What do heavily latin based languages use for scientific terminology?

No; we don't always use Latin words. Some of our root words are in fact Greek; not Latin. English is a Germanic language, Spanish French and Italian are Romanesque; they already have root words. But Latin was used in all of Europe at one time as the language of the educated; so the custom has stayed on. Latin was not used for one thousand years, though. Nor is it from Greek; they are two distinct languages.