A line transect uses a tape/string stretched across the ground in a straight line. Any organism the crosses the line is recorded
A belt transect is a *****, usually a metre wide, marked by putting a second line parallel to the first. The species occurring within the belt between the lines are recorded
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Measuring abundance
Abundance is the number of individuals of a species within a given space
Frequency – the likelihood of a species occurring in a quadrat. Useful when species is hard to count; gives quick idea of general distribution within area. Doesn’t give info about density and detailed distrubution.
Percentage cover – an estimate of the area within a quadrat that a plant species covers. Useful when species is difficult to count, data can be collected quickly and individual plants don’t need to be counted. Less useful in overlapping layers
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Random sampling
Used to avoid bias
Lay out 2 tape measures at right angles along 2 sides of the area
Get coordinates using random number generator eg calculator
Place quadrat in the coordinates
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Quadrats
Size of quadrat – depends on size of plant of animal being counted and how they are distributed. Large species, large quadrats. Groups of species, lots of small quadrats
Number of sample quadrats to record – more quadrats means more reliable results. More species in the area means more quadrats needs to be used
Position of each quadrat – random sampling must be used.
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Mark-release-recapture
A known number of animals are caught, marked in some way and then released
Later a given number of individuals is collected randomly
Marked number of individuals is recorded
Techniques assumes:
Proportion of marked to unmarked individuals in 2nd sample is the same as the proportion of marked to unmarked individuals in the population as a whole
Marked individuals distribute themselves evenly within the rest of the population
No immigration into or emigration out of the population
Few deaths and births within the population
Method of marking is not toxic and it doesn’t make the individual more obvious to predators
Mark not lost during investigation
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Analysing data
qualitative data can be presented in a graph/ table to make comparisons easier and more precise
however when comparing 2 sets of data different factors may affect it
significance tests can be used to show if the results are due to a particular facter or just chance
statistical tests used to calculate the strength and direction of any correlation between 2 variables eg spearmans rank
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