Ecologists investigated the diversity of invertebrate species in two different aquatic habitats: a slow-flowing stream and a fast-flowing stream.
Table 1 shows the raw data for the number of individuals of five invertebrate species found in a sample from the fast-flowing stream.
| Invertebrate species | Number of individuals (nnn) |
|---|---|
| Mayfly nymph | 4 |
| Stonefly nymph | 12 |
| Freshwater shrimp | 8 |
| Caddisfly larva | 6 |
| Water beetle | 10 |
Suggest one reason why the ecologists used the index of diversity rather than just species richness (the number of different species) to compare the two habitats.
The ecologists used this equation to calculate the index of diversity (ddd):
d=1−∑(nN)2 d = 1 - \sum \left(\frac{n}{N}\right)^2 d=1−∑(Nn)2where nnn is the number of individuals of each species and NNN is the total number of individuals of all species.
Use this equation and the data in Table 1 to calculate the index of diversity for this habitat.
