BSCZOZ - 201 B. Sc. II YEAR CCHORDATA DEPARTMENT OF ZOOLOGY SCHOOL OF SCIENCES UTTARAKKHAND OPEN UNIVERSITY BSCZO-201 CHORDATA DEPARTMENT OF ZOOLOGY SCHOOL OF SCIENCES UTTARAKHAND OPEN UNIVERSITY Phone No. 05946-261122, 261123 Toll free No. 18001804025 Fax No. 05946-264232, E. mail [email protected] htpp://uou.ac.in MEMBER OF THE BOARD OF STUDIES Prof. B.D.Joshi Dr. H.C.S.Bisht Retd.Prof. Professor Department of Zoology Department of Zoology Gurukul Kangri University DSB Campus, Kumaun University, Haridwar. Nainital. Dr.N.N.Pandey Dr. H.C.Tiwari Principal Scientist, Retd.Professor & Principal Directorate of Coldwater Fisheries (DCFR) Department of Zoology, Indian Council of Agriculture Research (ICAR) MB Govt.PG College Bhimtal (Nainital). Haldwani Nainital. Dr.Shyam S. Kunjwal Coordinator Department of Zoology Uttarakhand Open University Haldwani(Nainital) PROGRAMME COORDINATOR Dr. Shyam S. Kunjwal Department of Zoology & Biotechnology School of Sciences Uttarakhand Open University Haldwani(Nainital). UNIT WRITER UNIT NO 1. Dr.Anju Thapliyal Unit: 1, 2, 3, 4,5,6,7 &8 Assistant Professor Department of Zoology BGR Campus Pauri, HNB Garhwal, (A Central University Srinagar) Garhwal. 2. Dr.Shyam S. Kunjwal Unit: 9 & 10 Department of Zoology School of Sciences, Uttarakhand Open University, Haldwani, Nainital COURSE EDITOR Dr. P.K.Gupta Professor Department of Zoology, DSB Campus, Kumaun University, Nainital. Course Title and code : CHORDATA (BSCZO201) ISBN No. : Copyright : Uttarakhand Open University Edition : 2018 Published by : Uttarakhand Open University, Haldwani, Nainital- 263139 Printed by : CONTENTS COURSE 1: CHORDATE COURSE CODE: BSCZO201 CREDIT: 3 Unit Block and Unit title Page number number Block I (Primitive chordates) 1-108 1 Origin of chordates: Introduction and charterers of chordates. Classification of 1-17 chordates up to order level. 2 Hemichordates: General characters and classification up to order level. Study of 18-45 Balanoglossus and its affinities. 3 Urochordata: General characters and classification up to order level. Study of 46-70 Herdmania and its affinities. 4 Cephalochordates: General characters and classification up to order level. Study of 71-87 Branchiostoma (Amphioxus) and its affinities. 5 Cyclostomata (Agnatha) General characters and classification up to order level. 88-108 Study of Petromyzon and its affinities. Block II (Lower chordates) 109-275 6 Fishes: General characters and classification up to order level. Types of scales and 109-141 fins of fishes, Scoliodon as type study, migration and parental care in fishes. 7 Amphibians: General characters and classification up to order level, Rana tigrina 142-176 as type study, parental care, neoteny and paedogenesis. 8 Reptilia: General characters and classification up to order level, extinct reptiles. 177-208 Uromastix as type study. Identification of poisonous and non-poisonous snakes and biting mechanism of snakes. 9 Aves: General characters and classification up to order level. Study of Columba 209-245 (Pigeon) and Characters of Archaeopteryx. Flight adaptations & bird migration. 10 Mammalia: General characters and classification up to order level, affinities of 246-275 Prototheria, Metatheria and Eutheria. Study of rabbit (Oryctolagus) and dentition in mammals. Economic importance of mammals. UNIT 1: ORIGIN OF CHORDATES CONTENTS 1.1 Objective 1.2 Introduction 1.3 Origin of chordates 1.4 Ancestory of chordates 1.5 General Characteristics 1.6 Classification of Chordates 1.7 Summary 1.8 Glossary 1.9 Self Assessment Questions 1.10 Terminal Questions 1.11 Suggested Readings 1.12 Terminal Question Answers 1.13 References :$V 1.1 OBJECTIVE We will understand the basic characters of chrodates, origin and Ancestrory of chordates.After reading this chapter we will also know about about the general characters and classification of chordates upto order level. 1.2 INTRODUCTION Animal kingdom is basically divided into two sub kingdoms: (a) Nonchordata- including animals without notochord. (b) Chordata- This comprising animals having notochord or chorda dorsalis.While the Chordata has a notochord at some stage during the life, it is not known to exist in the Nonchordata. Fig.1.1 some animals of chordate phylum :$V • The Chordata is the animal phylum with which everyone is most intimately familiar, since it includes humans and other vertebrates However, not all chordates are vertebrates. • All chordates have the following features at some stage in their life (in the case of humans and many other vertebrates, these features may only be present in the embryos). • Pharyngeal slits – a series of openings that connect the inside of the throat to the outside of the “neck”. These are often, but not always, used as gills. • Dorsal tubular nerve cord – A bundle of nerve fibers which runs down the “back”. It connects the brain with the lateral muscles and other organs. Fig 1.2 Pharyngeal slits dorsal nerve cord & notochord • Notochord – cartilaginous rod running underneath, and supporting, the nerve cord. • Post-anal tail – an extension of the body post the anal opening. :$V 1.3 ORIGIN OF CHORDATES It is believed that chordates originated from invertebrates. However, it is difficult to determine from which invertebrate group of the chordate developed. It is almost constant that chordate ancestors were soft bodied animals. Hence, they were not preserved as fossil. Many theories have been put forward to explain the evolution of chordates, few of them are as follows:- (a) COELENTERATE THEORY: According to this theory chordates developed from coelenterates. It is belived that radial symmetry coelenteron, cnidoblasts etc, disappeared and advanced characters developed to giverise the chordates. This theory infers that chordates might have acquired higher characters independently. This theory is not acceptable. :$V Fig.1.3 Origin of chordates (b) ANNELID THEORY: This theory suggests that the chordates have evolved from an annelid stock, like many chordates the annelids show bilateral symmetry, metasmerism, head, lateral coelome complete digestive tract, closed circulatory system, haemoglobin, etc. The resemblance is enhanced, if an annelid is turned upside down. But the mouth would be dorsal which is unlike that of chordates. Metamerism and appendages of annelids differ in nature from those of the chordates. Bilateral symmetry, head and complete digestive tract occur in other non-chordate phyla also. Coelome is schizocoelic in annelids and enterocoelic in lower :$V chordates. Haemoglobin is dissolved in the plasma in annelids but it is present in the red blood corpuscles in chordates. Annelid nerve cord is double and ventral in contrast to single, hollow, dorsal nerve cord of chordates. Some striking differences exist between the annelids and the chordates in their embryology too, hence it is difficult to accept this theory. (c) ECHINODERM -HEMICHORDATE THEORY-ORIGIN OF CHORDATES: This theory infers origin of chordates, hemichordates and echinoderms from a common ancestor. This theory is based on the following evidences. 1. EMBRYOLOGICAL EVIDENCE: Both echinoderms and chordates have enterocoelic coelome, mesoderm and deuterostomous mouth. There is resemblance between the bipinnaria larva of certain echinoderms and the tornaria larva of hemichordates. In echinoderms chordates the central nervous system develops from a dorsal strip of ectoderm. 2. SEROGICAL EVIDENCE: Similarity exists between the protines of the body fluid of chordates and echinoderms. Hence the chordates and echinoderms are closely related. The radial symmetry of adult echinoderms will disapprove their relationship with the bilaterally symmetrical chordates. In echinoderms radial symmetry is secondryly developed from a basically bilateral symmetry. Both the primitive and the early echinoderm larve show bilateral symmetry. 1.4 ANCESTORY OF CHORDATES The unique chordate body plan evolved within the deuterostome animals sometimes before the Cambrian (Valentine, Jablonski Erwin 1999; Blair and Hedges 2005). Chordates traditionally include vertebrates, lancelets (cephalochordates) and tunicates, but tunicates do not exhibit a chordate body plan as adults. Hemichordates are sister group to echinoderms and both phyla are an outgroup to the rest of the chordates). :$V Xenoturbella has been recently included in the deuterostomes as molecular evidence unites them with hemichordates and echinoderms, but their exact position within the deuterostomes is not yet clear.m All five chordate characteristics (postanal tail, dorsal nerve cord, notochord, endostyle and pharyngeal gill slits) at one time or another been suggested to have homologous structures present in hemichordates, but all these features are lacking in echinoderms and Xenoturbella, the closest relatives to hemichordates, suggesting that they were lost during their evolution. :$V 1.5 GENERAL CHARACTERSTICS Aquatic, aerial or terrestrial all free living with no fully parasitic forms. Bilaterally symmetrical and metamerically segmented. Exoskeleton often present well developed in most vertebrates. Bodywall triploblastic with 3 germinal layers: ectoderm, mesoderm and endoderm. Coelomate animals with a true coelom, enterocoelic or schizocoelic in origin. A skeletal rod, the notochord, present at some stage in life cycle. Digestive system complete with digestive glands. Blood vascular system closed. Heart ventral with dorsal and ventral blood vessels. Hepatic portal system well developed.