IB Biology Exam Prep

Answer: D, Lobster. The lobster is an arthropod, an invertebrate with an exoskeleton.

Key Takeaway: While toads, tigers, gila monsters, and hamsters are members of four distinct classes, they all share the characteristic of an internal skeleton. The lobster does not have an internal skeleton, but instead has a hard outer skeleton, or an exoskeleton, thus making it an invertebrate.