BSC 196 Lecture Notes - Lecture 20: Platypus, Ectotherm, Courtship Display
Document Summary
Chordates comprise all vertebrates and two groups of invertebrates, the urochordates and cephalochordates. All chordates share a set of derived characters (sometimes only during embryonic stages. Four key characters of chordates: notochord, dorsal, hollow nerve cord, pharyngeal slits or clefts, muscular, post-anal tail. Notochord: longitudinal, flexible rod between the digestive tube and nerve cord skeletal support throughout most of the body length: vertebrates: vertebral column largely replaces the notochord. Nerve cord: develops into the central nervous system (brain & spinal cord) Pharyngeal slits: (grooves in the pharynx) open to the outside of the body. Suspension-feeding structures in many invertebrate chordates: gas exchange in non-tetrapod vertebrates, develop into parts of the ear, head, and neck in tetrapods. Post anal tail: often greatly reduced during embryonic development, provides propelling force in many aquatic species. A skeletal system and complex nervous system have allowed vertebrates efficiency at moving and feeding: capturing food.
