Module 6 Bio AS

  • Created by: Jessinoch
  • Created on: 11-05-18 18:56
Define ecosystem
Dynamic system of interactions involving a community of living organisms and the abiotic factors of their environment
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Define population
A group of organisms of the same species who live in the same place at the same time and breed
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Define community
All the populations of different species living in the same place at the same time
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Define habitat
The place where an organism lives
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What are abiotic factors?
Effects of non-living components - pH, temperature, soil type
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What are biotic factors?
Effects of living components, food supply, predation, disease
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Define biomass
The combined total weight of a defined set of organisms
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Explain how energy transfer between trophic levels can be measured
1. Each sample is dried in an oven 2. Then weighed 3. Then burned in a bomb calorimeter 4. Energy produced passes to known mass of water and temperature rise of water measured 5. Energy released per gram calculated
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How is energy lost between trophic levels?
Animals never eat all of the available food, cannot digest all food they eat, use energy to respire, lose heat energy to surroundings, lose energy in urine and faeces
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How can human activities manipulate the flow of energy through ecosystems?
Replacing natural vegetation and fauna with crops and livestock, deflecting natural succession to maintain grassland, soil improvement, irrigation, fertilisers, removal of competing weeds and pests, selective breeding/genetic engineering and shelter
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What stages occur within the nitrogen cycle?
1. Nitrogen Fixation 2. Ammonification 3. Nitrification 4. Denitrification
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What is nitrogen fixation?
Atmospheric nitrogen is reduced to ammonia by bacteria called rhizobium
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What is ammonification?
Decomposers convert nitrogen compounds in dead animals and plants into ammonium compounds by nitrosomonas
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What is nitrification?
Ammonium is converted first into nitrites, then nitrates by nitrobacter
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What is denitrification?
Nitrates in the soil are converted into nitrogen gas by denitrifying bacteria via anaerobic respiration
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Define primary succession
The development of communities from bare ground
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How does primary succession occur?
1. Pioneer community grow on bare rock 2. Rock is eroded and dead organisms build up 3. Produces soil for larger plants 4. Larger plants continue to succeed smaller plants until final stable community is established (climax community)
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Define pioneer species
First species to colonise an abiotic area
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Define deflected succession
When deflection stops or is interfered with
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Define secondary succession
The sequential community changes that happen following deflection, when the environment is altered somehow
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What factors affects population size?
1. Availability of resources 2. Nesting sites 3. Shelter 4. Predation 5. Parasites
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Define carrying capacity
The maximum population size that can be maintained over a period of time in that particular habitat
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Define conservation
Maintenance of existing biodiversity, including interspecies, genetic, intraspecies, habitat and ecosystem diversity
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Define preservation
Maintenance of habitats and ecosystems in their present condition by minimising human impact
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What are the reasons for conversation?
Ethical, economic (many plant & animal species are rich food source, natural predators drive out pests, conservation of wild/rare species boosts local tourism), social (microorganisms and plants can be a source of medicinal drugs)
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How is small-scale timber production undergone?
Coppicing - cutting a tree trunk close to the ground to encourage growth (also done by rotational coppicing by dividing trees into 3 sections and cut one section a year)
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How is large-scale timber production undergone?
Clear-felling of trees - can destroy areas of woodland, felled trees are replaced
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Other cards in this set

Card 2


Define population


A group of organisms of the same species who live in the same place at the same time and breed

Card 3


Define community


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Card 4


Define habitat


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Card 5


What are abiotic factors?


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