DP Bio Topic 4-3 Carbon Cycling

1. Topic 4.3 Carbon Cycling
IB Biology
R. Price
v. 1 2015

2. Allott 220

3. #1: Autotrophs convert carbon dioxide into carbohydrates and other
carbon compounds
• Autotrophs absorb carbon
dioxide from the atmosphere
and convert it into
carbohydrates, lipids, & other
carbon compounds
• Reduces the carbon dioxide
concentration in the atmosphere
• Lower carbon dioxide
concentrations above parts of
the earth where photosynthesis
rates are high

4. Allott 221

5. #2: In aquatic habitats, carbon dioxide is present as a dissolved gas and
hydrogen carbonate ions
• Carbon dioxide is soluble in
water
•Can combine with water to form
carbonic acid -> hydrogen &
hydrogen carbonate ions. (can
lower pH of water)
•Dissolved carbon dioxide and
hydrogen carbonate ions are
absorbed by aquatic plants and
other autotrophs

6. #3: Carbon dioxide diffuses from the atmosphere or water into
autotrophs
• Autotrophs use carbon dioxide
during photosynthesis
• Reduces amount of carbon
dioxide inside the cell
• Concentration gradient between
cell and atmosphere/water
• Carbon dioxide diffuses into the
cell
• Stomata / aquatic plant surface

7. #4: Carbon dioxide is produced by respiration and diffuses out of
organisms into water or the atmosphere
• Carbon dioxide is a waste
product of aerobic cell
respiration
• Diffuses out of the cells and into
the atmosphere/water

8. Allott 222

9. #5: Methane is produced from organic matter in anaerobic conditions
by methanogenic archaeans and some diffuses into the atmosphere
• Methanogenic archaeans
produce methane from carbon
dioxide, hydrogen, and acetate.
• Found in anaerobic conditions
such as water logged soil,
swamps, guts of ruminant
animals (cows), human
intestines, and landfills
By ms:User:PM Poon (ms:Imej:Arkea.jpg) CC-BY-SA-3.0 via Wikimedia Commons

10. #6: Methane is oxidized to carbon dioxide and water in the atmosphere
•Methane only lasts about 12
years in the atmosphere
•Oxidized in the stratosphere
•Reacts with monatomic oxygen
(O) & hydroxyl radicals (OH+)
•Oxidized -> carbon dioxide &
water

11. #7: Peat forms when organic matter is not fully decomposed because of
anaerobic conditions in waterlogged soils
• Saprotrophs normally oxygen in
soil air pockets
• Can’t thrive in water logged soils
• Dead organic matter only
partially decomposed
• Acid conditions also develop
• Material compresses to make
peat

12. Allott 224

13. #8: Partially decomposed organic matter from past geological eras was
converted into oil and gas in porous rocks or into coal
•Oil and natural gas formed in the
mud at the bottom of seas & lakes
•Coal formed when peat is buried
under other sediments
•Anaerobic conditions + partially
decomposed organic matter +
heat & pressure = oil, gas, coal

14. #9: Carbon dioxide is produced by the combustion of biomass and
fossilized organic matter
•Organic matter heated to ignition
temperature + oxygen =
combustion
•Periodic grass fires or forest fires
are natural in some ecosystems
•Humans clear rainforest or fields
•Coal, oil, & natural gas are
fossilized organic matter and will
also release carbon dioxide when
burned

15. #10: Animals such as reef-building corals and molluscs have hard parts
that are composed of calcium carbonate and can become fossilized in
limestone
•Mollusc shells and hard corals
contain calcium carbonate
•Deposits of shells and corals form
on the sea bed
•Forms sedimentary rock called
limestone (fossils may be visible)
•Carbon stores locked up in
limestone

16. Allott 226

17. DiagramadaptedfromU.S.DOE,BiologicalandEnvironmentalResearchInformationSystem.[Publicdomain],viaWikimedia
Commons

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22. Sources
Content
Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014
ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.
Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge:
Cambridge UP, 2014. Print.
Images
Unless otherwise noted, images are obtained from Pixabay
(www.pixabay.com) and used under the CC0 Public Domain license.