Group x4

__**Members: **__ Chantalle Berkhout, Gobitharshan Ongaranathan, Santhiya Kumarakulasingam, Hetty Claudino, Catherine Santucci and Cinderella Jawahar

=**__Determining a Suitable Sampling Method __**=

__Definitions from Oxford Dictionary__

**Sample:** a small part or quantity intended to show what the whole is like: **Gene Flow:** any movement of genes from one population to another. **Genetic Drift:** along with natural selection, mutation, and migration—this is one of the basic mechanisms of evolution. (It is the random change in allele frequency over time in a closed population.) **Polymorphism:** Genetically, it is the existence of many forms of DNA sequences at a locus within the population. Biologically, it refers to the occurrence of more than one kind or form of organisms of the same species that exist together in one locality. **Speciation:** the process in which new genetically distinct species evolve usually as a result of genetic isolation from the main population.

__Hypothesis__

**Null hypothesis:** There is no significant difference between the polymorphic characteristic of snails’ shells (the phenotype) and the area (woodland or grass) the snail is sampled from. **Alternative hypothesis:** There is a significant difference between the polymorphic characteristic of snails’ shells (the phenotype) and the area (woodland or grass) the snail is sampled from.

__Method __

 Samples will be taken along a transect stretching from within the woods to the area around it. The transect will be **600m** long with samples removed every **120m**. The samples will be removed from an area with a diameter of 10m to ensure consistency throughout the study. Sampling along the transect helps us distinguish how the distribution of snail polymorphism changes along the gradient with relation to the habitat; hence making it easier to observe the environmental influence on polymorphism. Systematic line sampling will be used to minimise bias and procure a sufficient number of snails from each sampling area to conduct statistical analysis. A total of **100** adult snails would be removed for sampling – **20** from each sampling area. <span style="font-family: Arial,Helvetica,sans-serif;">There are 3 sampling areas that cover the grass because grass constitutes to roughly **75%** of the habitat. In comparison, the bushes only cover around **7.5%** while the woods cover around **17.5%** of the total habitat.
 * <span style="font-family: Arial,Helvetica,sans-serif;">The sampling areas include: **
 * **<span style="font-family: Arial,Helvetica,sans-serif;">1 – woods **
 * **<span style="font-family: Arial,Helvetica,sans-serif;">1 – woods + grass **
 * **<span style="font-family: Arial,Helvetica,sans-serif;">3 – grass **
 * **<span style="font-family: Arial,Helvetica,sans-serif;">1 – bush **

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

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

__Justification__

Following feedback from our colleagues, we have decided to revise and improve our initial sample design. We ensured that we repeat our woodland readings at two different heights. We have also incorporated more bush areas. We now have more repeats - especially repeats that take the height into consideration. As our sampling area positions were initially based on how much of the habitat each area covers, we have tried our best to adhere to this. We have positioned our sampling areas in a manner that still covers mostly grass, then woodland and finally bush.

Our independent variable is the **//area of habitat//** and our dependent variable will be the **//phenotype of snails//**.

Other variables will be minimized as much as possible to ensure reliable and valid findings.

__Reliability and Validity__

When planning our sample design, we have strongl<span style="font-family: Arial,Helvetica,sans-serif;">y considered reliability and validity. Reliability is the degree to which an assessment tool produces stable and consistent results. Validity refers to how well a test measures what it is purported to measure. (Definitions based on: <span style="font-family: Arial,Helvetica,sans-serif;">https://www.uni.edu/chfasoa/reliabilityandvalidity.htm)

We have investigated the percentage covered by each area of the habitat (woodland, grass and trees). From this, we were able to estimate six sample points covering the entire habitat. Reliability is represented by the fact that we have chosen 6 sampling areas, which is a fairly large number of sampling areas and is likely to produce a more valid mean. Usually, the more data you have (here represented by our sampling areas), the more reliable the study will be. Moreover, the more reliable the results, the more valid the conclusions tend to be.

Furthermore, we have decided to sample our snails along a range of different heights, in a transect. Validity of our findings is reflected here by the fact that we are taking samples from a range of different heights and we can therefore infer our findings to the entire habitat with validity.

=__**Final Sampling Method**__=

As we were over-ambitious with the number of variables we wished to test, we have planned to control the type of habitat (grasslands) and change the height instead. We have planned to test the various altitudes at a diagonal to ensure enough spacing between the sampling sites to minimise effects of genetic drift. Hence, we will be testing the effects of altitude on the snail shell polymorphism.

=__**Final Sampling Method - Improvisation at the site**__= <span style="background-color: transparent; color: #252525; font-family: Arial; font-size: 15px; text-decoration: none; vertical-align: baseline;">Upon seeing the area we would be sampling from, we revised our sampling strategy in order to make it more efficient and realistic. Although we stuck to our original idea of sampling from various heights, we sampled from three separate hills at two different heights on each. This gave us 6 samples (of 15 snails): 3 from higher grassland, 2 from mid-grassland and 1 from lower grassland. = **__Introduction__** =

Polymorphism can be defined as naturally occurring diversity in genes, DNA sequences or chromosomes that results in the development of variety among the members of a single population. (1) (2) Usually, polymorphisms are seen to have no unfavourable effects on the individuals involved. (1) There are cases where no visual indications are given to suggest polymorphism, requiring biochemical techniques to identify differences between organisms; (2) in the case of Cepaea nemoralis however, its striking variety in banding pattern and colour has attracted the interest of geneticist and layman alike. (3) Polymorphism can occur at any level, from chromosomal to phenotypic; this study focuses on the colour and patterning of the shells. Many evolutionary forces are believed to be acting on the C. nemoralis snail populations, thus placing it at the centre of studies that have sought to ascertain the mechanisms that led to this vast polymorphism. (4) Moreover, shell colour polymorphism of Cepaea nemoralis is a well-known and thoroughly explored model in evolutionary research with relation to genetics. Even so, despite all the information acquired from studies spanning across over a century, “knowledge on the ecological causes driving its evolution remains incomplete”. (5) Historically, researchers have come to separate conclusions to explain the variety displayed. Diver believes the wide range of differences was random, whereas Boettger suggested natural selection to be the primary influence. Others including Lamotte and Schilder focused on mutations and gene flow. (3) The theories mentioned above, as well as migration, climatic selection, habitat heterogeneity, landscape structure and predation work simultaneously; however they differ in the extent to which they influence polymorphism in a particular population. (5)This study is conducted to ascertain whether selection is responsible for differences in allele frequencies, to comprehend the effects of the various drivers of evolution and to explore the significance of altitude in determining the patterning on the shells. This can be accomplished by observing the polymorphic distribution in C. nemoralis at different heights. If selection were the dominating force, the most common patterning in the population would possess some selective advantage over others.

The null hypothesis states that there is no significant relationship between polymorphism expressed on shells and the altitude. However, the alternative hypothesis of this investigation suggests that allele frequencies differ with altitude of Cepaea nemoralis sampling area.

References

1) Pagon. R.A., Adam. M.P., Ardinger. H.H., et al., editors. (2014). Illustrated Glossary. NCBI Bookshelf. Available: [|__http://www.ncbi.nlm.nih.gov/books/NBK5191/#IX-P__].

2) polymorphism. (2014).Encyclopædia Britannica Online. Available: [|__http://www.britannica.com/EBchecked/topic/468786/polymorphism__].

3) Cain. A.J, Sheppard. P.M. (1954). Natural Selection in Cepaea. Genetics. [|__http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1209639/__].

4) Jones. J.S., Leith. B.H., Rawlings. P. (1977) Polymorphism in Cepaea: A Problem with Too Many Solutions?. Annual Review of Ecology and Systematics, Vol. 8 (1977), pp. 109-143

[|__http://www.jstor.org/stable/2096723__].

5) Rosin, Z. M., Kobak, J., Lesicki, A., Tryjanowski, P. Differential Shell Strength of Cepaea Nemoralis Colour Morphs—implications for Their Anti-predator Defence. Naturwissenschaften. (2013). [|__http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1209639/__]

Introduction Word Count: 461 (Initially); 380 (Altered)

=**__Results__**=

__Table of Results__ __Chi-Squared Test__