Vertebratesfish

Vertebratesfish is a term used to describe the aquatic vertebrates commonly known as fish. In scientific terms, fish are vertebrates that live in water, breathe by gills, and typically move with fins. The group includes both jawless and jawed forms and spans a broad evolutionary history.

Major groups include jawless fish (cyclostomes: lampreys and hagfish) and jawed fish (gnathostomes). Jawed fish split into cartilaginous fish (Chondrichthyes) and bony fish (Osteichthyes). Bony fish are further divided into ray-finned (Actinopterygii) and lobe-finned (Sarcopterygii); the latter lineage gave rise to tetrapods.

Anatomy and physiology: most fish have gills, fins, and scales. Bony fish often possess a swim bladder that helps regulate buoyancy; cartilaginous fish rely on other means for buoyancy. Reproduction varies from external fertilization with free-swimming larvae to internal fertilization in some species; development ranges from eggs to live births in a few taxa.

Ecology and evolution: fish first appeared over 500 million years ago and underwent major diversification in the Paleozoic era. They inhabit nearly every aquatic environment and are key predators, prey, and ecological drivers. They also provide important models for studying vertebrate evolution, development, and physiology.

Human interactions and conservation: fish support global food systems and economies through fishing and aquaculture. Many species face threats from overfishing, habitat loss, pollution, and climate change. Conservation efforts include sustainable fisheries management, habitat restoration, and responsible aquaculture practices.