essential idea
Continued availability of carbon of carbon in ecosystems depends on carbon cycling
nature of science
Making accurate, quantitative measurement - it is important to obtain reliable data on the concentration of carbon dioxide and methane in the atmosphere
understandings
4.3.1 Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds
4.3.2 In aquatic ecosystems, carbon is present as dissolved carbon dioxide and hydrogen carbonate ions
4.3.3 Carbon dioxide diffuses from the atmosphere or water into autotrophs
4.3.4 Carbon dioxide is produced by respiration and diffuses out of organisms into
4.3.5 Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuse into the atmosphere or accumulates in the ground
4.3.6 Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic condition in waterlogged soils
4.3.7 Partially decomposed organic matter from past geological eras was converted either into or into oil and gas that accumulates in porous rocks
4.3.8 Carbon dioxide is produced by the combustion of biomass and fossilized organic matter
4.3.9 Animals such as reef-building corals and Mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone
4.3.2 In aquatic ecosystems, carbon is present as dissolved carbon dioxide and hydrogen carbonate ions
4.3.3 Carbon dioxide diffuses from the atmosphere or water into autotrophs
4.3.4 Carbon dioxide is produced by respiration and diffuses out of organisms into
4.3.5 Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuse into the atmosphere or accumulates in the ground
4.3.6 Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic condition in waterlogged soils
4.3.7 Partially decomposed organic matter from past geological eras was converted either into or into oil and gas that accumulates in porous rocks
4.3.8 Carbon dioxide is produced by the combustion of biomass and fossilized organic matter
4.3.9 Animals such as reef-building corals and Mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone
applications and skills
4.3.10 A Estimation of carbon fluxes due to processes in the carbon cycle
4.3.11 A Analysis of data from monitoring stations to explain annual fluctuations
4.3.12 S Construct a diagram of the carbon cycle
4.3.11 A Analysis of data from monitoring stations to explain annual fluctuations
4.3.12 S Construct a diagram of the carbon cycle
guidance / international mindedness / theory of knowledge
Guidance:
Carbon fluxes should be measured in gigatonnes
Carbon fluxes should be measured in gigatonnes
carbon dioxide in solution
- In aquatic habitats carbon dioxide is present as as dissolved gas and hydrogen carbonate ions
- Carbon dioxide is soluble in water
- It can either remain in water as a dissolved gas or it can combine with water to form carbonic acid
- Carbonic acid can dissociate to form hydrogen and hydrogen carbonate ions
- This explains how carbon dioxide can reduce the pH of water
- Both dissolved carbon dioxide and hydrogen carbonate ions are absorbed by aquatic plants and other autotrophs that live in water
- They use them to make carbohydrates and other carbon compounds
absorption of carbon dioxide
- Carbon dioxide diffuses from the atmosphere or water into autotrophs
- Autotrophs use carbon dioxide in the production of carbon compounds by photosynthesis or other processes
- This reduces the concentration of carbon dioxide inside autotrophs and sets up a concentration gradient between cells in autotrophs and the air or water around
- Carbon dioxide therefore diffuses from the atmosphere or water into autotrophs
- In land plants with leaves this diffusion usually happens through stomata in the underside of the leaves
- In aquatic plants the entire surface of the leaves and stems is usually permeable to carbon dioxide, so diffusion can be through any part of these parts of the plants
release of carbon dioxide from cell respiration
- 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. It is produced in all cells that carry out aerobic cell respiration, These can be grouped according to trophic level of the organism:
- Non-photosynthetic cells in producers for example root cells in plants
- Animal cells
- Saprotrophs such as fungi that decompose dead organic matter
- Carbon dioxide produced by respiration diffuses out o cells and passes into the atmosphere or water surround these organisms
methanogenesis
- Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere
- In 1776 Alessandro Volta collected bubbles of a gas emerging from mud in a reed bed on the margins of Lake Maggiore in Italy and found that it was inflammable
- He discovered methane, though Volta did not give in this name. Methane is produced widely in anaerobic environments, as it is a waste product of a type of anaerobic respiration
- Three different groups of anaerobic prokaryotes are involved
- Bacteria that convert organic matter into a mixture of organic acid, alcohol, hydrogen and carbon dioxide
- Bacteria that use the organic acids and alcohol to produce acetate carbon dioxide and hydrogen
- Archaeaens that produce methane from carbon dioxide , hydrogen and acetate
- The archaeans in this third group are therefore methanogenic. They carry out methanogenissi in many anaerobic environments
- Mud along the shores and in the bed of lakes
- Swamps, mires, mangrove forests and other wetlands where the soil or peat deposits are waterlogged
- Guts of termites and ruminant mammals such as cattle and sheep
- landfill sites where organic matter is in wastes that have been buried
oxidation of methane
- Methane is oxidized to carbon dioxide and water in the atmosphere
- Molecules of methane released into the atmosphere persists there on average for only 12 years, because it is naturally oxidized in the stratosphere
- Monatomic oxygen and highly reactive hydroxyls radical are involve in methane oxidation
- This explains why atmospheric concentration are not high, despite large amounts of production of mathane by both natural processes and human activities
Peat formation
- Peat forms when organic matter is not fully decomposed because of anaerobic conditions in waterlogged soils
- In many soils all organic matter such as dead leaves from is eventually digested by saprotrophic bacteria and fungi
- Saprotrophs obtain the oxygen that they need for respiration from air spaces in the soil
- In some environments water is unable to drain out of soils so they become waterlogged and anaerobic
- Saprotrophs cannot thrive in these conditions so dead organic matter is not fully decomposed
- Acidic conditions tend to develop, further inhibiting saprotrophs and also methanogens that might break down the organic matter
fossilized organic matter
- Partially decomposed organic matter from past geological eras was converted into oil and gas in porous rocks or into coal
- Carbon and some compounds of carbon are chemically very stable and can remain unchanged in rocks for hundreds of millions of years
- The are large deposits of carbon from past geological eras
- These deposits are the result of incomplete decomposition of organic matter and it's burial in sediments that become rock
- Coal is formed when deposits of peat are buried under other sediments
- The peat is compressed and heated, gradually turning into coal
- large coals deposits were formed during the Pennsylvanian sub-period of the Carboniferous
- Oil and natural gas are formed in the mud at the bottom of seas and lakes
- Conditions are usually anaerobic and so decomposition is often incomplete
- As more and mud and other sediments are deposited the partially decomposed matter is compressed and heated
combustion
- Carbon dioxide is produced by the combustion of biomass and fossilized organic matter
- If organic matter is heated to it's ignition temperature in the presence of oxygen it will set light and burn
- The oxidation reactions that occur are called combustion
- The products of complete combustion are carbon dioxide and water
- Fuels are substances that react with oxygen to release useful energy. Most of the energy is released as heat, but light energy is also released
- Incomplete combustion occurs when the supply of air or oxygen is poor. Water is still produced, but carbon monoxide and carbon are produced instead of carbon dioxide
- Coal, oil and natural gas are different forms of fossilized organic matter
- They are all burned as fuels
- The carbon atoms in the carbon dioxide released may have been removed from the atmosphere by photosynthesizing plants hundreds of millions years ago
limestone
- Animals such as reef-building corals and mollucscs have hard parts that are composed of calcium carbonate and can become fossilized in limestone
- Some animals have hard body pars composed of calcium carbonate ( CaCO3) :
- Mollusc shells contain calcium carbonate
- Hard corals that build reefs produce their exoskeletons by secreting calcium carbonate
- When these animals die, their soft parts are usually decomposed quickly
- In acid conditions the calcium carbonate dissolves away but in neutral or alkaline conditions it is stable and deposits of ir from hard animals parts can form on the sea bed
- In shallow tropical seas calcium carbonate is also deposited by precipitation in the water
- The result is limestone rock, where the deposited hard parts of animals are often visible as fossils
carbon cycle
Sources:
Chapter 4 Ecology Notes
https://www.youtube.com/watch?v=2D7hZpIYlCA
https://www.youtube.com/watch?v=2D7hZpIYlCA