Ecology

• Community

  Many different populations interact in the same habitat
• Ecosystem


  The interaction of a community with non-living (abiotic) parts of the environment
• Organisms

  • Adapted to live in the conditions of their environment
• Competition

  Can be within a species or between different species
• Things plants may compete for

  • Light
  • Space
  • Water
  • Mineral ions
• Things animals may compete for

  • Space
  • Food
  • Water
  • Mating partners
• Interdependence

  Organisms in a community depend on other organisms for vital services like food, shelter and reproduction
• The removal or addition of a species to the community can affect the populations of others greatly, as it changes prey or predator numbers
• Stable community

  Where all the biotic (living) and abiotic (non-living) factors are in balance, resulting in population sizes remaining roughly constant
• Abiotic factor

  A non-living factor
• Abiotic factors that can affect a community

  • Light intensity
  • Temperature
  • Moisture levels
  • Soil pH and mineral content
  • Wind intensity and direction
  • Carbon dioxide levels
  • Oxygen levels for aquatic animals
• Biotic factor

  A living factor
• Biotic factors that can affect a community

  • Food availability
  • New predators
  • New pathogens
  • Competition
• Types of adaptations

  • Structural
  • Behavioural
  • Functional
• Extremophiles

  Organisms that live in environments with extreme conditions like high temperatures, pressures or salt concentrations
• Adaptations for different scenarios

  • Cold climates: Smaller surface area to volume ratio, lots of insulation
  • Dry climates: Adaptations to kidneys, active in early morning/evening, larger surface area ratio
  • Plant adaptations: Curled leaves, extensive root systems, waxy cuticle, water storing tissue
• Producer

  Photosynthetic organisms (usually a green plant or algae) that make glucose through photosynthesis
• Primary consumer

  Organisms that eat the producers
• Secondary consumer

  Organisms that eat the primary consumers
• Tertiary consumer

  Organisms that eat the secondary consumers
• Transects and quadrats

  Tools used to work out the distribution and abundance of species in an ecosystem
• A stable community will show population cycles between the predators and prey
• Carbon cycle

  CO2 is removed from the air in photosynthesis and returned to the air through respiration and combustion
• Water cycle

  Water evaporates, forms clouds, and returns to land through precipitation
• Factors affecting decomposition rate

  • Temperature
  • Water
  • Availability of oxygen
• Compost

  Produced when biological material decays, used as a natural fertiliser
• Methane gas

  Produced by microorganisms decomposing waste anaerobically, can be burnt as a fuel
• Environmental changes affect the distribution of species in an ecosystem, such as changes in temperature, water availability, and atmospheric gas composition
• Biodiversity


  The variety of different species of organisms on Earth or within an ecosystem
• High biodiversity means the ecosystem will be stable.
• Many human activities are having a negative effect on biodiversity
• Ways human activities negatively impact biodiversity

  • More land used for houses, farming, shops, roads and factories, destroying habitats
  • Pollution killing plants and animals
  • Using up raw materials quicker than they are being produced
• The future of humans on Earth depends on maintaining biodiversity – for example for food and new medicines
• The impact of our activities is getting bigger as the population is increasing, as more resources are being used and more waste is being produced
• Negative human impacts on ecosystems

  • More land is being used for houses, farming, shops, roads and factories, which destroys habitats
  • Pollution kills plants and animals
  • Sewage, fertiliser and toxic chemicals pollute the water
  • Smoke and acidic gases pollute the air
  • Landfill and toxic chemicals can result in the pollution of the land
  • We are using up raw materials quicker than they are being produced
• Humans have only recently tried to reduce their impact
• Peat

  A material that forms when plant material has not fully decayed as there is not enough oxygen
• Peat bogs

  • They accumulate in acidic and waterlogged areas
  • They are a habitat for many species, in particular for migrating birds
  • They are being destroyed - drained for farming, used as compost, or dried to use as fuel as it contains carbon (releasing CO2 into the atmosphere)
  • They are being used up quicker than they are being formed, as the formation process is slow
• Deforestation


  The cutting down of a large number of trees in the same area, in order to use the land for something else
• Reasons for deforestation in tropical areas

  • Provide land for cattle and rice fields
  • To grow crops (e.g. sugarcane, maize) for biofuels which are used to produce energy