Genes that retain their function yet change over evolutionary time as organisms diverge are called orthologs. Organisms with identical or very similar orthologous genes belong to the same .

Organisms with identical or very similar orthologous genes belong to the same phylotype.

Explanation:

A gene is a unit of heredity which is made up of DNA( deoxyribonucleic acid). The genetic make up of an individual determines it's appearance, it's survival, it's behavior in its environment. As organisms diverge, orthologous genes retain their function yet change over evolutionary times.

Phylotypic organisms that has similar orthologous genes are made up of genes in different species that originated by vertical descent from a single gene of the last common ancestor. This can be detected by collecting all the genes in two species and comparing them all to one another. If genes from two species identify each other as their closest partners then they are considered orthologs.