There are plenty of animals and plants to explore and paths in the game's areas that will take you in multiple directions. My suggestion is to traverse each area from side to side and push both
and
as the prompts for each new plant and animal pop up. If you move too fast, you may miss a prompt that popped up. The game does not let you know which plants or animals you have already viewed the entries for, so I suggest that you play through each area in one sitting so you can easily remember which entries you have already viewed.
The first time you push
on any of the plants or animals, you should unlock the Researcher achievement.