Phylum Chordata Invertebrate chordates examples Urochordata Tunicates sea

Phylum Chordata Invertebrate chordates examples – Urochordata • Tunicates, sea squirts, ascidians – Cephalochordata • lancelets Share 4 “chordate” characteristics • Notochord – Flexible rod-like structure • Dorsal nerve cord – Tube for nerves • Pharyngeal gill slits – Respiration and feeding • Post-anal tail – Reabsorbed in some species

Phylum Chordata, subphylum Vertebrata • Share the 4 chordate characters with lancelets and sea squirts • Backbone, vertebral column, spine – Series of hollow vertebrae – Protects nerve cord (spinal cord) • Bilateral symmetry • endoskeleton

Agnatha (jawless fishes) • Lack: paired fins, scales, & well developed vertebrae • Hagfish (slime eels) – Mucus for protection – Feed on decaying flesh • Lampreys – Parasitic – Anadromous • Marine adults, breed in freshwater

Chondrichthyes (cartilagenous fishes) • Sharks, rays, skates, & ratfishes • Movable jaws of ventral mouth • Paired fins • Placoid scales – Dentricles (same composition as teeth)

Sharks • • Heterocercal caudal fin Two dorsal fins Paired pectorals 5 -7 gill slits Many rows of teeth Oily liver Diverse examples: hammerhead, sawfish, thresher, whale sharks

Rays, Skates, & Ratfishes • Flattened • Demersal • 5 prd ventral gill slits • Expanded pectorals Rays vs. skates rays: reduced or no dorsal fin – Stingrays • Venomous defensive spine – Electric rays • Upto 200 volts for defense and predation – Ratfishes (chimaeras) • Deep, bottoms, long skinny tail • Paired (pelvic) & unpaired (forehead) male claspers for copulation & holding female --seen in rabbitfish

Lateral line

Osteichthyes (bony fishes) • • Swim bladder Operculum (gill cover) Homocercal tail Scales of bony origin – Smooth cycloid – Spiny ctenoid

Circulatory system: 2 chambered heart (“one way flow”) …ventricle chamber to gills, “fresh” blood to tissues, back to atrial chamber

Gill function and diffusion of gas • High surface area from many folds or lamellae of gill filaments • The water : blood relationship is in a counter-current orientation -enhances diffusion – higher [Oxygen] in water than blood

Fish reproduction & development • Internal fertilization – w/specialized copulatory structures • External fertilization – Broadcast spawning • Millions of eggs released as part of plankton – Some fishes deposit eggs on bottoms – Some bury in sandy shores • Unique examples: – Male carriers • • e. g. At Birch aquarium Oviparous – Eggs released, fertilized, developed externally, lots of yolk • Viviparous – Internal development, direct nourishment; birth live young • Ovoviviparous – Internal egg development; yolk; birth live young

Class Amphibia • First terrestrial vertebrates (tetrapods) • Frogs, salamanders, newts • “Two lives”-- Transitions from aquatic to land – lose post anal tail & gill slits • Requires moist environments – At least for reproduction & early development • External fertilization • Three chamber heart

Class Reptilia • Dinosaurs, turtles, lizards, snakes, crocodiles, alligators • Evolved from amphibious ancestor – broke dependency to aquatic environment • Tough, scaly skin – Prevents desiccation • First sign of amniotic egg – Key for transition to land – Keeps embryo moist • Internal fertilization

Class Aves (Birds) • Descendants of reptiles • Adapted for flight – – Feathers Wings Light bones Flight muscles/breastbone • Four-chamber heart • Extensive respiratory system

Class Mammalia • Brain sizes are larger pound of body weight than most other animals'. • Mammals have more efficient control over their body temperatures than even birds. • Hair provides insulation. • Mammary glands provide milk to nourish the young. • Teeth are specialized for cutting, shearing or grinding; thick enamel helps prevent teeth from wearing out.

Order Monotremata • Egg laying mammals – Australia & New Zealand – Only 2 extant Families that include: • Platypus • Echidna

Order Marsupialia • Pouched mammals – Born in the embryonic stage; finish outside the mothers body (pouch) – Largely Australian • Koala, Kangaroo, Tasmanian Devil – Few North American • opossum

Placental Mammals • Embryos nourished by placenta for extended gestation periods – 9 mos. = human – 2 yrs. = elephant • 12 Orders that include: – Bats, horses, whales, rodents, cats, dogs, and primates (monkeys, apes, & humans)