Analysis
1. In the student-designed experiment in which the preference of substrates was tested, it was determined that the pill bugs preferred the soil to the grass. Pill bugs are detritivores, meaning they consume dead and decaying organic material (like leaf litter and fallen branches). The pill bugs preferred the soil because it provided both a food source and an environment to camouflage from predators.
In the experiment that tested moisture preference, it was determined that the pill bugs equally preferred both the damp and the dry environments. The preference for the damp environment is due to pill bug anatomy- pill bugs are land-dwelling crustaceans that possess gills, and thus require damp environments to best absorb oxygen. While it was expected that the pill bugs would universally prefer the damp environment, the preference for the dry environment can be attributed to aggregational behavior. Although aggregations are not considered a social behavior, this tendency to cluster together reduces the amount of moisture lost by each individual, and is a beneficial adaptation to life on land. When density is low and thereby competition for resources is low, the benefit of spending more time searching for others with which to aggregate outweighs the cost of spending less time searching for food and of expending energy to walk. Aggregation behavior may have influenced habitat selection, making individual decisions partially dependent on whether they sought or encountered other individuals.
2. Throughout the classroom, other experiments have demonstrated that isopods either prefer damp environments or equally prefer damp and dry environments. The experiments which were conducted for longer periods of time (generally by a few minutes) showed the preference of wet environments over dry. Had these experiments been conducted for a longer duration of time, results may have shown that the pill bugs universally preferred the wet environments. It is important to note, however, that some moisture may have escaped the wet environment and diffused to the dry environment, making the dry environment more hospitable. This might explain the reason for some preference for the dry environment.
3. The isopods use their antennae to locate appropriate environments. Their antennae are sensitive and respondent to all kinds of stimuli- for example, temperature and humidity. Pill bugs have both simple and compound eyes. Their eyesight is not particularly good, however, so the isopods rely on their antennae to detect stimuli. Kinesis is also responsible for their location abilities. The pill bugs move around very fast in undesirable environments and slow down once they approach a more suitable habitat.
4. If a rock was turned over, the isopods would most likely scurry rapidly and burrow themselves under the soil. This is in response to the sudden influx of sunlight stimulus.
5. The isopods’ response to moisture is best classified as taxis because the isopod chose to move towards or away from a specific stimulus. The amount of moisture determined the movement of the isopod. Because pill bugs are land-dwelling crustaceans, they require damp environments in order to thoroughly absorb oxygen through their gills. Background research shows that isopods prefer high moisture environments, which indicates taxis.