What is the difference between "the + singular countable noun" and "zero article + plural countable noun" when we make generalisations about classes of things.
"The singular countable noun" for generalisations was only, I think, ever used for animals and humans (eg "The lion is a carnivore").
Its use for animals is now old fashioned. Its use for humans is not only old fashioned, but often regarded today as offensive.
Edit: Jason has pointed out that this is not used exclusively for animals and humans (though I think it was always mostly used that way). I still maintain that it is old fashioned.