Quantitative investigations of variation

• Variation is the difference found in a population due to the result of genetic and/or environmental differences
• Interspecific variation = variation between different species
• Intraspecific variation = variation within a species
• Variation can be down to genetic differences and environmental influences
• Genetic differences are characteristics that cannot be measure across a continuous scale

  • measurable/observable characteristics fall into distinct classes/categories
  • controlled by alleles of a single gene
  • shown as data on a bar/pie chart as it is categorical data
• Environmental influences are a complete range of measurements from one extreme to another

  • influence where within a range, an organism actually lies
• Why it is difficult to draw conclusions on the causes of variation

  • mixture of genetic and environmental factors in different combinations
  • characteristics are coded for by more than one gene
• A population is all members of a specified group
• A sample is a part of a population used to describe the characteristics of the whole population
• The size of a sample can never be the same as the whole population
• To overcome the possibility of a sample being down to chance, a large sample size should be used as it's more reliable and representative
• The sample must be taken at random so that there is an equal chance for any individual to be selected