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41 Cards in this Set
- Front
- Back
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What is an ecosystem?
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a distinct, self-supporting system of organism interacting with each other and with the physical environment
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What is a population?
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all the organisms of a particular species found in an ecosystem at any one time
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What is a community?
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populations of all species found in a particular ecosystem at any one time
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What are biotic factors?
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the living factors of an ecosystem like food supply, predation and disease
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What are abiotic factors?
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the non-living factors of an ecosystem such as temperature, pH and soil type.
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What is the niche?
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the role of an organism within its ecosystem, including what it feeds, its habitat and its effect on the environment
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An ecosystem is dynamic. What does this mean? |
The interactions between organisms and their environment will cause fluctuations in population sizes
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What do food chains and webs show?
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energy transfer in an ecosystem
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What does a trophic level show?
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the position that something occupies in a food chain
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What is a producer?
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covert sun's energy into chemical energy
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What is a primary consumer?
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herbivores, feed on producers
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What is a secondary consumer?
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carnivorous, feed on primary consumers
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What are tertiary consumers?
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eat secondary consumers
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What is a decomposer?
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feed on waste material and dead organism
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How much of the total energy is passed on in a food chain and how much is lost?
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10% is passed on, 90% is lost as waste, respiration, kinetic, chemical and heat energy
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What are energy pyramids? |
pyramids that represent energy transfer
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What are the bars proportional to on a pyramid of biomass? |
the dry mass of all the organism on the trophic level
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What must happen to measure dry mass? what is the alternative?
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-must dry out an organism of all their water -this is impractical so ecologists measure wet mass instead |
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How are the bars worked out on a pyramid of energy?
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-organisms are burned in a calorimeter -equation Q=mc(delta)t |
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What are the problems with using energy pyramids?
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-only take a snapshot of an ecosystem at one moment in time -population sizes fluctuate |
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What is productivity?
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the rate of energy flow
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What is the gross primary productivity (GPP)?
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the rate at which autotrophs convert light energy into chemical energy
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What is the net primary productivity (NPP)?
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the remaining energy left for the primary consumer
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How can human manipulate primary productivity?
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-greenhouses and light banks (increase rate of photosynthesis by, maintaining an optimum temp and supply sufficient nutrients to increase NPP) -GM plants that become pest or drought resistance can increase NPP. pesticides can increase yield and decrease competition. |
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How can humans manipulate secondary productivity?
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-harvesting young animals -selectively breeding -treating animals with antibodies -stopping animals moving (zero grazing) |
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what is succession? |
a directional change in a community of organisms over time
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what is a pioneer community?
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the first animals to arrive
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what is a climax community?
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A final and stable outcome of succession
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Explain the succession of sand dunes. |
1)pioneer plants like sea holly colonise the sand around the high watermark (they can tolerate salt water spray, a lack of fresh water and unstable sand) 2)wind-blown sand builds up around the base forming a mini sand dune. death and decay of plants allow nutrients to build up and sustain different plants like sea couch grass which has stems that can stabilise sand 3)marram grass and other plants grow which traps sand. more nutrients accumulate meaning bacteria in root nodules can covert them into nitrates. more nitrates means more species can colonise the dunes and stabilise the community further. |
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What are the three main ways of sampling and when are they used?
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-random: sampling an area -stratified: comparing two different areas (random sampling used in the two areas) -systematic: used where there is an environmental gradient (transect lines used) |
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How can a transect and a quadrat be used in conjunction?
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-interrupted belt transect (use quadrat at set intervals) -continuous belt transect (move quadrat along the line |
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Why must sampling be random?
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to avoid bias
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Why must sample sizes not be too small?
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they might not be representative of the whole population |
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What is a point quadrat?
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-pin placed through a bar -used to sample vegetation where there are differences in height |
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What are saprotrophs?
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-organisms that secrete enzymes externally onto dead and waste material -enzymes digest material into small molecules which are then absorbed back into the organisms body |
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Can you name an example of a saprotroph? |
-fungi -certain types of bacteria |
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What is the nitrogen cycle?
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the recycling of nitrogen in an ecosystem
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Why is nitrogen needed in ecosystems?
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nitrogen is used to make proteins and nucleic acids
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Name the nitrogen fixing bacteria. |
Rhizobium
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Name two nitrifying bacteria.
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Nitrosomonas and Nitrobacter
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What happens in the nitrogen cycle?
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-Rhizobium lives in root nodules of plants and share a mutualistic relationship -proteins (e.g. leghaemoglobin) absorb oxygen in nodules, keeping conditions anaerobic so bacteria use nitrogen reductase to reduce nitrogen to NH4+ ions for use by the host plant -Nitrosomonas oxidises NH4+ to NO2- -Nitrobacter oxidises NO2- to NO3- (both above are chemoautotrophic) -nitrates are absorbed from the soil by plants -denitrifying bacteria converts nitrates back to N2 gas. under anaerobic conditions they use nitrates as a source of oxygen for respiration |
