Groupx+15

Mahta Zadeh-kochek Huda Awad Naomi Ese Bridget Sigba Lam Ting Wai Ng Man Dik

Null hypothesis: There will be no significant phenotypic variations (shell colour and number of bands) observed between the populations in the different areas sampled. Alternative hypothesis: There will be significant phenotypic variations (shell colour and number of bands) observed between the populations in the different areas sampled.

The aim of our experiment is trying to find the evolutionary force that is in large responsible for shell polymorphism.We aim to solve this by taking samples of the C.nemoralis species from 2 different habitat and analysing the shell colour and patterns and therefore gene frequencies thereby hoping to discover the evolutionary force that is in effect. We are studying snails in order to show us the effects of genetic drift, selection and gene flow. These result can then be extrapolated to other species. There are several advantages of studying this particular species and those include that they are range of different individuals that can be easily sampled leading us to gather a large amount of data fairly quickly and therefore apply our findings to different species.

The inspiration behind our experiment is Jones et al. (1977), whom with his colleagues also tried to determine the reason behind why the Cepea species was polymorphic.

Jones et al.(1977) conducted an experiment using 2 sister species, C.nemoralis and C.hortensis, order to establish the reason behind shell polymorphism. This resulted in them finding 8 evolutionary forces all affecting the differences in the shell phenotype. They were: Visual selection, Climatic selection, Frequency-dependent selection, Disruptive selection, Density-dependent selection, Heterozygote Advantage and Stabilising selection, Random Process and Linkage Disequilibrium and Coadaptation. Each one was able to explain the shell polymorphism in the Cepea species but there was not one complete explantation. It varies from population to population and habitat to habitat indicating that they are more factors here at play.

By discovering the primary principle of polymorphism, this will then hopefully enable us to explain the evolution of the C.nemoralis. 

__<span style="font-family: Arial,Helvetica,sans-serif;">Technical terms and abbreviations: __

<span style="font-family: Arial,Helvetica,sans-serif;">Evolutionary ecology - the study of the evolutionary histories of species <span style="font-family: Arial,Helvetica,sans-serif;">Adaptation - when an organism possesses a trait with a functional role that has been maintained and evolved by the process of natural selection <span style="font-family: Arial,Helvetica,sans-serif;">A founder effect - when a small group of individuals colonise a new region and as a result there is a loss of genetic variation <span style="font-family: Arial,Helvetica,sans-serif;">Natural selection - the process where organisms that are well- adapted to their environment are more likely to survive and produce offspring <span style="font-family: Arial,Helvetica,sans-serif;">Range expansion - when a species expands its range to occupy new areas <span style="font-family: Arial,Helvetica,sans-serif;">Microclimate - the climate of a small area, which sometimes differs from that of the surroundings. <span style="font-family: Arial,Helvetica,sans-serif;">Microevolution - refers to evolutionary changes in a species, which often occurs over a short period of time <span style="font-family: Arial,Helvetica,sans-serif;">Polymorphism - when there are different forms occurring within the members of a population, and therefore natural selection can occur <span style="font-family: Arial,Helvetica,sans-serif;">Gene flow - when alleles are transferred from one population to another <span style="font-family: Arial,Helvetica,sans-serif;">Genetic drift -when the frequency of an allele in a population changes. Genetic drift continues to occur until the allele involved is either lost or becomes the only allele left in a population, therefore leading to a decrease in genetic diversity.

__<span style="font-family: Arial,Helvetica,sans-serif;">Initial Sampling Method: __



<span style="font-family: Arial,Helvetica,sans-serif;">1: Deep woodland- low altitude <span style="font-family: Arial,Helvetica,sans-serif;">2: Grassland (closer to woodland)- low altitude <span style="font-family: Arial,Helvetica,sans-serif;">3: Isolated grassland- low altitude <span style="font-family: Arial,Helvetica,sans-serif;">4: Isolated grassland- high altitude <span style="font-family: Arial,Helvetica,sans-serif;">5: Shrubs- high altitude <span style="font-family: Arial,Helvetica,sans-serif;">6: Grassland- high altitude

<span style="font-family: Arial,Helvetica,sans-serif;">Method: <span style="font-family: Arial,Helvetica,sans-serif;">We will be sampling six different areas within the habitat which will allow us to observe any phenotypic variations between the snails (both dead and alive). 20- 30 samples will be taken in each area. All six sample sites will be of the same size (4mx4m) to ensure consistency within the samples. <span style="font-family: Arial,Helvetica,sans-serif;">Two altitudes will be compared in order to establish whether there are phenotypic differences between snails in a lower and higher altitude and if the amount of oxygen affects the shell colours and band types. Therefore Samples 1, 2 and 3 will be taken at a lower altitude while samples 4, 5 and 6 will be taken at a higher altitude. <span style="font-family: Arial,Helvetica,sans-serif;">Furthermore we will be comparing samples in different areas within the same altitude. We will compare samples 1, 2 and 3 which are in the woodland, grassland (close to the woodland) and grassland (isolated) respectively. We will also be comparing samples 4, 5 and 6 which are located in the grassland, shrubs and grassland (on the other side of the shrubs) respectively.

__<span style="font-family: Arial,Helvetica,sans-serif;">Revised Sampling method: __



<span style="font-family: Arial,Helvetica,sans-serif;">In order to carry out our experiment we will be taking samples of the C.nemoralis species, both dead and alive, and analyzing and recording their shell colour and number of bands on their shells. We will be sampling six different areas within the habitat which will allow us to observe any phenotypic variations between the snails in each area. Our experimental design will be controlled for some factors. For example, all six samples will be taken at the same medium height in order to control for altitude. This will ensure humidity and wind exposure will remain the same throughout. We will also only be studying only two different types of area within the habitat. Three of these areas in which samples will be taken will be grassland and the other three areas will be shrub land. By doing so we will ensure that we are eliminating pseudo replication. To ensure consistency within the samples, 20- 30 samples will be taken in each areaand all six sample sites will be of the same size (4mx4m). We will also make sure that all our samples are taken at the same distance of 15cms apart from each other.

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**<span style="font-family: Arial,Helvetica,sans-serif;">Introduction : **
// Cepaea nemoralis ////, // is awestern European species of snails. They have a wide range of habitats, such as sand dunes, cultivated area and even high mountains( Jones , et al , 1977 ). They have a sibling species, //C// // epaea //// hortensis //. The aim of this experiment is to determine the underlying cause of natural selection and evolution of // Cepaea nemoralis ////. // Also, we would like to figure out the cause of polymorphism between // Cepaea nemoralis // and //C// // epaea //// hortensis // , also explaining their distribution pattern.

Polymorphism refers to two or more variants of a trait present in the same population. A polymorphism can be maintained when the fitness of a given phenotype depends on its frequency in a population, a phenomenon known as frequency-depend selection ( Sadava, et al , 2009 ). In this case, the reasons behind polymorphism are expected to be genetic drift ( the random fluctuation of gene frequencies in a population due to chance event ) and gene flow ( movement of individuals into or out of the population / reproductive contact with other location ), but instead there are more factors such as predation , climate and food availability. Thus, according to previous research done on // Cepaea nemoralis // ( Jones , et al , 1977 ), it is suggested that different variations of factors mentioned above will give rise to different of phenotype, therefore it is necessary to justify the underlying cause of polymorphism of // Cepaea nemorali //// s. //

In this study, we collect and analyze samples of // Cepaea nemorali //// s // in the Pulpit Hill nature reserve in Monks Risborough. By observing population within different habitats such as grassland, shrub , woodland in both high and low attitude, we can record their size and shell colour and size. They have colour variation ( brown, yellow , pink ) and different number of bands shown on shell ( 0-5 ). Due to the fact that genes controlling the major polymorphisms for shell colour, presence or absence of bands are borne together as a supergene ( Jones, et al , 1977 ), therefore // Cepaea nemorali //// s // is an ideal model for this study. Moreover, we have to repeat the collection in order to give accurate and precise results.

Therefore the null hypothesis of our group is that there will be no significant phenotypic variations (shell colour and number of bands) observed between the populations in the different areas sampled, while the alternative hypothesis is there will be significant phenotypic variations (shell colour and number of bands) observed between the populations in the different areas sampled.

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