Diversity Index Lab

The measure of the biodiversity of organisms in a given area is known as the diversity index. The diversity index values will vary between 0, which would indicate no diversity, and 1, which is very diverse. Any values above 0.5 usually indicate a relatively diverse population. For example, a healthy forest or woodland should have a diversity index of 0.7. An area that is not very diverse, like a cornfield, might have a diversity index of 0.02 or less.

In this investigation, each bag of candy represents a different habitat. Each color represents a different plant in the habitat.

Materials

notebook paper
1 small bag of fruit candies of different colors
1 small bag of chocolate candies of different colors
2 dishes or plastic containers

Procedures
1. Pour each bag of candy into a separate container or dish so you can see all the colors in each bag. Assign a letter to each color of chocolate candies and fruit candies, and record your key.

2. Without looking, randomly choose nine candies from each container one at a time. Using the letter symbols, record each candy as it is removed. Record your results using the following table.

3. Count the number of species in each sample. Each color represents a different plant in the habitat.
Example: R, Bl, G, G, Y, Y, G, Bl, Bl has 4 species of plants.

4. Calculate the diversity index of both the bag of chocolate candies and fruit candies number of species using the following formula for each trial: Diversity Index = number of samples

5. Repeat the process two more times to verify your results. Make sure you replace the candy back into the container after each trial. Record the diversity index after each trial in the table. Calculate the average from the three trials.

Average

Analysis
1. How did the diversity index values vary from the chocolate candies and fruit candies?

2. Which habitat is the most diverse?

3. Why are populations that are more diverse usually more stable?

4. Why would a diverse population be more resistant to disease, predation, and invasion?

5. Assume two habitats have the same number of species. One habitat is predominantly one species with just a few of the other species. The other habitat has equal numbers of all the different species. Which will have the highest diversity index?

6. Why do you think the process was repeated three times?

7. There are many human-caused losses of biodiversity, such as habitat destruction and introduction of invasive species. Are there any natural events that could alter the diversity index?

8. How do invasive species change the diversity index?

9. What do you think would happen to a habitat if the plant diversity declines?