Human diseases can decimate animal populations, from such well-meaning activities as ecotourism.
The answer to the question of what relationship is classified as host-parasite. A parasitic relationship is one in which one organism, the parasite, lives off of another organism, the host, harming it and possibly causing death. A few examples of parasites are tapeworms, fleas, and barnacles. The parasite lives on or in the body of the host.
The gradual evolution for the family Equidae (horse family) has been well documented within the fossil record.
The answer is 0.000000315