What defines a vertebrate?

The definition of a vertebrate refers specifically to animals that possess a segmented backbone or spinal column. This feature is a fundamental characteristic that distinguishes vertebrates from invertebrates, which do not have a backbone. The segmented nature of the backbone allows for greater flexibility and mobility in vertebrates, which include groups such as mammals, birds, reptiles, amphibians, and fish.

In terms of context, the other options do not accurately describe what defines a vertebrate. An animal lacking a backbone refers specifically to invertebrates, which comprise the majority of animal species. A type of pest control product and a plant species that transmits diseases are completely unrelated to the biological classification of vertebrates. Understanding these distinctions helps in grasping key concepts about animal biology and classification in the study of ecology and pest management.