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Quadrats and Transects
What you need to know
Reflections and Exam tips
Distribution of living things
Where do we find living things? Good question!
Living things are found where the requirements that they need are vailable. Distribution is about where we find living things (their spread).
Plants and animals need:
Exams require you to be aware that some of these environmental/physical factors (abiotic factors) can be measured using Datalogging sensors e.g. Oxygen sensors, light sensors, pH meters
Sometimes it is necessary to counts living things in order to find out about their distribution. At times its is difficult to count individual organisms because:
In such circumstances, we may have to take a sample.
Some key definitions first:
There are many ways of sampling, including: Quadrats and transects
A quadrat is a square frame, usually 1m x 1m.
How to use a quadrat
Randon sampling- is done where there are no obvious variations in the habitat
Systematic sampling- is done where there are obvious variations in the habitat
Validity and reproducibility
The more throws, the more valid and reproducible the results are
Random sampling and the fixed size of quadrats also make the results more valid and reproducible
Leaf size estimation
A common investigation concerns the variations in leaf size depending on how exposed they are to sunlight.
Exposed leaves tend to have a smaller surface area than those hidden behind.
Estimating leaf area
1.Place the leaf on square paper .............›2. Trace the Leaf...................................› 3. Count squares which are half full or mor, ignore the rest (x).