distribution of organisms

• 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
• Scientists use equipment to measure abiotic factors within a particular environment. These are:

  • light intensity - light meter/probe
  • soil moisture - moisture meter
  • pH - pH meter/probe
  • temperature - thermometer
• • light meter - accidental covering of the probe, must be taken at the same time of day
• • soil moisture - must be placed at the same depth in the ground at each site and wiped clean between readings
• • pH probe - must be placed at the same depth and wiped clean between readings
• • temperature - thermometer must be held in the same position/depth at every sample point, time must be allowed for the reading to be taken
• there is one limitation and source of error that can apply to all equipment:

  • not enough samples are taken within the area
• A pitfall trap is used to measure small invertebrates that live on the ground.
• A limitation/source of error of pit fall traps:

  • Some animals within the trap may eat other captives
  • Not enough samples taken
• How to solve these issues with pitfall traps:

  • Check traps regularly and record
  • Set up more traps within the sample site
• A quadrat is used to sample plants and animals that don’t move
• Limitations of quadrats are :

  • not enough samples taken within the sample site
  • deliberately 'choosing' good spots
• With a paired statement key you will have to fill in questions or use it to identify diagrams of organisms.
• Both biotic and abiotic factors can increase or decrease biodiversity in an area and affect the distribution of organisms.
• human influences on biodiversity:

  • air pollution
  • water pollution
  • habitat destruction by deforestation
  • desertification
  • overfishing
• An indicator species by their presence or absence will indicate environmental quality/levels of pollution in an area.