An animal without a backbone.

An animal without a backbone.

• A. Mammal
• B. Invertebrate
• C. Bird
• D. Vertebrate

Answer: (B)

Animals without a backbone are invertebrates. The backbone, or vertebral column, is what defines vertebrates. Mammals and birds are vertebrates because they have a backbone, as do fish, reptiles, and amphibians. In contrast, invertebrates lack this internal skeleton and include insects, mollusks, crustaceans, and worms. So naming an animal without a backbone points to the invertebrate group.

Animals without a backbone are invertebrates. The backbone, or vertebral column, is what defines vertebrates. Mammals and birds are vertebrates because they have a backbone, as do fish, reptiles, and amphibians. In contrast, invertebrates lack this internal skeleton and include insects, mollusks, crustaceans, and worms. So naming an animal without a backbone points to the invertebrate group.