Download Shannon Weiner Lab

Name__________________________
Date________________
Shannon-Weiner Diversity Index Lab
Background:
A study of biodiversity requires an understanding of several terms and concepts:
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Biodiversity is the population heterogeneity of a community, or the number of
species in a given area.
Species diversity is a combination of species richness and species evenness.
Species richness is the total number of species present in the community.
Species evenness is the relative distribution of individuals among the species
present in a community.
Evenness contrasts with dominance, and is maximized when all species have the
same number of individuals.
Maintaining biodiversity is important for a variety of reasons.
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New medicines have been discovered by screening diverse ecosystems.
Genetic diversity in crop plants and their wild relatives provides breeders with the
"raw material" needed to select for traits in response to new agricultural
challenges.
Diverse communities are generally less susceptible to perturbation than similar
but less diverse communities.
Biodiversity provides an aesthetic value that humans find appealing.
When pollution is present or a human disturbance has occurred in a community,
biodiversity is typically lower than in an undisturbed community. The Shannon Index is
a measurement used to compare diversity between habitat samples. This comparison can
be between two different habitats or a comparison of one habitat over time.
The Shannon-Weiner index is determined by both the number of species and the even
distribution of individuals among those species (relative dominance). It indicates the
degree of uncertainty of predicting the species of a given individual picked at random
from the community. In other words, if the diversity is high, you have a poor chance of
correctly predicting the species of the next individual picked at random. The actual
formula for the Shannon-Weiner Diversity Index is:
Where the Relative Abundance
And where:
(pi): pi = ni /N
ni = number of individuals in species i
N = total number of individuals in all species
S = the number of species
Shannon-Weiner Index (H) (the uncertainty of predicting the species) will range from 0
for a community with a single species, to over 7 for a very diverse community.
Other Shannon measurements include “S” which is the number of species present in the
sample, and E which is the evenness of those species. If the E value is 1, the species are
equally present in the habitat. The formula to find E is: E = H / ln (S).
APES
Bethpage HS
1
Mr. Clark
Name__________________________
Date________________
Procedure: Obtain a jar with beans representing habitat one and habitat two. Assume
each type of bean is a new species in the habitat. You will need to use a copy of the
natural log tables
Fill in the charts for each Habitat using Shannon’s Diversity Index.
Data for Habitat One:
Species (i)
Number of
that species
in sample
Pi (number of
that species /
total)
ln (Pi)
Pi *ln (Pi)
_____Total
from all
species
Should add
up to 1.0
Use the
natural log
table
H = _____
(add this column
and remove the
negative sign)
Questions from Habitat One:
1. What is the H value and what use would this value have if I did a second sample from
this habitat three years from now (assuming it was real animals and not food)?
2. What would be the E value (evenness) for this habitat?
APES
Bethpage HS
2
Mr. Clark
Name__________________________
Data for Habitat Two:
Species (i)
Date________________
Number of
that species
in sample
Pi (number
of that
species/total)
ln (Pi)
Pi *ln (Pi)
_____Total
from all
species
Should add
up to 1.0
Use the
natural log
table
(add this column
and remove the
negative sign)
H = _____
Questions from Habitat two:
1. What is the H value for habitat two?
2. Compare the H value of habitat one and two and use that comparison to describe
which habitat has more diversity to it.
3. What is the E value for Habitat two?
4. List two advantages to using a Shannon Index instead of simply a population count to
determine diversity.
5. List two disadvantages to using a Shannon Index to determine diversity.
APES
Bethpage HS
3
Mr. Clark
Name__________________________
Shannon Index Practice Calculation
Date________________
Shannon Index Calculation
Sample I
Pi=(N/T) Ln(pi)
pi*ln(pi)
Species N
A
24
-0.81
B
20
-0.99
C
7
-2.04
D
3
-2.89
Total
54
1
H'=
1
H'=
Sample II
A
48
B
40
C
14
D
6
Total
108
Sample III
A
24
-0.88
B
20
-1.06
C
7
-2.11
D
3
-2.96
E
3
-2.96
F
1
-4.06
Total
58
1
H'=
Note that:
Note that the index is invariant with respect to sample size, but rare species add to
it. In other words, the higher the “H” value ________________________________
APES
Bethpage HS
4
Mr. Clark
Name__________________________
Answers to Practice Calculation
Date________________
Shannon Index Calculation
Sample I
Pi=(N/T) Ln(pi)
pi*ln(pi)
Species N
A
24
0.44
-0.81
-0.36
B
20
0.37
-0.99
-0.37
C
7
0.13
-2.04
-0.26
D
3
0.06
-2.89
-0.16
Total
54
1
H'= 1.15
Sample II
A
48
0.44
-0.81
-0.36
B
40
0.37
-0.99
-0.37
C
14
0.13
-2.04
-0.26
D
6
0.06
-2.89
-0.16
Total
108
1
H'= 1.15
Sample III
A
24
0.41
-0.88
-0.37
B
20
0.34
-1.06
-0.37
C
7
0.12
-2.11
-0.26
D
3
0.05
-2.96
-0.15
E
3
0.05
-2.96
-0.15
F
1
0.02
-4.06
-0.07
Total
58
1
H'= 1.36
Note that the index is invariant with respect to sample size, but rare species add to
it. In other words, the higher the “H” value the more diverse the community.
APES
Bethpage HS
5
Mr. Clark