The truth? It’s likely that your concerns are unfounded. You probably do not need outside references, and you most likely did not misunderstand the passage. To put it bluntly, the ACT wants you to feel uncomfortable when you’re grinding through the science passages; it hopes you question your comprehension abilities and begin to doubt yourself. The key is to accept that it is completely fine to feel slightly uncomfortable looking at the content that the ACT science section presents!
Here’s a secret about the ACT science section: the test purposely does not give you enough information to make you feel well-acquainted with the subject matter. If it did, I’d be ready for a PhD in science thanks to all the science passages I’ve done! Don’t rely on my word, though. The next time you take a glance at a science section, look at the small wording beneath a table or chart. Often, there will be information saying the table or graph was adapted from somewhere. This means the passage is giving you the CliffsNotes version of a real experiment. If you’ve ever used CliffsNotes for English class instead of reading The Scarlet Letter, then you know that CliffsNotes leave out a lot of details. Expect the same in a science passage. The information to answer the questions will be there, but you will rarely get enough information that you could walk away from the passage and fully explain all of the science behind it.
On the ACT Science section, knowing strategies and tricks is important; however, developing a sense of confidence when dealing with unfamiliar content can be just as key, especially since it is unlike the science tests you see in school. If anything, knowing that it’s okay to feel uncertain should be refreshing. The next time you’re on a passage, and you see a reference to a term or a species that you’ve never heard of and the passage doesn’t bother defining it, you can rest easy that it almost certainly won’t affect your ability to correctly answer the questions.