Vertebrates are a diverse group of animals defined by the presence of a backbone, an internal skeletal structure that provides support. This defining feature distinguishes them from other animal forms, from the smallest fish to the largest mammals.
Key Features of Vertebrates
Vertebrates possess several distinct anatomical features that enable their complex body plans and functions. A notochord, a flexible rod-like structure present during embryonic development, typically develops into the vertebral column (backbone) in adults. This column provides structural support and protects the spinal cord.
The cranium, or skull, is a bony or cartilaginous structure that encases and protects the brain. This protection is important for the central nervous system.
Vertebrates also possess an endoskeleton, an internal framework of bone or cartilage, which provides attachment points for muscles, enabling movement and body support. They also have a dorsal, hollow nerve cord that develops into the brain and spinal cord. Pharyngeal slits are present at some developmental stage.
Diverse Groups of Vertebrates
The vertebrate subphylum encompasses a wide array of animals, traditionally categorized into five major classes. Fish, an aquatic group, are characterized by gills for breathing underwater and fins for propulsion; examples include salmon and sharks. Amphibians, like frogs and salamanders, have a dual life cycle, often starting in water and moving to land, and possess moist skin.
Reptiles, including snakes, lizards, and turtles, are known for their scales and generally lay eggs on land. Birds are distinguished by feathers, wings, and egg-laying reproduction, with examples like sparrows and eagles. Mammals, including humans, dogs, and whales, possess fur or hair, mammary glands for feeding their young, and typically give live birth.
How Vertebrates Differ from Invertebrates
The primary distinction between vertebrates and invertebrates is the presence or absence of a backbone. Vertebrates have a vertebral column, which provides internal structural support and protects the spinal cord. In contrast, invertebrates, comprising about 97% of all animal species, lack this internal skeletal support.
Without a backbone, invertebrates are often smaller and slower-moving than vertebrates. While all vertebrates exhibit bilateral symmetry, meaning their bodies can be divided into two mirrored halves, invertebrates can display various body symmetries, including radial symmetry, as seen in jellyfish or starfish. Common examples include insects, worms, jellyfish, and snails.