Quadrat
From Wikipedia, the free encyclopedia
A quadrat is a measured and marked rectangle, often a square, used in ecology to isolate a sample.
When an ecologist wants to know how many organisms there are in a particular habitat,it would not be feasible to count them all.Instead,he would be forced to count a smaller representative part of the population,called a sample.Sampling of plants,or animals that do not move much(such as snails),can be can be done using a sampling square called a quadrat(people often mistakenly call quadrats "quadrants".A quadrant is quite different:it is a quarter of a circle).A quadrat is usually made from metal,wood or plastic.A suitable size of a quadrat depends on the size of the organisms being sampled.For example,to count plants growing on a school field,you could use a quadrat with sides 0.5or 1 meter in length.
It is important that sampling in an area is carried out at random,to avoid bias.For example,if you were sampling from a school field,but for convenience only placed quadrats next to a path,this might not give you a sample that was representative of the whole field.It would be an unrepresentative,or bias,sample.It usually consists of a 100 squares.One way you can sample randomly is to place the quadrats at coordinates on a numbered grid.You can try this for yourself.
How to measure: 1.Select two areas of the school feild that seem to have a different plant community(your hypothesis is that the communities are different). 2.In the first area,lay out two 10 meter tape measures to form the sides of a square. 3.Generate a pair of random numbers using the random number function on a calculator. 4.Use the pair of numbers as coordinates to position the quadrat in the large square. 5.Count the numbers of each plant species in the quadrat. 6.Repeat the nine more quadrats in the area of the field,then move the tapes to the second part of the field and use the same method to carry out ten quadrat samples there. 7.Summarise your results as a table and plot them as two bar charts showing the total numbers of each species in the two areas of the field.
[edit] External links
 |
This ecology-related article is a stub. You can help Wikipedia by expanding it. |
