Ecosystems

• Outline the levels of organisation in an ecosystem

  individual, population, community, ecosystem
• Define population


  All the organisms of one species in a habitat
• Define community


  All of the populations of different species living together in a habitat.
• Define ecosystem


  is the both and and the abiotic parts of an environment and how there interact?
• Organism within a community are described as being 'interdependent'. What does this mean?

  Organisms are dependant upon each other

  A change in the population of one species can affect other populations within a community
• What are biotic factors?

  Living factors of the environment e.g. food, competition and predation
• Whare abiotic factors? Give some examples

  Non-Living aspects of an ecosystem eg temperature, water availability, light intensity, polluntants
• Give Some examples of interdependence in a community

  Plants depend on pollinators e.g. bees

  Herbivores are dependent on plants

  Animals are dependent on mates
• Describe how communities are affected by environmental conditions

  environmental conditions affect the abundance and distribution of organism within communities

  eg light intensity affects the rate of photosythesis in producers.
• Describe how communities are affected by pollutants

  Toxic chemicals bioaccumulate in food chains to deadly concentrations at higher tropic levels.

  
  

  Fertilisers that contaminate water sources can cause eutrophication

  
  

  Air Pollution can affect the ability of some plants
• Describe how competition affects communities

  - the presence of competitors affects population distribution and size

  - if one species is better adapted to survive in a certain environment, it will outcompete other species, causing their populations to decline
• Describe how predation affects communities

  ● Predation affects prey populations within a community

  ● e.g. if the number of predators decreases, the number of prey will increase as fewer are killed

  ● Populations of all other organisms within the food chain will also be affected
• What does a food chain show?

  It describes the feeding relationships between organisms and the resultant stages of biomass transfer.
• Define biomass


  The total mass of living material
• What are trophic levels?

  The stages in a food chain
• What are producers the first trophic level?

  Producers provide all biomass for the food chain
• Why are there rarely more than four or five trophic levels in a food chain?

  Above this, there is insufficient energy to support another breeding population
• Describe a food chain

  producer, primary consumer, secondary consumer, tertiary consumer