Chapters 30-32 Biology – Miller • Levine The Chordates Chapters 30-32 Biology – Miller • Levine

Chordates Phylum Chordata Includes two invertebrate subphyla: lancelets and tunicates Subphylum Vertebrata

Chordate Characteristics Dorsal, hollow nerve cord – the brain and spinal cord Notochord – flexible, longitudinal rod located between the digestive tract and the nerve cord Pharyngeal pouches – gill structures in the pharynx Post-anal tail – tail to the rear of the anus

Chordate Characteristics The characteristics are not always visible in the adult form, but are always present in the embryo

Vertebrates Subphylum that includes mammals, birds, reptiles, amphibians and the various classes of fishes Unique features include cranium and backbone

Fishes

Agnathans Jawless fish Class Myxini (hagfishes) Class Cephalaspidomorphi (lampreys)

Class Chondrichthyes Cartilaginous fishes Include sharks and rays Have a flexible skeleton made of cartilage Lateral line system – row of sensory organs running along each side of the body, detects minor vibrations

Class Chondrichthyes

Class Osteichthyes Bony fishes (trout and goldfish) Also have a lateral line system Operculum – protective flap that covers the gills Swim bladder – gas-filled sac that keeps them buoyant

Class Osteichthyes Most are ray-finned fishes – fins supported by thin, flexible rays Lungfishes – must surface to gulp air into their lungs Lobe-finned fishes – fins are supported by stout bones

Amphibians

Class Amphibia Frogs and salamanders Exhibit a mixture of aquatic & terrestrial adaptations Need water to reproduce Depend on their moist skin to supplement lung function in exchanging gases

Class Amphibia First vertebrates to colonize land Tetrapods (“four legs”) – terrestrial vertebrates (amphibians, reptiles, birds & mammals)

Reptiles

Class Reptilia Snakes, lizards, turtles, crocodiles, and alligators Have many additional adaptations for living on land Water-proofed scales to prevent dehydration Amniotic egg – water-containing egg enclosed in a shell

Class Reptilia Ectotherms – warms itself by absorbing external heat Can survive on less than 10% of the calories required by mammals Mesozoic era – “age of reptiles” – the time of the dinosaurs

Birds

Class Aves Birds Reptilian features – scales on legs, amniotic egg Almost all species are able to fly

Class Aves Adaptations for flight: Light, hollow bone Absence of some internal organs Are toothless Endotherms – maintain temperature using metabolic heat Wings – strong muscles, feathers

Mammals

Class Mammalia Probably evolved from reptiles Most are terrestrial, some are aquatic (dolphins, whales), some can fly (bats) Two unique features: hair and mammary glands Are endotherms Have a fluid filled amniotic sac

Three Major Groups Monotremes – egg-laying mammals (platypus) Marsupials – pouched mammals (kangaroo) Eutherians – placental mammals Make up almost 95% of mammals Marsupials and Eutherians both have a placenta which joins the embryo to the mother and provides nutrients to the embryo

Class Mammalia

Primates Order that includes monkeys, apes & humans Early primates were small, arboreal (tree-dwelling) mammals Limber shoulder joints, dexterous hands, eyes close together on face, excellent hand-eye coordination

Primates Divided into two main groups: Prosimians (lemurs) Anthropoids (monkeys, apes & humans) Humans are most closely related to apes