Lab: Wednesday 9 a.m.
An organism’s environment can impact it in several different ways a few examples of this are temperature, lighting, and food sources. Some organisms have evolved certain structures to aid in the sensory of light and dark; one such example is certain members of the class Turbellaria have developed structures called photoreceptors (Pike et al. 1986). Certain organisms can only thrive in low levels of light, while others depend on light for survival. The organisms that were observed during this study belong to a group that is known as the Flatworms. Some common characteristics of the Flatworms are that they attach themselves to hosts and suck all the nutrients that are needed for survival (Jokiel et al. 1974). In this particular study the specific organism that is focused on is Dugesia tigrina (Figure 1.) also known more commonly as the brown planarian. Dugesia belong in the phylum Plateyhelminthes and in the class Turbellaria. These organisms despite being known as a member of the Flatworms are not parasitic. Instead they feed on Dugesia are mostly found in freshwater such as ponds and lakes. Figure 1. An example of a Dugesia, which is observed in this study.
The experiment performed investigated if Dugesia prefer light or dark situations. Our group hypothesized that Dugesia would prefer the darker side of the petri dish more that the light side. This hypothesis was based on observations of the planarians before the experiment and the type of environment Dugesia are found in. We also noticed that the planarians preferred the edge of the dish, the most which is where the cover is the thickest allowing the least light through. We thought that the darker side would draw the most planarians. Methods...