Recycling within an ecosystem

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What is decomposition?
A chemical process in which a compound is broken down into smaller molecules
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What is a decomposer?
An organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic nutrients for plants
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What type of feeder are decomposers?
Saprotrophs
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How do decomposers eat?
Secrete enzymes which break down complex molecules into simpler ones which can be absorbed because they are soluble
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What is a detritivore?
Another class of organism which are involved in decomposition, they feed on detritus (dead/decaying material) increasing surface area for decomposers to work on
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How do the detritivores feed?
Internally digest the food
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What is nitrogen used for in organisms?
Producing amino acids thus producing proteins and also producing nucleic acids
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How do animals and plants obtain nitrogen?
Animals- from food they eat, Plants- have to take it in from environment
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How do plants get the nitrogen?
They cant take it from the air in the form it is in so plants rely on nitrogen fixing bacteria by combining them with oxygen or hydrogen
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Name 2 nitrogen fixing bacteria
Azotobacter and rhizobium
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What enzyme do azotobacter and rhizobium contain?
The enzyme nitrogenase
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Describe the process of nitrogen fixing in bacteria
The enzyme nitrogenase combines atmospheric nitrogen with hydrogen to produce ammonia (NH2), which can be absorbed and used by plants
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Where does azotobacter live?
It is a free-living soil bacterium
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Where does rhizobium live?
Nodules on roots of leguminous plants, having a mutualistic relationship with the plant
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How do rhizobium and leguminous plants have a mutualistic relationship?
Rhizobium provide plants with ammonium to make amino acids, plants provide rhizobium with carbohydrates which is used as an energy source
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What is nitrification?
The process why which ammonium compounds IN THE SOIL are converted into nitrogen containing molecules that can be used by plants
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What bacteria is involved in nitrification?
Free-living bacteria in the soil
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What are the 2 processes involved in nitrification?
Oxidation reaction- 1)Nitrifying bacteria oxidise ammonium compounds into NITRITES, 2) Nitrobacter oxidise NITRITES into NITRATES
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Why is ammonium compounds converted into nitrates?
Because nitrates are highly soluble and are the form in which most nitrogen is taken up by plants
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What is denitrification?
In the absence of oxygen, the nitrifying bacteria use nitrates as a source of energy for respiration and so nitrates are converted back into nitrogen atmospheric gas and released back into the atmosphere
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What is ammonification?
The name given to the process by which decomposers convert molecules from dead matter into ammonium compounds
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Name 2 examples of nitrogen fixing by non-living processes
Lightning and the harber process
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Why is the atmospheric carbon dioxide content higher at night than at day?
Plants and animals respire night and day, plants photosynthesise using CO2 during the day
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How does carbon dioxide levels fluctuate seasonally?
CO2 levels lower on warm summer day as higher rate of photosynthesis, low photosynthesis rate in cold winter days so higher CO2 atmosphere content
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What are the 2 main reasons to the increase in global atmospheric carbon dioxide levels?
Combustion (burning of fossil fuels with trapped carbon in them releases carbon dioxide) and deforestation (less photosynthesising plants etc, usually burned as well releasing their carbon in the form of CO2)
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What affects the amount of CO2 dissolved into the ocean?
Temperature, the warmer it is the less gas is dissolved (global warming)
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Explain how global warming is like a positive feedback mechanism
More CO2 released into atmosphere, increasing temperature by trapping thermal energy, earth gets warmer so less CO2 is dissolved into the ocean, meaning more CO2 left in atmosphere and so on
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Other cards in this set

Card 2

Front

What is a decomposer?

Back

An organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic nutrients for plants

Card 3

Front

What type of feeder are decomposers?

Back

Preview of the front of card 3

Card 4

Front

How do decomposers eat?

Back

Preview of the front of card 4

Card 5

Front

What is a detritivore?

Back

Preview of the front of card 5
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