Randomly sampling organisms - practical - Field investigations - OCR Gateway - GCSE Biology (Single Science) Revision - OCR Gateway

Example practical to randomly sample organisms in a field

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Greg Foot describes how to carry out a field investigation into distribution and abundance of organisms in an ecosystem

To measure the species richness on the school field in areas in which the grass is regularly and irregularly cut.

Choose a starting point on the school field in an area where the grass is often cut
Use numbers to generate a set of coordinates to place your first
Count the number of different plant within this quadrat (the species richness)
Return to your starting position and repeat steps two and three a further 14 times using different random numbers
Repeat steps one to four for a part of the school field where the grass is infrequently cut
Compare your results by calculating a for each location

Quadrat number	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Number of dandelions per quadrat on cut area	1	2	1	2	3	1	3	1	1	1	2	3	2	1	1
Number of dandelions per quadrat on uncut area	3	2	4	6	1	1	1	4	5	3	6	4	5	3	4

Number of dandelions per quadrat on cut area
1
2
1
2
3
1
3
1
1
1
2
3
2
1
1

Number of dandelions per quadrat on uncut area
3
2
4
6
1
1
1
4
5
3
6
4
5
3
4

What are the totals and means for the two different locations?

Draw conclusions from the data [4 marks]

What limitations might there be in drawing these conclusions?