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Sampling and Variation…read more

Slide 2

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* Sampling bias: selection process may be biased; the investigators may be making
unrepresentative choices
* Chance: Sample may be unrepresentative by chance
* Random Sampling: reduces sampling bias
* Large sample: more individuals selected; smaller chance that chance will influence results
*Analysis of results: data analysed using statistical tests to determine the extent to which
chance may have influenced the data. Allows us to understand whether any variation shown
is the result of chance or have some other cause.…read more

Slide 3

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Intraspecific: the variation between the members of the same species
Interspecific: the variation between different species
Causes of variation:
* Mutations- sudden changes to genes and chromosomes which may be pssed down
* Meiosis- nuclear division forms gametes which mixes up genetic information/ material
before being passed into gametes
* Fusion of gametes: offspring inherit characteristics from both parents. Every egg and
sperm are different and you never know which ones will fertilise
* Environmental: influence way genes are expressed; genes set limits but the environment
determines where within those limits an organism lies in.…read more

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Types of variation
Genetic variation
* Discontinuous
* Discrete
* controlled by a single gene or small number of genes
* Organisms fit into a few distinct forms
Environmental variation
* Some characteristics of organisms grade into one another- forms continuum
* Continuous
* Polygenic; the combined effect of many genes
* Normal distribution curve…read more

Slide 5

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Mean: measurement at height of curve; average value; useful for comparing
Standard deviation: measurement of width of curve; indicates range of values
either side of mean from convex to concave; shows 68.26%…read more


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