Vertebrates Vertebrate Survey Anatomy and Physiology of Vertebrates

Vertebrate Evolution Phylum Chordata is the group of animals with a notochord – a flexible, supporting structure along the back Contains the invertebrate chordates, and Subphylum Vertebrata, which have evolved vertebral columns Serves as site for muscle attachment, protects nerve cord

Trends in Vertebrate Evolution Development of true bony jaws Development of paired pectoral and pelvic limb girdles Development of bones Most vertebrates have two sets of appendages (arms and legs), a closed circulatory system with a ventral heart, and either gills or lungs for breathing

Class Agnatha Jawless fish Ex. Lampreys and hagfishes Only living vertebrates without jaws Parasites – survive by attaching themselves to other fish or aquatic animals, feeding on their blood and body fluids Scavengers – eat decaying carcasses

Class Chondrichthyes Cartilaginous fish Ex. Sharks, skates, rays Skeletons made of cartilage Some are fearsome predators, other eat small fish, mollusks, or plankton

Class Osteichthyes Bony fish Contain half of all vertebrate species, all aquatic habitats Ray-finned fish – sub-class containing almost all fish species – well-developed bone systems, specialized jaws with teeth Lobe-finned fish – sub-class with lungs and gills, relatives of amphibians

Class Amphibia (amphibians) Lay eggs in water and spend part of their life cycle there (gills) As adults, live on land and breathe through lungs Most have moist skin, as part of their respiration occurs through skin

Class Amphibia Examples include: Newts and salamanders (lay eggs in water, hatch into young that resemble adults – larvae have gills that disappear and are replaced by lungs as they grow) Frogs and toads (eggs hatch in water as tadpoles, which look completely different from adults)

Class Reptilia (reptiles) Fully terrestrial Reproduce by internal fertilization – egg/sperm fuse within body of the female Produce leathery eggs to prevent water loss Dry scaly skin to retain moisture Developed lungs

Class Reptilia Order Chelonia – turtles and tortoises, protective shell of bony plates (long fossil record) Order Crocodilia – crocodiles, alligators, caimans (long fossil record) Order Squamata – lizards and snakes, most abundant group

Class Aves (Birds) Only vertebrates with feathers Used for flight and conservation of body heat Lay eggs

Class Mammalia (mammals) Named for presence of mammary glands, enable females to nourish young with milk Have hair to retain body heat

Class Mammalia Three groups: Monotremes – egg-laying mammals like duck- billed platypus – have body hair/fur, lay leathery eggs Marsupials – live young born very early in their development and continue to develop within marsupium – kangaroos, koalas, opossums Placental mammals – largest group, names for placenta (organ that connects mother with developing embryo, allows for nutrient, gas, and waste exchange)