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Freshwater Snail Populations Investigation

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Freshwater Snail Populations Investigation Aim: I aim to investigate how the flow rate of a stream affects the distribution of freshwater snails. Prediction: Freshwater-snails are a type of mollusc; they graze on algae encrusting the stones of the streambed. They have a spiralled, streamline shell that helps them to move more easily through the water against stronger currents. Algae grow in a large supply in well-oxygenated water where the oxygen is trapped by flying water in the fast current. The algae cling to stones where the fast water sweeps away all the mud from the seabed, leaving bare stones. The snails have adapted to their lifestyle with their streamlined shell for gliding against the current. If the temperature becomes too cold, then the snails will not feed and become inactive, as they are cold-blooded. I predict that the snails will be found in the faster stretches of the stream, (where the bare algae encrusted stones lay). Fresh water snail Streamline shell for gliding against the current Flow of water Suction cup and Algae mouth for grazing Variables: Variable Effect on ...read more.


into a plankton net (facing upstream). After the sample has been taken we will carefully pour the contents of the nets into a sample tray with some water. The sample will then be left for 5 minutes to settle. After this period I will remove the majority of the water, all the large stones and all the large organisms e.g. fish and eels etc. We will then begin the process of hand counting the snails. Once the snails are counted we will pour the sample back where we found, so not to disturb the streams Eco-system. Each experiment will be repeated so my results can be reliable as possible. The experiment will be controlled and fair as well as safe, with particular care taken when wading through the stream as it disturbs the wildlife and carries a caution of drowning in deeper stretches of water. Preliminary experiment: I think my results will be sufficient enough to use as evidence to support my prediction as a preliminary experiment showed that generally more organisms thrived in the faster moving stretches of the stream. ...read more.


Evaluation: I believe the experiment was a success, as my prediction was proved correct. I found out that the flow-rate of a stream has a direct affect on the distribution of freshwater snail populations that inhabit the stream. I think our results were accurate because each test was repeated and our results were incredibly similar. All the factors were just right for the experiment; the temperature (being my main concern) was ideal and despite the rain the snails (who are cold-blooded) were not reluctant to feed. There was only one result that did not fit the pattern; we believe that this was not an anomalous result because it was repeated in the second set of test. This 'odd' result occurred on both graphs where the stream was fastest, this is because the water was moving too fast for the snails to cling to the rocks. The experiment was fair and controlled; this is reflected in our results, which are very encouraging. I think I could improve the experiment by completing another sample in faster flowing water than the result that did not fit the pattern. This will then test if the. ...read more.

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