ecosystems

• define ecosystem


  All the living organisms found in one area, and the non-living aspects of their environment.

  • known as dyamic = abiotic + biotic factors
• biotic 


  living features of an ecosystem e.g. predators disease
• abiotic 


  non living feature of an ecosystem e.g. light, temperature
• what is biomass and how is it transferred?

  The total weight of living matter in a certain area transferred up trophic levels through consumption = carbon mass or dry mass of tissue
• formula for biomass

  efficiency = biomass transferred / biomass intake x100
• how can human activities affect biomass transfer?

  • light, water, temperature maximised
  • increased nutrients in soil
  • pests and weeds removed
  • growth rates boosted through steroids, selective breeding
• outline the roles of microorganisms in the nitrogen cycle

  • nitrogen-fixing bacteria e.g. Rhizobium in roots and Azotobacter in soil = converts gaseous nitrogen into ammonia
  • Nitrifying bacteria = Nitrosomonas convert ammonium compounds into nitrites = Nitrobacter then converts nitrites to nitrates
• outline the role of organisms in the carbon cycle ?

  • respiration of plants and animals ass CO2 into the atmosphere
  • photosynthesis of plants removes CO2 from atmosphere
  • decomposers decay plants and animals materials into CO2
• what is meant by primary succession?

  Where an area previously devoid of life is colonised by a community of organisms
• summarise the process of primary

  • pioneer species, able to survive harsh conditions, colonise the area
  • they die, decompose, and add nutrients to the ground
  • over time, this allows more complex organisms to survive
• what is the climax community and how is it reached?

  the final stage of succession where the ecosystem is balanced and stable. it is reached when the soil is rich enough to support large trees or shrubs and the environment is longer changing
• what is deflected succession?

  where succession is interrupted, usually by human interference
• what is sampling?


  Selecting a group of individuals that will represnt the whole target population. allow us to measure the distribution and abundance of organisms
• ways to sample

  Quadrats =used in small areas random + % cover calculated

  transects = larger area sample taken over belt transect
• Define carrying capacity 


  the maximum population size that a habitat can support defined by the presence of limiting factors
• Give factors that limit the maximum size of a population

  • food
  • water
  • light
  • oxygen
  • nesting site
  • shelter
  • parasites
  • preadators
• describe the pattern of a typical predator-prey relationship in terms of population change?

  • prey is eaten by predator = predator pop ^ prey pop decrease
  • fewer prey = competition for food
• intraspecific competition 


  competition between organisms of the same species
• interspecific competition 


  competition between organisms of different species
• conservation 


  maintains biodiversity of a habitat by allowing sustainable use of the resources there
• preservation 


  maintains biodiversity of a habitat by minimising human impact
• reasons why we conserve and preserve habitats

  • economic = food source, natural pest control
  • social = many organism can be used in medicine
  • ethical = we have a responsibility to maintain habitats for future generations
• sustainability 


  using resources in a way that also maintains them for future generations
• what methods allow sustainable use of an ecosystem resources?

  timber production = coppicing to encourage growth

  fishing = stocks not depleted no overfishing
• Give an example of how humans effects are controlled in sensitive ecosytems?

  Galapagos islands

  = many species endangered due to hunting and tourism