Distribution of organisms

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  • Distribution of organisms
    • Organisms live in different places because the environment varies
      • The distribution of an organism is where an organism is found
      • Where an organism is found is affected by environmental factors, such as:
        • The temperature
        • How much water there is
        • The amount of light
        • How much oxygen and carbon dioxide there is
        • If there are enough nutrients around
      • An organism might be more common in one area than another due to differences in environment factor between the two areas
      • To study the distribution of an organism you can use quadrats or transects
    • Use quadrats to study the distribution of small organisms
      • You can see how common an organism is in two different areas- these are called sample areas
      • 1) Place a 1m2 quadrant on the ground at a random point within the first sample area.
        • E.g. divide the area into a grid and use random number tables to pick coordinates
      • 2) Count all the organisms within the quadrat
      • 3) Repeat steps 1 and 2 as many times as you can
      • 4) work out the mean number of organisms per quadrat with the first sample area
      • 5) repeat steps 1-4 in the second sample area
      • Finally compare the two means
        • E.g. you might find 1 daisy per m2 in the shade, and 7 daisies per m2 in the open field
    • Population size
      • Population size= mean No of organisms per 1m2 quadrat X total area ( in m2 )
        • E.g. there are 7 daisies per m2 in a 100m2 field. so population size= 7x100=700 daisies


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