What are 3 major pieces of evidence that prove different species are related?

Three different ways the relatedness of species could be assessed is through:

1. Their genotype. Similarity in DNA between the species is a good indication of their relatedness.

2. Their phenotype. If the two species have similar body form and function, then there is a good possibility that they are related.

The presence of intermediates, either living or in the fossil record, can show relatedness between two species.