Introduction-+Bahga+Said+Mohamud

__Polymorphism in//Cepaeanemoralis//__ __Introduction__ The snail species //Cepaeanemoralis// is a very common species to observe all across Europe. It also displays a wide range of polymorphs, these are displayed in their [shell] colours and banding patterns, ranging from white to dark brown, with a varying number of bands. It is for this reason that the snail is widely studied and at one point around the 1800s a species name for every colour variant was used, this was however later dropped. It is believed the colours play a role in the snails’ ecology, dark brown a more often found in dark woodlands, whereas the lighter snails are found in more commonly in grassland areas. This difference in environmental gradient could be due to the fact that the darker colours will absorb heat more rapidly than the lighter shells. This enables the metabolic rate to beraised to a sufficient level for survival in darker areas by having a darker shell. The snail is a hermaphrodite and for fertile offspring to be produced sexual reproduction has to occur, this involves a complicated courtship which involves the use of a love dart by both parties to excite one another until the courtship is complete and reproduction can occur. This need for sexual reproduction means that metapopulations displaying different polymorphisms can be observed in the same field due to the snails’ limited immigration and emigration due to the small range of the snail. Polymorphism occurs when two or more different phenotypes exist in the same population of a species. This can be seen on the shells of the specie //Cepaeanemoralis//, which differ in colour (yellow, pink and brown) and number of bands. There has been many disagreements on whether polymorphism occurs in the snails is either due to natural selection or random processes. However we must remember that there are many different types of evolutionary force which act upon the //Cepaea// polymorphism. It is a difficult task to identify whether it is genetic drift or natural selection which causes the variation in gene frequency. Some researchers believe that polymorphism in the snail is due to natural selection i.e. due to predation and habitat. The song thrush is a well know[n] predator of the //Cepaea// snail and they can have a directional effect upon the morph frequency of the snail. This occurs because the song thrush hunt visually, there fore the darker the colour of the shell the more chance the snail can survive and pass on its genes to its offspring. It was also shown that depending where the snails were; the colour of the shell reflected the colour the background area. For example, snails that were found in the woodland had a higher frequency of the brown colour allele. It was thought that the genetic difference between the species was just a random process, i.e. due to genetic drift and had no biological significance. However, as more research was carried out it showed that natural selection occurred but genetic drift was not totally ruled out. There have been many experiments which had shown that random processes do have an effect on polymorphism of //Cepaea//; one was with the French colonies of //C.nemoralis// and another was with the same species but in Scotland. Although these experiments did show evidence of random processing, some were ruled out to be ‘sampling error’. Nevertheless, neither genetic drift nor natural selection can be ruled out in the search to why polymorphism occurs. Our data was collected at Pulpit Hill nature reserve near Monk’s Riseborough in Buckinghamshire. Along with the Grangelands, Pulpit Hill is a Site of Special Scientific Interest (SSSI), meaning that it is one of UKs best wildlife and geological sites. SSSI sites cover around 7% on the UKs total land area. Pulpit Hill is described as a nature reserve with unimproved areas of chalk grassland. This type of grassland has been in decline in the United Kingdom for the last 50 years and is home to some of the most lush and diverse flora. This wealth of types of flora is the effect of the chalk or limestone found in the soil below. As a result, chalk grasslands are a suitable habitat for animals such as glow worms, bee orchids, blue butterflies and roman snails. Atop Pulpit Hill, within Pulpit Woods, the remains of an Iron Age hill fort can be found. Our experiment consists of trying to distinguish a statistical link in polymorphism of //Cepaea nemoralis// by performing a chi squared ( c 2) test of data of 4 different locations. The four locations each have had 40 pieces of data collected; 20 from a high altitude and 20 from a low altitude. The snails’ polymorphism varies within the shell colour, the number of bands on the snails shell and the age of the snail (whether they were an adult or sub-adult). We have decided to work on the aspect of whether the colour of the shell has a statistical link to the altitude. Our first null hypothesis is ‘there is no substantial difference between phenotypes in high ground’.

Word Count: 835 __Contributors:__ Ashlie Brabon, Thomas Bruce, Andre Castro Correia Da Luz Emily Morshuis, Joseph Pender, Bahga Said-Mohamud*, Callum Upfield