Question

The range of potential scores of Index of Biotic Integrity is-

• A. 10- 20
• B. 12- 60
• C. 10- 40
• D. 10- 30

Hint:

Karr's biological index uses a scale of 1, 3, and 5 for its 12 metrics.
This yields a convenient, easy-to-remember score range of 12 to 60.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The Index of Biotic Integrity (IBI) was developed by James Karr in 1981 to evaluate the ecological health of water bodies, particularly streams, based on the composition and functional characteristics of their fish or macroinvertebrate communities.
Key Formula or Approach:
The biological index consists of 12 distinct metrics reflecting species richness, trophic composition, abundance, and condition.
Each metric is graded on a qualitative scale:
- Poor condition: 1 point
- Moderate condition: 3 points
- Good condition: 5 points
The total IBI score is the sum of the scores of these 12 metrics:
\[ \text{Total Score} = \sum_{i=1}^{12} \text{Metric Score}_i \]

Step 2: Detailed Explanation:
Let us calculate the range of potential scores:
- The minimum potential score occurs when all 12 metrics score the minimum value of 1 point:
\[ \text{Minimum Score} = 12 \times 1 = 12 \]
- The maximum potential score occurs when all 12 metrics score the maximum value of 5 points:
\[ \text{Maximum Score} = 12 \times 5 = 60 \]
Thus, the potential range of total scores is from 12 to 60.

Step 3: Final Answer:
The potential score range for the Index of Biotic Integrity is 12-60.