Final answer:
Fungi are most closely related to animals due to genetic and evolutionary relationships. Key groups for medical importance include Zygomycota, Ascomycota, Basidiomycota, and Microsporidia, which contain species that impact human health.
Step-by-step explanation:
Of the groups mentioned below, the fungi are most closely related to animals. Fungi are one of the kingdoms of the domain Eukarya and are known to be more closely related to animals rather than to plants or other groups that were formerly categorized as protists. This is due to genetic similarities and evolutionary history. Fungi are heterotrophic eukaryotic organisms with chitin in their cell walls, and they can be either unicellular or multicellular.
Medically important species of fungi are found in groups such as Zygomycota, Ascomycota, Basidiomycota, and Microsporidia. These groups include pathogens that can impact human health and include species that produce deadly toxins. Targets for antifungal medications often look to exploit important differences in fungal cells, such as the presence of ergosterols in fungal membranes. However, Öomycetes, which have similarities to fungi and were once classified with them, have significant differences like having cell walls of cellulose. Thus, they are no longer considered true fungi.