Which of the following is the best definition of a laboratory animal?

The definition of a laboratory animal is best captured by identifying vertebrate animals, as they encompass a significant portion of species used in research, testing, and teaching. The term "vertebrate" refers to animals that possess a backbone, which includes a variety of species such as mammals, birds, reptiles, amphibians, and fish. These animals are commonly utilized in laboratory settings due to their complexity and relevance in biomedical research, as they often exhibit physiological and genetic traits similar to humans.

Moreover, regulations and guidelines governing animal research tend to focus predominantly on vertebrate species, reinforcing the importance of classifying laboratory animals within this group. In many jurisdictions, specific protections and ethical considerations are afforded to vertebrate animals, recognizing their higher cognitive abilities and welfare needs.

In contrast, options that refer to invertebrates or broader categories of animals do not align as closely with the common definitions used in laboratory research. While invertebrates may be used to some extent in research contexts, vertebrates are more prominently recognized in regulatory frameworks and ethical considerations related to laboratory animal use.