AS level Biology (AQA)- Variation

• Intersepecific variation: differences between different species
• Intraspecific variation: differences within species
• Genetic Factors--> species have the same genes, but individuals within a species have different versions of the genes called alleles. Different genotypes result in variation in phenotype. Genetic variation is inherited.
• Environmental Factors--> phenotype of an individual is affected by the environment. Plant growth is affected by the amount of minerals, light etc it receives. Any differences between identical twins are purely environmental as they have the same genes i.e. different accents
• Most variation is the result of both environmental and genetic factors.

• To study variation you need to sample the population as it would be too time consuming to study the whole.
• The sample needs to be representitive and unbiased
• Averages:
  • 1) mean
  • 2)median
  • 3)mode
  • 4)Standard deviation

A low standard deviation means that the sample data varies little and a large standard deviation means that the data varies a lot.