Name: _______________________ Date: ___________ Period: ______
Biotic Index Lab
*Please Turn This Assignment In**
Directions:
Determine the stream quality of the three sample streams (A, B and C) by calculating the biotic index value for
each stream and interpreting your results. Use the reference information and example to help you in your
research of the three streams. Show all work for full credit. Please turn this assignment in!
Reference Information:
• Invertebrates are categorized into three different classes:
•
For this activity different taxa are denoted by their background shading
Taxa Type
Taxa Type
Taxa Type
Taxa Type
Formula:
Biotic Index = 2(n Class I) + (n Class II)
Where n is the number of taxa. The different kinds of species found, not the number of individual
invertebrates found.
Biotic Index Range
Stream Evaluation
10 or greater
Clean Stream
3–9
Moderate Pollution
0 -2
Gross Pollution
Example:
Organism
Mayfly Nymph
# of Taxa (n)
3
Class
I
Stonefly Nymph
4
I
Cranefly Larva
3
II
Aquatic Sowbug
1
II
Lung Snail
1
III
Biotic Index = 2(n Class I) + (n Class II)
Biotic Index = 2(7) + (4) = 18
Therefore the stream is clean because 18 is greater than 10
Your Turn!!
Stream ‘A’
1) Complete the table using the reference information
2) Calculate the biotic index using the formula (Show your work!)
3) Evaluate the quality of the stream
Organism
# of Taxa (n)
Class
Salamander
2
Scud
3
Tubifex
Worms
Flatworm
1
Fairy Shrimp
4
Leech
3
Water Penny
1
1
Stream ‘A’ Quality Evaluation Answer: _____________
Stream ‘B’
1) Count the number of taxa present for each organism by looking at the water sample from stream ‘B’
2) Complete the table
3) Calculate the biotic index using the formula (Show your work!)
4) Evaluate the quality of the stream
Organism
# of Taxa (n)
Class
Fingernail
Clam
Water Penny
Lung Snail
Riffle Beetle
Fish
Stream ‘B’ Quality Evaluation Answer: _____________
Stream ‘B’ Water Sample
Stream ‘C’
1) Complete the table
2) Calculate the biotic index using the formula
3) Evaluate the quality of the stream
Organism
# of Taxa (n)
Class
Stream ‘C’ Quality Evaluation Answer: _____________
Stream ‘C’ Water Sample