Approximately what percentage of animal species are invertebrates?

• A. 5%
• B. 95%
• C. 70%
• D. 100%

Answer: (B)

The idea here is that most of animal diversity lies in invertebrates. Animals without backbones include insects, mollusks, crustaceans, worms, corals, and many other groups. Vertebrates—fishes, amphibians, reptiles, birds, and mammals—are comparatively few in number of species. Because insects alone account for a huge share of described species, and all the remaining invertebrate groups add even more to that total, invertebrates constitute the vast majority of animal species. So the best takeaway is that invertebrates make up essentially the overwhelming majority of animal life.