This document discusses biodiversity and methods for measuring it. It explains that biodiversity has three main components: species diversity, ecosystem diversity, and genetic diversity. It also describes different categories for measuring diversity within habitats (alpha diversity), between habitats (beta diversity), and across landscapes (gamma diversity). The document focuses on the Simpson index, which measures the probability that two randomly selected individuals belong to the same species. It provides the formula for calculating the Simpson index and discusses how it can be adapted to better represent diversity. An example calculation using species data from a woodland is also included.

2. BY
PRIYANKA KUJUR
M.SC. ZOOLOGY

3.  Number and variety of organisms within a particular
area.
 3 main components :
 Species diversity = no. of different species and no. of
individuals of each species within
any one community.
 Ecosystem diversity = diversity of ecosystems within
an area.
 Genetic diversity = genetic variability of species.

4.  Using functional categories
ecosystem, species, genetic
 Using theoretical categories
Alpha
Beta
Gamma

5.  α diversity : diversity within one habitat.
 β diversity : diversity along environmental gradient.
Diversity comparable between 2
adjacent ecosystems.
 γ diversity : diversity of the whole landscape.

6.  To get a better description of the community we need
to get a measure of species richness and evenness of
their distribution.
 Over 60 indices are used in ecology to measure
biodiversity.
 Indices are used to measure proportional abundance.
 Two major forms :
Dominance Indices (eg. Simpson index)
Information Indices (eg. Shannon Weiner index)

7.  The Simpson index was introduced in 1949
by Edward H. Simpson.
 This index assumes that the proportion of
individuals in an area indicates their importance to
diversity.
 So, it measures not only diversity but dominance as
well.
 Simpson’s index considered a dominance index
because it weights towards the abundance of the
most common species.

8.  Can actually refer to any one of 3 closely related
indices.
 Simpson's Index (D) measures the probability
that two individuals randomly selected from a
sample will belong to the same species.
 There are two versions of the formula for
calculating D.
D = (n / N)2
n = the total number of organisms of a particular species
N = the total number of organisms of all species

9.  The value of D ranges between 0 and 1.
 With this index, 0 represents infinite diversity and 1,
no diversity. That is, the bigger the value of D, the
lower the diversity.
 This is neither intuitive nor logical, so to get over
this problem, D is often subtracted from 1 to give:

10.  Simpson's Index of Diversity (1 - D)
 The value of this index also ranges between 0 and 1,
but now, the greater the value, the greater the sample
diversity.
 This makes more sense. In this case, the index
represents the probability that two individuals
randomly selected from a sample will belong to
different species.

11.  Simpson's Reciprocal Index (1 / D)
 It provides the number of equally common
categories (e.g., species) that will produce the
observed Simpson's index.
 Ranges between 0 and total no. of species
collected.
 The higher the value, the greater the diversity.

12. The diversity of the ground flora in a woodland.
Species Number (n) n(n-1)
Woodrush 2 2
Holly (seedlings) 8 56
Bramble 1 0
Yorkshire Fog 1 0
Sedge 3 6
Total (N) 15 64

13. Putting the figures into the formula for Simpson's
Index
D = 0.3 (Simpson's Index)
Then:
 Simpson's Index of Diversity 1 - D = 1 - 0.3 = 0.7
 Simpson's Reciprocal Index 1 / D = 1 / 0.3 = 3.3

14. Low species diversity suggests:
 Relatively few successful species in the habitat.
 The environment is quite stressful with relatively few
ecological niches and only a few organisms are really
well adapted to that environment.
 Food webs are relatively simple.
 Changes in the environment would probably have
quite serious effects.

15. High species diversity suggests:
 A greater number of successful species and a more
stable ecosystem.
 More ecological niches are available and the
environment is less likely to be hostile.
 Complex food webs.
 Environmental changes is less likely to be damaging
to the ecosystem as a whole.

16.  Does not require all species be represented.
 Measures chance that two individuals are from same
species
 Sensitive to changes in common species
 Weighted towards most abundant species
 Opposite of dominance