Life processes in the biosphere

• Range of tolerance

  The range of a specific factor that any member of the population can survive
• Organisms/populations with narrow range of tolerance

  • More vulnerable to changing conditions
  • More likely to have low genetic diversity
• Abiotic factors

  • Light
  • Water
  • Nutrients
  • pH
  • Dissolved oxygen
• Biotic factors

  • Food
  • Control of predation
  • Pollination
  • Seed dispersal
• Adaptations important for survival of abiotic factors

  • High chlorophyll levels in woodland floor plants to survive in shade
  • Polarised eye lenses in fish-eating birds to see into clear water
  • Moist skin in frogs to survive
  • Ability to survive in nutrient-poor grasslands
  • Exoskeletons to survive low pH
  • High oxygen requirement in fish species
• Management methods

  • Coppicing to increase light
  • No fertiliser use
  • Adding crushed lime to neutralise acids
  • Reducing river width to increase turbulence
  • Providing dead wood for food for woodpeckers
  • Reducing predation risk
  • Providing essential pollinators
  • Providing essential dispersal species
• Species

  A group of organisms that resemble each other more than members of other species, naturally breed with other members of the same species to produce fertile offspring, and do not naturally interbreed with members of other species
• Ecological community

  A community of interacting species and their abiotic environment
• Habitat

  The place where a species or community of species is found
• Indigenous species

  A native species that is naturally in that area
• Endemic species

  A species that is indigenous to an area and is not found naturally anywhere else
• Biosphere

  All the living organisms of Earth and the parts of the hydrosphere, atmosphere and lithosphere where they are found
• Biodiversity


  The variety and abundance of living organisms in an area
• Ecological succession


  1. Colonisation and pioneer species

  2. Seres (sequence of changing communities)
• Changes during succession

  • Increased vegetation density and height produces less extreme temperatures, reduced wind, increased humidity, reduced light, increased soil depth and organic matter, more reliable water and nutrients
  • Reduced ability to survive extreme abiotic conditions
  • Increased reliance on animal pollination and seed dispersal
  • Increase in inter-species relationships
• Climax community

  • High biodiversity
  • High biomass
  • Tallest vegetation
  • Least extreme abiotic conditions
  • Most inter-species relationships
  • Greatest ecological stability
• Deflected succession

  Succession altered by human activity producing a different community e.g grazing
• Plagioclimax communities

  Grassland, heathland, reedbeds, coppiced woodland
• Secondary succession


  Ecological succession restarting after ecosystem disturbance or ceasing of processes that maintained a plagioclimax
• Methods of maintaining plagioclimax communities

  • Grazing
  • Mowing
  • Burning
  • Coppicing
  • Pollarding
• Effects of different grazing methods


  • Different grazers have their own food preferences and height of eating, producing different plant communities
• Effects of mowing


  • Mechanical cutting cuts all plants to the same height, timing controls survival of non-grasses
• Effects of burning

  • Removes old, often dead vegetation, roots may survive and regrow, dormant seeds stimulated to germinate
• Coppicing

  Trees cut to ground level on a rotational cycle, regrow from cut stump, creates areas of different ages to increase habitat and wildlife diversity
• Pollarding


  Cutting higher up to prevent livestock/deer eating regrowth
• Management of desirable species


  • Release programmes
  • Habitat management
• Control of undesirable species


  • Culling/eradication (trapping, poisoning, shooting)
  • Manual removal
  • Selective herbicide use
  • Biological control
  • Grazing
• What is a K selected species?

  
  

  Species that breed at a young age and produce many offspring, recover from over-exploitation relatively rapidly
• What is an R selected species?

  Species that breed at an older age and produce few young, recover from over-exploitation slowly