Genotype & Phenotype (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Genetic & Environmental Variation

• Variation is defined as differences between individuals of the same species

• Phenotypic variation is the difference in features between individuals of the same species

• Phenotypic variation can be caused in two main ways:

  • It can be genetic – controlled entirely by genes (this is called genetic variation)

  • It can be environmental – caused entirely by the environment in which the organism lives

  • Or it can be due to a combination of genes and the environment

Genetic variation

• Examples of genetic variation in humans include:

  • blood group

  • eye colour

  • gender

  • ability to roll tongue

  • free or fixed earlobes

Whether earlobes are attached (lobeless) or free (lobed) is an example of genetic variation

Environmental variation 

• Characteristics of all species can be affected by environmental factors such as climate, diet, accidents, culture and lifestyle

• In this instance, ‘environmental’ simply means ‘outside of the organism’

• Examples include:

  • An accident may lead to scarring on the body

  • Eating too much and not leading an active lifestyle will cause weight gain

  • Being raised in a certain country will cause you to speak a certain language with a certain accent

  • A plant in the shade of a big tree will grow taller to reach more light

Genetic & environmental causes

• Some features vary because of a combination of genetic and environmental causes, for example:

  • Height is determined by multiple genes with multiple different alleles

  • Tall parents will pass alleles to their children for height

  • Their children have the genetic potential to also be tall

  • However, if their diet is poor then they will not grow very well

  • Therefore their environment also has an impact on their height

• Another way of looking at this is that although genes decide what characteristics we inherit, the surrounding environment will affect how these inherited characteristics develop