The simple act of observing phenomena such as that shown on the previous page is the first step in conducting a scientific investigation. From these observations, a researcher starts to ask questions.

  !   Click the image to view the animation.

In the animation above, the overall amount of vegetation covering North America increases and decreases over the course of the year. These changes do not occur equally everywhere. Some areas are never covered with vegetation, and other areas remain green all year.

Possible questions that arise from these observations might include the following:

• "Does the amount of rainfall in an area directly affect the amount of vegetation?"
• "Is the amount of energy an area receives from the sun closely related to the changes in the vegetation?"
• "Is the amount of vegetation in an area dependent on the local temperatures found there?"