Vertebrate diversity and evolution refers to the wide range of distinct vertebrate groups which exist and have evolved slowly over time, becoming more complex. Vertebrates have evolved to possess a certain set of characteristics, with each further subdivision within the vertebrate category being representative of more similar groups which maintain quite specific traits.
The defining feature of vertebrates, separating them from invertebrates, is the vertebral column. Additionally, vertebrates have several derived features which are common across all classes. For example, all vertebrates are bilaterally symmetrical, have a well-developed body cavity lined with cellular tissue and their heads possess well-developed sense organs. However, the development and complexity of these traits may vary between different vertebrate classes. For instance, the complexity and uniqueness of the eye in a human is different from the eye of a bony fish.
The traditional classification of vertebrates separates all species into seven distinctive classes.
- Agnatha – Jawless fish
- Chondrichthyes – Cartilaginous fish
- Osteichthyes – Bony fish
- Amphibia – These are amphibians such as frogs.
- Reptilia – These are reptiles such as snakes.
- Aves – Birds
- Mammalia – These are mammals such as apes.
These vertebrates get further subdivided within their own classes until they eventually reach the species division, the smallest possible classification grouping, which contains individuals that are not reproductively isolated from each other. Furthermore, the list above of the seven vertebrate classes, presents these classes in their order of appearance on the planet. Thus, mammals were the last vertebrates to evolve.
Evidently, there exists a large range of diversity in all of the world's environments. It is through the process of evolution that the intricacy of vertebrates has become more advanced through each subsequent generation.