ICS 1 sem1 block 4 Biogeochemical cycles Packet Standards ES 7 a, b, c, d To be accepted for grading it must be in order and signed Parent/Guardian: Print_________________________________ Sign______________________________________ Date_______ Content Objective Students know the carbon cycle of photosynthesis and respiration and the nitrogen cycle. Students know the global carbon cycle: the different physical and chemical forms of carbon in the atmosphere, oceans, biomass, fossil fuels, and the movement of carbon among these reservoirs. Students know the movement of matter among reservoirs is driven by Earth’s internal and external sources of energy. Students know the relative residence times and flow characteristics of carbon in and out of its different reservoirs. Language Objective Understand the proper use of the words, carbon dioxide, oxygen nitrogen, photosynthesis and respiration. Be able to explain the path of carbon through the world using key concepts such as calcification, bicarbonate’s, greenhouse effect, and fixation. Explain the internal and external heat sources of the Earth which control energy movement, flow properties, and reservoir times. Explain the materials for, the creation process, and the storage of fossil fuels. Fossil fuels are the major source of energy for today, coal, gasoline, natural gas and oil are all fossil fuels. Be able to Describe the path of the carbon among these components and how this influences the environment. Period_______ Name Print__________________________ Sign___________________________ 1. Cover Sheet / Agree-Disagree 2. WCW-warm-up, critical thinking, wrap-up 3. Standard ES 7 a, b, c, d 4. Vocabulary- Biogeochemical Cycles of Earth 5. Carbon Cycle Notes 6. Carbon Cycle Handout 7. Nitrogen cycle Notes 8. Nitrogen cycle Handout 9. Global Carbon Cycle Notes 10. Global Carbon Cycle Handout 11. Matter-Energy Notes 12. Matter-Energy Handout 13. Study-guides 14. CST-Practice-Questions
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Biogeochemical cycles Packet Period Standards ES 7 a, b, c, d€¦ · atmosphere, and within and among organisms as part of biogeochemical cycles. As a basis for understanding this
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ICS 1 sem1 block 4
Biogeochemical cycles Packet
Standards ES 7 a, b, c, d
To be accepted for grading it must be in order and signed
More than any other element, carbon is associated with our changing
climate.
Where does carbon reside?
What trends in atmospheric CO2 have been observed?
What regulates the flow of carbon between its various reservoirs?
Is it possible that feedback mechanisms regulate the amount of
atmospheric CO2?
How is carbon cycled at a global scale? • Cell Respiration: – An animal produces carbon dioxide and consumes oxygen in its metabolism of food.
Glucose is a typical food and a metabolic reaction can be represented by:
– C6H12O6 + 6O2 6 CO2 + 6 H2O
• Photosynthesis: – A plant and green bacteria, on the other hand, produces oxygen and consumes carbon
dioxide. – Energy in the form of electromagnetic radiation (or photons) is supplied so that the low-
energy-content carbon dioxide can be converted to high-energy-content glucose. – An overall reaction for the complicated multi-step photosynthesis reaction can be
represented by:
– 6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O
Item # 10 Global Carbon Cycle
1. If 100 kg of carbon dioxide is photosynthesized, does this contribute to the amount of free oxygen (O or O2)
in the atmosphere or deduct from it? How much oxygen is produced or destroyed? How much carbon is
produced or destroyed?
Photosynthesis generates free oxygen. The atomic weight of CO2 is 44 with 12 AMU from Carbon and 32 AMU
from Oxygen. If 100 kg of CO2 is photosynthesized, 72.7 kg of free oxygen (2 atoms for every one molecule of
CO2) is produced and 27.3 kg of Carbon (in the form of carbohydrates) is produced. (The carbohydrates would
weight 68.25 kg.)
The reaction for photosynthesis is:
CO2 + H2O + hv --> CH2O + O2
2. During the early evolution of the earth, what was an important source of free oxygen? Did it eventually help
sustain a new processes of oxygen production? What was that new process?
Free oxygen may have been created by photodissociation of water vapor in the early Earth. This created free
oxygen and eventually ozone which enabled plantlife and photosynthesis to exist on land. It is probably that
photosynthesis already existed in the oceans before the ozone layer.
3. If under global warming, the amount of photosynthesis decreases (due to reduced extent of boreal forests)
from 200 Gt-O/yr to 100 Gt-O/yr, how long will the oxygen in the atmosphere last?
In steady state, photosynthesis and respiration are in balance. If photosynthesis were to decrease by 50%, this
represents a net sink of 100 Gt-O/yr. Given that the reservoir is 1.1x106 Gt. Oxygen would last 1.1x106/100
years or about 10,000 years.
4. Identify at least one rapid process not mentioned in class that may constrain the amount of atmospheric
oxygen between certain minimum and maximum bounds.
Fire may help constrain the levels of atmospheric oxygen. If oxygen levels become too high, fires will burn
stronger and longer thus depleting atmospheric O2. If oxygen levels decrease, fewer fires will occur and they
will not burn as strongly. It is believed that this has helped constrain levels of oxygen in recent millenia to
between roughly 10% and 30%.
5. Why is the amount of "free" oxygen in the atmosphere related to the amount of carbon in the atmosphere? If
one increases the amount of carbon in the atmosphere does this increase or decrease the amount of "free"
oxygen?
Carbon in the atmosphere is precominantly found in CO2. If carbon reacts (to form sediments for example) this
releases free oxygen in the atmosphere. If carbon reacts to re-enter the atmosphere (through respiration for
example) this removes oxygen from the atmosphere. If one were to increase the amount of carbon in the
atmosphere, this would decrease the amount of free oxygen.
1. Estimate the time scale for emptying the sedimentary reservoir by geologic processes given that volcanic
outgassing amounts to about 0.05 Gt C/yr and the reservoir is contains roughly 60 million Gt-C.
Volcanic outgassing is a process that depletes sedimentary carbon and would deplete a reservoir of 60 million
Gt in about 1.2 billion years.
2. If the oceans were to stop absorbing carbon (due to saturation for example), what percentage increase in
atmospheric carbon (per year) would initially occur?
The oceans absorb about 50 GtC per year. If this were to stop, the atmosphere would gain 50 GtC per year
which is about 6.7% of the 750 GtC held by the atmosphere. If you tried to use the numbers from Table 10.10 it
would be incorrect because that Table shows the net imbalance between dissolution and evaporation of carbon,
not the net dissolution.
3. What carbon compounds are produced by photosynthesis and exploited by living beings for energy? What
reactants are required to generate these compounds?
Carbohydrates (C-H2O) and oxygen are produced by photosynthesis from the reactants of CO2, H2O and light.
4. If the deep ocean circulation were to accelerate and thus increase the existing exchange of carbon with
surface oceans, what impact might this have on the surface ocean and, eventually, the atmosphere?
In the net, the exchange of carbon between the deep ocean and the surface ocean contributes bicarbonate ions
to the surface ocean. If upwelling were to increase the surface ocean would have more bicarbonate ion and
would eventually saturate, reducting the amount of CO2 that would disolve in the upper ocean and atmospheric
carbon levels would eventually increase.
5. Propose an investigation aimed at reducing the amount of carbon dioxide in the atmosphere based on what
you know about the long-term or short-term carbon cycles. To do so, simply state a process relevant to
atmospheric CO2 levels and suggest an hypothesis you'd like to investigate for modulating its rate.
There are many possible answers to this. For example, one might attempt to modulate the rate of carbon uptake
by the surface oceans by enhancing photosynthesis in the surface oceans. Currently, experiments that contribute
iron to the upper ocean are exploring this possibility. Many other experiements can be envisioned.
Notes matter energy item#11
The movement of matter among reservoirs is driven by Earth’s internal and external sources of energy
The
relative
residence
times and
flow
characteri
stics of
carbon in
and out of
its
different
reservoirs
Carbon
moves at
different
rates from
one
reservoir
to another,
measured
by its residence time in any particular reservoir.
Example
Carbon may move quickly from the biomass to the atmosphere and back because its residence time in
organisms is relatively short and the processes of photosynthesis and respiration are relatively fast.
Carbon may move very slowly from a coal deposit or a fossil fuel to the atmosphere because its residence time
in the coal bed is long and oxidation of coal by weathering processes is relatively slow.
The energy to move carbon from one reservoir to another originates either from
Internal sources of energy External sources of energy