Vertebrate

Animals with backbones

Vertebrates are animals that are characterized by the presence of a backbone or spinal column, which is part of an internal skeleton that supports the body. Vertebrates are members of the subphylum Vertebrata, within the phylum Chordata. This group includes the most complex and highly evolved animals on Earth, including fish, amphibians, reptiles, birds, and mammals.

Characteristics

Diagram of a vertebrate body plan

Vertebrates are distinguished by their vertebral column, which replaces the notochord found in all chordates during development. The vertebral column is a series of interconnected bones or vertebrae that protect the spinal cord.

Other key characteristics of vertebrates include a well-developed brain encased in a skull, a complex nervous system, and an endoskeleton made of bone or cartilage. Vertebrates also have a closed circulatory system with a heart that pumps blood throughout the body.

Evolution

Haikouichthys, an early vertebrate

The earliest vertebrates appeared during the Cambrian explosion, around 525 million years ago. One of the earliest known vertebrates is Haikouichthys, which possessed a primitive backbone and a simple skull.

Vertebrates have undergone significant evolutionary changes over millions of years, leading to the vast diversity seen today. The transition from water to land was a major evolutionary step, giving rise to the tetrapods, which include amphibians, reptiles, birds, and mammals.

Classification

Vertebrates are classified into several major groups:

• Agnatha - Jawless fish, such as lampreys and hagfish.
• Chondrichthyes - Cartilaginous fish, including sharks and rays.
• Osteichthyes - Bony fish, the largest group of vertebrates.
• Amphibia - Amphibians, such as frogs, toads, and salamanders.
• Reptilia - Reptiles, including snakes, lizards, and turtles.
• Aves - Birds, characterized by feathers and beaks.
• Mammalia - Mammals, distinguished by the presence of mammary glands and hair.

Anatomy

Gills of a fish

Vertebrates exhibit a wide range of anatomical features adapted to their environments. Fish, for example, have gills for extracting oxygen from water, while terrestrial vertebrates have lungs for breathing air.

The skeletal system of vertebrates provides structural support and protection for internal organs. The muscular system works in conjunction with the skeleton to facilitate movement.

Adaptations

Vertebrates have developed numerous adaptations to survive in diverse habitats. For instance, birds have evolved wings and lightweight bones for flight, while mammals have developed specialized teeth and digestive systems to process a variety of foods.

Related pages

• Chordate
• Invertebrate
• Evolution of vertebrates
• Tetrapod