Variation

• Variation is the differences in the characteristics of individuals in a population.
• The three main causes of variation are the alleles that individuals have inherited, which are genetic causes.
• Examples of genetic variation include hair color and eye color, with red hair, blond hair, and dark hair being genetic, and blue eyes and brown eyes also being genetic.
• Some variations are caused by the environment, for example, the color of these flowers depends on the pH of the soil.
• Language in humans is another example of variation caused by the environment.
• Some variation is caused by a combination of genes and the environment, for example, height in humans, where some people have alleles which make them likely to grow taller, but their diet must also include enough calcium for their bones to fully develop.
• In any population of a species, there is a massive amount of genetic variation, which is due to mutations.
• Mutations are random changes to DNA, and most mutations have no effect on the phenotype.
• Some mutations can influence the phenotype, for example, alleles for tallness may lead to tallness as a person's diet is suitable.
• Very rarely, a mutation can lead to a new phenotype, and if the environment changes, this can lead to a rapid change in the species.
• In the 1950s, a virus was heading to the UK, and a mutation occurred which made the surviving rabbits resistant to the virus, giving the rabbit a new phenotype.
• The beneficial phenotype of this mutation is widespread in the UK rabbit population.