jimtrue.com : school : BSC2011L : Lab 08: Animalia III: Phyla Echnodermata & Chordata
Posted by Jim True on October 26, 2004 2:31 PM. Last Updated October 22, 2006 9:23 PM
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Last two Phyla of Animalia (highest phylogenetic tree)
Superficially couldn't be more different in appearance, though embryologically closely related to the Echinodermata (spiny skin) .
Echinoderms, evolutionarily unusual. Up to this point bilateral symmetry (radial is considered lesser evolved characteristic). Radial symmetry is 'secondary' radial symmetry. Bilateral, because all their larvae is bilateral; they undergo metamorphosis into a radial symmetrical animal.
** Pentaradiate radial symmetry. Subdivided into 5 distinct axis. Number of arms is always divisible by 5.
** Extensive body cavity. Entire cavity is open (coelom)
** Do not use musculature to move; not used for locomotion; they use hydraulic power. Water vascular system - system of interconnected vessels used to generate fluid pressure to move specialized tubes to allow animal to move &/or grasp objects. pressure plate (madreporite) for water intake; feed water into ambulacra that hydraulically fill tube feet.
Cannot osmoregulate, so they are only found in marine environments (cannot deal with changes in salinity).
Pedicellaria (look at live on slide).
Left, right, dorsal, ventral has no meaning. Side with mouth is 'oral surface'; no mouth, 'aboral' surface. All Echnoderms except for one, mouth lays DOWN on surface of ocean.
Asteroidea
Calcareous plates are called 'ossicles'.
Madreporite very distinct.
Ophiuroidea (arms are also in multiples of 5)
Chordata (possess 3 distinct Sub-Phyla)
4 Defining characteristics -
Notochord, early development, mesoderm develops into vertebral column (part of the skeletal system)
Dorsal Hollow Nerve Cord (DHNC) (neural tube or neural canal), created from ectoderm on the dorsal region, hollow tube of nervous tissue... some will disappear or fill in with nervous material and become spinal cord. Two completely separate systems; DHNC is nervous system; Notochord is part of skeletal system.
Pharyngeal slits - pharynyx evolutionary devolves into passageway between respiratory and digestion. 3 evolutionary sequences (feeding modification - filtering water; feeding & respiratory (gills); ultimately into respiratory, all chordates during development up to and including embryonic humans.
post-anal tail - continuation of muscle, notochord and DHNc posterior to the anus. Used for propulsion, balance, and communication in terrestrial chordates. Humans do have post-anal tail, usually removed at child-birth.
Three sub-phylum (first two or invertebrates)
Urochordata - amorphous looking blobs, all four CC's are lost in adults, except pharyngeal slits
Cephalochordata (fish-like forms) - Lancelets, look like flattened blade. All four CC's retained throughout life.
SP Vertebrata (all possess, with one exception, rigid internal backbone of cartilage or bone). One class retains notochord. Posession of capsular structure around the brain. Other S.P. are 'acraniate' ... all vertebrates are 'craniate'. Degree of CC retention is variable.
Retention means that in the adult, the ORIGINAL formation is kept. Spinal column is not the same as a DHNC, Vertebrate backbone is not the same as Notochord. Transformed or disappeared.
Class Agnatha - "lacking jaws" - lampreys, jawless fishes, have no paired appendages.
Class Chondrichthyes ("cartilage fishes") - cartilage skeleton, sharks, stingrays, skates, chimeras. paired appendages
Class Osteichthyes ("bony fishes") - predominate vertebrata, entire skeleton of bone, paired appendages
Class Amphibia ("between life") - two worlds, terrestrial, but must be wet and must be water for reproduction, young are aquatic. Bone or cartilage.(toads, salamanders, frogs). Paired appendages (four walking or hopping limbs - tetrapods (four feet or four limbs); skin is naked (no scales, fur, feather, etc.)
Class Reptilia - TRULY terrestrial animals, scales for protection against loss of water; tetrapods (snakes have secondarily lost their limbs);
Class Aves - birds, skeltons are VERY porous for flight; no teeth in jaws
Class Mammals - epidermal derivatives called hair or fur; 7 cervical vertebrate in the neck, mammary glands that secrete lactose to nourish infant mammal.
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