Vertebrates Biology Lecture 5 PDF

VERTEBRATES BIOLOGY BIO131  Phylum Chordata (1) Aquatic, aerial or terrestrial. All free-living with no fully parasitic forms. (2) Body small to large, bilaterally symmetrical and metamerically segmented. (3) A postanal tail usually projects beyond the anus...

VERTEBRATES BIOLOGY BIO131  Phylum Chordata (1) Aquatic, aerial or terrestrial. All free-living with no fully parasitic forms. (2) Body small to large, bilaterally symmetrical and metamerically segmented. (3) A postanal tail usually projects beyond the anus at some stages (4) Exoskeleton often present; well developed in most vertebrates. (5) Body wall triploblastic with 3 germinal layers (6) Coelomate animals having a true coelom. (7) A skeletal rod, the notochord, present at some stage in life cycle. (8) A cartilaginous or bony, living endoskeleton is present  General Characters of Phylum Chordata (9) Pharyngeal gill slits present at some stage; may or may not be functional. (10) Digestive system complete with digestive glands. (11) Blood vascular system closed. Heart ventral with dorsal and ventral blood vessels. (12) Hepatic portal system well developed. (13) Excretory system comprising proto-or meso-or meta-nephric kidneys. (14) Nerve cord dorsal and tubular. Anterior end usually enlarged to form brain. (15) Sexes separate with rare exception.  Major Subdivisions of Phylum Chordata Subphylum 1. Hemichordata Subphylum 2.Urochordata(or Tunicata) Subphylum 3. Cephalochordata Subphylum 4. Vertebrata  Subphylum I: Hemichordata Hemichordates (hemi, half; chorde, cord) have long been traditionally considered to be the lowest chordates. Generally considered the sister group of the echinoderms. Recently were considered not a true notochord. Hence the hemichordates are removed from the chordates and treated as an independent Acorn worm invertebrate phylum.  Subphylum II: Urochordata 1. Exclusively marine and cosmopolitan in all seas and at all depths 2. Mostly sedentary (fixed), some pelagic or free-swimming 3. Living solitary or in groups or composite (colonial) 4. Size (0.25 to 250 mm), shape and color variable 5. Adult body degenerate, sac-like, unsegmented and without tail 6. Body covered by tunicine, similar to cellulose, so named Tunicates 7. Acoelomate. Instead, an ectoderm-lined atrial cavity present which opens to outside through atrial aperture  Subphylum III: Cephalochordata The members of the subphylum Cephalochordata are small, marine and superficially fish-like chordates They are of special significance because they possess the three primary chordate characters such as notochord, dorsal tubular nerve cord and pharyngeal gill slits Thus, they display the simple primitive chordate and are considered a blueprint of the phylum Chordata The most extensively studied cephalochordate type is Branchiostoma (lancelet). First described by the German scientist Pallas in 1778. An Italian scientist Costa (1834) first recognized as Branchiostoma lanceolatum. In 1836 Yarrel named it as Amphioxus lanceolatus. Amphioxus lanceolatus  Subphylum Vertebrata (L., vertebratus, backbone) is subdivided into 9 classes (Ostracodermi, Cyclostomata, Placodermi, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves and Mammalia).  Subphylum IV: Vertebrata What are Vertebrates? 1. Names is from the presence of serially arranged ‘’Vertebrae’’ which form together the vertebral column. 2. Elaboration of anterior skeletal elements into a 'cranium' or skull’ 3. There are No other group of animals possesses these two fundamental and related characters which have existed in vertebrates  Neural Crest Cells Neural Neural A unique feature of Dorsal edges of neural plate crest tube Ectoderm Ectoderm vertebrates is the neural crest, a collection of cells that appears near the dorsal Migrating neural margins of the closing neural Notochord crest cells (b) Neural crest cells migrate to tube in an embryo. (a) The neural crest consists of bilateral bands of cells near distant sites in the embryo. the margins of the embryonic folds that form the neural tube.  Neural Crest Cells Neural crest cells give rise to a variety of structures, including some of the bones and cartilage of the skull. Common features among chordates and Vertebrates Besides, the prementioned characters, vertebrates also possess the three fundamental chordate characteristics as in the protochordates: i. notochord ii. pharyngeal-gill-slits iii. and dorsal hollow nerve cord The others are only 'satellite characteristics' not necessarily unique among vertebrates.  General Characteristic Features of Vertebrates 1) Lower vertebrates are aquatic, higher vertebrates predominantly terrestrial 2) Body typically made of head, trunk and a postanal tail; neck may also be present 3) Trunk bears typically two pairs of appendages; may be reduced or absent 4) The integument is a stratified epithelium made of epidermis and dermis 5) Skin covered by a protective exoskeleton comprising scales, feathers, hairs,…..etc 7) Notochord stops shortly beneath the fore brain, and replaced by a vertebral column  General Characteristic Features of Vertebrates 7) Digestive canal more or less convoluted and the liver massive enlarged 8) Respiration in lower aquatic forms by paired gills; in terrestrial by lungs 9) Closed blood vascular system; Heart ventral, contractile made of 2 - 4 chambers 11) Sensory organs include optic and auditory organs, derived from the brain 12) An endocrine system (ductless glands) regulating several body processes 13) Sexes separate and the development direct or indirect Classes of vertebrates https://youtu.be/qRKoGO7hNXg  General Characters of Class Cyclostomates 1) Body is elongated and eel-like form with soft and no scales 2) Endoskeleton fibrous and cartilaginous. Notochord persists throughout life 3) Digestive system lacks a stomach and the intestine with a fold (typhlosole) 4) Gills 5 - 16 pairs in lateral sac-like pouches of pharynx 5) Many aortic arches in gill region 6) Sexes separate or united. Gonad single, large, without gonoduct 8) Fertilization external; Development direct or with a prolonged larval stage Example: Petromyzon fluviatilis  General Characters of Class Chondrichthyes 1. Mostly marine and predaceous with fusiform or spindle body shape. 2. Fins both median and paired, all supported by fin rays 3. Pelvic fins bear claspers in male. 4. Skin tough containing minute placoid scales and mucous glands. 5. Endoskeleton entirely cartilaginous. 6. Notochord persistent and vertebrae are complete and separate. 7. Mouth ventral with Jaws. 8. Teeth are modified placoid scales. 20  Ex. Dogfish 21  Ex. Dogfish 22  Class 5. Osteichthyes General Characters 1. Inhabit all sorts of water—fresh, brackish; warm or cold. 2. Body spindle-shaped and streamlined. 3. Skin hallmark with 3 types of dermal scales; ganoid, cycloid or ctenoid. 4. Some without scales. No placoid scales. 5. Endoskeleton chiefly of bone and cartilage in sturgeons. 6. Notochord replaced by distinct vertebrae. 7. Respiration by 4 pairs of gills on bony gill arches, covered by an operculum. 23  Class 6. Amphibia The greatest event in the phylogenetic history was a transition from aquatic to terrestrial mode of life, and Amphibia were the first animals to attempt this transition. But they are not fully terrestrially adapted and hover between aquatic and land environments. The name of the class also indicates this double life (Gr., amphi. dual, double + bia, life). Structurally, Amphibia are between the fish on one hand, and the reptiles on the other.  Class: Amphibia 1) Amphibians are cold blooded vertebrates which can hue on land and in water 2) Amphibians show four limbs with which they can swim jump or walk 3) Exoskeleton is absent with small cycloid scales in some species 4) In adult animals lungs are present and gills are absent 5) Amphibians skin is a respiratory organ 6) Amphibians Ribs are absent 7) Body divided into head and trunk  Class 7. Reptilia 1. Class reptilian (L. Reptilia= creeping) includes animals which are cold blooded. 2. The skin has a few cutaneous glands and high levels of keratin, to prevent water loss. 3. Reptiles are considered as tetrapods animals. 4. Most of these animals have five clawed toes on each limb. 5. All reptiles have spinal columns and a strong skeletal system with a rib cage. 6. Unlike amphibians, reptiles do not pass through an embryonic stage with gills. 7. These animals breath with well-developed lungs, except some snakes. 8. Reptiles have a digestive system which has a muscular opening at the base of the tail. 26  Class 7. Reptilia 27 Dr. Abdelsadik  Class 8. Aves Distinctive Characters 1. Birds are bipedal feathered and warm blooded (homoiothermous) animals. 2. Most of them can fly except flightless birds. 3. The hind-limbs are adapted for perching, walking or swimming. 4. The upper and lower jaws are modified into beak, which lacks teeth. 5. Beaks are adapted to many ways of feeding; seed-crushing, fruit-scooping, flesh-tearing, wood-chiselling. 6. Legs are modified for walking, hopping, grasping, perching, wading and swimming. 7. Legs bear horny epidermal scales. 28  Mammals 1. Hair-clad, mostly terrestrial, air-breathing, warm-blooded 2. Body distinctly divisible into head, neck, trunk and tail 3. Exoskeleton includes hairs, spines, scales and claws…. etc. 4. Skin richly glandular containing sweat, sebaceous (oil) and scent glands in both the sexes. 5. Females also have mammary glands producing milk for suckling the young. 6. A diaphragm, separates the anterior thoracic cavity from the posterior abdominal cavity.  Mammals 7. Alimentary canal terminates by anus with no cloaca. 8. Teeth are of several types (heterodont). 9. Respiration always by lungs (pulmonary). 10. Brain highly evolved with 12 pairs of cranial nerves emerged. 11. Senses well developed. Eyes protected by lids, the upper of which is movable. 12. External ear opening protected by a large fleshy and cartilaginous flap called pinna.