These eras are divides into periods, and the periods into epochs. Geologic Time Chart. Linnaeus developed the system used today called Binomial Nomenclature. Each level is called a taxon. The most specific taxon is the species and the most general is the kingdom.
Homology is likeness due to shared ancestry.
Sometimes organisms resemble each other but are not related. This is caused by a process called convergent evolution. Organisms living in the same or similar environments develop similar structures based on natural selection. They evolve to fill a niche and help the organism survive. This is called analogy.