LibreOffice only knows how to spell a few scientific names, and the more scientific names you use in a Writer document, the more your pages fill up with squiggly red underlining – indicating misspelled or unrecognised words (see main image). You can add scientific names to LibreOffice's spell checker using the application's spelling dialog box, but only one word at a time.
Is there an easier way? Yes. This article explains how you can save a lot of time and effort by adding hundreds of scientific names to the spell checker all at once.