Questions: Vertebrates vs. Invertebrates

Question 1

Approximately what percentage of all animal species are invertebrates?

• A. About 25%
• B. About 50%
• C. About 75%
• D. About 97%

Answer: (D)

About 97% of all known animal species are invertebrates. Insects alone account for a huge proportion — there are more species of beetles than there are species of all vertebrates combined. Vertebrates (fish, amphibians, reptiles, birds, mammals) make up only about 3% of animal species, though they tend to be the most visible and familiar.

Question 2

Snakes are invertebrates because they do not have legs.

• T. True
• F. False

Answer: False

Having legs is not the defining characteristic of a vertebrate — having a backbone is. Snakes have a backbone (spine) with many vertebrae, making them vertebrates. In fact, snakes are so flexible precisely because they have many vertebrae (up to 400 in some species), each connected by flexible joints.

Question 3

Name the five main classes of vertebrates and give one example of each.

Model answer: Fish (salmon), Amphibians (frog), Reptiles (lizard), Birds (eagle), Mammals (dog). Each class is defined by specific characteristics like body temperature regulation, body covering, and how they reproduce.

These five classes represent the major divisions within vertebrates. Fish breathe with gills and live in water. Amphibians live in water and on land. Reptiles have scaly skin and lay hard-shelled eggs. Birds have feathers and most can fly. Mammals have hair or fur and feed young with milk.