Define "autotroph."
An autotroph is an organism capable of making energy-containing organic molecules from inorganic sources via photosynthesis (involving light energy) or chemosynthesis (involving chemical energy).
State the molecular formula for carbon dioxide.
Carbon dioxide = CO₂
One carbon atom with double bonds to two oxygen atoms.
State the role of photosynthesis in the carbon cycle.
Autotrophs take in carbon from the atmosphere in the form of CO₂. They then use the carbon atoms from the CO₂ in the process of photosynthesis to make sugars, proteins and lipids for their growth. Photosynthesis converts inorganic carbon molecules into organic carbon molecules.
State the molecular formula for the hydrogen carbonate ion.
Hydrogen carbonate ion=Bicarbonate= HCO₃⁻.
Outline the process that converts carbon dioxide to hydrogen carbonate ion in water.
CO₂ diffuses into water. Some will remain as a dissolved gas. The remainder will combine with water to form carbonic acid (CO₂ + H₂O ⇄ H₂CO₃) which dissociates to form hydrogen and hydrogen carbonate ions (H⁺ and HCO₃⁻).
Explain the reduction of the pH in water when carbon dioxide is added.
In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions. When CO₂ combines with H₂O, hydrogen and hydrogen carbonate ions (H⁺ and HCO₃⁻) are formed. The increased [H⁺] will cause a reduction in the pH of the solution. Reduced pH = more acidic
Define "diffusion."
Diffusion is the net movement of particles down their concentration gradient (from areas of higher concentration to areas of lower concentration).
Outline the role of diffusion in the carbon cycle.
CO₂ diffuses into autotrophs from the atmosphere or water. Without diffusion of CO₂, autotrophs would not have a carbon source for performing photosynthesis.
A waste product of cellular respiration, CO₂ diffuses out of living things to the atmosphere or water.
State the role of respiration in the carbon cycle.
All living things respire, the metabolic process of converting biochemical energy from nutrients into adenosine triphosphate (ATP) for cellular work. CO₂ is a waste product of respiration. Respiration converts organic carbon molecules into inorganic carbon molecules which then diffuse into water or the atmosphere.
State the molecular formula for methane.
Methane=CH₄.
Outline the role of methanogenic archaea in the transformation of organic material into methane.
Methanogenic archaeans are microorganisms that produce methane as a metabolic byproduct in anaerobic conditions. The methane produced will either accumulate underground (forming natural gas) or diffuse into the atmosphere.
Define "oxidation."
Oxidation is the gain of oxygen or loss of hydrogen in a "redox" reaction.
State the formula for the oxidation of methane to carbon dioxide that occurs in the atmosphere.
In the atmosphere, methane (CH₄) is oxidized (gains oxygen and loses hydrogens) when it reacts with atmospheric oxygen (O₂). The result is carbon dioxide and water vapor.
CH₄ + 2O₂ → CO₂ + 2H₂O
Define "decomposition."
Decomposition is the process of complex, carbon compounds in dead organisms, urine and faeces being broken down into simpler carbon compounds by bacteria or fungi.
Define "peat."
Peat is a brown deposit resembling soil, formed by the partial decomposition of organic matter in wet acidic conditions (such as in bogs).
Outline formation of peat.
Peat forms when organic material (mostly plants/Sphagnum moss) does not fully decompose. Peat forms in acidic, waterlogged and/or anaerobic conditions where decomposers (such as bacteria, fungi and other saprotrophs) are inhibited.
Define "fossilization."
If conditions are not favourable for the process of decomposition, dead organisms decay slowly or not at all. These organisms build up and, if compressed over millions of years, can form fossil fuels (coal, oil or gas).
Outline formation of coal.
Coal forms from peat over long periods of time. Heat and pressure produce chemical and physical changes in the peat layers which force out oxygen and leave rich carbon deposits called coal.
Outline formation of oil and natural gas.
All of the oil and gas available today began as microscopic plants and animals living in the ocean millions of years ago. As these microscopic plants and animals lived, they stored carbon molecules in their bodies. When they died, they sank to the bottom of the sea. Over millions of years, layer after layer of sediment were formed. As they became buried ever deeper, heat and pressure began to rise. The amount of pressure and the degree of heat, along with the type of biomass, determines if the material becomes oil or natural gas. The gas or oil then accumulates in tiny pores in the surrounding rock.
Outline the role of combustion in the carbon cycle.
Combustion occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide and water. In the carbon cycle, combustion converts carbon stored in organic molecules (biomass, coal, gas and oil) to atmospheric CO₂.
State the products of a combustion reaction.
Combustion occurs when an organic molecule reacts with oxygen to produce carbon dioxide and water.
State sources of fuel for a combustion reaction.
Combustion reactions are commonly referred to as "burning." Biomass (such as wood), coal, gas and oil are common fuel sources in combustion reactions.
State the molecular formula for calcium carbonate.
The calcium carbonate chemical formula is CaCO₃.
State that hard shells, such as in mollusk and coral, are made of calcium carbonate.
Hard shells are the exoskeletons of corals and mollusks such as snails, clams and oysters. The shells are composed mostly of calcium carbonate, CaCO₃.
Outline the role of lithification in the carbon cycle.
Lithification is the compaction of sediments into rocks through compaction and cementation. In the carbon cycle, lithification creates limestone from calcium carbonate.
Outline the formation of limestone.
Limestone is primarily composed of calcium carbonate (CaCO₃). It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal, and fecal debris in shallow, calm, warm marine waters.
Define "carbon cycle."
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere (living things), pedosphere (soil), geosphere (rocks), hydrosphere (water), and atmosphere of the Earth.
Define "flux" as related to the carbon cycle.
A carbon flux is the exchange of carbon between Earth's carbon pools.
List flux processes in the carbon cycle.
Photosynthesis
Respiration
Decomposition
Diffusion
Lithification
Combustion
Fossilization
Feeding
Define "pool" as related to the carbon cycle."
Carbon pools are locations or systems that have the capacity to both take in and release carbon.
List pools of carbon in the carbon cycle.
Biosphere (living things, terrestrial and aquatic)
Pedosphere (soil)
Geosphere (rocks and Earth's crust)
Hydrosphere (water, mostly ocean)
Atmosphere
Fossil fuels
State the unit of measure for carbon flux values.
Global carbon fluxes are estimated in gigatonnes (1 gigatonne = 1 billion metric tonnes).
Sketch a graph of the annual fluctuation in atmospheric carbon dioxide concentration.
Sinusoidal shape with a peak in May and a trough in October.
Axis labeled:
X axis = month
Y axis = Atmospheric CO₂ level (ppm)
Explain the annual fluctuation in atmospheric carbon dioxide concentration in the northern hemisphere.
The annual, seasonal fluctuations of CO₂ levels are caused by increased photosynthesis during Northern hemisphere spring/summer. Photosynthesis uses CO₂; lowering carbon dioxide level in atmosphere during the spring and summer months.
Draw a diagram of the terrestrial carbon cycle.
CO₂ in atmosphere linked to producer (plant) with an arrow labeled photosynthesis;
Producer linked to consumer (animal) with an arrow labeled feeding;
Producer and consumer linked to CO₂ in the atmosphere with an arrow labeled (cell) respiration;
Producer and consumer linked to decomposers (bacteria or fungi) with an arrow labeled decomposition;
Decomposers linked to CO₂ in the atmosphere with an arrow labeled cell respiration;
Producer linked to CO₂ in the atmosphere with an arrow labeled combustion;
Producers, consumers and decomposers linked to fossil fuels (coal, oil, natural gas) with arrow labeled fossilization;
Fossil fuels linked to CO₂ in the atmosphere with an arrow labeled combustion;
Methanogenic bacteria linked to methane in the atmosphere with an arrow labeled anaerobic respiration;
Methane linked CO₂ in the atmosphere with an arrow labeled oxidization;
Explain why accurate measurements of carbon dioxide and methane in the atmosphere are important.
It is important to make observations and collect data regarding greenhouse gas levels (such as CO₂ and methane). The information helps scientists understand trends and test whether actions to reduce greenhouse gases are working.
Outline how data on the concentration of atmospheric carbon dioxide and methane are collected.
Scientists measure the amount of greenhouse gases in the atmosphere in several ways. They use satellites and other instruments to measure the amount of greenhouse gases in the air all around the world. They also collect samples of air from specific places and then analyze these samples in a laboratory. We also have clues about the levels of greenhouse gases that existed in the past. For example, ancient air bubbles trapped deep in the ice of Greenland and Antarctica reveal how much atmospheric CO₂ was present long ago.