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30 Cards in this Set
- Front
- Back
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Why do organisms need carbon? |
•To make protein... •To make fats... •To make carbohydrates... |
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How is carbon returned to the atmosphere? |
By the events of the carbon cycle. |
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How is CO2 returned to the atmosphere? |
Respiration Combustion Weathering |
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What increases the level of CO2 in the atmosphere? |
•Increased burning of fossil fuels(due to industrialisation). •Deforestation(less trees to absorb CO2) |
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Why is increased level of CO2 a problem? |
CO2 is a greenhouse gas. This means it allows the sun's heat into the atmosphere but does not allow the reflected heat back out efficiently. This heat stays in the atmosphere causing global warming. |
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What are the consequences of global warming? |
•Polar ice caps melt causing flooding due to rising seas. •Loss of habitat eg. polar bears, arctic fox. •Changing weather patterns ie. hot air rises causing increased storms and hurricanes. •Altered agricultural and tillage zones. |
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Why do plants need nitrogen? |
Protein DNA RNA Chlorophyll formation |
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What form of nitrogen can plants absorb? |
Compound form ie. NO3, NO2, NH3. |
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Define nitrogen fixation |
The conversion if nitrogen gas into nitrates. In this compound form nitrogen can be absorbed by plants. |
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What can nitrogen fixation be brought about by? |
Nitrogen fixing bacteria Lightning Volcanic activity Industrial processes |
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What are the two types of nitrogen fixing bacteria? |
Free living nitrogen fixing bacteria. Symbiotic nitrogen fixing bacteria. |
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What are free living nitrogen fixing bacteria? |
Bacteria that live freely in the soil. They absorb N2 gas and release nitrates(NO3). |
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What are symbiotic nitrogen fixing bacteria? |
These bacteria live in nodules in the roots of legumes (beans, peas, clover, soya). They absorb N2 gas and release nitrates (NO3) which are then absorbed by plant. |
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Define assimilation. Give example. |
The uptake and incorporation of elements into the molecules of an organism. Absorbed nitrates become part of the protein of an animal. |
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Define decomposition |
The breaking down of dead plants and animals and their excretory products into ammonia. |
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What is nitrification? |
This is the conversion of ammonia into nitrates. Step 1: converts ammonia into nitrite(NO2). Step 2: converts nitrite into nitrate(NO3). |
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What is denitrification? |
The conversion of nitrates into nitrogen gas. |
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Define ecological pyramids |
A diagram representing the number of individual organisms at each trophic level in a food chain. |
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How are ecological pyramids prepared? |
The number of organisms at each trophic level are counted and are represented by a block drawn to scale. |
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What might big blocks at top of pyramid represent? |
Bacteria Viruses Parasitic wasps Fleas |
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What are the limitations of ecological pyramids? |
•Size of organisms not considered in a pyramid of numbers eg. one rosebush can support thousands of greenfly. •The number of organisms can be so great that the pyramid cannot be drawn to scale ie. cannot accurately represent one oak tree versus 500 greenfly in a pyramid. |
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Why is energy transfer in an ecosystem not a cycle? |
•There is a flow of energy into the ecosystem from the sun. •In the ecosystem, the energy flows along the different trophic levels in the food chains. •Finally the energy flows out of the ecosystem into the atmosphere as heat loss in respiration. |
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Define nutrient recycling |
The way in which elements are continuously being broken down and exchanged for reuse between the abiotic and the biotic components of an ecosystem. |
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What is the purpose of nitrogen fixing bacteria in the soil? |
To convert atmospheric nitrogen into nitrates. |
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What is the purpose of nitrifying bacteria in the soil? |
They convert NH3 into nitrite NO2 and then convert NO2 into NO3. It makes nitrogen available to plants. |
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What is the purpose of denitrifying bacteria in the soil? |
To convert nitrate NO3 into nitrogen gas. |
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What is the purpose of decomposing bacteria and fungi in the soil? |
They break down dead plants and animals and animal excretory products into ammonia NH3 in the soil. |
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What are the three types of ecological pyramids? |
Pyramid of numbers Pyramid of energy Pyramid of mass |
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Where are denitrifying bacteria mainly found? Are they aerobic or anaerobic? |
Flooded land and land contaminated by sewage. Anaerobic. |
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How else might nitrates enter the soil? |
The addition of nitrogen rich fertilisers to the soil. |
