Organisms and their Environment

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Distribution of Organisms

There are a number of physical factors that affect organisms:

  • temperature
  • availability of nutrients
  • amount of light 
  • availability of water
  • availability of oxygen & carbon dioxide 
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Random Sampling with Quadrats

A student wants to know how many species of plants there are in her school field. 

1. the student sets out a sample area

2. a 1m^2 quadrat is placed randomly in the field. 

3. the number of different plant species found in the quadrat is recorded

4. a mean is calculated from the data by adding up the number of speceies found in each quadrat & dividing by the total number of quadrats used

5. the total number of organisms in the school field can the be estimated by multiplying the mean number by the total area of the school field 

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Sampling Along a Transect

A student wants to find out if the shade of a big hedge in his school field affects the number of species of plants that are able to grow near it. 

1. the student stretches some string from the hedge out into the field, producing a transect. 

2. a quadrat is placed at 5m intervals along the transect moving away from the hedge

3. the student records the number of plant species found in each quadrat along the transect

4. to increase the reliability of the data, the student repeats his investigation b using more transects 

3 of 4

Sampling Along a Transect

A student wants to find out if the shade of a big hedge in his school field affects the number of species of plants that are able to grow near it. 

1. the student stretches some string from the hedge out into the field, producing a transect. 

2. a quadrat is placed at 5m intervals along the transect moving away from the hedge

3. the student records the number of plant species found in each quadrat along the transect

4. to increase the reliability of the data, the student repeats his investigation b using more transects 

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