Variation: Differences in characteristics of individuals within a population.
Causes of Variation:
Genetic Causes: Differences in alleles inherited from parents.
Examples: Hair color (red, blond, dark), eye color (blue, brown).
Environmental Causes: Differences influenced by external factors.
Examples: Flower color influenced by soil pH, language development in humans.
Combination of Genes and Environment: Traits influenced by both genetic and environmental factors.
Example: Human height depends on genetic predisposition and environmental factors like diet.
Genetic Variation
Mutations: Random changes in DNA, occurring constantly.
Most mutations have no effect on the phenotype.
Some mutations influence the phenotype; for example, alleles for tallness may lead to increased height if diet supports it.
Rarely, mutations determine the phenotype directly, such as eye color.
Impact of Mutations
New Phenotypes: Occasionally, mutations create a new phenotype.
Beneficial mutations can lead to rapid changes in a species.
Example: In the 1950s, a virus in the UK killed 99% of wild rabbits, but a mutation made surviving rabbits resistant, creating a new, widespread beneficial phenotype.
Study Resources
For further practice on variation, refer to the revision workbook available through the provided link.