During my last visit to Observatory Park, I had noticed a singular oak tree on the southwest corner of the park. It had stood out to me because at that time it was the only tree whose leaves had begun to change.  Now, a little less than a month later, the leaves have almost all fallen and the trees around it have only just started changing colors. The green color of leaves comes from chlorophyl, a pigment that performs photosynthesis for plants. As the temperature begins to drop amidst the changing seasons, trees perceive a threat and begin to shut down, therefore stopping their production of chlorophyl. The decrease in chlorophyl causes the leaves to lose their green coloring and instead turn shades of red, orange, and yellow. This singular tree exists in the same environment - temperature, sunlight, soil - as those around it, and furthermore is an oak tree just like many of its neighbors. Therefore, it would be expected that they would all go through their processes of fall changes on a relatively similar time frame. However, because this one tree has turned yellow and lost its leaves so far ahead of the others means that the tree may possibly be experiencing excessive stress. These stressors, such as insects, nutrient deficiency, disease, drought, or others, cause the tree to react to the threat of the changing temperature sooner than other trees and therefore change colors and lose leaves faster. I found this interesting to learn about in how trees and humans alike both experience stress and have reactions to their environment that may differ from those around them.