Fish

Fish are aquatic, gill-bearing animals that are typically covered with scales and equipped with fins. They are a diverse group of vertebrates that mostly live in water, although some species can also inhabit freshwater or brackish environments. Fish can be classified into three main groups: bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), such as sharks and rays, and jawless fish (Agnatha), including lampreys and hagfish. They have a streamlined body which aids in swimming, and they rely on gills for extracting oxygen from water. Fish are ectothermic (cold-blooded), meaning their body temperature is regulated by their environment. They play crucial roles in aquatic ecosystems as both predators and prey and are an important source of food for humans and wildlife. Fish can be found in nearly every aquatic habitat, from deep oceans to freshwater rivers and lakes, showcasing remarkable adaptations to various environments.