Behaviour of Wood Lice Experiment

Behaviour of Wood Lice Experiment
In the experiment I was offered the choice to investigate the
behaviour of woodlice in a wet or dry environment or a light or dark
environment. I chose to investigate the behaviour of woodlice in a wet
or dry environment.Woodlice belong to the biological class crustacea. Most of the animals in this class are aquatic, and though the terrestrial species can breathe with the aid of primitive Â?lungsÂ? they lack the features found in most other land-dwelling arthropods. They have no waterproof waxy cuticle on their exo-skeleton and are therefore more likely to suffer from dessication compared with other arthropods such as insects which have a well developed waxy layer. These animals excrete their nitrogenous waste as ammonia gas directly thorough their exo-skeleton (rather than as urea or uric acid).This means that their exo-skeleton needs to be permeable to ammonia and is therefore also permeable to water vapour. In my experiment I am testing whether the woodlice prefer the environment to be wet or dry. I predict that they will prefer it wet rather than dry. I think this because when you find them in the wild, they are in dark damp places like under big rocks or a log. Method First of all in my experiment I will set up a Â?choice chamberÂ? with wet cotton wool under one side and keeping it dry on the other. I will putt a bit of netting over the top so the woodlice can walk over it. We chose to use 15 woodlice because the more you use it makes it less likely for the results to be due to chance. There is a problem with the woodlice clumping up with each other (this is one of the things they naturally do when the get close to something or each other). It may affect the distribution but there isnÂ?t really anything I can do to solve the problem. Diagram [image] Text Box: = DryText Box: = Wet I will take down the results every minute for twenty minutes to put in a graph. I am doing it for twenty minutes because it will enable me to do a chi2 (Ï? 2) at the end of the experiment. The chi2 test is a test that checks to see if your results are reliable and not just due to chance. For example you, you could flip five heads in a row on a coin but if you did it fifty times it would balance out. The chi2 test helps find occasions like this. Results Minutes Wet Dry 1 6 6 2 8 7 3 10 5 4 8 7 5 9 6 6 10 5 7 11 4 8 8 7 9 7 8 10 9 6 11 13 2 12 12 3 13 14 1 14 14 1 15 15 0 16 14 1 17 15 0 18 12 3 19 15 0 20 15 0 The results show that the wood lice preferred the wet environment to the dry, This may be easier to see in a graph. Graph [image] The results do say that that the woodlice prefer it in a wet environment but this could be due to chance. To make sure its not due to chance I shall do the chi² test. Text Box: X² = Σ (O Â? E) ² E Observed Expected X² 9 7.5 0.3 8 7.5 0.033333333 8 7.5 0.033333333 9 7.5 0.3 10 7.5 0.833333333 11 7.5 1.633333333 8 7.5 0.033333333 7 7.5 0.033333333 9 7.5 0.3 13 7.5 4.033333333 12 7.5 2.7 14 7.5 5.633333333 14 7.5 5.633333333 15 7.5 7.5 14 7.5 5.633333333 15 7.5 7.5 12 7.5 2.7 15 7.5 7.5 15 7.5 7.5 Total 59.83333333 According to the X² distribution for 20 woodlice for a one in twenty chance of the results being due to chance X² should be above 31.41; my total is well above that. For a one in hundred chance of the results being due to chance its 37.57. Mine is just under sixty so my results are almost definatly not due to chance at all. Woodlice prefer their environment to be wet. They prefer to live in a wet environment because they are permeable to water vapor they need to be in wet places to get their water supply. That is why they are found under big rocks and under logs in the wild; they are both damp places. Evaluation Overall; I think the experiment went very well. There werenÂ?t really any problems at all. I think the way we obtained our results worked very well. The results we got were very good as well there were no really strange results compared with the rest of them. I donÂ?t think I would change the way we got our results because there isnÂ?t really another way to do it. I think our results were very reliable as the chi² test proved that they were not due to chance, they are definatly sufficient to support the conclusion I have made. The only problem we did have with the test was getting the woodlice in the choice chamber. In the end we just decided to open the lid throw them in and hope that none of them would escape; and they didnÂ?t.

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