Gordon+Burns


 * Group Members: *Rowena Gordon*, Jacob Pearson, Milly Fellows, Mansur Batchelor **

The polymorphism observed in //Cepaea nemoralis// is known to be caused by a super-gene within the genome of the snail, which simultaneously dictates shell colour and banding pattern in the phenotype. This property is advantageous with regards to studying selection within the species in that the effect of the super-gene can be observed directly. By contrast, human polymorphism is more complex in origin, as environmental factors are likely to play a significant role, and there are multiple genes across the human genome which control aspects of the same phenotype. //Cepaea nemoralis //have a short generation time and the distance covered by individuals in a lifetime is no more than 20m; this means that the snails can be sampled over a small area with minimal cost and effort compared with sampling larger organisms. The tests remain with their colour and banding pattern after death, therefore the polymorphism can still be observed even if no live organisms are found. Research into //Cepaea nemoralis// has been going on for many years and in many different studies to determine whether selection acts on the polymorphism due to climate, predation by song thrushes, or not at all.

 We will conduct a belt transect that will sample individuals from 2 habitat types: the scrub and the open grassland. We will attempt to take the same number of individuals, where possible, from each sample site from a predetermined, set area in order <range type="comment" id="380958792_7">to standardise the effort used for each sample.</range id="380958792_7"> This will be determined by the ease of finding individuals and time allocated on the day.

<span style="font-family: Cambria,serif;"> Taking samples from only 2 habitats means that we can take more repeat samples, as we are taking the same number of snails from each habitat<range type="comment" id="380958792_8"> the results will be qualitative and so comparable with other studies. </range id="380958792_8">With all of the samples taken from the same altitude we will be able to <range type="comment" id="380958792_9">eliminate</range id="380958792_9"> a variable and test whether the habitat type is a determining factor in the selection of //<span style="font-family: Cambria,serif;">Cepaea nemoralis. // <span style="font-family: Cambria,serif;">From our experiment we want to be able to determine whether there is any evidence of selection, or a founder event in the populations of //Cepaea nemoralis// sampled. If we find, after analysing our results that there is a significant difference in the polymorphisms observed in the snails of different habitat types then we can choose to not accept the null hypothesis. We cannot prove from our study that selection has definitely taken place - as genetic drift can cause very similar effects to selection –<range type="comment" id="380958792_10"> but we can prove that the chances of the morph patterns being due to chance is very unlikely (less than 5%).</range id="380958792_10">

__<span style="font-family: Cambria,serif;">Hypothesis __ <span style="font-family: Cambria,serif;"> There will be <range type="comment" id="380958792_11">significant</range id="380958792_11"> difference between the frequencies of morphs in the scrub habitats and grassland habitats, attributable not only to genetic drift and gene flow, but also to selection.

<span style="font-family: Cambria,serif;"> __Null Hypothesis__ <span style="font-family: Cambria,serif;"> There will be no significant difference between the frequencies of morphs in the scrub habitats and the grassland habitats, implying the absence of selection. Observable polymorphism will <range type="comment" id="380958792_12">be due to genetic drift and gene flow.</range id="380958792_12">