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Biodiversity. Tuesday, 07 May 2013. What do we understand by species diversity? How is Simpson’s Diversity Index used as a measure of species diversity?. Biodiversity. Species diversity: the number of different species and the number of individuals of each species within any one community. - PowerPoint PPT Presentation
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BiodiversityWhat do we understand by species diversity?
How is Simpson’s Diversity Index used as a measure of species diversity?
Saturday 22 April 2023
Biodiversity Species diversity: the number of different
species and the number of individuals of each species within any one community.
Genetic diversity: the variety of genes possessed by individuals that make up any one species
Ecosystem diversity: the range of different habitats within a particular area
Species Diversity Can be used to measure biodiversity
Two components:• Number of different species in a given
area• The proportion of the community that is
made up of an individual species
Measuring species diversity
Species found Number in habitat X
Number in habitat Y
A 10 3B 10 5C 10 2D 10 36E 10 4No. of species 5 5No. of individuals
50 50
Measuring species diversity
The table on the previous slide does not show us much about the differences in the two habitats.
In both cases the number of species and individuals are the same
If we now calculate species diversity, then we get a different picture.
Measuring species diversity
d= N(n-1) .
Σn(n-1)
Where: d = species diversity indexN = total number of organisms of
all speciesn = total number of organisms of
each speciesΣ= sum of
Calculate the species diversity index of each habitat from the table on the previous slide.
d= N(n-1) .
Σn(n-1)
Species n in habitat X
n(n-1) n in habitat Y
n(n-1)
A 10 3B 10 5C 10 2D 10 36E 10 4
Σn(n-1) Σn(n-1)
Species n in habitat X
n(n-1) n in habitat Y
n(n-1)
A 10 10(9)=90
3 3(2)= 6
B 10 10(9)=90
5 5(4)= 20
C 10 10(9)=90
2 2(1) = 2
D 10 10(9)=90
36 36(35)= 1260
E 10 10(9)=90
4 4(3)= 12
Σn(n-1) 450 Σn(n-1) 1300
Use this to calculate the species diversity index
Now we can calculate the species diversity index:
Habitat Xd = 50 (49) = 4250 = 5.44
450 450 Habitat Y
d = 50 (49) = 2450 = 1.881300 450
The higher the value, the greater the species diversity
Species Diversity & human activities
What is the influence of deforestation and the impact of agriculture on species diversity?
Saturday 22 April 2023
The impact of agriculture
Impact of agriculture Natural ecosystems develop from complex
communities
Agricultural ecosystems are carefully controlled by humans
Farmers select crops that are more productive.
The frequency of alleles is reduced
For economic reasons, the crop yield needs to be large.
Any one area can only support a certain amount of biomass – if most of this area is taken up by a crop, then there is little area left for anything else
Crops are sprayed with pesticide and man made fertiliser.
This further disadvantages and excludes species that the farmer does not want
This all acts to reduce species diversity
Impact of deforestation
Impact of deforestation Forests contain many varied and different
habitats = high species diversity
Permanent clearing of the forest leads to loss of habitats and in turn loss of biodiversity
What might you want to clear a forest for?
You should be able to… Explain what we mean by species diversity.
Explain how Simpson’s Diversity index is used to compare habitats
Calculate Simpson’s Diversity when given the formula
Outline the effects of agriculture and deforestation on species diversity