There are 2 types of sampling: random sampling and systematic sampling.
Random sampling
> avoids bias
a) Quadrats
 a square frame that marks off area of ground or water
 used to identify the different species present and/or to measure abundance
 use results to calculate:
Systematic sampling
Correlation  plot a scatter graph or calculate correlation coefficient (r)
*strength of correlation = how close the points are to the straight line
1. Pearson's correlation coefficient
use with 2 sets of data when data:
 rank data for each variable and assess the difference between the rankings
Simpson's Index of Diversity
When you have collected information about the abundance of he species in the are you are studying, use the results to calculate a value for species diversity in that area
Random sampling
 should be used when an area looks reasonably uniform
 there is no clear pattern to the way the species are distributed
> avoids bias
a) Quadrats
 a square frame that marks off area of ground or water
 used to identify the different species present and/or to measure abundance
 use results to calculate:
 species frequency: measure of chance of a particular species being found within any one quadrat
 species density: measure of how many individuals there are per unit area
 use results to estimate:
 percentage cover: the percentage of area inside the quadrat that is occupied by each species
 abundance scale (e.g.: BraunBlanquet scale) for number and plant cover
b) Markreleaserecapture: estimating the population size of mobile organisms
 As many individuals caught as possible
 Individuals get marked (in a way that will not affect its future chances of survival)
 Marked individuals are counted (a)
 Marked individuals are returned to their habitats to mix randomly with their population
 After enough time has elapsed (at least 24 hours, maximum __ hours), a large sample is recaptured
6. Number of marked (b) and unmarked individuals are counted
_____________________

(c)
Systematic sampling
 investigate species distribution where physical conditions change
 e.g.: altitude, soil moisture content, soil pH, exposure/ light intensity
 record identity of organisms that touch the line at set distances
 data shown as a drawing
b) Belt transect
 place quadrats at regular intervals along line > record abundance of species within quadrat
 data plotted as bar chart or kite diagram
Correlation  plot a scatter graph or calculate correlation coefficient (r)
*strength of correlation = how close the points are to the straight line
1. Pearson's correlation coefficient
use with 2 sets of data when data:
 continuous data has been collected
 must be normally distributed
 may be a linear correlation (draw scatter diagram first)
 quantitative data collected as measurements/counts
 number of paired observations is at least 5, ideally 10 or more
2. Spearman's rank correlation
use when data:
 data points are independent of each other
 data is correlated, but not linear (draw scatter diagram first)
 number of paired observations: at least 5, ideally between 10 and 30
 make a null hypothesis
Simpson's Index of Diversity
When you have collected information about the abundance of he species in the are you are studying, use the results to calculate a value for species diversity in that area
 n = total number of organisms in one species
 N = total number of organisms of all species
 D = Index of Diversity
18.1 Biodiversity Biodiversity is much more than a list of all the species in a particular area. a) define the terms species, ecosystem and niche b) explain that biodiversity is considered at three different levels:
• variation in ecosystems or habitats
• the number of species and their relative abundance
• genetic variation within each species
c) explain the importance of random sampling in determining the biodiversity of an area d) use suitable methods, such as frame quadrats, line transects, belt transects and markreleaserecapture, to assess the distribution and abundance of organisms in a local area e) use Spearman’s rank correlation and Pearson’s linear correlation to analyse the relationships between the distribution and abundance of species and abiotic or biotic factors 
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