Ecology

• Ecology is the study of the interactions between living things (organisms) and between organisms and their environment
• Environment


  All the external factors that influence an organism
• Biosphere


  That part of the planet containing living organisms
• Ecosystem


  A group of clearly distinguished organisms that interact with their environment as a unit
• Examples of ecosystems


  • Temperate deciduous forest
  • Desert
  • Tropical rain forest
  • Grassland
  • Freshwater
  • Marine
• Habitat


  The place where a plant or animal lives
• Population


  All the members of the same species living in a particular area
• Community


  All the different populations in an area
• Abiotic factors


  Non-living factors
• Biotic factors


  Living factors
• Climatic factors


  Weather over a long period of time
• Edaphic factors


  Relate to soil
• The four categories of factors that influence the life and distribution of organisms are abiotic, biotic, climatic and edaphic factors
• These four factors can affect living things by their variations in levels and from season to season
• Climatic factors and most of the edaphic factors are also abiotic factors
• Abiotic factors


  • Altitude
  • Aspect (the direction a surface faces)
  • Steepness
  • Exposure
  • Currents
• Higher altitudes


  • Cooler, wetter and windier than lower altitudes
  • Trees and other producers cannot live at higher altitudes
• North-facing slopes


  • Cooler and darker than south-facing slopes
  • More plants grow on south-facing slopes
• Biotic factors


  • Food
  • Competition
  • Predation
  • Parasitism
  • Pollination
  • Seed dispersal
  • Human intervention
• More food available


  • Greater the number of organisms that will survive
• Competition


  • Plants and animals fight for scarce resources such as food, space, mates and shelter
• Climatic factors


  • Temperature
  • Rainfall
  • Humidity (the amount of water vapour in the air)
  • Day length
  • Light intensity
  • Wind
  • Salinity (salt concentration)
• Temperature


  • Affects the rate of reactions in living things
  • Higher temperatures cause rapid plant growth in summer
  • Lower temperatures cause hibernation in hedgehogs and frogs in winter
• Rainfall


  • Provides the water that is essential for life
  • Only plants such as cacti can live in areas of low rainfall (deserts)
  • Plants in tropical rain forests require high and regular rainfall (along with high temperature)
• Edaphic factors


  • Soil pH
  • Soil type
  • Organic matter in the soil
  • Water content
  • Air content
  • Mineral content
• Acid soils


  • pH less than 7
  • Support bog moss and heather
• Neutral soils


  • pH values close to 7
  • Preferred by most plants
• Alkaline soils


  • pH values greater than 7
  • Preferred by lime-loving plants, e.g. birdsfoot trefoil and bee orchid
• Sandy soils


  • Large soil particles
  • Good drainage and air content
  • Low mineral and water content
  • Few earthworms (due to lack of decayed organic matter or humus)
  • Maram grass has long, deep roots to absorb moisture deep down
• Clay soils


  • Small soil particles
  • Impermeable to water and air
  • Easily waterlogged
  • Plants do not grow well as the soil is too wet and difficult for roots to penetrate
• Aquatic environments


  Ponds, lakes, oceans, rivers, streams
• Aquatic environments


  • Temperature is less important as it doesn't vary so rapidly
  • Water is plentiful, but lack of light may be a problem
• Light in aquatic environments

  • Water interferes with the penetration of light
  • Plants limited to upper layers of water
  • Attached plants can only grow in shallow waters
  • Animals can be found at great depths, feeding off organisms that fall down from upper layers
• Currents in aquatic environments

  • Flowing water will cause plants to be carried away if not attached
  • Animals better able to resist currents as they can move
• Wave action in aquatic environments

  • Waves create currents and cause physical damage to organisms
  • Seaweeds avoid this by being flexible
  • Animals often protected by a shell
• Salt content in aquatic environments

  • Most organisms adapted to either freshwater or saltwater environments
  • Some organisms (especially in rock pools) can survive changes in salinity due to rain or fresh water
• Oxygen concentration in aquatic environments

  • Much lower than in air
  • Affects plant and animal life
  • Organisms must be able to extract oxygen from the water
• Every ecosystem requires a constant input of energy from an external source in order to function properly
• The Sun is the primary source of energy for our planet
• Producers


  Organisms that carry out photosynthesis