blacher's 7th Grade Biology

4. 2. CARBON (CO2) CYCLE
Mr. Blacher's 7th Grade Biology

5. 2. CARBON (CO2) CYCLE PHOTOSYNTHESIS & CELLULAR RESPIRATION
Producers take in carbon as CO2 and produce oxygen, while consumers take in the oxygen and give off CO2. Nice
Photosynthesis (mostly in the chloroplasts of plants):
6CO2 + 6H2O O2 + C6H12O6
This is making FOOD (Sugar/Carbohydrates) from ENERGY (sunlight)
Cellular Respiration (mostly in the mitochondria of ALL organisms):
6O2 + C6H12O CO2 + 6H2O + ATP (Energy)
This is making ENGERGY (ATP) from FOOD (sugar…the oxidation of glucose)
Sunlight
Mr. Blacher's 7th Grade Biology

6. The Essence! Carbon is cycled (converted) from Inorganic Carbon into Organic Carbon…and the other way around.
Now…don’t get mad at me, but…CO2…it’s inorganic even though it has carbon. Sorry…it wasn’t my idea! Technically organic compounds have to have carbon bonded to hydrogen (hydrocarbon).
Mr. Blacher's 7th Grade Biology

7. Photosynthesis: The Big Take Away Here? Cellular Respiration:
Plants make FOOD from ENERGY
Cellular Respiration:
Organisms make ENERGY from FOOD.
Mr. Blacher's 7th Grade Biology

8. HUMAN IMPACT: Carbon Cycle
 For 800 years before the Industrial Revolution the global CO2 levels were fairly consistent.
Over the past 200 years there has been measureable change in levels.
Human activity is largely responsible for this.
Burning of fossil fuels and deforestation are the primary causal factors.
Consequence: increase in CO2 levels result in higher global temperature. The rate is prohibitive to the dispersal of plants and animals to regions in which they can survive. Polar summer ice is jeopardy, and sea level rise is imminent as well.
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9. The NITROGEN CYCLE
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10. The NITROGEN CYCLE
Nitrogen is another important element for living things. It is needed to synthesize amino acids, proteins, and nucleic acids (DNA/RNA).
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.
Mr. Blacher's 7th Grade Biology

11. Organisms require nitrogen-compounds, (a. a
Organisms require nitrogen-compounds, (a.a.’s, 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 (NH3)
Ammonium (NH4+)
urea (NH2)2CO
Nitrite (NO2-)
nitrate ions (NO3−)
Mr. Blacher's 7th Grade Biology

12. 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.
Mr. Blacher's 7th Grade Biology

13. 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!
Mr. Blacher's 7th Grade Biology

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.
Nitrification: bacteria converting ammonia to nitrites and then to nitrates (which what plants can assimilate).
Decay: waste from life processes (ammonification).
Denitrification: bacteria converting nitrates to nitrogen gas again.
Mr. Blacher's 7th Grade Biology

15. 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!
Mr. Blacher's 7th Grade Biology

16. Human Impact: Nitrogen Cycle
Burning of fossil fuels and use of nitrogen-based fertilizers alter the amount of bio-available nitrogen (this is HUGE limiting factor for ecosystems).
Fresh water aquatic ecosystems: nitrogen is a major limiting factor for plant growth. Increased plant populations mean more dead plants eventually. These decompose which depletes O2 levels. This leads to the death of other organisms. The sciency word for all of this…EUTROPHICATION
Terrestrial ecosystems: Extra nitrogen can lead to nutrient imbalance in trees, changes in forest health, and declines in biodiversity.
Since more nitrogen is available, carbon storage is affected. There’s more than just the nitrogen cycle getting jacked up.
With factory farming, fertilizers are spread to increase crop yield, but the unused nitrogen (nitrate mostly), can leach out of the soil into the streams and rivers. This stuff ends up in our drinking water
Marine Ecosystems…too much nitrogen = depleted O2 and toxic dinoflagellate blooms (RED TIDE).
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17. 4. The Phosphorus Cycle
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18. 4. The Phosphorus Cycle
Phosphorus is a super-important element that is a key part of ATP, nucleic acid molecules (more on DNA & RNA later…a lot more!), the phospholipid membranes in cells, 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-).
Mr. Blacher's 7th Grade Biology

19. Most Phosphorus is stored in the crust as the mineral Apatite aka…Calcium Phosphate aka Ca5(PO4)3
The intrusive 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.
Mr. Blacher's 7th Grade Biology

20. Human Impact: Phosphorus Cycle
Well…here we are again with out fertilizers…and to get them…we mine! Runoff from mining and from fertilizer use leads to buildup of phosphorus.
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
Mr. Blacher's 7th Grade Biology