# 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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