GCSE Biology (AQA)

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Quadrats & Transects

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Ecology Organisation of an Ecosystem

Quadrats & Transects

2:05 Understanding Feeding Relationships
Spec 4.7.2.1
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  • Quadrats and transects are tools used to sample ecosystems and study the distribution and abundance of organisms.
  • Distribution refers to the location of organisms, such as grass being less abundant under trees.
  • Abundance indicates the number of individuals per species, like the number of grass plants in an area.
  • A quadrat is a square frame placed on the ground to record organisms within its boundaries, often subdivided into smaller sections for detailed analysis.
  • The size of a quadrat can vary, commonly being 25 centimeters squared.
  • Quadrats help in counting the percentage coverage of plants, the number of individual organisms, or the number of different species.
  • Placement of quadrats can be random, determined by using tape measures at right angles and a random number generator to select coordinates.
  • At least 10 samples are usually taken to ensure random sampling and reduce bias.
  • A transect involves placing quadrats at regular intervals along a line to systematically sample and observe changes in distribution or abundance across a specific area, like a pathway or shoreline.
  • This method of using a transect is systematic and not random.

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