Term
List the roles of microbes in ecosystems, including producers, nitrogen fixers and decomposers.
Producers |
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Definition
- Microscopic algae and some bacteria use chlorophyll to trap sunlight
- Chemosynthetic bacteria use chemical energy
- Change inorganic molecules into organic molecules that can be used by other organisms for food |
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Term
List the roles of microbes in ecosystems, including producers, nitrogen fixers and decomposers.
Nitrogen Fixers |
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Definition
| - Bacteria which remove nitrogen as from the atmosphere and fix it into nitrates which are usable by producers |
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Term
List the roles of microbes in ecosystems, including producers, nitrogen fixers and decomposers.
Decomposers |
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Definition
| - Breakdown detritus (organic molecules) and release inorganic nutrients back into the ecosystem |
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Term
| State the roles of Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter and Pseudomonas denitrificans in the nitrogen cycle. |
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Definition
Nitrogen Fixation
- Mutualistic: Rhizobium lives in symbiosis with legumes (its root nodules) and fixes nitrogen for them
- Free-living: Azotobacter fixes nitrogen and lives freely in the soil without a host
Nitrification
- Nitrosomonas converts ammonia (NH3) into nitrite (NO2-)
- Nitrobacter changes nitrite into nitrate (NO3-) which is usable by plants
Dentrification
- Conversion of nitrates to nitrogen gas
- Pseudomonas dentrificans removes nitrates and nitrites and puts nitrogen gas back in atmosphere |
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Term
| Outline the conditions that favour denitrification and nitrification. |
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Definition
Conditions favouring nitrification
- available oxygen/aerated soils
- neutral pH
- warm temperature
Conditions favouring denitrification
- No available oxygen/anaerobic soils (flooding or compacted soil)
- High nitrogen input |
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Term
Explain the consequences of releasing raw sewage and nitrate fertilizer into rivers.
Raw Sewage |
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Definition
| - Raw sewage consists of organic matter and may contain pathogens, which are dangerous if drunk/bathed in -> amount of saprotrophs increase to break down organice matter -> a biochemical oxygen demand (BOD) occurs due to high levels of oxygen used -> deoxygenation of water -> oxygen-dependent organisms are forced to emigrate/die -> death and decay -> decomposition -> ammonia, phosphorus and minerals released -> nitrification -> eutrophication occurs due to high nutrient levels -> algae proliferate -> provided no algal bloom occurs, the river recovers eventually |
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Term
Explain the consequences of releasing raw sewage and nitrate fertilizer into rivers.
Nitrate Fertilizer |
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Definition
| - Rivers leech off nitrate from soil -> if application of nitrate fertilizer is great enough, eutrophication occurs -> algae proliferate (increasing oxygen levels) -> if nitrate levels in excess, algal bloom occurs -> due to large amount s of algae, some are deprived of sunlight and die -> saprotrophs are needed to break down the organic matter -> this creates a biochemical oxygen demand (BOD) -> deoxygenation occurs -> oxygen-dependent organisms are forced to emigrate/die -> increase in ammonia and phosphorus levels -> nitrification -> eutrophication -> algae proliferate -> algal population can decrease -> provided no new algal bloom occurs, river recovers eventually |
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Term
Explain the consequences of releasing raw sewage and nitrate fertilizer into rivers.
Simply |
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Definition
-High and excess nitrates and phosphates fertilize the algae in water
- Increased growth of algae (algal bloom)
- Algae decomposed by aerobic bacteria which use up oxygen in water, resulting in deoxygenation
- The high use of oxygen is called biochemical oxygen demand (BOD)
- Results in eutrophication |
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Term
Outline the role of saprotrophic bacteria in the treatment of sewage using trickling filter beds and reed bed systems.
Trickling Filter System |
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Definition
• Bed of stones 1-2 meters wide
• A biofilm of aerobic saprotrophs are on the rocks, which feed on organic matter, cling to the stones and act on the sewage trickled over (this is done to aerate the sewage), until it is broken down.
• Cleaner water trickles out the bottom of the bed to another tank where the bacteria are removed and the water treated with chlorine to disinfect |
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Term
Outline the role of saprotrophic bacteria in the treatment of sewage using trickling filter beds and reed bed systems.
Reed Bed System |
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Definition
• Artificial wetland used to treat waste water
• Waste water provides both the water and nutrients to the growing reeds
• The reeds are harvested for compost and the organic waste is broken down by saprotrophic bacteria
• Nitrification of ammonia to nitrite and nitrate
• Nitrates and phosphates released are used as fertilizer by the reeds
• Remaining nitrates are denitrified |
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Term
| State that biomass can be used as raw material for the production of fuels such as methane and ethanol. |
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Definition
| • Biomass (organic matter) can be used as raw material for the production of fuels such as methane and ethanol. Examples include manure and cellulose. |
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Term
| Explain the principles involved in the generation of methane from biomass, including the conditions needed, organisms involved and the basic chemical reactions that occur. |
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Definition
• One group of Eubacteria are needed to convert the organic matter into organic acids and alcohol
• A second group of Eubacteria convert these into acetate, carbon dioxide and hydrogen
• Methanogenic bacteria are needed to create the methane, by two chemical reactions:
1. carbon dioxide + hydrogen -> methane + water
2. acetate -> methane + carbon dioxide (breakdown of acetate)
Conditions required:
• No free oxygen (anaerobic)
• Constant temperature of about 35°C
• pH not too acidic |
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