4.3 Carbon cycling Flashcards
What do autotrophs convert carbon dioxide into?
Autotrophs absorb carbon dioxide from the atmosphere and convert it into carbohydrates, lipids and all the other carbon compounds that they require
What does autotrophs absorbing carbon dioxide do to the atmosphere?
This has the effect of reducing the carbon dioxide concentration of the atmosphere
* there is a lower concentration of CO2 in earths surface where photosynthesis rates are high
What is carbon fixation?
The incorporation of carbon into organic compounds by living organisms, chiefly by photosynthesis in green plants.
Is carbon dioxide soluble in water?
Yes
Is carbon dioxide soluble in water?
Yes
How is carbon dioxide presented in aquatic habitats?
As dissolved gas and hydrogen carbonate ions
How is carbonic acid formed?
When CO2 combine with water
What does carbonic acid formed when dissociated?
Hydrogen and hydrogen carbonate ions (H+ and HCO3-)
* this explains how carbon dioxide can reduce the pH of water
What do aquatic plants and other autotrophs that live in water absorb?
Dissolves to carbon dioxide and hydrogen carbonate ions
* to make carbohydrates and other carbon compounds
How does autotrophs reduce the concentration of carbon dioxide inside them?
Autotrophs use carbon dioxide in the production of carbon compounds by photosynthesis or other processes
How is carbon dioxide able to diffuse from the atmosphere or water into autotrophs?
Due to a concentration gradient between cells in autotrophs and the air or water around
* Set up by lower concentrations in autotrophs since they use them
What does diffusion usually happen in land plants?
Through stomata in the underside of the leaves
How does carbon dioxide diffuse into aquatic plants?
The entire surface of the leaves and stems is usually permeable to CO2, so diffusion can be through any part of these parts of the plant
How is carbon dioxide produced and where does it diffuse to?
By respiration and diffuse out of organims into water or the atmosphere
What is a waste product of aerobic cell respiration?
Carbon Dioxide
What produces methane?
Methane is produced from organic matter in anaerobic conditions by methanogenic archaens
Where is methane widely produced in?
Is produced widely in anaerobic environments, as its a waste product of a type of anaerobic respiration
What are the 3 different groups of anaerobic prokaryotes involved in the production of methane?
- Bacteria that convert organic matter into a mixture of organic acids, alcohol, hydrogen and carbon dioxide
- Bacteria that use the organic acids and alcohol to produce acetate, carbon dioxide and hydrogen
- Archeans that produce methane from carbon dioxide, hydrogen and acetate.
What does bacteria that convert organic matter convert it into?
A mixture of organic acids, alocohol, hnydrogen and carbon dioxide
What does bacteria that use the organic acids and alocohol produce?
Acetate, carbond dioxide and hydrogen
How does archeans produce methane?
From carbon dioxide, hydrogen and acetate. They do this by two chemical reactions
* CO2 + 4H2 -> CH4 + 2H2O
* CH3COOH -> CH4 + CO2
What does being methanogenic mean?
Being able to carry out methanogenesis
What are some anaerobic environments that archaeans carry out methanogenisis in?
- 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 of ruminant mammals such as cattle and sheep
- Landfill sites where organic matter is in wastes that have been buried
Where does the methane produced by archaens in anaerobic environments go?
Some diffuses into the atmosphere
Where does the methane produced by archaens in anaerobic environments go?
Some diffuses into the atmosphere
Where does methane produced from organic wastes in anaerobic digesters go?
It is not allowed to escape and instead is burned as a fuel
What is methane oxidized into?
Carbon dioxide and water in the atmosphere
why do molecules of methane released into the atmosphere persist there only for 12 years on average?
Because it is naturally oxidized in the stratosphere
* Monatomic oxygen and highly reactive hydroxyl radicals are involved in methane oxidation.
* This explains why atmospheric concentrations are not high despite large amounts of production by natural processes and human activities
How is peat formed?
When organic matter is not fully decomposed because of anaerobic conditions in waterlogged soils. Then are accumulated and compressed to form a dark brown acidic material called peat.
Where do saprotrophs obtain oxygen needed for respiration in soil?
From air spaces in the soil
What happens to some environments where water is unable to drain out of soils?
They become waterlogged and anaerobic
What conditions can saprotophs not thrive in?
Waterlogged, anaerobic and acidic conditions
What happens when saprotrophs are in an environment where they cannot thrive?
They can not fully decompose dead organic matter.
* Acidic environments further inhibit their activity
What is the effect of anaerobic, waterlogged and acidic conditons in soil?
Saprotrophs and methanogens are inhibited from breaking down organic matter
What happens to partially decomposed organic matter in the ecosystem?
Large quantities accumulate and become compressed to form a dark brown acidic material called peat
What is partially decomposed organic matter from past geological eras converted to?
Oil and gas in porous rocks or coal
What is the reason that carbon and some compounds of carbon can remain unchanged in rocks for hundreds of millions of years?
They are chemically very stable
What are the large deposits of carbon from past geological eras resulted from?
These deposits are the result of incomplete decomposition of organic matter and its burial in sediments that became rock
How is coal formed?
Coal is formed when deposits of peat are buried under other sediments.
The peat is compressed and heated, gradually turning into coal
Where are oil and natural gas formed? What are the conditions?
In the mud at the bottom of seas and lakes
* Usually anaerobic conditions
Why are the conditions for the production of oil and natural gas anaerobic?
So decomposition is often incomplete
What happens when more mud or other sediments are decompositied in mud at the bottom of seas?
The partially decomposed matter is compressed and heated
Chemical changes occur in mud at the bottom of seas to produce what?
Complex mixtures of liquid carbon compounds or gases. We call these complex mixtures crude oil and natural gas.
What forms the largest part of natural gas produced at the bottom of seas?
Methane
Where are deposits found in the mud at the bottom of seas?
In porous rocks that can hold them such as shales and also impervious rocks above and below the porous rocks that prevent the deposit’s escape
What do porous rocks do to deposits at the bottom of the sea?
It prevent the desposit’s escape
What does the combustion of biomass and fossililzed organic matter produce?
Carbon dioxide
What is combustion of organic matter?
The oxidation reactio that occurs.
* If organic matter i sheated to its ignition temperature in the presence of oxygen it will set light and burn.
What are the products of complete combustion?
Carbon dioxide and water
What are the products of complete combustion?
Carbon dioxide and water
In what situations do carbon dioxide get relased from combustion?
- Periodic fires of dorests or grassland - CO2 is released from the combustion of the biomass in the forest or grassland
- Man made fires used to clear areas of tropical rainforest for planting oil palms or for cattle ranching
What are the 3 different forms of fossilized organic matter?
Coal, oil, and natural gas
* They are all burned as fuels
What are animals with hard body parts composed of?
Calcium carbonate CaCO3
What animals are composed of calcium carbonate?
- Mollusc shells contain calcium carbonate
- Hard corals that build reefs produce their exoskeletons by secreting calcium carbonate
What happens to the soft parts of animals?
Usually decomposed quickly
What happens to the calcium carbonate on dead animals in acidic conditions?
They dissolve away
What happens to the calcium carbonate on dead animals in neutral or alkaline conditions?
It is stable and deposits of it from hard animal parts can form on the sea bed
How is calcium carbonate deposited in shallow tropical seas?
By precipitation in the water
What is the result of calcium carbonat being deposited by precipitation in the water?
Limestone rock, where the deposited hard parts of animals are often visible as fossils
What is carbon flux and sink?
- A carbon flux refers to the amount of carbon exchanged between carbon stocks over a specified time
- A carbon sink is anything that absorbs more carbon from the atmosphere than it releases
