Phylum Chordata Contains ALL fishes amphibians reptiles birds
Phylum Chordata • Contains ALL fishes, amphibians, reptiles, birds, and mammals • ALL chordates have a notochord; - a flexible rod that supports a chordates back (all embryonic, some retain, some change)
CHARACTERISTICS • Cold blooded • Paired Fins • Gills, Scales • • EVOLUTION OF FISHES Agnathans – jawless, 1 st vertebrae, round mouth for sucking or filter feeding Jaws (from gill arches) & Paired fins improved swimming and feeding Cartilage Skeletons (Sharks, Rays, Skates – still considered vertebrates) Bony Skeletons (Modern Fish)
FORM & FUNCTION • Feeding – Everything you can imagine – carnivores (“big teeth”), herbivores (pharyngeal bone – small “teeth” on jaw, omnivores (random), detritivores (mouth on bottom), parasitic (“suckers”) • Respiration – Hard bony flap covering the gills - operculum – Air breathers – Obligate – must breathe air or will die (African Lungfish) – Facultative – whatever is convenient (some Catfish) – Usually found in tropical waters – because… • Circulation – Closed Circulatory System, Single Loop – Atrium --Ventricle -- Gills -- Body -- Back to Atrium
• Osmoregulation – balance of water levels in body – - Salt water fish tend to lose water & gain salt - Fresh water fish tend to gain water & lose salt - Homeostasis maintained by the kidneys • Brain Responses – - Cerebrum - thinking, voluntary activities - Cerebellum - coordination - Medulla Oblongata - functions of internal organs - Lateral Line System - senses vibrations • Movement – - Very muscular – make great swimmers and good food - Swim Bladder - buoyancy
Reproduction Oviparous (lays eggs) • Ovoviviparous (eggs stay in mom) • Viviparous (babies get nourishment from mom. Ex. Humans, cats, some fish) •
Classes of Fish • Class Myxini: “Jawless Fish” – EX: hagfish and lampreys • Class Chondreichthyes: “Cartilaginous fish” – EX: sharks, rays, chimaeras • Class Osteichthyes: “Bony Fish”
Class Myxini • Hagfish and Lampreys • Slow enough metabolism that they can eat once. Hagfish every 6 months! • They are scavengers (eat dead organisms) • Tie themselves into a knot to A) clean themselves, B) escape prey, C) pull on food Lamprey’s oral disk Hagfish knot Lamprey
Class: Chondrichthyes • Means “Cartilage fish” • Skeleton composed entirely of cartilage – still considered a vertebrate • Contains ALL sharks, stingrays, skates, and chimaeras • Characteristics: jaws, paired fins, skin covered w/ placoid scales (armor) • Denticles: teeth-like scales, feels like sandpaper
2 Subclasses Whale shark World’s Largest Fish • Elasmobranchs: Sharks and rays Sandtiger Tiger Manta Ray Blue Spotted Stingray • Holocephalans: chimaeras (ratfish) Chimaera
Class Osteichthyes • Means “bony fish” • About 25, 000 spp. of bony fish • Characteristics: swim bladder, bony scales, and fin rays • 2 sub-classes of fish – Sarcopterygii: Lobefin fish – Actinopterygii: Ray-finned fish
Sub-class: Sarcopterygii • • Lobefin Fish; have round fleshy-lobes EX: Coelacanth and Lungfish Coelacanth: is over 400 million years old Thought to be extinct; found in 1938 • • Lungfish: Lives in Africa & South America Lungfish Facultative air breathers Lungfish gave rise to land vertebrates Can live out of water for short time periods
Sub-class: Actinopterygii • Ray-finned fish; most numerous group Perch • Fusiform body shape: stream-lined allows fish to move through watch w/ great efficiency • • Scale types Ganoid: Thick bony scales that don’t overlap Lookdown Cycloid: Thin, smooth overlapping scales Ctenoid: Thin, spiny overlapping scales
Fins • • • ______: on the top of fish used for stability _____: tail fin used for locomotion & stability ______: bottom of fish used for stability ______: used for steering (anterior) ______: used for steering (posterior)
Functions • Bony fish are Oviparious: (reproduce by laying eggs) • Air Bladder: gas-filled sac used to maintain buoyancy • Fish have a closed cardiovascular system • Lateral line system: canals on the side of the fish used to detect movement in the water
Coloration Countershading Iridophore • *Chromatophore: specialized cells that contain pigments • *Iridophore: crystals that produces a mirror-like silver color • *Countershading: camouflage where top of fish is dark, and bottom of fish is light, used to blend into the ocean
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