BIOGEOCHEMICAL CYCLES http://youtu.be/2D7hZpIYlCA
The first 5 min review the hydrologic cycle and the second 5 min is new about carbon cycle
Biogeochemical cycles are processes in which elements, compounds and other forms of matter are
___________from one organism to another and from one part of the biosphere to another.
As matter moves through these cycles, it is transformed, which means that it is never created or
destroyed, just changed. Remember the Law of Conservation of Matter. So, materials in the
ecosystem are constantly reused. We will look at the carbon cycle, nitrogen cycle, and phosphorus
cycle. We have already discussed the water cycle in detail.
THE CARBON CYCLE
As you know, carbon is an essential component of proteins, f_____, c______________ and nucleic
acids. The carbon cycle is the process where carbon is cycled between the atmosphere, land, water,
and organisms. In the carbon cycle, __________ ___________ is continuously exchanged between
the atmosphere, oceans, and living organisms through chemical and physical processes.
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Plants ______ ___ CO2 during photosynthesis and use it to build carbohydrates. These
nutrients then pass through food webs to consumers.
Many animals combine carbon with calcium and oxygen as they build their skeletons.
Organisms release carbon in the form of CO2 gas by ______________ __________________.
When organisms die, ______________________ break down the bodies
__________________carbon to the environment.
Geologic forces turn accumulated carbon into carbon-containing rocks or f______
f_________.
CO2 is released into the atmosphere by v___________ activity and by human activities such as
_____________ fossil fuels, as well as clearing and burning forests.
Carbon cycle questions: http://youtu.be/dDBU0lg-HYE
1. Describe the 2 main processes of the carbon cycle (photosynthesis and cellular respiration).
2. How does burning fossil fuels affect the carbon cycle?
Match the term associated with the carbon cycle with the best description:
a. photosynthesis
b. cellular respiration
c. fossil fuels
1. ____________ Carbon-containing compounds that were once part of ancient forests,
marine organisms or other animals that have been buried and transformed into energy–rich
fuels.
2. ____________ Plants use CO2 during this process and release O2 into the atmosphere.
They also produce glucose during this process.
3. ____________ Organisms use glucose and oxygen and release CO2 during this process.
4. What are 3 types of fossil fuels http://youtu.be/cJ-J91SwP8w
5. What is a problem associated with humans burning too many fossil fuels? What gas does this
release into the atmosphere in great quantities? What problem has this led to?
http://youtu.be/jakJ-Tf79ac
THE NITROGEN CYCLE – http://youtu.be/372K0jyO0hQ
All organisms need nitrogen to build p____________ and n____________ ________. Nitrogen
makes up ____% of the gases in the atmosphere, but most organisms cannot use atmospheric
nitrogen because they cannot break the triple bond between the nitrogen atoms. It must be altered
or fixed before organisms can use it. The only organisms that can fix atmospheric nitrogen into
chemical compounds are a few species of bacteria known as nitrogen-fixing bacteria. All other
organisms depend upon these________________ to supply nitrogen.
Important steps in the Nitrogen cycle:
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Nitrogen fixation – nitrogen fixing bacteria convert nitrogen gas into ________________.
Some of these bacteria live in the soil, while others live on the roots of certain plants called
l__________________ (peanuts, peas, soybeans)
Plants that do not have nitrogen fixing bacteria get their nitrogen from the s_____.
Other bacteria in the soil convert the ammonia into n__________ and n________. These are
called n_______________ bacteria. Plants are able to take up nitrates and nitrites.
Consumers eat these p____________ to obtain their nitrogen.
Decomposers release nitrogen from waste and dead organisms as ammonia, nitrates and
nitrites, that producers may take up again!
Denitrification – In this process, other bacteria convert nitrates back into _____________ ___,
which is then released back into the atmosphere.
Atmospheric nitrogen fixation – A relatively small amount of nitrogen gas is converted into
usable forms by l__________________ (not thunder but ……...)
Humans add extra nitrogen to the biosphere through the manufacture and use of fertilizers. Excess
fertilizer is often carried into surface water or ground water by precipitation.
Nitrogen cycle questions:
1. All organisms require nitrogen to build _____________ and ________________ (which 2
groups of organic compounds – choose carbohydrates, lipids, proteins, nucleic acids)
Match the term with the best description involving the nitrogen cycle:
a. decomposers
b. nitrogen fixation
c. denitrification
2. ____________ The process in which certain types of bacteria convert nitrogen gas into
ammonia.
3. ____________ These organisms release nitrogen from waste and dead organisms.
4. ____________ The process by which some bacteria convert nitrates into nitrogen gas which is
released back into the atmosphere.
5. Bacteria responsible for nitrogen-fixation are found in the roots of
a. All plants
b. certain plants such as legumes
c. evergreen trees
6. Which statement about the nitrogen cycle is true?
a. All nitrogen obtained by animals can be traced back to the eating of plants
b. Plants fix nitrates into atmospheric gas
c. Nitrogen atoms are continually created and destroyed
7. Which statement about this cycle is false?
a. Plants but not animals are part of the nitrogen cycle
b. The nitrogen cycle requires nitrogen-fixing bacteria
c. Bacteria convert nitrogen gas into a form in which it can be used as a pant nutrient
d. Bacteria and fungi break down dead plant and animal tissues into nitrates that plants can
use.
8. Organic compounds in dead organic matter and wastes are converted into ammonia as a
result of________________
a.
nitrogen fixation
b. denitrification
c. decomposition
9. Animals get their organic nitrogen compounds by______________
a. feeding
b. breathing
c. performing photosynthesis
10. Why is it so difficult for most organisms to use nitrogen gas from the atmosphere?
a. Nitrogen is a non-reactive atom
b. A strong triple covalent bond holds the molecule together.
c. Oceans quickly absorb nitrogen gas, so not much is available in the air.
11. _____ are the primary organisms which drive the nitrogen cycle.
a. Bacteria
b. animals
c. plants
Go to the following website, and watch the animation about the nitrogen cycle. After you have
watched it, write a brief description of the nitrogen cycle. In other words, summarize the nitrogen
cycle in your own words. Try to include the main processes (nitrogen fixation, denitrification,
decomposition)
http://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitrogen/em05_pg20_nitrogen.swf
The Phosphorous Cycle - http://youtu.be/_IBx0zpNoEM
The phosphorus cycle is the movement of phosphorus from the environment to organisms and then
back to the environment.
Phosphorus is part of many molecules that make up cells of living things. Phosphorus is needed to
form b______ and t_________ in animals. Plants get the phosphorus they need from s_____ and
water, while animals get it by eating p__________ or other animals that have eaten plants. This cycle
is slow and does not normally include the atmosphere because phosphorus rarely occurs as a gas.
Phosphorus enters soil and water in a few ways. When rocks e___________, a little P dissolves as
p________________ in soil and water. Plants a__________ phosphates in the soil through their
roots. P is added to soil and water when excess P is excreted in w__________ from organisms and
when organisms die and d________________. Some P washes off land and eventually ends up in
o___________. Many phosphate salts are not soluble in water, so they sink to bottom of ocean and
accumulate as sediment.
How do humans affect phosphorus cycle?
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Fertilizer use! Fertilizers contain both N and P. If excessive amounts of fertilizer are used, the
fertilizer can enter both terrestrial and aquatic ecosystems through r__________. Excess N
and P in aquatic ecosystems can cause rapid and overabundant growth of algae, which results
in an a______ b________. This is a dense, visible patch of algae that occurs near the surface
of water. This can deplete the ecosystem of oxygen and other important nutrients.
Acid Precipitation – when we burn fuel, nitric oxide is r______________ into the atmosphere.
Nitric oxide can combine with oxygen and water vapor in the atmosphere to form n_____ acid.
This dissolves in rain and snow and contributes to acid rain.
Questions:
1. Explain how the excessive use of fertilizer affects the nitrogen cycle and the phosphorus cycle.
http://youtu.be/IndPs2XobLs
http://www.answers.com/Q/How_does_the_use_of_fertilizer_affect_the_nitrogen_cycle_and
_phosphorus_cycle
2. What is one way that a person can help to reduce the level of carbon dioxide in the
atmosphere? (hint: do you drive a car?)
3. Which organic macromolecules contain phosphorus?
http://umm.edu/health/medical/altmed/supplement/phosphorus