“Original Research” means that you cannot put some facts about an organism into a Wikipedia article just because you know them to be true – the content is all supposed to be based on published sources. However if the facts are completely uncontroversial, like saying a species of gull is a bird, you don’t have to cite a source for those kinds of facts.
And yes, it is true that species are all inherently notable, so you don’t have to establish “notability” up front, as you would need to do for an article about an individual human.