Distribution of Organisms and Environment

Distribution of Organisms and Environment

1. organisms live in different places because environment varies

   • distribution of an organism is where it is found many factors affect where an organism is found
     • - Temperature - Availability of water - Availability of oxygen and CO2 - Availability of nutrients - Amount of light
       • These may mean an organism may be common in certain areas and less common in other areas E.G daisies in middle of field and none under the trees due to light levels
         • to study the distribution of organisms you could use quadrats in two areas then compare them or study how the oranisms' distribution changes by placing quadrats along a transect.
           • Quadrats: study the distribution of small organisms
             • basically place a quadrat in a random area (usually 1M squared) and count the organisms inside that quadrat.
           • Transects: study distribution of organisms along a line
             • For example to see if a plant becomes less common as you move from a hedge to the middle of the field
               • to do this you can simply measure a line using a tape measure then count the number of organisms which touch that line( which you're interested in) or use quadrats which can be placed next to each other on the line or at intervals

2. work out population size multiply mean number of organisms per quadrat by the total area the quadrats covered

3. when collecting environmental data

   • Reliability
     • Quadarts and Transects are good tools
       • but the results must be reliable and reproducible
         • larger sample size is better in terms of reliable results and reproducible results
   • Validity
     • to be valid results must be reliable
       • all variables need to be controlled
         • the real question is whether a difference in distribution is due to only 1 environmental factor
           • random samples improve validity