1. Biodiversity What do we understand by species diversity?
Wednesday, 14 November 2018
What do we understand by species diversity?
How is Simpson’s Diversity Index used as a measure of species diversity?

2. 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

3. 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

5. Measuring species diversity
Species found
Number in habitat X
Number in habitat Y A 10 3 B 5 C 2 D 36 E 4
No. of species
No. of individuals 50

6. 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.

7. Measuring species diversity
d= N(n-1) .
Σn(n-1)
Where: d = species diversity index
N = total number of organisms of all species
n = total number of organisms of each species
Σ= sum of

8. Calculate the species diversity index of each habitat from the table on the previous slide.
d= N(n-1) .
Σn(n-1)

9. Species
n in habitat X
n(n-1)
n in habitat Y A 10 3 B 5 C 2 D 36 E 4
Σn(n-1)

10. Species
n in habitat X
n(n-1)
n in habitat Y A 10
10(9)=90 3
3(2)= 6 B 5
5(4)= 20 C 2
2(1) = 2 D 36
36(35)= 1260 E 4
4(3)= 12
Σn(n-1)
450
1300
Use this to calculate the species diversity index

11. Now we can calculate the species diversity index: Habitat X 450 450
Habitat Y
d = 50 (49) = 2450 = 1.88
The higher the value, the greater the species diversity

12. Species Diversity & human activities
Wednesday, 14 November 2018
Species Diversity & human activities
What is the influence of deforestation and the impact of agriculture on species diversity?

13. The impact of agriculture

14. Impact of agriculture
Natural ecosystems develop from complex communities
Agricultural ecosystems are carefully controlled by humans

15. 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

16. 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

17. Impact of deforestation

18. 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?

19. 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