Variation

Variation

1. Genes

   • Characteristics are determined by the genes inherited from its parents, some from the mother and some from the father.
   • Combination of genetics causes variation so no two are genetically identical
   • It is also due to genetic mutations.
   • Some characteristics are determined solely by genetics (e.g. blood type and inherited disorders like cyctic fibrosis and haemophilia.

2. Environment

   • Occurs over a wise range of differences (e.g. sun tan or getting yellow leaves).
   • Factors include diet, exercise, temperature, light level and water volume.

3. Continuous

   • When the individuals within a population vary within a certain range with no distinct categories
   • For example humans mass, E. coli width or number of leaves on tree.
   • Graph takes the place of a normal distribution curve where the curve is symmetrical around the mean.

4. Discontinuous

   • Where there are 2 or more distinct categories and each individual only falls into one of the categories, there are no intermediates.
   • For example blood group, whether bacteria are antibiotic-resistant or not and courgette colour.
   • Graph is a bar graph (bars don't touch).

5. Most characteristics are determined by a mix or genetic and environmental factors (e.g. body weight, height, skin colour).

   • For example, a plant's maximum height is caused by genes but whether or not it reaches that height depends on the environment in which it grows.