Distribution Of Organisms

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Key Terms

  • Interspecific Competition: Competition between different species
  • Intraspecific Competition: Competition in the same species
  • Repeatable: The original experimenter repeats the investigation using the same method and equipment and obtains the same results
  • Reproducible: A different experimenter repeats the investigation using a different method and equipment and obtains the same results

Factors affecting the Distribution Of Organisms:

Availability of Water:

  • Water means that the plants can flower and set seeds faster

Oxygen and Carbon Dioxide Levels:

  • Some organisms can survive well in areas with little oxygen, but most need a high level of oxygen
  • Plants which live in areas with high carbon dioxide levels are more vulnerable to mosquitos
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Factors affecting the Distribution of Organisms


  • A cold climate may limit the amount of photosynthesis carried out so organisms may not grow as big

Nutrients/ Minerals: 

  • Carnivorous plants (Eg. Venus Flytrap) can live in areas with less nutrients as they eat insects instead
  • Other plants may find it difficult to survive in areas with less nutrients as they cannot grow

Light Intensity:

  • Most plants need a lot of light for photosynthesis so they can grow
  • Some plants have adapted so they can live in areas with less light
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Random Sampling

You use one quadrat which is placed in random co-ordinates inside a measured area

Random co-ordinates must be generated completely randomly- eg picking out of a hat or a random number generator

You count the number of organisms which you are measuring inside the quadrat and note down each result

You must repeat the experiment multiple times as we cannot control some factors, eg. light intensity and amount of nutrients in the ground

You take the average of the repeated results

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A line transect stretches a tape measure between 2 points, usually with some variation in factors, eg. half in the shade, half in the sun

You use a quadrat to sample the number of organisms in the quadrat at regualr intervals along the tape measure- eg. every metre

You can also measure other factors along the way

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