Unit 2 - Quadrat Sampling
How would you estimate the population of daisies in a field? Find out in this quiz.

Unit 2 - Quadrat Sampling

Ecology is the study of organisms in their habitats. The distribution of the organisms in a particular habitat can be affected by such physical factors as light, shelter from the wind and temperature. In order to try to make a scientific analysis of the organisms and their distribution in a habitat, quadrat sampling and line transects are useful tools. This GCSE Biology quiz is all about quadrat sampling.

Quadrats provide quantitative data either as numbers of individuals or as percentages. They are generally square, wire frames that are 50 cm by 50 cm and they can be used to estimate or count plants and slow moving animals. Their main limitation is that, due to their size, quadrats can only really be used to study the ecology of habitats where trees and bushes are widely spread or completely absent.

Quadrat sampling consists of randomly placing a quadrat on the ground in the area to be sampled. The position of the quadrat must not be chosen by the experimenter. Numbers and types of plants and animals can then be estimated for the whole habitat by counting them in the individual quadrats. The method is very useful as it is quick and easy to do but needs to be used with care to give valid results. When using quadrat sampling, either actual numbers can be counted or the percentage area covered by each species of plant is estimated. The results can then be scaled up to the area of the area being studied. If the total area of habitat is 200 square metres and the total area sampled using quadrats was 10 square metres, the quadrat count just needs multiplying by 20 to give a result for the full habitat.

Where the environment is not uniform, analysis along a line transect can also be carried out to establish gradual changes (across a field that is boggy at one side but dry at the other for example). A relationship between the number of organisms and the environmental conditions can be worked out using this method.

Try this quiz to see how much you know about using quadrat sampling when studying the ecology of habitats.

What do we call the square frame, usually 0.5m by 0.5m, used in sampling organisms?
A quadrant
A quadrangle
A quadrat
A quadratic
It is placed randomly in the field
What is the name for sampling along a line across the area of interest in the field?
This helps ecologists measure gradual changes from one side of a habitat to the other
Which of these is an abiotic factor?
Light intensity
Some plants are adapted to growing in low light conditions - they have large leaves and high levels of chlorophyll
How would you estimate the population of daisies in a field?
Random quadrat sampling, counting daisies in the frame then multiplying up to the whole field area
Counting every daisy in the field
Throwing the quadrat and counting how many daisies there are inside the frame
Counting all the daisies that touch the line
Just throwing a quadrat and hoping for the best is not random sampling. Scientists divide the field into coordinates and use a random number generator to select the sampling sites
What are biotic factors?
Non-living conditions
Living conditions
Dead conditions
Absent conditions
Biotic factors include competition and predation
What are abiotic factors?
Non-living conditions
Living conditions
Dead conditions
Absent conditions
Examples are temperature and humidity
Lichens can be found growing on quite exposed walls and on rocks. This is because they are adapted to withstand...
high temperatures
drying out (dessication)
the sun
They can survive long periods without water. They are called composite organisms because they are a symbiotic combination of fungus with an algae or cyanobacteria
Which of the following factors could limit the distribution of moss?
Grazing animals
That's because mosses are adapted to a moist environment
In a field, why would there be very few daisies under a tree?
Not enough light
Temperature too low
pH too acidic
The ground under a tree is also low in moisture and nutrients as the tree removes both for its own use
What do we call the place where an organism lives?
Its habit
Its habitat
Its ecosystem
Its environment
Each habitat has a unique set of plants and animals that are adapted for life there
You can find more about this topic by visiting BBC Bitesize - Organisation of an ecosystem

Author:  Donna Maria Davidson

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