Isopod Lab

By Abbey Audesse and Calum Yule

Hypothesis:  Isopods prefer moist soil over dry soil.

Prediction(s):   If terrestrial isopods prefer moist soil over dry soil, then they will spend more time in moist soil than dry soil during a given period of observation. If several levels of moisture are used in the experiment with an increasing difference in moisture level, then an increase in time spent on the moist side of the container will also be observed in accordance with moisture level. The isopods should spend more time in the higher moisture levels.

Methods:  This experiment involves the simple linear regression model. In this experiment there were six sample groups, of differing moisture levels in the soil. Each sample had a cup, filled halfway with lightly compacted peat moss, with half of the surface of the moss moistened with a known amount of water. Sample 1 has 1mL of water poured on the surface, Sample 2 has 2mL, and so on to Sample 6 with 6mL of water. For each sample, five isopods (placed individually for each replicate) were placed directly on the centre of the soil, with its central axis parallel to the dividing line between the moist and dry sides of the cup so as to account for moving towards one side or another due to the isopod’s facing. After giving the isopod enough time to unroll itself and begin to move, a timer was set for 2 minutes and a stopwatch activated whenever the isopod walked onto the moist side of the cup. If the isopod walked back onto the dry side, the stopwatch was halted until it returned to the moist side. The amount of time (in seconds) that an isopod spent on the moist side of each sample was recorded, with each sample having a different isopod to account for fatigue in repeated experiments involving just one isopod.

Results:

Moisture Level (mL)Time points



Mean time (s) spent in moist side of cup







1034283.4
2162115171817.4
3282323252725.2
4303127292728.8
5504245494846.8
6384842464644

Our predictions were correct in that the more moisture in the soil, the more time will be spent on it in comparison to drier soil. Our experiment used a One-Way ANOVA t-test, with p<0.01 and F-stat of 162.7. Thus, the data collected indicates a significant relationship between moisture level and the time spent on either side of the cup. As seen by the graph above, R^2=.93 which is a significant correlation between the two variables.

2 Replies to “Isopod Lab”

  1. Shannon and I did a similar experiment but I like how you used 6 different soil moistures instead of just 2. Something I wish we had done was start recording after the isopods opened up and started moving, maybe then we would have different results.

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