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  • Level: GCSE
  • Subject: Maths
  • Word count: 3009

Studies on the shape of limpets at two different zones in a sheltered rocky shore.

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Studies on the shape of limpets at two different zones in a sheltered rocky shore Aim The aim of this experiment is to investigate whether the exposure to wave action affects the limpet shell morphology and find the possible reasons for this. I am going to do this by looking at the height/width ratio of limpets at two different zones in a sheltered rocky shore. Introduction Limpets are dome-shaped molluscs with no spiralling of the shell. They have a distinctive, oval shaped shell with the peak more-or-less near the centre. After four years growth they can be 5 cm across at the base. They can live up to 15 years or so on the upper shore. Patella is the genus name for the most abundant group and is best known for its ability to cling onto rocks. The muscular foot and the secretion of a chemical allow the limpets to grab small imperfections in the rock surface and grasp very strongly. They can hold on to the rock with a force of 75 lbs/in2. Clamping down at low tide will prevent them from drying out. As limpets settle down they rotate the shell and grind it into rock, which produces a good fit but also, on death, leaves a scar on the rock surface. To breathe they remove oxygen from the water, which is drawn in to the gills via a hole above the head. When the tide goes out, they have a problem with the lack of water. However they clamp down and reduce their metabolism, which in turn reduces the need for water. The shell has a high degree of waterproofing to conserve water. ...read more.


This will be done by measuring the height and width of the limpet and then divide the height by the width in order to get the ratio. This would allow me to compare the ratios at different levels. I will take 20 samples in each case. Risk Assessment I will consider the following safety aspects in my experiment: > Walk slowly and carefully on the sheltered rocky shore > Being careful where I step on, since I do not want to harm any organisms > Handle the limpets with great care > Wear gloves, Wellington boots and waterproof clothes, if it rains Hypothesis (H1) The limpets will have a lower mean height/width ratio on shores more exposed to wave action. The following things could explain this: In sheltered areas, limpets tend to be flattened but in exposed areas with wave action, they are more domed. The reason is complex and indirect. One might think that flattened ones would have the advantage of streamlining. In fact, it is probably the wave affect causing more muscles to develop, stronger shells to form and a clamping down on the rock for longer, giving less chance for shell material to form on the outside rim. Null Hypothesis (H0) There will be no difference between the means at different zones in a sheltered rocky shore. Results Limpets measured at 4m Limpets measured at 7m n height (mm) width (mm) ratio (2sf) ratio2 (3sf) height (mm) width (mm) ratio (2sf) ratio2 (3sf) 1 5 18 0.28 0.078 11 37 0.30 0.090 2 7 21 0.33 0.109 7 20 0.35 0.123 3 4 11 0.36 0.130 16 36 0.44 0.194 4 10 26 0.38 0.144 15 33 0.45 0.203 5 12 32 0.38 0.144 16 35 0.46 ...read more.


This will not be much of a problem on the lower/middle shores because shore crabs do not thrive in exposed conditions and few will be found there. A shorter, more rounded shape (as you tend to find on exposed shores) will be easier for other predators like gulls to swallow. Evaluation Overall, I believe that my experiment was carried out in an orderly fashion. However, there is always space for improvement. The main area I believe I could have gained more accurate results was if I used something different from a calliper to measure the limpets. This is because it was quite difficult to measure the height of the limpet when the ground was bumpy. This could have caused an increase or a decrease in my results. I personally think that the block of wood with the plastic arrow was not accurate at all. I am saying this because if you stand at one point and measure the height you will find 4m. However if you move 1m to the right and measure the height again, you will see that it is slightly higher or lower than 4m. This is caused by the sheltered rocks. In my data, I have one clear anomalous result, which I have pointed out on graph no.2. This anomalous result could have been caused by the unknown boundaries for the upper/middle/lower shores. But this problem can be easily solved by doing a continuous belt transect before starting the experiment. Although I did do one the day before (see preliminary work); however it would have been more helpful to do it on the day. Even if there are some limitations, they would unlikely overturn highly significant results. After all this said, I personally think that my data is very good, since I have proven this with the "t" test, graphs and theories. ...read more.

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