Why are so many of the same genes found in almost all living organisms

Molecular homology occurs when different species inherit similar molecules, such as nucleic acids or proteins, from an evolutionary common ancestor. In many cases, especially for essential housekeeping genes involved in protein synthesis or DNA replication, genes are homologous across most, if not all, living organisms. Hope this helps!

Explanation:

the sphincter muscles at the end of the digestive tract is the anus.