Distribution of organisms

• BIOTIC FACTORS are any living component that affects another organism.
• ABIOTIC FACTORS are non-living conditions which can influence where plants or animals live.
• Biodiversity of an ecosystem is affected by

  biotic and abiotic factors and human activities,

  such as over-hunting and habitat destruction.

  Some factors increase biodiversity, many cause

  a decrease in biodiversity.
• Grazing – biotic factor
• Grazing is a biotic factor that can affect species

  diversity in grassland. For example, rabbits are

  unselective grazers and their affect on grassland

  diversity depends on levels of grazing.
• pH and temperature are abiotic factors that can

  affect the variety of fish species in an ecosystem.
• Abiotic factor are non-living factors.

  
  

  For example

  
  

  – temperature

  
  

  - moisture

  
  

  - light intensity

  
  

  - pH

  
  

  - soil moisture
• Some plant species prefer particular pH

  ranges.

  
  

  An increase in acidity in ponds can kill fish species.
• pH –

  pH probe or chemical test

  (universal indicator)

  
  

  -

  be sure to wipe the probe

  before

  use to remove any residue from

  previous sample.

  
  

  Temperature - Thermometer

  
  

  - allow time for the reading to

  settle before noting down

  the temperature.
• A quadrat can be used to compare the numbers of

  different types of plants in an area. A quadrat cannot be used to count organisms that are able to move.
• -Quadrats should always be

  placed randomly

  
  

  -A number of quadrats should

  be placed to get a reliable

  average
• A pooter is useful for catching small and fragile organisms like insects as it prevents them from being damaged.
• As the bacterial level increases the O2

  level decreases because the bacteria use it

  up in respiration in polluted water.