distribution of organisims

• Biotic factors are living factors which can affect biodiversity in an area.

  Examples of biotic factors are:

  • competition for resources
  • disease
  • grazing
  • predation
• Abiotic factors are non-living factors which can affect biodiversity in an area.

  Examples of abiotic factors are:

  • light intensity
  • soil moisture
  • pH
  • temperature
• Light Meter: light intensity

  • all measurements should be taken at the same time
  • No shadows should be cast from the user
  • The reliability of the results should be checked by taking many samples
• Moisture meter: soil moisture

  • the probe should be pushed to the same depth each time
  • The probe should be wiped each time to avoid contamination
  • The reliability of the results can be checked by taking many samples
• pH meter: pH of soil/water

  • the probe should be pushed to the same depth each time
  • The probe should be wiped each time to avoid contamination
  • The reliability of the results can be checked by taking many samples
• Thermometer/temperature probe: temperature of soil/water

  • Theremometer should be left for one minute to allow an accurate reading
  • the probe should be pushed to the same depth each time
  • The probe should be wiped each time to avoid contamination
  • The reliability of the results can be checked by taking many samples
• An indicator species by their presence or absence will indicate environmental levels of pollution in an area.
• Overgrazing occurs when the herbivore population is high, more animals feed on limited plants in the habitat, this means plant species can disappear. Biodiversity is reduced
• Under-grazing occurs when the population is reduced. Dominant plants outcompete less dominant plants and hold them in check. This means that they do not get the chance to grow. biodiversity is reduced.
• Morderate grazing increases biodiversity, grazing allows less dominant plants to survive. Reduction in dominant species allow more light and soil nutrients for less dominant plants.
• pitfall traps

  • used for small invertebrates living on the ground (slugs, spiders, centipedes, ants)
  • They need to be checked regularly as organisms like spiders could eat the other organisms
  • The leaves are used not to trick the insects but to camouflage the trap so predators such as birds do not eat all the insects inside.
  • The hole needs to be deep enough so invertebrates fall in and cannot escape
  • There needs to be a drainage hole so the organisms do not drown

  
• Quadrats

  • used to sample slow moving animals and plants in an ecosystem
  • The grid is usually divided into a number of smaller squares to make counting organisms easier
  • they should be thrown randomly to avoid biased results
  • It should be repeated several times for more reliable results