How do I complete nataralist? Is there a checklist?

Im running round taking samples for harriet trying to win her heart but I think she's never gonna gonna fall for me and leave the behind her experiments in the wild.

It's finally time to accept I must move on..So How i do I complete the naturalist? Is there some section I can see to track my progess and give a a list of what to do next? Do I have to collect more herbs and flowers and stuff besides sampling animals?

thanks,