Planaria Laboratory Report
As defined from the experiment, taxis the reaction of an organism in terms of movement depending upon the stimulus presented. There were also two distinct forms of taxis specified, negative and positive taxis. The difference relies upon the reaction of the organism in response to the stimulus, if it moves away from the stimulus then it is negative taxis and if it moves towards or along the stimulus then it is considered as a positive taxis. From the experiment, three different kinds of taxis, which are rheotaxis, chemotaxis, and phototaxis, were analyzed through observations on Planaria.
In Figure 1 below, the number of observed taxis type in relation to the number of setup wherein the taxis types were observed is presented. In this case, the independent variable is of course the taxis observed. On the other hand, the independent variable is the number of setups wherein the observations were gathered. The determination of which was the dependent and independent variable of course relies upon which factor dictates the other. For the experiment, the taxis type become the independent variable since it has been predefined and the number of observations were dependent upon it.
A low number of setups were produced, basically just three in this case; thus, the line of graph created has no indications of any variation between the numbers of observations. This is of course still valid and no fluctuations in the line are expected. There are of course other implications of this figure in relation to the validity of the methodologies used. Since the figure presents that in all setups a taxis type was observed, hence implying that the induction of movement based reactions of the Planaria has been generally successful.
In addition to this, it becomes apparent that rheotaxis, chemotaxis, and phototaxis have all been successfully observed from the experimental procedure. Therefore, the figure presented can be utilized in providing proof regarding the effectiveness of the methodologies used in the study. Aside from the points mentioned, it must also be taken into account that the results were indicative of the validity of the concept of taxis, due to the fact that all organisms tested with specific stimulus reacted in a specific manner.
The first figure presented were indicative of the total taxis observations, but provided no insights upon the whether negative or positive taxis were induced. To be specific, data regarding the number of observed cases of positive and negative stimulus were not presented. In Figure 2 below however, these parameters are the main focus. Figure 2. Number of Positive and Negative Taxis Reactions from Planaria Setups. As discussed, when a Planaria moves away from the stimulus presented then it is considered as negative taxis, and the opposite of this is called positive taxis.
In this case, the independent variables are the movement or reactions induced by each type of stimuli. The number of resulting observations of each reaction was of course the dependent variable since these were merely counts of the results in based upon the movement of Planaria samples. As a side note, one must keep in mind that in some graphs of the horizontal bar variant, the representation of X and Y axes are commonly misinterpreted due to the fact that the X axis is sometimes positioned to the left while the Y axis is placed at the bottom for better readability.
From figure 2, it can be assessed that of the three stimuli used, two were able to induce negative taxis and thus only one induced positive taxis. Reflecting upon the experimental results as presented in Table 1 below, phototaxis and chemotaxis both provided negative taxis while rheotaxis resulted in positive taxis. Given that Planaria populations are generally inhabitants of aquatic low light environments and feed upon species that they are able to swallow, then such results were indeed correct (Niles Biological Inc.
, 2006). Given that Planaria live in low light environments then it is expected for Planaria samples move away from direct light sources. In relation to chemotaxis, since boiled egg yolks are understandably not among the food sources of the Planaria, then negative taxis was also expected. Considering rheotaxis on the other hand, a positive taxis was expected due to the methods of movement as well as natural habitat of Planaria. Table 1. Taxis responses of Planaria towards different stimuli.
Type of taxis Response of planarian Positive taxis Negative taxis Rheotaxis + Phototaxis – Chemotaxis – Since in the graph, two instances of negative taxis and a single case of positive taxis are presented, and upon reviewing the experimental results which indicates that it was indeed tests of rheotaxis that resulted in positive taxis while negative taxis observations were from chemotaxis and phototaxis, then it attests to the success of the experimental procedures as the theoretical results were attained.
Thus, the actual experimental results regarding whether negative or positive taxis will be induced in phototaxis, chemotaxis, and rheotaxis experimental methods are all generally conclusive and convincing. References Niles Biological Incorporated. (2006). Platyhelminthes – Planaria. Live Invertebrates. Retrieved May 7, 2009 from http://www. nilesbio. com/subcat348. html
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