Groupx+30

Asma Qureshi, Nishbda Naufal, Nasria Begum, Sahjan Soomro, Madiha Islam, Kadija Mahmed

__Sampling design to identify whether Polymorphic snail distribution is due to genetic drift or selection__

null hypothesis: the proportion of the snails will be the same in each site both inside and outside of the forest (if proved true this will then be due to selection)

Alternative hypothesis: The proportions of the snails will be different in each site (if true then the this would be due to drift)

__Method__ We located three different sites inside and outside of the forest. We then preformed a transect in each of these site and recorded the proportion of the polymorphic snails in these sites obtaining 25 in each site. The colour of the snails in each sample area will be noted.



__INTRODUCTION:__

Polymorphisms is a variation of a phenotype within a population. In this experiment we are looking at what causes polymorphism, and in particular we are looking at what causes polymorphism within the //Cepaea Nemoralis// population located in Pulpit Hill reserve near Monk's Riseborough. There are many small populations of //Cepaea Nemoralis// in this area and these small populations can be tested to see whether these variations in shell colour and number of bands is due to selection or genetic drift.

//Cepaea Nemoralis// is a suitable organism to use in this study as there is huge variation within its population. Variation appears in its shell colour which can be red, pink, brown, yellow or white, with or without dark brown colour bands. The number or bands can vary between zero and five and the apertural lip is usually dark brown, rarely white, umbilicus narrow but open in juveniles, closed in adults. These snails are often found in a wide range of habitat ranging from grassland to wooded areas. Snails are harmless and testing on the shells is ideal as even if the snail dies the shell remains.

 In previous experiments such as Jones et al (1977) the problem of identifying a single force which directs the polymorphic distribution has been highlighted. In this experiment we aim to distinguish whether these polymorphic differences are due to selection or drift. We will be recording the proportions of snail in two sites both inside and outside the forest. If the proportions are the same in each replication then we can conclude this is due to selection because they all share the same selective pressures, however, if it is due to drift the proportions would be different in each site both inside and outside of the forest. The population size is small and so genetic drift will be strong and so we expect different results in every repeat.

N0 Hypothesis: There is no significant difference between the number of polymorphisms in the population N1 Hypothesis: There is a significant difference between the number of polymorphisms in the population.

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