Fish Fish ➔ Kingdom: Animalia ➔ Phylym: Chordata ➔ Three Classes: 1. Jawless fish (agnatha) 2. Cartilaginous fish (chondricthyes) 3. Bony Fish (osteichthyes) Fish Characteristics ➔ Gills for breating ➔ Backbone (vertebrae) ➔ Paired fins ➔ Closed circulatory System ➔ Two-chambered heart Wat te s ar t he! Fish Anatomy Internal Features Fish Anatomy External Features Fins Fish Respiration ➔ Water flows over gills as fish opens mouth and swims ➔ Water flows opposite direction of blood flow ➔ O2 diffuses from the water into the blood ➔ Gills are made of thousands of gill filaments ➔ Gills are covered by the operculum (gill cover) Fish Respiration Reproduction ➔ Most reproduce sexually, and fertilize their eggs externally ➔ Sharks/rays fertilize internally ◆ Some keep their eggs in their uterus (viviparous) ◆ Others will lay the eggs oviparous) ➔ Spawning is the process of fertilizing eggs ➔ Baby fish are called FRY Jawless Fish ➔ Class: Agnatha ➔ No Jaws ➔ Skeleton made of cartilage ➔ Soft skin (no scales) ➔ 7 gills ➔ Lack a swim bladder ➔ Examples: Lampreys, Hagfish Cartilaginous Fish ●Class: Chondrichthyes ●Swim constantly to force oxygen into their gills ●Caudal fin (tail) is large/strong ●Skeleton made of cartilage (not bone). ●5-7 gill slits located on each side of the body ●Examples: Sharks and Rays ● 350 different species of sharks ● 300 species of rays and skates Bony Fish ➔ Class: osteichthyes ➔ Skeleton made of bone ➔ Teeth are fixed onto the upper jaw ➔ Swim bladder: air filled sac that helps them with buoyancy ➔ Do not have to swim to breathe (can move gill covers to force water over gills.) ➔ Examples: Trout, Perch, Pike, Goldfish .