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Download Measuring Biodiversity - Mrs Jones A
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Measuring Biodiversity You need to know: •What we mean by ‘biodiversity’ •How to estimate biodiversity Biodiversity Species richness Species evenness Number of different species in the habitat •Relative abundance of individual species •Qualitative measurement •Quantitative measurement Measuring species richness =Quantitative. • Count the number of different species. • Can use random quadrat technique • No need to identify the species •NB this measurement means that 1 daisy is worth as much as 100 buttercups…..so… Measuring species evenness = Quantitative • Plants – use random quadrats , count the number of each species or % cover. • Calculate RELATIVE abundance. Species evenness - Animals • Count individuals or use mark and recapture method. Mark individuals and release. = C1 Catch a sample of animals eg using sweep net Calculate total population = (C1 x C2) C3 After period of time catch new sample = C2 Count number of marked individuals = C3 Worked example:Two different fields were sampled for wildflowers Numbers of individuals Species Sample 1 Sample 2 Daisy 300 20 Dandelion 335 49 Buttercup 365 931 Total 1000 1000 Which field do you think is the most biodiverse, and why? A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance. As species richness and evenness increase, so diversity increases. Simpson's Diversity Index is a measure of diversity which takes into account both richness and evenness. Simpsons diversity index D = 1 - [ Σ(n / N)2 ] D = diversity of habitat Σ = sum of n = the total number of organisms of a particular species or percentage cover N = the total number of organisms of all species or % cover Using 1- means that as D increases so does the diversity. Work out the Simpsons Diversity index for the 2 fields. Species Daisy Dandelion Buttercup Total Species Daisy Dandelion Buttercup Sum Σ 1-Σ n Numbers of individuals Sample 1 Sample 2 300 20 335 49 365 931 1000 1000 n/N (n/N)² Now try this example on your own. Species n Woodrush 2 Holly 8 Bramble 1 Yorkshire fog 1 Sedge 3 n/N (n/N)² Ans. Simpsons index of diversity for this area = 0.7 The results that you have just used were collected from 1 quadrat. Is this a reliable indication of the diversity of the habitat? Explain your answer.
