IB Biology 2015 Curriculum Ecology 4.3

1. 4.3 Carbon cycling
• Essential idea: Continued availability of carbon in
ecosystems depends on carbon cycling.

2. Understandings
Statement Guidance
4.3 U.1 Autotrophs convert carbon dioxide into carbohydrates and other carbon
compounds.
4.3 U.2 In aquatic ecosystems carbon is present as dissolved carbon dioxide and
hydrogen carbonate ions.
4.3 U.3 Carbon dioxide diffuses from the atmosphere or water into autotrophs.
4.3 U.4 Carbon dioxide is produced by respiration and diffuses out of organisms
into water or the atmosphere.
4.3 U.5 Methane is produced from organic matter in anaerobic conditions by
methanogenic archaeans and some diffuses into the atmosphere or
accumulates in the ground.
4.3 U.6 Methane is oxidized to carbon dioxide and water in the atmosphere.
4.3 U.7 Peat forms when organic matter is not fully decomposed because of
acidic and/or anaerobic conditions in waterlogged soils.
4.3 U.8 Partially decomposed organic matter from past geological eras was
converted either into coal or into oil and gas that accumulate in porous
rocks.
4.3 U.9 Carbon dioxide is produced by the combustion of biomass and fossilized
organic matter.
4.3 U.10 Animals such as reef-building corals and mollusca have hard parts that are
composed of calcium carbonate and can become fossilized in limestone.

3. Applications and Skills
Statement Guidance
4.3 A.1 Estimation of carbon fluxes due to processes
in the carbon cycle.
Carbon fluxes should be measured
in gigatonnes.
4.3 A.2 Analysis of data from air monitoring stations
to explain annual fluctuations.
4.3 S.1 Construct a diagram of the carbon cycle.

4. What are the factors that effect an ecosystem like
the coral reef below?
• Abiotic (nutrients and energy)
• Biotic individual organisms that live in that
ecosystem

5. Factors controlling and ecosystem:
I. Nutrients (Closed System)
II. Energy (Open System)
III. Interactions between species
* In this section we will focus on nutrients

6. Remember what plants
need…
4.3 U.1 Autotrophs convert carbon dioxide into carbohydrates and other
carbon compounds.
To make carbohydrates

7. Nutrient Cycles Are Closed Systems in an Ecosystems
• Biogeochemical cycles are cycles of matter between the abiotic
and the biotic components of the environment
– The carbon, nitrogen, and phosphorus cycles are central to life on
Earth
– Carbon and nitrogen cycles have atmospheric components, and
cycle on a global scale
– Phosphorus has no atmospheric component, and cycles on a local
scale

8. 4.3 U.2 In aquatic ecosystems carbon is present as dissolved carbon
dioxide and hydrogen carbonate ions.
CO2 + H2O → H2CO3 → H+ + HCO3
–
CO2 + H2O → H2CO3 → H+ + HCO3
–
• Carbon dioxide dissolves in water and some of it will remain as a dissolved gas
• Some of the carbon dioxide will combine with water to form carbonic acid
CO2 + H2O <--> H2CO3.
• Carbonic acid can then disassociate to form H+ and HCO3
-
(H2CO3 <-->HCO3
− + H+)
• This is why the pH decreases
• Autotrophs in water absorb both CO2 and hydrogen carbonate ions, and use them
to produce organic compounds

10. 4.3 U.3 Carbon dioxide diffuses from the atmosphere or water into autotrophs
• Autotrophs use carbon dioxide for
photosynthesis, as the CO2 is
depleted by the autotroph, the
concentration of CO2 in the
surrounding atmosphere or water
is greater than inside the
autotroph; therefore a
concentration gradient is created
• Carbon dioxide diffuses into the
autotroph, following the
concentration gradient created
• In aquatic organisms carbon
dioxide can diffuse directly into
the autotroph as all parts of the
plant are usually permeable to CO2
• For land plants, carbon dioxide
diffuses through stomata
(openings on the bottom of the
leaf)

11. 4.3 U.4 Carbon dioxide is produced by respiration and diffuses out of
organisms into water or the atmosphere.
• All organisms carry out cellular respiration and produce carbon dioxide as a waste
product
• The carbon dioxide will be released by these organisms into the atmosphere or
water. Examples
• saprotrophs and decomposers, e.g. fungi and bacteria
• autotrophs, e.g. plants
• heterotrophs, e.g. animals
https://s-media-cache-
ak0.pinimg.com/736x/3a/7e/5b/3a7e5b
b986dc898403935fcea4aae574.jpg

12. 4.3 U.5 Methane is produced from organic matter in anaerobic
conditions by methanogenic archaeans and some diffuses into the
atmosphere or accumulates in the ground.
• Methane is produced in anaerobic
conditions as a waste product by
bacteria (methanogenic archaeans)
who use organic acids and alcohol to
produce acetate, carbon
dioxide and hydrogen, which is in turn
used to produce methane as a waste
product. These reactions occur
without oxygen in swamps, wetlands
and mangroves, in mud along the
banks of rivers and lakes, and in the
digestive tracts of mammals and
termites.
• In addition, large herds of domestic
cattle and sheep being raised
worldwide produce methane, which is
contributing to the greenhouse effect http://pre13.deviantart.net/d828/th/pre/i/2012/156/0/e/herd_of_c
ows_by_yuveza-d52e16l.jpg

13. 4.3 U.6 Methane is oxidized to carbon dioxide and water in the
atmosphere.
• Methane is the main ingredient in natural gas. When you burn
methane the reaction involves oxygen gas from the atmosphere
to produce carbon dioxide and water
• When methane is actually released into the atmosphere through the
anaerobic reactions, it can persist in the atmosphere for about 12
years, as it is naturally oxidized by monatomic oxygen (O) and
hydroxyl radicals (OH-)
• This is why methane concentrations are not very great in the
atmosphere, even though large amounts are produced

14. 4.3 U.7 Peat forms when organic matter is not fully decomposed
because of acidic and/or anaerobic conditions in waterlogged soils.
• In soils organic matter, e.g.
dead leaves, are digested
by saprotrophic bacteria and
fungi.
• Saprotrophs assimilate
some carbon for growth and
release as carbon dioxide
during aerobic respiration
(requiring O2).
• Waterlogged soils are an
anaerobic environment
leaving these organisms
unable to complete the
process.
• Large quantities of (partially
decomposed) organic
matter build up. The organic
matter is compressed to
form peat Youtube video

15. • In soils organic matter, e.g.
dead leaves, are digested by
saprotrophic bacteria and
fungi.
• Saprotrophs assimilate some
carbon for growth and release
as carbon dioxide during
aerobic respiration (requiring
O2).
• Waterlogged soils are an
anaerobic environment leaving
these organisms unable to
complete the process.
• Large quantities of (partially
decomposed) organic matter
build up. The organic matter is
compressed to form peat

17. 4.3 U.7 Peat forms when organic matter is not fully decomposed
because of acidic and/or anaerobic conditions in waterlogged soils.
Saprotrophs assimilate some carbon for
growth and release as carbon dioxide during
aerobic respiration.
Aerobic respiration
requires oxygen
Waterlogged soils are an
anaerobic environment
Partial
decomposition
causes acidic
conditions
saprotrophs and
methanogens [4.3.U5] are
inhibited
Organic matter is only
partially decomposed
Large quantities of
(partially decomposed)
organic matter build up.
The organic matter is
compressed to form peat
http://commons.wikimedia.org/wiki/File:Peat-bog-Ireland.jpg
Organic matter

18. http://commons.wikimedia.org/wiki/File:Coal_lump.jpg
The peat is compressed and heated over millions years eventually
becoming coal.
4.3 U.8 Partially decomposed organic matter from past geological eras
was converted either into coal or into oil and gas that accumulate in
porous rocks.

19. Very few types of organism play a role in
the cycling of nutrients
Saprotrophic Bacteria
cycle Nitrogen
Fungi Cycle Carbon

20. Carboniferous
• Extended from 359 million years ago, to the about 299.
• A time of glaciation, low sea level and mountain building. With many
beds of coal were laid down all over the world during this period.
4.3 U.8 Partially decomposed organic matter from past geological eras
was converted either into coal or into oil and gas that accumulate in
porous rocks.

21. Carboniferous period
• The world’s large coal deposits
occurred during this time
period
Two factors
1. The appearance of bark-
bearing trees (containing bark
fiber lignin).
2. Lower sea levels
• Development of extensive
lowland swamps and forests.
• Large quantities of wood were
buried during this period.
• Animals and decomposing
bacteria had not yet evolved
that could effectively digest the
new lignin.
4.3 U.8 Partially decomposed organic matter from past geological eras
was converted either into coal or into oil and gas that accumulate in
porous rocks.

22. Basidiomycetes (fungi)
• Appear 290 million years ago. They can degrade it Lignin. The
substance is insoluble, to heterogeneous because of specific
enzymes, and toxic, they are one of the few organisms that can.
http://andreas-und-angelika.de/galleries/andreas/2014-
05_Autumn_Colours/photos/aka-Autumn-Colours-2014-04-
19__D8X7633.jpg

23. http://commons.wikimedia.org/wiki/File:Coal_lump.jpg
4.3 U.8 Partially decomposed organic matter from past geological eras
was converted either into coal or into oil and gas that accumulate in
porous rocks.
The cycle of sea-level changes that happened during the Carboniferous period caused costal
swamps to be buried promoting the formation of coal.
https://www.biv.com/media/filer_public_thumbnails/filer_public/68/05/6805c17b-255c-48c8-
8db3-4708d6435ab0/aussies-coal.jpg__0x400_q95_autocrop_crop-smart_subsampling-
2_upscale.jpg

24. 4.3 U.8 Partially decomposed organic matter from past geological eras
was converted either into coal or into oil and gas that accumulate in
porous rocks.

25. 4.3 U.9 Carbon dioxide is produced by the combustion of biomass and
fossilized organic matter.
Fossil/Biomass fuel + O2 → CO2 + H2O
• When organic compounds rich in hydrocarbons are heated and reach
their ignition temperature in the presence of oxygen they
undergo combustion(burning). This is an oxidation reaction.
• The products of combustion are carbon dioxide and water

26. 4.3 U.10 Animals such as reef-building corals and Mollusca have hard
parts that are composed of calcium carbonate and can become
fossilized in limestone.
Some animals secrete
calcium carbonate
(CaCO3) structures to
protect themselves:
• Shells of mollusks
• Hard corals
exoskeletons

27. http://www.discoveringfossils.co.uk/chalk2.jpg http://www.discoveringfossils.co.uk/ammonite_nautilus.jpg
4.3 U.10 Animals such as reef-building corals and Mollusca have hard
parts that are composed of calcium carbonate and can become
fossilized in limestone.
• Hard corals produce their exoskeletons by secreting calcium carbonate and
mollusks have shells that contain calcium carbonate
• The calcium carbonate in alkaline or neutral conditions from a variety of these
organisms, settle onto the seafloor when they die
• Through lithification, these sediments form limestone. The hard parts of many of
these animals are visible as fossils in the limestone rock

28. Carbon Cycle *
• Is exchanged of the element carbon among the biosphere. Or
geosphere, hydrosphere, and atmosphere of the Earth.
• Carbon interconnected by pathways of exchange with these
reservoirs is mainly through plants and other living things.
4.3 S.1 Construct a diagram of the carbon cycle.

29. 4.3 S.1 Construct a diagram of the carbon cycle.
You need to be able to produce a simplified carbon cycle. Use the
following sinks and flows (processes) to build a carbon cycle:
CO2 in the atmosphere and
hydrosphere (oceans)
Carbon compounds
in fossil fuels
Carbon compounds in
producers (autotrophs)
Carbon compounds
in consumers
Carbon compounds in
dead organic matter
Key:
Sink
Flux
n.b. some of the fluxes will need to be used more than once.
Cell respiration Photosynthesis
Combustion Feeding
Egestion
Death
Incomplete
decomposition
& fossilization

30. 4.3 S.1 Construct a diagram of the carbon cycle.
You need to be able to produce a simplified carbon cycle. Use the following
sinks and flows (processes) to build a carbon cycle:
CO2 in the atmosphere and
hydrosphere (e.g. oceans)
Carbon compounds
in fossil fuels
Carbon compounds in
producers (autotrophs)
Carbon compounds
in consumers
Carbon compounds in
dead organic matter
Key:
Sink
Flux
Incomplete
decomposition &
fossilisation
Feeding

31. 4.3 S.1 Construct a diagram of the carbon cycle.
You need to be able to produce a simplified carbon cycle. Use the following
sinks and flows (processes) to build a carbon cycle:
CO2 in the atmosphere and
hydrosphere (e.g. oceans)
Carbon compounds
in fossil fuels
Carbon compounds in
producers (autotrophs)
Carbon compounds
in consumers
Carbon compounds in
dead organic matter
Key:
Sink
Flux
Incomplete
decomposition &
fossilisation
Feeding

32. 4.3 A.1 Estimation of carbon fluxes due to processes in the carbon cycle.
Estimation of carbon fluxes (measured in gigatons) due to processes in the carbon
cycle.
* There is tremendous in the data, the large fluctuation that occur

33. 4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.
Many field stations globally use the same
standardised method. All stations show a clear
upward trend with annual cycles.

34. http://cdiac.ornl.gov/trends/co2/sio-keel.html
4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

35. http://cdiac.ornl.gov/trends/co2/sio-keel.html
4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

36. http://cdiac.ornl.gov/trends/co2/sio-keel.html
4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

37. 4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

38. 4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

39. 4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

40. https://www.ncdc.noaa.gov/cdo/f?p=518:1:0:::APP:PROX
YTOSEARCH:7
4.3 A.2 Analysis of data from air monitoring stations to explain annual fluctuations.

41. Bibliography / Acknowledgments
Jason de Nys