The affect of temperature on the rate of movement of woodlice
Aim: The aim of this experiment is to establish whether a change in temperature affects the rate in which woodlouse move. I measured the rate by timing the woodlouse to move a set distance of 20cm, and altered the surrounding temperature by submerging a clear tube in water with different temperatures controlled by a water bath.
Research: It is to be believed there over 3000 different species of woodlice, a total of 42 species have been recorded living in the United Kingdom, although not all of them are native (1). Woodlouse is a crustacean, which fit into the class of arthropods, crustaceans are primarily aquatic animals. It is for this reason that woodlice become dehydrated in dry conditions, and their outer shells aren’t waterproof (1). Therefore damp environments are preferable for woodlouse to survive.
The structure of woodlice are similar to all arthropods, the body is split up into segments, with an exoskeleton and jointed limbs. Firstly, the head and next the pereon (thorax), the third is the pleon (abdomen). Also, woodlice are often described to have a structure shown in figure 1. Porcellio scaber contain two pairs of antennae although second pair is extremely small in size and well hidden, and two compound eyes (consist of thousands of individual photoreceptor units or ommatidia) (2).
Male woodlice have genital projections whereas females just have a pouch which contains eggs, positioned at the bottom of the abdomen. Figure 2 shows an example of the ventral (lower) structure of a male Porcellio scaber. As you can see the lungs are situated in the first pleopod, gases are able to diffuse in and out from the lungs through miniscule pores (2). These pores are unable to close, therefore it is common for woodlice to become desiccated.
Woodlice show kinesis behaviour, in which their movement is in response to a stimulus. The movement they show is non-directional and either move at a faster or slower rate. Movement of woodlouse is achieved by the movement of its seven pairs of jointed limbs. Muscle contraction needed for the movement of legs requires Adenine Triphosphate (ATP) which provides energy for the contraction. ATP is the most important energy transfer molecule within cells and is created via the reactions of cellular respiration where biochemical energy from nutrients such as carbohydrates and fats are converted to produce the ATP molecule. These reactions occur in four main stages, glycolysis, the links reaction, the Krebs cycle and oxidative phosphorylation. Many of the reactions that occur in respiration are controlled by enzymes which are used throughout the process and allow the reactions to occur at body temperature.
Woodlice feed on decaying vegetation, and play a vital role in the decomposition of deciduous woods and compost heaps by digesting decaying matter and releasing them as faecal pellets which decompose rapidly. Often fungal spores are contained in the faecal pellets of woodlouse, when these pellets decompose in deep moist leaf litter it stimulates further decomposition in woodlands. Thus, the feeding activities of woodlice speed up the decomposition process and help to return essential nutrients to the soil, making the activeness of woodlice in a woodland environment important.
Hypothesis: The overall increase in temperature will cause the rate of woodlouse movement to increase.
Null hypothesis: The change in temperature will not affect the rate of movement of woodlouse, movement will stay at a regular rate, and therefore there will be no correlation.
The aim of my preliminary experiments was to investigate which method would be most accurate and reliable to measure the movement of the woodlice. During these experiments I could gather information about woodlouse behaviour and also be able to observe variables which I will need to control in my final experiment.
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