Vertebrater

Vertebrates, or vertebrater, are animals within the subphylum Vertebrata of the phylum Chordata. They are distinguished by a vertebral column (backbone) that protects the spinal cord and provides structural support, and by a cranium that houses the brain. Most vertebrates also have an endoskeleton made of bone or cartilage.

Other defining features include a dorsal hollow nerve cord, a segmented body plan, and a high degree of cephalization. Vertebrates have closed circulatory systems with a heart, and most possess specialized respiratory organs (gills in aquatic species and lungs in many terrestrial species). They also possess complex digestive, excretory, and reproductive systems and advanced nervous and sensory organs.

Diversity and habitats: The group includes fishes, amphibians, reptiles, birds, and mammals. They inhabit a wide range of environments, from oceans and rivers to forests, deserts, and skies, and they display varied life histories and adaptations.

Reproduction and development: Most vertebrates reproduce sexually. Fertilization can be internal or external depending on the species, and development ranges from egg-laying to live birth. In many groups, early development features the formation of the backbone and skull.

Evolution and classification: The vertebrate lineage arose in the early Paleozoic era from chordate ancestors. The emergence of jaws in gnathostomes spurred extensive diversification, leading to the broad array of fishes, amphibians, reptiles, birds, and mammals seen today.