UNIT 4 ECOLOGY

• Ecosystem


  All the living organisms and non-living components in a particular environment
• Habitat


  Where a particular organism lives in an ecosystem
• Population


  All the individuals of one species in a habitat
• Community


  All the populations of organisms in the same habitat
• Producer


  The organism at the start of a food chain that synthesises its own food molecules
• Primary consumer


  Eats producers
• Secondary consumer


  Eats primary consumers
• Tertiary consumer


  Eats secondary consumers
• Predator


  Consumers that kill and eat other animals
• Prey


  Animals that are eaten by other animals
• Abiotic factors


  Non-living features of an ecosystem
• Biotic factors


  Living features of an ecosystem
• Biodiversity


  The range of different species in an ecosystem
• In an ecosystem, plants compete for light, space, water and nutrients
• In an ecosystem, animals compete for food, territory and mates
• Within a community each species depends on other species for food, shelter, pollination, seed dispersal etc.
• A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant
• Abiotic factors


  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH & mineral content
  • Wind intensity and direction
  • Carbon dioxide levels
  • Oxygen levels
• Biotic factors


  • Availability of food
  • New predators being introduced
  • New diseases
  • Competition with other organisms
• Biodiversity is greater when there are many different habitats in an ecosystem
• Small populations are in greater danger of dying out if an ecosystem is disrupted in some way
• Ecosystems with high levels of biodiversity help to provide the resources needed to sustain life, including human life
• Ecosystems with higher biodiversity offer economic benefits by sustaining the resources needed for agriculture, fishing and forestry
• Examples of human interactions with local ecosystems that can diminish or destroy biodiversity


  • Building, quarrying, farming, clearing woods and other activities that destroy habitats
  • The destruction of peat bogs, and other areas of peat, to produce garden compost
  • Pollution of streams, rivers and lakes by sewage, toxic wastes and fertilisers
• Programmes to reduce negative effects on ecosystems and biodiversity


  • Breeding programmes for endangered species
  • Protecting and regenerating habitats
  • Reintroducing wider field margins and hedgerows in areas of monoculture
  • Recycling resources rather than dumping waste in landfill
  • Production of peat-free composts
  • Reducing deforestation and carbon dioxide emissions
• Random sampling to compare number of organisms in different habitats


  1. Use a quadrat

  2. Count the number of squares that contain the organism

  3. Do this in a random selection of locations

  4. Take the mean number of squares

  5. Scale up to find the number in the whole area
• Sampling along a transect to see a change caused by a particular abiotic factor


  1. Lay out a line

  2. Place your quadrat at each location along that line, in order

  3. Count the number of squares that contain the organism you're interested in

  4. Look for a pattern in the results
• How destroying peat bogs reduces biodiversity


  1. When dug up, the peat decomposes, releasing CO2 to the atmosphere (global warming climate change)

  2. When burnt, peat releases CO2 into the atmosphere (global warming climate change)

  3. Peat bogs are unique habitats – so if destroyed, this leads to many species dying out
• How water pollution reduces biodiversity


  1. Fertiliser from farms washes in rivers/lakes/streams

  2. This causes algae to grow more quickly on the surface

  3. This blocks sunlight

  4. Plants at the bottom of the water die (no photosynthesis)

  5. Decomposers break down the dead plants and use up the oxygen in the water