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Investigation of factors affecting the distribution of Chironomus larvae in Nant Iago (James' Stream) Nr. Abergavenny, S. Wales.

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Introduction

Biology April Jane Alarcon Title: Investigation of factors affecting the distribution of Chironomus larvae in Nant Iago (James' Stream) Nr. Abergavenny, S. Wales. Method: Biotic Data 1. The stream was split into 14 sections and groups of 3 were each assigned to work at different sections of the stream, which began at the beginning, right at the top, and ended further down stream. 2. The method we used for our experiment was Disturbance Sampling. This was accomplished with the aid of a Surber Sampler which we used in one riffle and one pool in our section. The Surber Sampler consisted of a net which had a 1.0mm2 mesh at the end where all the samples were collected and a quadrat which was placed over a part of the riffle or pool and gave us our area of sampling. 3. By laying the quadrat flat on the bed, I disturbed the stream bed and washed any lying organisms into the mesh. I then washed the water through the mesh to collect any samples in the water. 4. Once this was done the invertebrates were identified, counted and recorded Physical Data: 1. To accomplish my physical data, I measured the pH of the water, the Total Dissolved Solids (TDS), the dissolved oxygen, the depth and the temperature. 2. All were measured using specialised probes which were placed in the water of the riffles or the pool. The probes gave us readings of whichever piece of data we were trying to achieve after 30 seconds. The readings were then recorded. 3. The amount of detritus was estimated using estimation by eye, recorded and measured using a scale of 1-4: 1. None 2. Little 3. Some 4. Abundant The pool was 4 and the riffles was 2. 4. The substrate was also identified as to what matter was present, i.e. Riffles: gravel's and pebbles. Pools: twigs, soil, leaves, detritus. ...read more.

Middle

This haemoglobin is, however, not found in cells, but is found in the body cavity in a fluid named haemolymph. The only main difference between the Chironomus haemoglobin and mammalian haemoglobin is that Chironomus haemoglobin has a much higher affinity for oxygen. This signifies that the oxygen will bind to the haem groups at extremely low partial pressures and will be released only when needed. This assists them when burrowing in anoxic conditions, in the sediment on the pool bed, where oxygen is very restricted. The haemoglobin act as an oxygen store and will this can be demonstrated on an oxygen dissociation graph. As shown, the O2 dissociation curve for the Chironomus haemoglobin is to the left of the mammalian O2 dissociation curve. This means that it has a higher affinity and will bind oxygen at especially low partial pressures. The reason why the Chironomus dissociation curve is straight is due to the fact that it has only two polypeptides so it is extremely easy for the molecules to bind to the haem groups. The mammalian dissociation curve is s-shaped (sigmoid). This is because it has four polypeptides. With the first haem group, it is tough for the O2 molecule to bind to it, but once it has then this makes it easier for the second and third O2 molecule to bind to the haem groups. The reason why the curve lines off is due to the fact that it is harder for oxygen to bind to the fourth haem group. Benefits of living in anoxic sediments: Living in anoxic conditions requires special adaptations which can be found in Chironomus. Examples of why it may be beneficial for the Chironomus to live in anoxic conditions are that it helps them avoid predation from predators such as the stone fly nymphs; Perlodidae. It also helps Chironomus avoid competition such as interspecific competition from other organisms, for example, the shrimp (gammaridae) ...read more.

Conclusion

Another alternative to the surber sampler's which we used is a piece of apparatus called the 'Eckman Grab'. These 'grabs' do not have nets attached to the end of them, but instead act as a set of claws. After your sample has been picked up by these 'grabs', you cleanly drop all of its contents into your tray where after, you can record the results. This will develop the results because one of the core setbacks with surber samplers is that the nets tend to lose samples (through or under), whereas with these 'grabs' they do not have nets and so keeping all the samples within its hold will assure the results are more accurate and improved. Final Conclusion: As my final conclusion, I will articulate that the trial my group carried out had a quantity of inaccuracies, but not enough for me to completely reject the whole experiment. The results are reasonable as they reflect the way nature works, regardless of the main sources of error. Also, the statistics and chi squared number shows a highly significant difference in the number of Chironomus in the pools and riffles with more found in the pools. The experimental errors are not large enough to cause a 99.9% rejection of the null hypothesis. To determine the whole pattern of invertebrates and Chironomus along the stream, the experiments should have been carried out every month, instead of just one day. By doing the experiments on just one day we are left with results that are only able to give us a general idea and impression of the patterns of the distribution of invertebrates and Chironomus along the stream. I had to reject my null hypothesis, as I was 99.9% confident that there was a difference. In my opinion, if I was to repeat this experiment even with the improvements I have suggested, then the results obtained would still be the same. ?? ?? ?? ?? Biology Coursework April Jane Alarcon ...read more.

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