Enter the pollution tolerance value and the number of individuals for each species, as well as the total number of individuals of all species into the calculator to determine the Biotic Index.

## Biotic Index Formula

The following formula is used to calculate the Biotic Index.

BI = Σ (ai * ni) / N

Variables:

- BI is the Biotic Index ai is the pollution tolerance value of species i
- ni is the number of individuals of species i
- N is the total number of individuals of all species

To calculate the Biotic Index, multiply the pollution tolerance value of each species by the number of individuals of that species. Sum up these products for all species. Then, divide this sum by the total number of individuals of all species.

## What is a Biotic Index?

A Biotic Index is a scientific measurement tool used to assess the health of an ecosystem, particularly water bodies, by examining the presence, abundance, and diversity of various species, particularly invertebrates. These species are chosen because their sensitivity or tolerance to pollution, temperature changes, or other environmental factors can provide valuable information about the overall quality and health of the environment. The higher the biotic index, the more polluted the water is considered to be.

## How to Calculate Biotic Index?

The following steps outline how to calculate the Biotic Index using the given formula:

- First, determine the pollution tolerance value (ai) for each species.
- Next, determine the number of individuals (ni) for each species.
- Multiply the pollution tolerance value (ai) by the number of individuals (ni) for each species.
- Sum up all the results obtained in the previous step.
- Finally, divide the sum by the total number of individuals (N) of all species.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge:

pollution tolerance value (ai) = [2, 3, 4, 1]

number of individuals (ni) = [10, 15, 8, 12]

total number of individuals (N) = 45