The first word of the scientific name functions as a noun, as it is used to identify a class of things. It tells us biological classification ranking between family and species, consisting of phylogenetically and/or structurally related species or a single isolated species with a specific diferentiation - the genus.
Therefore, the correct answer is:
The first word of the scientific name is capitalized, functions as a(n) noun and tells us the genus of the organism.
