What Do Plants Need?

In an introductory discussion, students identify the physical needs of animals and then speculate on the needs of plants. With teacher guidance, students then design an experiment that can take place in the classroom to test whether or not plants need light and water in order to grow. This prepares them to conduct the associated activity in which sunflower seeds are planted in plastic cups, and once germinated, are exposed to different conditions. In a classroom setting it is easy to test for the effects of light versus darkness, and watered versus non-watered conditions. During exposure of the plants to these different conditions, students measure growth of the seedlings every few days using non-standard measurement. After a few weeks, they compare the growth of plants exposed to the different conditions, and make pictorial bar graphs that demonstrate these comparisons.