"Snow," is a mass, or noncount, noun. It has no other form (except in literary or other specialized language).
"Panda" is a count noun. Count nouns have three possible forms for the generic. The basic generic form for count nouns is plural:
Pandas are very playful when THEY are young
There are two other generic forms for count nouns: the singular indefinite form "A panda" ("any member of the category") and the form used to refer to the abstract category, the singular "the panda," as in "THE panda is still an endangered species."
The pronoun used for the indefinite singular noun "a panda" is "one." "One" refers, again, to "any member of the category."
In contrast, "snow" is definite and therefore is represented by "it." For example,
Snow is beautiful when IT'S newly fallen
"It" for generic noncount nouns corresponds to the plural generic "they" for count nouns.