20/11/08 Diversity To measure species diversity of an ecosystem/ habitat...we need to take into account the number of species and their relative abundance. •We can use the Simpson diversity index It is sometimes useful to have an overall measure of species richness in an ecosystem.The Simpson diversity index is one of the most commonly used. Diversity is often considered to be a function of both the number of different species present and the number of individuals of each species. A high index indicates high species diversity, whilst a low number indicates low diversity. D =N(N-1) Σ n(n-1) N= Total number of organisms n= Number of individuals of each species. •The highest the number, the higher the species diversity. EXAMPLE
ECOSYSTEM
A
B
C
D
Kidney Beans
17
3
8
31
White Beans
31
-
2
12
Chick Peas
19
28
54
24
Penne Pasta
1
9
3
2
Macaroni Pasta
1
-
-
-
Sunflower Rice
15
-
3
9
Rice
-
2
3
-
TOTAL
84
42
73
78
DIVERSITY
3.97
2.06
1.79
3.56
•From the table we see that A has the higher diversity and C has the lowest Diversity.
Diversity
To measure species diversity of an ecosystem/ habitat...we need to take into account the number of species and their relative abundance.
•We can use the Simpson diversity index
It is sometimes useful to have an overall measure of species richness in an ecosystem. The Simpson diversity index is one of the most commonly used. Diversity is often considered to be a function of both the number of different species present and the number of individuals of each species. A high index indicates high species diversity, whilst a low number indicates low diversity.
D = N(N-1)
Σ n(n-1)
N= Total number of organisms
n= Number of individuals of each species.
•The highest the number, the higher the species diversity.
EXAMPLE
•From the table we see that A has the higher diversity and C has the lowest Diversity.