Earthworm Essay

Many communities are impacted by exotic species that are introduced over time (Lankau 2009). These exoctic species can result in either positive or negative effects on the community through interacting with the native species (Lankau 2009). Exotic species are moved by humans outside of their native range; species become invasive when they cause harm to their new environment. Earthworms are exotic in many areas that they are introduced to over time. Earthworms are a major influence on soil composition, but to this day there is still many unknown factors about the species (Zirbes L et. al 2011). Responding to the environment is important for many species to be able to be productive in their ecosystem. Studies have shown have shown that earthworms use their senses when responding to their environment (Zirbes L et. al 2011). An unknown factor of earthworm species is whether or not there are light senses to be able to locate the top of the soil compared to the bottom layers of the underground. Prior observation showed that Earthworms moved towards the darker area of the observing tray. It is important to understand how the earthworm species detects light versus darkness to know its location in the soil. If the earthworm knows the location, this may lead to explanations on how earthworms burrow and why they know where the topsoil is. Our

Time (mean + standard error) of nightcrawler earthworm (Lumbricus terrestris) spent in the dark, covered area of the 13 x 9 observing tray with damp paper towel. Expected time shows half of the timed five minutes (175 seconds) if the earthworms had randomly moved around. Time (sec) was measured with a stopwatch. 20 worms were observed to find the average.

In this experiment, the earthworms spent more time in the dark area than the light (Figure 1). The time spent in the dark observed was 1.6 times longer than the expected statistical time if their movement was random (t-test: t=3.3330, DF= 19, p=0.0035; Figure