**Measuring diversity and the reasons for maintaining it **

**Ex-situ and in-situ conservation**

**Measuring diversity and the reasons for maintaining it**

**Measuring diversity**

Species diversity is described as the number of species in a community. The more species, the higher the diversity. What if there are two separate communities like this:

Community #1 has 150 individuals per each of 20 different species (3000 individuals in total)

Community #2 has 10 individuals per each of 19 species, and 2990 individuals of the last species (3000 individuals in total)

It doesn’t take a complex formula to figure out that community #1 is far more diverse compared to community #2, despite them having the same number of species and individuals. **The distribution of individuals to species** is important in determining a community’s diversity.

The above example is easy enough, but for most purposes a **formula **is needed. This formula measures the **index of diversity**, which is simply a measure of diversity in a community. By calculating it and obtaining a **numerical value**, different communities can be easily compared.

Right, here it comes…

No, don’t run away yet! Wait and see how easy it is to work out.

**D** = Diversity index

**N** = total number of all organisms

**n** = total number of organisms of each species

**Σ **= sum of

Now it’s simply a matter of replacing numbers. Look, I made it all purple so you would enjoy looking at it. Let’s work out the index of diversity for community #1 (from above).

Firstly, we need a value for N. What’s the total number of organisms? 3000. Sorted.

Next, we need a value for N – 1. No calculators! …2999, sorted.

Finally, we need a value for n and n – 1. n = 150, while n – 1 = 149……..