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

Question

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

Note: If you cannot obtain 2 bags of candy, you can use anything that has at least 5 different colors. For example, colored thumb tacks, colored paper clips, etc.

Procedures
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.
For example, red=R, purple=P

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. Example, R for red, Bl for blue, and so on.

Color

Color

Color

Color

Color

Color

Color

Color

Color
Number of different colors in total for this trial
Fruit Candy Trial 1

Fruit Candy Trial 2

Fruit Candy Trial 3

Chocolate Candy Trial 1

Chocolate Candy Trial 2

Chocolate Candy Trial 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 (R, Bl, G, and Y).
You will then be dividing the # of different species (which is the # of different colors) in the next step.

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

Example:
R, Bl, G, G, Y, Y, G, Bl, Bl is 4/9 = 0.44
The # of species is 4 because there are 4 different colors.

Put the diversity index for each of the 6 trials in this table. This will always be a number less than 1, but more than zero.
Calculate the average from the three trials.
Diversity Index Table

Sample
Trial 1
Trial 2
Trial 3
Average
Fruit

Chocolate

Analysis (Make sure you scroll down to see all 7 questions.)

Please answer each in full sentences.
Is the chocolate or fruit habitat the most diverse?

In regards to disease and predation, why are diverse communities more stable? Please answer in at least 2 sentences.

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

Why do you think the process was repeated three times? Please answer this in relation to any scientific experiment.

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

How do invasive species change the diversity index?

What do you think would happen to a habitat if the plant diversity declines? Relate this question to producers and consumers.

Answer 1

Diversity Index Table

| Sample | Trial 1 | Trial 2 | Trial 3 | Average | |----------|---------|---------|---------|-----------| | Fruit | | | | | | Chocolate| | | | |

(You will fill in the table based on your own findings from the candy trials.)

Analysis Questions

1. Is the chocolate or fruit habitat the most diverse? The habitat that is most diverse can be determined by comparing the diversity index values of the fruit and chocolate candy trials. The one with the higher average diversity index indicates a greater variety of species, making it the more diverse habitat.

2. In regards to disease and predation, why are diverse communities more stable? Diverse communities are more stable because they can better withstand diseases and predation due to the variety of organisms present. A high number of species means that if one species is affected by disease or predation, there are other species that can fulfill ecological roles, allowing the community to maintain its functions.

3. Assume two habitats have the same number of species. Habitat A is predominantly one species with just a few of the other species, while Habitat B has equal numbers of all the different species. Which will have the highest diversity index? Habitat B, with equal numbers of all the different species, will have the highest diversity index. This is because diversity index measures not only the number of different species but also their relative abundance. Since Habitat B has a more even distribution of species, it will result in a higher index.

4. Why do you think the process was repeated three times? Please answer this in relation to any scientific experiment. The process was repeated three times to ensure reliability and accuracy of the results. In scientific experiments, multiple trials help to account for variability and reduce errors, allowing researchers to obtain a more accurate average and draw valid conclusions about the diversity of the habitats.

5. There are many human-caused losses of biodiversity, such as habitat destruction and introduction of invasive species. What are some natural events that could alter the diversity index? Natural events such as wildfires, floods, hurricanes, and droughts can significantly alter the diversity index. These events can destroy habitats, lead to the extinction of certain species, or promote the dominance of others, changing the balance of species and their numbers in an ecosystem.

6. How do invasive species change the diversity index? Invasive species can lower the diversity index by outcompeting native species for resources such as food, space, and light. As they proliferate, they often displace or eliminate native species, leading to a reduction in the overall number of different species present in the habitat.

7. What do you think would happen to a habitat if the plant diversity declines? Relate this question to producers and consumers. If plant diversity declines in a habitat, it would lead to a decrease in the variety of food sources for consumers (herbivores and subsequently predators). This could disrupt food webs, reduce the availability of habitats for animals, and ultimately threaten the stability of the entire ecosystem, as producers play a crucial role in supporting all levels of consumers within the food chain.