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• Levels of organisation in an ecosystem


  • Individual
  • Population
  • Community
  • Ecosystem
• Ecosystem


  The interaction between the living components and non-living components
• Factors that plants may compete for


  • Light
  • Space
  • Water
  • Mineral ions from soil
• Factors that animals might compete for


  • Food
  • Mates
  • Territory
• Intraspecific competition


  Competition within a species
• Interspecific competition


  Competition between different species
• Interdependence


  Different species in a ecosystem depend on each other for various resources, if one species is removed, the whole community may be affected
• Stable community


  A community in which all the biotic factors (the different species) and all abiotic factors are balanced so that population sizes remain relatively constant
• Abiotic factors


  Non-living factors
• Abiotic factors that may affect an ecosystem

  • Light intensity
  • Temperature
  • Moisture
  • Soil pH and mineral content
  • Wind intensity and direction
  • Carbon dioxide level
  • Oxygen level
• Light intensity affects an ecosystem


  Different species of plants may have different optimum light intensities for growth
• Temperature affects an ecosystem


  Different species of plants and animals may have different optimum temperatures for growth and survival
• Soil pH affects an ecosystem

  • Certain plants may grow better in either alkaline or acidic soil
  • Soil pH may affect the appearance of the plant eg. colour of hydrangea
• Moisture level affects an ecosystem


  • Many plants cannot survive in waterlogged soil as their roots cannot respire
  • Certain plants are adapted to high moisture levels
• Wind intensity affects an ecosystem

  Plant seeds are more likely to germinate in locations with lower wind intensity, which may also attract animals that depend on the plant to live nearby
• Soil mineral content affects an ecosystem


  Most plants require a high level of soil minerals to grow well
• Plants adapted to low soil mineral content


  • Carnivorous plants catch insects to compensate for the low level of soil mineral content
• Carbon dioxide concentration affects an ecosystem


  Higher carbon dioxide concentration leads to more plant growth
• Oxygen concentration affects an ecosystem


  Aquatic animals cannot survive in areas with low oxygen concentration
• Biotic factors that may affect an ecosystem


  • Food
  • New predators
  • New pathogens
  • Competition
• Adaptations


  Features that enable organisms to survive in their living environment
• Examples of extreme living environments

  • High temperature
  • High pressure
  • High salt concentration
• Where extremophile bacteria can be found


  • In deep sea vents
• Food chain


  Describes the feeding relationships between organisms and the resultant stages of biomass transfer
• Trophic levels


  The stages in a food chain
• Trophic levels


  • Represented by numbers, starting from 1
  • Numbered according to how far along the organism is in the food chain
• Trophic level 1


  Plants and algae which make their own food (through photosynthesis) - called producers
• Trophic level 2


  Herbivores which eat producers - called primary consumers
• Trophic level 3


  Carnivores that eat herbivores - called secondary consumers
• Trophic level 4


  Carnivores that eat other carnivores - called tertiary consumers
• Apex predator


  A carnivore with no predators
• How decomposers break down dead matter


  1. Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules

  2. Soluble small food molecules then diffuse into the microorganisms
• Biomass


  The dry mass of all of the living organisms in an area
• Biodiversity


  The variety of the different species on earth or within an ecosystem
• Importance of biodiversity


  • To maintain the stability of an ecosystem
• How to calculate the efficiency of biomass transfer


  efficiency = (energy transferred / total energy available) × 100
• How biodiversity ensures the stability of an ecosystem


  It reduces the dependence on particular species for resources eg. food and shelter, so that even if one species is removed other species can still survive
• Rapid rise in human population

  Increase in standard of living
• Where pollution occurs


  • Air
  • Land
  • Water
• Water pollutants


  • Sewage
  • Fertiliser
  • Chemicals