Life processes in the biosphere

• Adaptation

  Organisms must be adapted to the range of abiotic and biotic conditions in their habitat to survive
• Evolution


  1. Production of new characteristics by random mutations

  2. Natural selection

  3. Increased chance of survival for better adapted individuals
• Range of tolerance


  The range within which organisms can survive
• A population with a large gene pool is likely to survive environmental changes more effectively as some individuals will have adapted to new conditions
• Understanding adaptation


  • Important for environmental scientists in decision-making for conservation management
  • Helps decide how to manage the environment and provide conditions that increase chances of survival for high conservation priority species
• Survival and distribution of species is mainly controlled by abiotic factors
• Important abiotic factors affecting species distribution

  • Light
  • pH
  • Water
  • Mineral nutrients
• If abiotic conditions are within the range of tolerance of a species, it must also be adapted to the inter-species relationships involved with biotic factors
• Important biotic factors affecting species distribution

  • Food supply
  • Pollination
  • Seed dispersal
  • Disease
• Ecological succession


  1. Colonisation of new habitats

  2. Changing habitat conditions

  3. Replacement of pioneer species by new colonisers

  4. Development of climax community
• Sere


  Sequence of stages in ecological succession as an uncolonized habitat develops into the climax community
• Types of seres


  • Hydrosere
  • Lithosere
  • Psammosere
• Hydrosere


  • Colonisation of freshwater areas by algae, rooting plants, floating plants
  • Gradual filling in of lake with sediments and organic matter
  • Transition to drier conditions and tree colonisation
• Lithosere


  • Colonisation of bare rock by lichens, mosses, grasses, then trees
  • Gradual accumulation of soil and improvement of abiotic conditions
• Psammosere


  • Colonisation of sand dunes, stabilisation of sand, improvement of nutrient and water availability
• Plagioclimax


  A new community of species that develops when human activity regularly deflects the climax community, preventing it from reforming
• Examples of plagioclimax communities

  • Grassland
  • Lowland heathland
  • Moorland
• Conservation of climax communities

  Typically involves minimal human impact
• Conservation of plagioclimax communities


  Usually involves maintenance of the traditional activities that created them
• Approaches used to manage plagioclimax communities

  • Grazing
  • Burning
  • Mowing
  • Ploughing
  • Felling at intervals
  • Cutting
• Secondary succession


  Type of ecological succession in which plants and animals recolonize a habitat after a major disturbance that significantly alters an area but has not rendered it completely lifeless
• Secondary succession is distinguished from primary succession, in which a biological community develops where no life had existed previously
• Population dynamics


  The study of changes in the size and age structure of populations over time
• Simpson's Diversity Index


  A measure of diversity which takes into account the number of species present, as well as the relative abundance of each species
• The higher the value of D, the higher the biodiversity
• As species richness and evenness increase, so diversity increases
• New species are currently being discovered at a rate of about 20,000 per year
• Current estimates for the total number of species vary significantly from 5 to 100 million, with only two million species having so far been named
• Some ecosystems are so inaccessible, for example, the deep-sea floor and the canopy of tropical rainforests, that they have yet to be fully researched