Ch 34 Chordates

4 anatomical features chordates are characterized by

Notochord, dorsal, pharyngeal slits, and a muscular post anal tail

Notochord

A flexible rod between the digestive tube and the nerve chord; it is composed of large fluid filled cells encased in stiff, fibrous tissue; provides skeletal support

Dorsal, hollow nerve chord

Develops in vertebrae embryo from a plate of ectoderm that rolls into a tube dorsal to the notochord; in chordate embryos it develops into central nervous nervous system

Pharyngeal Slits

Allows water entering the mouth to exit the body without passing through the entire digestive tract

Muscular, post anal tail

Contains skeletal elements and muscles, provides propulsive force in aquatic species

Subphylum Vertebrata

In Phylum Chordata; characterized by a neural crest, pronounced cephalization, a vertebral column, and a closed circulatory system

Neural Crest

A group of embryonic cells that forms near the dorsal margins of the closing neural tube, it contributes to the formation of certain skeletal elements and other structures

Cephalochordata

Lancelets, they most closely resemble the ideal chordate, all 4 chordate characteristic persist in adult stage

Urochordata

Tunicates; most are sessile animals that adhere to rocks, docks, and boats and are suspension feeders; have all 4 chordate characteristics in larval form but only pharyngeal slits in adult stage

Gnathostomes

All vertebrates except lampreys and hagfishes, defined by having true jaws and 2 sets of paired appendages

Tetrapods

The paired appendages are modified as legs to support movement on land

Clade Amniotes

Consists of mammals, birds, and reptiles; have adaptations, like amniotic eggs, waterproof skin, and an increasing use of the rib cage to ventilate lungs, for terrestrial living

Cyclostomes or agnathans

The 2 extant classes of jawless vertebrates, hagfishes and lampreys

Hominid

Term referring to great apes and humans collectively

Hominin

Twigs in the evolutionary tree that represent animals more closely related to humans than any other living species

Australopithecus

“Southern ape”, walked fully erect, had human like hands and teeth, had a brain 1/3 the size of a modern human’s brain, Lucy