Evolution in action?

You've probably heard about the extinction of some species of amphibians. Since 1980, scientists think we lost between nine and 122 species. Now they feel that because of changes in land use, disease, invasive species pushing out native amphibians and, the old bugbear - commercial exploitation, we are in danger of losing one-third of the existing 6000 species of amphibians. The biggest threat is from disease; a fungus causes the animals to reduce their intake of air and moisture. Is this fungus simply part of evolution?