210 likes | 228 Views
Explore the key characteristics and groups within Phylum Chordata, including Urochordates, Cephalochordates, and Vertebrates like Fish, Amphibians, Reptiles, Birds, and Mammals. Learn about their derived features and classification.
E N D
Derived Characters of Chordates • All chordates share a set of derived characters • Chordatesare bilaterian animals that belong to the clade of animals known as Deuterostomia • There are four key characters of chordates (Some species have some of these traits only during embryonic development)
Four distinctive features: • Dorsal, hollow nerve cord (in most chordates, the front end of it develops into a brain) • Notochord (flexible, longitudinal rod located between the digestive tract and the nerve cord) (In vertebrates, it is replaced by the vertebral column) • Pharyngeal gill slits (gill slits and structures supporting them in the pharynx, the region of the digestive tube just behind the mouth )Develop into parts of the ear, head, and neck in tetrapods • Post anal tail (posterior to the anus)
Groups in the Phylum Chordata • Subphylum Urochordata (tunicates) • Subphylum Cephalochordata (lancelets) • Subphylum Vertebrata Although they are invertebrates, the urochordates and cephalochordates, are more closely related to vertebrates than to other invertebrates
Fig. 34-5 Incurrent siphon to mouth Water flow Notochord Dorsal, hollow nerve cord Excurrent siphon Tail Excurrent siphon Excurrent siphon Atrium Muscle segments Incurrent siphon Pharynx with slits Intestine Anus Stomach Intestine Tunic Atrium Esophagus Pharynx with slits Stomach An adult tunicate A tunicate larva
Tunicates • Tunicates(Urochordata) are more closely related to other chordates than are lancelets • They are marine suspension feeders commonly called sea squirts • As an adult, a tunicate draws in water through an incurrent siphon, filtering food particles (adults are sessile) • Tunicates most resemble chordates during their larval stage, which may last only a few minutes
Lancelets • Cephalochordata are named lancelets for their bladelike shape • They are marine suspension feeders that retain characteristics of the chordate body plan as adults mouth pharyngeal slits notochord digestive tract dorsal, hollow nerve cord segmented muscles anus tail
Skull encloses brain • Vertebral column – composed of a series of segmented units called vertebrae (encloses nerve cord) • Endoskeleton is composed of either flexible cartilage or a combination of bone and cartilage • Because of its living cells, the endoskeleton can grow with the animal (unlike the arthropod’s exoskeleton)
Vertebrata • Classes • Mixini – Jawless Fish (Hagfish) • Cephalospidomorphi – Jawless Fish (Lamprey) • Chondrichthyes - Cartilagenous Fish (sharks, skates, rays) • Osteichthyes – Bony Fish (Tuna, Salmon, Bass) • Amphibia – Frogs, Toads, Salamanders, Caecilians • Reptilia – Snakes, Lizards, Crocodiles, Alligators, Turtles, Tortoises, Tuatara • Aves (currently placed in the class Reptilia) - Birds • Mammalia - Mammals