Rain Forests

Biodiversity and the Health ©f a Plant (©©mmimity

& Real-World Question-

Some plant diseases are carried from plant to plant by specific insects and can spread quickly throughout a garden. If a garden only has plants that are susceptible to one of these diseases, the entire garden can be killed when an infection occurs. One such disease—necrotic leaf spot—can infect impatiens and other garden plants. Could biodiversity help prevent the spread of necrotic leaf spot? A simulation can help you answer this question. How does biodiversity affect the spread of a plant disease?

& Procedure-

1. On a piece of white paper, draw a square that measures 10 cm on each side. This represents a field. In the square, make a grid with five equal rows and five equal columns, as shown. Number the outer cells from 1 through 16, as shown. The inner cells are not numbered.

2. Cut 1.5-cm X 1.5-cm tiles from colored paper. Cut out 25 black tiles, 25 red tiles, 10 orange tiles, 10 yellow tiles, 5 green tiles, and 5 blue tiles. The black tiles represent a plant that has died from a disease. The other colors represent different plant species. For example, all the red tiles represent one plant species, all the blue tiles are another species, and each remaining color is a different species.

3. There are four rounds in this simulation. For each round, randomly distribute one plant per square as instructed. Roll the die once for each square, proceeding from square 1 to square 2, and so on through square 16.

Round 1—High Biodiversity

Distribute five red, five orange, five yellow, five green, and five blue plants in the field.

Round 2—Moderate Biodiversity

Distribute ten orange, ten yellow, and five green plants in the field.

Round 3—Low Biodiversity

Distribute all 25 of the red tiles in the field.

144 ♦ E CHAPTER 5 Conserving

Zig Leszczynski/Earth Scenes

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Round 4—Challenge

You want a harvest of as many red plants as possible. Decide how many red plants you will start with and whether you will plant any other species. Strategically place your tiles on the board. Follow steps 3 through 5 of the procedure.

4. To begin, place a black tile over half of square 1. Roll the die and use the Disease Key to see if the plant in square 1 is infected. If it is, cover it with the black tile. If not, remove the black tile. For example, suppose square 1 has an orange plant on it. Place a black tile over half of the square and roll the die. If you roll a 1, 3, 4, or 5, the plant does not get the disease, so remove the black tile. Proceed through all the squares until you have rolled the die 16 times.

5. If two plants of the same species are next to each other, the disease will spread from one to the other. Suppose squares 2 and 3 contain red plants. If you roll a 1 for square 2, the red plants on squares 2 and 3 die. In this case, the die does not need to be rolled for square 3. Similarly, if the inner square next to square 2 also contains a red plant, it dies and should be covered with a black tile.

6. For each round, record in a data table the number of tiles of each species you started with and the number of each species left alive at the end of the round.

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I Disease Key

Roll of Die

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