Causes of variation

1. Intra-species – the differences that occur within a species.
2. Inter-species – the differences that occur between members of different species.
3. Phenotype – this is an organism’s total physical appearance. It includes internal characteristics such as blood group or enzyme types. It also includes observable characteristics such as hair or eye colour and size.
4. Genotype – this refers to an organism’s genetic make-up. This means all of its genes and different forms of genes (alleles) that can be passed on from one generation from the next.