to carry out its investigation. The groups used a variety of sources to gather information about characteristics of trees, their life cycles, and their environments. For example, the “different ages” group answered their question fairly quickly. They contacted the PTA members who were involved in planting that part of the playground and found the original receipts for the purchase of the trees. A check with the nursery indicated that all three trees were identical and of approximately the same age when purchased. As some groups completed their investigations early, Mrs. Graham invited their members to join other groups still in progress.
Explain based on evidence
The water group decided to look at the ground around the trees every hour that they could. They took turns and jointly kept a journal of their individual observations. Since some students lived near the school, their observations continued after school hours and on weekends. They missed some hourly observations, but they had sufficient data to report to the class. “The tree without leaves is almost always standing in water, the middle tree is sometimes standing in water, and the green tree has damp ground but is never standing in water.”
One of the students recalled that several months ago the leaves on one of his mother’s geraniums had begun to turn yellow. She told him that the geranium was getting too much water. Mrs. Graham gave the group a pamphlet from a local nursery entitled “Growing Healthy Plants.” The water group read the pamphlet and found that when plant roots are surrounded by water, they cannot take in air from the space around the roots and they essentially “drown.” Based on their observations and the information they obtained from the pamphlet, the students concluded that the leafless tree was drowning, the middle tree was “kinda” drowning, and the third one was “just right.”
Consider other explanations
The water group continued its work by investigating the source of the water. They found that the school custodian turned on a lawn sprinkler system three times a week. He left it running longer than necessary, and the excess water ran off the lawn and collected at the base of the trees. Since the ground was sloped, most of the water collected at one end of the tree-growing area. Together with the other groups, they reported their results to the rest of the class.
As different groups gave their reports, the class learned that some observations and information — such as those from the group investigating whether the trees were different — did not explain the observations. The results of other investigations, such as the idea that the trees could have a disease, partly supported the observations. But the explanation that seemed most reasonable to the students, that fit all the observations and conformed with what they had