S. Chand & Company Ltd.

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2 For B.Sc. and B.Sc. (Hons.) Classes of all Indian Universities and also as per UGC Model Curriculum E.L. Jordan M.Sc., M.A. (Toronto) Formerly Head Zoology Department, Lucknow Christian College, Lucknow Dr. P.S. Verma M.Sc., Ph.D., F.E.S.I., F.A.Z. Formerly Reader Zoology Department Meerut College, Meerut S. Chand & Company Ltd. (An ISO 9001 : 2008 COMPANY) Ram Nagar, New Delhi

3 S. CHAND & COMPANY LTD. (An ISO 9001 : 2008 Company) Head Office: 7361, RAM NAGAR, NEW DELHI Phone: , , Fax: Shop at: schandgroup.com; info@schandgroup.com Branches : Ahmedabad : 1st Floor, Heritage, Near Gujarat Vidhyapeeth, Ashram Road, Ahmedabad , Ph: , , ahmedabad@schandgroup.com Bengaluru : No. 6, Ahuja Chambers, 1st Cross, Kumara Krupa Road, Bengaluru , Ph: , , bangalore@schandgroup.com Bhopal : Bajaj Tower, Plot No. 243, Lala Lajpat Rai Colony, Raisen Road, Bhopal , Ph: bhopal@schandgroup.com Chandigarh : S.C.O , First Floor, Sector - 22-C (Near Aroma Hotel), Chandigarh , Ph: , , chandigarh@schandgroup.com Chennai : No.1, Whites Road, Near Clock Tower, Royapettah, Chennai , chennai@schandgroup.com Coimbatore : 1790, Trichy Road, LGB Colony, Ramanathapuram, Coimbatore , Ph: , coimbatore@schandgroup.com (Marketing Office) Cuttack : 1st Floor, Bhartia Tower, Badambadi, Cuttack , Ph: ; , cuttack@schandgroup.com Dehradun : 1st Floor, 20, New Road, Near Dwarka Store, Dehradun , Ph: , , dehradun@schandgroup.com Guwahati : Pan Bazar, Guwahati , Ph: , guwahati@schandgroup.com Hyderabad : Padma Plaza, H.No , Opp. Ratna College, Narayanaguda, Hyderabad , Ph: , , hyderabad@schandgroup.com Jaipur : 1st Floor, Nand Plaza, Hawa Sadak, Ajmer Road, Jaipur , Ph: , , jaipur@schandgroup.com Jalandhar : Mai Hiran Gate, Jalandhar , Ph: , , jalandhar@schandgroup.com Kochi : Kachapilly Square, Mullassery Canal Road, Ernakulam, Kochi , Ph: , cochin@schandgroup.com Kolkata : 285/J, Bipin Bihari Ganguli Street, Kolkata , Ph: , , kolkata@ schandgroup.com Lucknow : Mahabeer Market, 25 Gwynne Road, Aminabad, Lucknow , Ph: , , lucknow@schandgroup.com Mumbai : Blackie House, 103/5, Walchand Hirachand Marg, Opp. G.P.O., Mumbai , Ph: , , mumbai@schandgroup.com Nagpur : Karnal Bag, Model Mill Chowk, Umrer Road, Nagpur , Ph: , nagpur@schandgroup.com Patna : 104, Citicentre Ashok, Govind Mitra Road, Patna , Ph: , , patna@ schandgroup.com Pune : 291/1, Ganesh Gayatri Complex, 1st Floor, Somwarpeth, Near Jain Mandir, Pune , Ph: , pune@schandgroup.com (Marketing Office) Raipur : Kailash Residency, Plot No. 4B, Bottle House Road, Shankar Nagar, Raipur , Ranchi siliguri Ph: , raipur@schandgroup.com (Marketing Office) : Flat No. 104, Sri Draupadi Smriti Apartments, East of Jaipal Singh Stadium, Neel Ratan Street, Upper Bazar, Ranchi , Ph: , ranchi@schandgroup.com (Marketing Office) : 122, Raja Ram Mohan Roy Road, East Vivekanandapally, P.O., Siliguri , Dist., Jalpaiguri, (W.B.) Ph (Marketing Office) Visakhapatnam : Plot No. 7, 1st Floor, Allipuram Extension, Opp. Radhakrishna Towers, Seethammadhara North Extn., Visakhapatnam , (M) , visakhapatnam@schandgroup. com (Marketing Office) 1965, E.L. Jordan & Dr. P.S. Verma All rights reserved. No part of this publication may be reproduced or copied in any material form (including photo copying or storing it in any medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) without written permission of the copyright owner. Any breach of this will entail legal action and prosecution without further notice. Jurisdiction : All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, tribunals and forums of New Delhi, India only. First Edition 1965 Subsequent Editions and Reprints 1968, 70, 73, 74, 76, 77, 78, 80, 81, 83, 86, 87, 88, 89, 90, 91, 93, 95, 96, 97, 98, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011, 2012, 14th Revised and Enlarged Edition 2013 ISBN : Code : 03A 251 printed in india By Rajendra Ravindra Printers Pvt. Ltd., 7361, Ram Nagar, New Delhi and published by S. Chand & Company Ltd., 7361, Ram Nagar, New Delhi

4 DEDICATED to My Respected Mother Late Smt. Gomti Devi who could not survive to see the fruits of this labour Dr. Prem Singh Verma

5 Preface To The Fourteenth Edition The dimensions of biology are fast increasing with more and more emphasis on cell biology, molecular biology, genetics, biochemistry, physiology, electron microscopy, biotechnology and development biology (embryology), etc. Many Indian Universities have already introduced some topics of these disciplines in their under-graduate syllabi. The importance of basic zoology, however, cannot be ignored; most teachers and researchers rightly feel the need for a strong base in general zoology as a prerequisite for all fields of specialisations. Jordan s Chordate Zoology has served a great deal towards the fulfilment of this aim. It has been a national best seller for more than four decades. It was, therefore, found necessary to bring out the same book in more useful and enlarged form. The book has been thoroughly revised and enlarged in this edition. I have retained all that was judged good and useful in the previous edition. However, a number of changes have been made in this edition. Subject matter have been revised and updated in the light of recent researches and new topics have been added at appropriate places keeping in view the changes in the syllabi of various Indian Universities. New chapters and topics which have been added in the present edition are : (i) Pisces (Fishes) : Labeo rohita (Type study); Comparison of Chondrichthyes and Osteichthyes; Dipnoi; Fin System; Scales; Air-bladder or Swim-bladder; Accessary respiratory organs; Parental care; Migration; and Economic importance. (ii) Amphibia : Parental care; Neoteny and Paedogenesis; Origin and Ancestry. (iii) Reptilia : Calotes versicolar (Type study); Snakes : General account; Reptilia: General account. (iv) Aves : Common Flightless birds (Ratitae); Types of beaks and feet or claws; Types of skull palate; Archaeopteryx and its significance; Birds are glorified reptiles; Birds as a flying machine; Aerial or flight adaptations; Migration; and Economic importance. (v) Mammalia : Prototheria (Order Monotremata); Metatheria; Dentition; Aquatic mammals and adaptations; Flying (Volant) mammals and adaptations; Adaptive radiations; Adaptive convergence; Origin and Ancestry; and Economic importance. (vi) Vertebrate Embryology and Comparative Anatomy: Several new topics have been added. (vii) Wildlife in India. (viii) Glossary. In addition to this, general topics, which are usually asked in the examinations, have been thoroughly revised and some new topics have also been added in all the classes of chordates. In the last few years, most of the universities have introduced long answer type, short answer type, very short answer type and multiple choice type (objective type) questions in the examination papers. To cater this requirement, various types of questions have been added at the end of each chapter. The examination oriented text is written for all students, even for those who do not have a good background in the subject. The language is simple, explanations are clear, and presentation is very systematic. To improve scientific accuracy, about 706 well-labelled diagrams have been included at appropriate (v)

6 places. Important words are given in bold face and definitions in italics. Subject matter is error free. Notwithstanding several Indian books on Chordate Zoology or Vertebrate Zoology, I hope the present edition of Chordate Zoology shall serve the purpose of learned teachers and students. I am thankful to the Management Team and the Editorial Department of S. Chand & Company Ltd., for all help and support in the publication of this book. I like to express my thanks to the esteemed teachers for sending their valuable suggestions and opinions and shall hope to receive the same in future. PREETI 121, New Mohanpuri Colony, Meerut Dr. P. S. Verma Disclaimer : While the authors of this book have made every effort to avoid any mistake or omission and have used their skill, expertise and knowledge to the best of their capacity to provide accurate and updated information. The authors and S. Chand do not give any representation or warranty with respect to the accuracy or completeness of the contents of this publication and are selling this publication on the condition and understanding that they shall not be made liable in any manner whatsoever. S.Chand and the authors expressly disclaim all and any liability/responsibility to any person, whether a purchaser or reader of this publication or not, in respect of anything and everything forming part of the contents of this publication. S. Chand shall not be responsible for any errors, omissions or damages arising out of the use of the information contained in this publication. Further, the appearance of the personal name, location, place and incidence, if any; in the illustrations used herein is purely coincidental and work of imagination. Thus the same should in no manner be termed as defamatory to any individual. (vi)

7 Preface To The First Edition There are some excellent textbooks of comparative anatomy and anatomy of vertebrates. It would be presumptive to present yet another book on chordate zoology without any justification. Yet the author feels justified in presenting this book to the students. Firstly it lays down the basic principles of the B.Sc. Zoology course of Indian Universities, secondly it is written in a manner which takes into account the morphology, physiology, histology, embryology, ecology, palaeontology and evolution of chordates. The book is a comprehensive guide though it does not burden the student with unnecessary details, yet it is a clear and complete study of Chordates and it includes not only the study of comparative anatomical structure, but also the origin of structure in terms of its embryology and evolution. The book contains numerous clear and well-labelled figures which make an understanding of the text an easier task. The first chapter takes into account the geological time chart and the origin and characters of chordates. Then it deals with Protochordata, but it does not take into account the Hemichordata. The Hemichordata in modern zoological literature are now regarded as a separate phylum of invertebrates. Then the Agnatha are described in outline. The next part is a comprehensive account of the comparative anatomy of vertebrates dealing with the development, morphology, and evolution of various systems. This major portion is followed by a classification of vertebrates along with a description of many representative types from each class. Hardly any two books have an identical scheme of classification of animals; in this book the best points of various classifications are taken on the basis of morphology and evolution, and are coordinated into a wholesome system. The last part of the book is devoted to general biology dealing with Heredity, Mendelism, and Evolution. Lucknow, Ist January, 1965 E.L. Jordan (vii)

8 Contents 1. Phylum Chordata : An Introduction 1 13 What is Chordata? 1; Chordate animals 2; Three fundamental chordate characters 2; Characters common to Chordates and higher Nonchordates 4; Comparison between Chordates and Nonchordates 5; Origin and ancestry of Chordata 5; Major subdivisions of phylum Chordata 6; General characters of phylum Chordata 7; Brief classification of phylum Chordata 7; Brief classification of phylum Chordata with characters 8; Phylum Chordata 8; Group A. Acrania (Protochordata) 9; Subphylum I Hemichordata 9; subphylum II Urochordata or Tunicata 9; Subphylum III Cephalochordata 9; Group B. Craniata 10; Subphylum IV. Vertebrata 10; Division I. Agnatha 10; Division II. Gnathostomata 11; Superclass 1. Pisces 11; Superclass 2. Tetrapoda 11; Class 1. Amphibia 11; Class 2. Reptilia 11; Class 3. Aves 12; Class 4. Mammalia 12; Important questions Type 1. Balanoglossus (A Tongue Worm) Systematic position 15; Habits and habitat 15; External morphology 16; Body wall 18; Coelom 19; Endoskeleton 20; Digestive system 21; Respiratory system 24; Blood vascular system 25; Excretory system 26; Nervous system 26; Sense organs 27; Reproductive system 27; Development 27; Affinities of Balanoglossus 30; Systematic position and phylogeny 33; Important questions Subphylum 1. Hemichordata : General Characters; Classification and Representative Types Definition 35; General characters 35; Classification 36; Representative types 37; Saccoglossus 37; Ptychodera 37; Cephalodiscus 37; Atubaria 38; Rhabdopleura 39; Important questions Type 2. Herdmania (A Sea Squirt) Geographical distribution 42; Systematic position 42; Habits and habitat 42; External morphology 43; General anatomy 47; Digestive system 48; Respiratory system 51; Circulatory system 52; Nervous system 54; Receptors 55; Excretory organ 55; Reproductive organs 56; Affinities and Systematic Position of Herdmania (Urochordata) 57; Important questions Subphylum 2. Urochordata : General Characters, Classification and Representative Types General Characters 60; Classification 61; Representative types 62; Molgula 62; Botryllus 63; Ascidia 63; Ciona 64; Clavelina 64; Pyrosoma 64; Doliolum 65; Salpa 67; Oikopleura 69; Important questions 70. (ix)

9 6. Type 3. Branchiostoma (= Amphioxus) The Lancelet Systematic position 72; Geographical distribution 72; Habits and habitat 72; External features 72; Body wall 74; Skeleton 75; Atrium 75; Coelom 77; Digestive system 78; Respiration 82; Circulatory system 83; Excretory system 85; Nervous system 86; Sense organs (Receptors) 87; Reproductive system 88; Important questions Subphylum 3. Cephalochordata : General Characters, Primitive, Degenerate and Specialised Characters and Affinities General characters 91; Primitive, Degenerate and Specialised characters of Branchiostoma (Cephalochordata) 92; Affinities of Cephalochordata 93; Important questions Protochordata : General and Comparative What are protochordates? 96; Significance of protochordates 97; Comparison of three protochordate subphyla 97; General comparison of three protochordate subphyla at a glance 97; Comparison : Habits and habitat of three protochordate types 98; Comparison : External features of three protochordate types 99; Comparison : Digestive system (Alimentary canal and associated glands) of three protochordate types 99; Comparison : Pharynx of three protochordate types 101; Comparison : Food and feeding mechanism of three protochordate types 102; Comparison : Excretory system of three protochordate types 103; Comparison : Nervous system of three protochordate types 104; Comparison : Circulatory system of three protochordate types 105; Comparison : Reproduction of three protochordate types 106; Important questions Subphylum 4. Vertebrata : General Characters, Origin and ancestry of Vertebrates What are vertebrates? 108; Chordate versus vertebrates 109; General Characters of subphylum Vertebrata 109; Diversity of vertebrates 110; Selected characters of classes 111; Phylogeny or Evolutionary history of vertebrates 111; Origin and ancestry of vertebrates (chordates) 113; Important questions Class 1. Ostracodermi (Extinct) : General Characters, Classification and Representative Types Occurrence 120; Important features 121; Classification 121; Biological significance of ostracoderms 123; Inter-relationship and affinities 123; Important questions Type 4. Petromyzon (The Lamprey) Systematic position 126; Distribution 126; Habits and habitat 126; External features 127; Anatomy and physiology 128; Body wall 128; Muscular system 129; Skeleton 129; Digestive System 130; (x)

10 Respiratory system 130; Circulatory System 131; Nervous system 131; Sense organs 132; Excretory system 132; Reproductive system 133; Life history 133; Ammocoete larva 134; Metamorphosis 134; Comparison between lamprey and hagfishes 134; Summary of characters of cyclostomes: Affinities of cyclostomes 136; Important questions Class 2. Cyclostomata : General Characters, Classification and Representative Types General characters 140; Classification 141; Representative types 141; Important questions Class 3. Placodermi (Extinct) : General Characters and Classification Earliest jawed vertebrates 144; Occurrence 145; Important features 145; Classification 145; Biological significance 146; Important questions Type 5. Scoliodon : A Cartilaginous Fish (The Dogfish) Systematic position 148; Distribution 148; Habits and habitat 148; External features 148; Skin 151; Exoskeleton 151; Endoskeleton 153; Musculature 159; Locomotion 160; Coelom and viscera 161; Digestive system 163; Respiratory system 166; Blood vascular system 168; Nervous system 176; Receptor organs (Sense organs) 180; Urinogenital organs 186; Reproduction 189; Economic importance 191; Important questions Type 6. Labeo rohita : Rohu (A Bony Fish) Systematic position 196; Distribution 196; Habits and habitat 196; External Features 196; Body wall or Integument 197; Exoskeleton 197; Endoskeleton 197; Digestive system 203; Air-bladder (Swimbladder) 205; Respiratory system 205; Blood vascular system 207; Nervous system 208; Urinogenital system 210; Economic importance 211; Important questions Superclass Pisces : General Characters, Classification and Representative Types General characters 213; Classification 214; Class 4. Chondrichthyes 215; Classification of Chondrichthyes 215; Some representative types of Chondrichthyes 216; Class 5. Osteichthyes 219; Classification of Osteichthyes 219; Some representative types of Osteichthyes 223; Lobe-finned fish 223; Lung fish 224; Ganoid fish 226; Advanced rayfinned bony fishes 228; Important questions 235. (xi)

11 17. Superclass Pisces and Fish : General Account Comparison of Chondrichthyes and Osteichthyes 237; Dipnoi 239; Fin system 245; Scales of fishes 249; Air-bladder or Swim-bladder 251; Accessory respiratory organs 255; Parental care in fishes 259; Migration in fishes 261; Economic importance of fishes 263; Important questions Type 7. Rana tigrina (Common Indian Bull Frog) Systematic position 269; Habit and habitat 269; External features 271; Skin 274; Endoskeleton 276; Digestive system 284; Respiratory system 296; Blood vascular system 300; Arterial system 304; Venous system 306; Lymphatic system 307; Blood 308; Nervous system 311; Receptors 318; Urinogenital system 324; Important questions Class 6. Amphibia : General Characters, Classification and Representative Types General characters 331; Classification 332; Representative types 334; Important questions Amphibia : General Account Parental care in Amphibia 342; Neoteny and Paedogenesis 345; Origin and Ancestry of Amphibia (Tetrapoda) 346; Important questions Type 8. Uromastix hardwickii (The Spiny-Tailed Lizard) Systematic position 351; Habit and habitat 352; External features 353; Skin or Integument 355; Exoskeleton 355; Endoskeleton 356; Skeleton of Varanus 356; Digestive system 369; Respiratory system 372; Blood vascular system 374; Arterial system 377; Venous system 379; Nervous system 381; Sense organs 384; Urinogenital system 387; Excretory system 387; Male genital organs 388; Female genital organs 389; Copulation and fertilisation 389; Important questions Type 9. Calotes versicolor (The Garden Lizard) Systematic Position 391; Natural history 391; External features 392; Digestive system 393; Respiratory system 394; Blood vascular system 395; Arterial system 396; Venous system 398; Nervous system 399; Excretory system 402; Reproductive system 402; Important questions Snakes : General Account External features 406; Hearing 406; Feeding mechanism 406; Poison apparatus 407; Biting mechanism 409; Swallowing mechanism 410; Snake venom 410; Types of venom 410; Treatment 411; Distinction between poisonous and non-poisonous snakes of India 411; Key for identification of poisonous and non-poisonous snakes of India 413; Important questions 414. (xii)

12 24. Class 7. Reptilia : General Characters, Classification and Representative Types General Characters 415; Classification 417; Representative types 419; Turtles and tortoises 419; Sphenodon 422; Lizards 424; Snakes 427; Non-poisonous snakes 427; Poisonous snakes 429; Crocodilia 432; Important questions Reptilia : General Account Origin of reptiles 438; Adaptive radiation in reptiles 440; Dinosaurs 440; Important questions Type 10. Columba livia (The Common Rock Pigeon) Early history (Origin) 444; Characteristics of Aves 445; Systematic position 446; Habit and habitat 447; Distribution 447; External features 448; Skin 450; Exoskeleton 450; Muscular system 459; Endoskeleton of Fowl (Gallus) 462; Coelom and viscera 475; Digestive system, 476; Respiratory system 479; Circulatory system 483; Arterial system 486; Venous system 487; Nervous system 490; Sense organs 493; Endocrine glands 498; Urinogenital system 498; Urinary or Excretory organs 498; Male reproductive organs 499; Female reproductive organs 499; Copulation 501; Important questions Class 8. Aves (The Birds) : General Characters, Classification, and Representative Types General Characters 505; Classification 506; Representative Types 511; Archaeopteryx 511; Common Birds of India 513; Important questions Aves (Birds) : General Account Flightless birds (Ratitae) 521; Origin of birds 526; Origin of flight in birds 528; Birds are glorified reptiles 529; Birds as a flying machine 530; Modes of flight 532; Flight or aerial adaptations of birds 534; Beaks of birds 537; Types of feet or claws in birds 539; Palate in birds 541; Migration of birds 543; Economic importance of birds 549; Important questions Type 11. Oryctolagus (The Rabbit) Distinguishing characters 554; Systematic position 554; Habit and habitat 555; Distribution 555; Enemies 555; Economic importance 555; Important adaptations 556; Rabbit and hare 556; External features 557; Locomotion 559; Integument 559; Endoskeleton 564; Axial skeleton 564; Appendicular skeleton 574; Coelom and viscera 577; Digestive system 579; Respiratory system 594; Blood vascular system 599; Heart 599; Blood vessels 603; Arterial system 603; Venous system 605; Hepatic portal system 607; Blood 607; Lymphatic system 608; Nervous system 609; Central nervous system 609; (xiii)

13 Peripheral nervous system 613; Autonomic nervous system 616; Sense organs 617; Urinogenital system 626; Excretory system, 626; Reproductive system 629; Endocrine system 633; Important questions Class 9. Mammalia : General Characters, Classification and Representative Types General characters 642; Classification 643; Representative types 651; Important questions Subclass Prototheria (Order Monotremata) Distinctive characters 674; Habit and habitat 674; External features 675; Exoskeleton 675; Body cavity 675; Endoskeleton 675; Digestive system 677; Respiratory system 677; Circulatory system 677; Excretory system 677; Nervous system 678; Receptors 678; Reproductive system 678; Development 678; Classification of Prototheria 679; Affinities of Prototheria 679; Important questions Infraclass Metatheria (Order Marsupialia) Distinctive characters 683; Distribution 683; Habits and habitat 683; External features 683; Exoskeleton 683; Body cavity 683; Endoskeleton 683; Digestive system 684; Respiratory, circulatory and excretory system 684; Nervous system 684; Reproductive system 684; Development 684; Classification of Marsupialia 685; Distribution of Metatheria 686; Affinities of marsupials 687; Systematic position 688; Phylogenetic consideration of Metatheria (Marsupialia) 688; Important questions Mammalia : General Account Dentition in mammals 689; Aquatic mammals and adaptations 697; Flying (Volant) mammals and adaptations 700; Adaptive radiation in mammals 702; Adaptive convergence in mammals 704; Origin and ancestry of mammals 706; Economic importance of mammals 708; Important questions Introduction to Vertebrate Embryology Historical review 714; Modern embryology 715; Scope of embryology 716; Gametogenesis 716; Embryonic development 716; Types of eggs 717; Classification of eggs on the basis of amount of yolk 717; Fertilisation 719; Cleavage 720; Stages of embryogeny 722; Morula 722; Blastula 722; Gastrula 722; Organogeny 723; Derivatives of germ layers 723; Important questions Development of Herdmania Gametes 727; Fertilisation 728; Presumptive areas 728; Embryonic or prelarval development 728; Larval development 729; Tadpole larva 729; Retrogressive metamorphosis 730; Embryological significance of Ascidian tadpole 732; Important questions 733. (xiv)

14 36. Development of Branchiostoma (Amphioxus) Gametes 734; Fertilisation 735; Presumptive areas 736; Early embryonic development 736; Cleavage and blastulation 736; Gastrulation 737; Fate of germ cells 738; Formation of notochord 738; Formation of neural tube 738; Development of mesoderm and coelom 740; Further development of coelom 740; Differentiation of myotome 740; Development of head 742; Development of gut 742; Hatching of larva 742; Post-hatching development 742; Metamorphosis 746; Important questions Development of Frog Spawning 748; Fertilisation 749; Cleavage and blastulation 749; Presumptive areas 750; Gastrulation 750; Neurulation 753; Notogenesis 754; Post-neural or pre-hatching development 756; Posthatching development of tadpole 756; Metamorphosis 758; Important questions Development of Chick (Fowl) Fertilisation 763; Structure of egg of hen 763; Cleavage and blastulation 764; Presumptive fate maps of blastula 766; Gastrulation 766; Formation of primitive streak 767; Formation of neural tube (Neurogenesis) 769; Formation of notochord and mesoderm 769; Formation of somites 769; Formation of coelom 770; Folding of embryo 771; Flexure and torsion 772; Extra-embryonic (Foetal) membranes of chick 772; Development of extra-embryonic membranes 772; Hatching 775; Important questions Development of Rabbit Egg 778; Fertilisation 779; Early embryonic development 779; Cleavage 779; Blastocyst 779; Implantation 780; Gastrulation 781; Neurulation 782; Development of extra-embryonic membranes of rabbit 782; Development of amnion and chorion 782; Development of allantois 783; Development of yolk-sac 784; Important questions Placenta and Placentation in Mammals Mode of origin and types of mammalian placentae 787; Choriovitelline placenta or chorionic placenta or yolk-sac placenta 787; Chorio-allantoic placenta or Allantoic placenta 787; Classification of chorio-allantoic placenta 788; Morphological classification of placenta 788; Classification of placentae according to the distribution of villi on chorion 789; Classification of placenta according to histology 790; Classification of placentae according to the mode of implantation 791; Physiology of placenta 792; Important questions Integument and its Derivatives in Vertebrates Structure of skin 795; Functions of integument 796; Derivatives of (xv)

15 the integument 797; Epidermal derivatives 798; Epidermal glands 798; Epidermal scales and scutes 800; Horns 802; Digital structures 803; Feathers 804; Hair 805; Dermal derivatives 806; Integument in different classes of chordates 809; Protochordata 811; Cyclostomata 809; Pisces 809; Amphibia 810; Reptilia 811; Aves 812; Mammalia 812; Important questions Endoskeleton in Vertebrates Dermal bony skeleton 815; Endoskeleton 815; Functions of endoskeleton 816; Bone 816; Axial skeleton 818; Skull 818; Skull in various classes of vertebrates 824; Cyclostomata 824; Chondrichthyes 824; Osteichthyes 824; Amphibia 824; Reptilia 825; Aves 825; Mammalia 826; Vertebral column 826; Vertebral column in fishes 831; Vertebral column in tetrapoda 832; Amphibia 833; Reptilia 833; Aves 833; Mammalia 834; Sternum 834; Pisces 835; Amphibia 835; Reptilia 835; Aves 835; Mammalia 835; Appendicular skeleton 835; Origin of appendages 835; Origin of girdles 837; Girdles and limbs in tetrapoda 837; Limbs 837; Origin of pentadactyle limbs 838; Girdles and limbs in Tetrapoda 838; Muscles 842; Swimming in bony fishes 843; Swimming in snakes 844; Important questions Coelom and Digestive System in Vertebrates Coelom 846; Digestive system 849; Buccal cavity 850; Pharynx 853; Oesophagus 853; Stomach 853; Small intestine 855; Large intestine 856; Digestive glands 857; Important question Respiratory System in Vertebrates Respiratory organs 860; Gills 860; Lungs 862; Mechanism of respiration 864; Accesory respiratory organs 864; Important questions Circulatory System in Vertebrates Parts of circulatory system 868; Evolution of heart in vertebrates 869; Single-chambered heart 869; Two-chambered heart 870; Threechambered heart 870; Four-chambered heart 872; Modification of aortic arches in vertebrates 872; Aortic arches in vertebrates 873; Cyclostomata 873; Pisces 873; Amphibia 873; Reptilia 873; Aves 874; Mammalia 874; Venous system 875; Modifications of veins 876; Lymphatic system 877; Spleen 879; Important questions Nervous System in Vertebrates Nervous system and its functions 881; Anatomy of nervous system: The neuron 882; Divisions of nervous system 883; Functional divisions of nervous system 884; Kinds of neurons 884; Development of central nervous system 885; Comparative account of brain in vertebrates 888; Cyclostomata 888; Elasmobranchi 889; Osteichthyes (Bony (xvi)

16 fish) 891; Amphibia 891; Reptilia 891; Aves 891; Mammalia 892; Peripheral nervous system 893; Cranial nerves 894; Spinal nerves 894; Autonomic nervous system 895; Important questions Receptor Organs in Vertebrates Cutaneous (General) receptors 898; Chemoreceptors 899; Olfactory organs in vertebrates 899; Gustatory or organs of taste in vertebrates 900; Eyes or Photoreceptors 900; Lateral line system 902; Ears or Statoacoustic organs 903; Internal receptors or Interoceptors 904; Important questions Urinogenital Organs in Vertebrates Vertebrate kidneys and ducts 907; Archinephros 907; Pronephros 908; Mesonephros 909; Metanephros 911; Urinary bladder 912; Gonads and their ducts 912; Testes and male genital ducts 913; Ovaries and female genital ducts 914; Types of uterus 917; Important questions Endocrine System in Vertebrates Endocrine and exocrine glands 918; Endocrine glands 919; Thyroid gland 920; Parathyroid glands 921; Adrenal glands 922; Pituitary gland 923; Thymus gland 925; Pineal gland 926; Pancreas 926; Mucous membrane 927; Gonads 927; Endocrine glands in vertebrates 928; Elasmobranchii 928; Amphibia 928; Reptilia 929; Aves 929; Molecular mechanisms of hormone action 929; Pheromones 934; Important questions Some Comparative Charts of Vertebrate Animal Types Table Comparison, Distribution, Habits and Habitat of Vertebrate Types 938; Table Comparison : External Features of Vertebrate Types 940; Table Comparison : Integument of Vertebrate Types 945; Table Comparison : Exoskeletal Structures of Vertebrate Types 947; Table Comparison : Skulls of Vertebrate Types 949; Table Comparison : Pectoral Girdles (Shoulder Girdles) of Vertebrate Types 952; Table Comparison : Pelvic Girdles (Hip Girdles) of Vertebrate Types 956; Limbs of Vertebrate Types 959; Table Comparison : Bones of Forelimbs of Vertebrate Types 960; Table Comparison : Bones of Hindlimbs of Vertebrate Types 962; Table Comparison : Vertebral Column of Vertebrate Types 964; Table Comparison : Digestive System of Vertebrate Types 969; Table Comparison : Respiratory System of Vertebrate Types 977; Table Comparison : Hearts of Vertebrate Types 980; Table Comparison : Brains of Vertebrate Types 985; Table Comparison : Excretory Systems of Vertebrate Types 991; Table Comparison : Reproductive Systems of Vertebrate Types 994. (xvii)

17 51. Wildlife in India Importance of wildlife 1001; Biodiversity 1003; Magnitude of biodiversity 1004; Status of biodiversity 1004; Uses of biodiversity 1004; Threats to biodiversity 1004; Vanishing wildlife 1004; Causes of destruction 1005; Conservation, Preservation, Protection and Categories of Wild Animals 1007; Extinction of species 1007; Extinct species 1007; Endemic species 1008; The IUCN Red List of Categories 1008; Protected Indian wildlife 1009; Table IUCN Red List of Some Indian Threatened Mammals 1009; Table IUCN Red List of Some Indian Threatened Reptiles 1011; Table IUCN Red List of Some Threatened Indian Birds 1011; Protected areas in India 1013; National Parks 1014; Sanctuaries 1014; Biosphere Reserves 1014; Safari Park 1014; Zoo 1014; Zoological Garden 1014; Zoological Park 1014; Sanctum sanctorum 1014; Conservation of wildlife 1014; Conservation strategies 1015; Important Indian wildlife 1016; Table Endangered Species of Indian Hornbills 1021; Project Tiger 1021; Table Details of Tiger Reserves in India Project Lion (Gir Lion Project) 1023; Project Elephant 1024; Crocodile Breeding Project 1024;Table Schemes of the Government of India Project, Crocodile Breeding and Management operating with FAO/UNDP Technical Assistance 1026; Sanctuary and National Park 1027; Table Differences between Sanctuary and National Park 1028; Indian Sanctuaries 1028; Table Statewise Break-up of Wildlife Sanctuaries 1029; National Parks 1030; Table Statewise Break-up of National Parks of India 1031; Some National Parks of India 1032; Table Famous National Parks of World created for Specific Endangered Species 1035; Table Some Wildlife Sanctuaries and National Parks of India 1035; Biosphere Reserves 1037; Table Biosphere Reserves of India 1038; Zoological Gardens and Museums 1039; Table Some Indian Zoological Gardens and Museums 1039; Wildlife Organisations 1040; Wildlife Institute of India (WII) 1042; Wildlife Act 1042; Need of Wildlife Management / Conservation 1043; Problems of Wildlife Management in India 1044; Methods of Wildlife Conservation 1044; Important questions Glossary Selected References Index (xviii)

18 1 Phylum Chordata : An Introduction C h a p t e r Contents of this Chapter What is ChordatA? The name of phylum Chordata is derived from two Greek words, the chorde ( = a string or cord) and ata (= bearing). The common characteristic feature of phylum Chordata is the presence of a stiff, supporting rod-like structure along the back, the notochord (Gr., noton = back; L. chorda = cord) which is found in all the members of the phylum at some stage of their lives. Thus, chordates are those animals which have a cord, i.e., notochord. The animals belonging to all other phyla of the Animal Kingdom are often called the nonchordates or the invertebrates since they do not have notochord or backbone in their body structure. The phylum Chordata was created by Balfour in The phylum Chordata includes primarily the Protochordata (Acraniata) and Vertebrata (Craniata). Ü Ü Ü Ü Ü Ü Ü Ü Ü Ü What is Chordata? Chordate Animals Three Fundamental Chordate Characters Characters Common to Chordates and Higher Nonchordates Comparison between Chordates and Nonchordates Origin and Ancestry of Chordata Major Subdivisions of Phylum Chordata General Characters of Phylum Chordata Brief Classification of Phylum Chordata with Characters Phylum Chordata

19 2 Chordate Zoology Chordate Animals Phylum Chordata is the largest of the deuterostome phyla. It is the highest and most important phylum comprising a vast variety of living and extinct animals. Most of the living chordate animals are well-known familiar vertebrate animals such as the fishes, amphibians, reptiles, birds and mammals. The less well-known animals include a number of marine forms such as the tunicates and lencelets. Diversity of Chordates The chordates exhibit great diversity of form (anatomy), physiology and habit. The phylum Chordata includes a vast group of diverse animals ranging from Ascidian to Man. Number (Numerical strength). The number of chordate species is not large. About 49,000 species are on record which are only half of the living species of molluscs, and less than onetenth those of arthropods. The two subphyla Urochordata and Cephalochordata include nearly 2,500 species. The subphylum Vertebrata includes 46,500 species. Among the vertebrates, fishes are the most numerous with approximately 25,000 species. The approximate number of species of amphibians is about 2,500, reptiles 6,000, birds 9,000 and mammals 4,500. Size. The urochordates and cephalochordates are mostly of small size. The vertebrates include animals of medium to large size, notably some huge sharks and whales. The gigantic blue whale (Balaenoptera musculus), which is about 35 metres in length and 120 tons in weight, is the biggest known animal. The whale shark (Rhineodon typus) attains a length of 15 metres and is the second biggest vertebrate after whales. The smallest fish is a Philippine goby (Pandaka) measuring only 10 mm long. Ecology. The chordates are not only the largest animals existing today, but ecologically they are among the most successful in the Animal Kingdom. They occupy various kinds of habitats and have adapted themselves to various modes of living than any other group, including the arthropods. Chordates are found in the sea, in freshwater, in the air and all parts of land from the equator to the poles. Birds and mammals are found in cold climates because they have a constant body temperature, which other animals do not have. All lower chordates (protochordates) are marine, fishes are aquatic (freshwater and marine both) and higher chordates are predominantly terrestrial. Amphibians are not found in salt water. Birds do not live permanently in water, while some amphibians, reptiles and mammals permanently occupy the water. Most tunicates are sessile, all chordates are free-living and none is strictly parasitic. Three Fundamental Chordate Characters All the chordates possess three common fundamental characteristics at some stage in their life history. These three common fundamental morphological features are as follows : 1. Notochord (a longitudinal supporting rod-like structure); 2. Dorsal tubular (hollow) nerve cord; and 3. Pharyngeal gill-slits. These three distinctive characteristics are unique for the phylum Chordata (Fig. 1.1). The existence of such common characteristics is considered as a result of inheritance from a common ancestry. Besides these three common characteristics, there are few other characteristics which have less diagnostic value. 1. Notochord or chorda dorsalis. The notochord (Gr., noton = back; chorda = cord) is a rod-like, elongated, elastic structure situated just above the alimentary canal and immediately beneath the dorsal tubular nerve cord. It is composed of large vacuolated notochordal cells enclosed in an outer fibrous and an inner elastic sheath of connective tissue (Fig. 1.2). It serves as a primitive internal skeleton and acts as a rigid axis, but permits movements of the body. It may persist throughout life, as in lancelet, lamprey and some fishes, or it may be replaced

20 Phylum Chordata : An Introduction 3 partially or completely by a backbone or vertebral column. The notochord originates from the endodermal roof of the embryonic archenteron. pharyngeal gills-slits dorsal hollow nerve cord notochord fibrous neural sheath nerve cord cartilage fibrous notochordal sheath elastica interna mouth pharynx trunk hepatic caecum anus digestive tube tail notochordal cells cartilage dorsal aorta Fig Diagrammatic side view of a chordate showing Fig Notochord of young dogfish. three fundamental chordate characters. 2. Dorsal tubular nerve cord. In chordates, there is a dorsal, hollow or tubular, fluid-filled nerve cord lying just above the antero-posterior axis of the body (Fig. 1.2). The nerve cord is formed by an infolding of mid-dorsal strip of neural ectoderm and encloses a cavity or canal, the neurocoel. The nerve cord lies above the notochord and outside the coelom, extending lengthwise in the body. This tubular nerve cord persists throughout the life in chordates. In vertebrates, the anterior region of nerve cord becomes specialised to form a cerebral vesicle or brain which is enclosed in a protective cartilaginous or bony cranium. The posterior part of nerve cord transforms into spinal cord which is protected within the neural canal of the vertebral column. 3. Pharyngeal gill-slits. The gill-slits have many alternative names, such as gill-clefts, pharyngeal or branchial-clefts, visceral-clefts, visceral or branchial-pouches. In all the chordates, at some stage of their life history, a series of paired internal gill-slits or gill-clefts perforate through the pharyngeal wall of the gut behind the mouth. Gill-slits are paired openings leading from the pharynx to the exterior. Lateral outpushing of the endodermal lining of pharynx meet and fuse with ectodermal inpushings from the exterior, the intervening walls being broken down, thus, gill-clefts are formed. Such gill-clefts appear during the development of every chordate, but in many aquatic forms they are lined with vascular lamellae which form gills for respiration. In terrestrial chordates which never breathe by gills, traces of gill-clefts are present during early development but disappear later in adults. Within these clefts are the gills in many aquatic animals. In many animals equipped with lungs, branchial-clefts, or branchial-grooves are always found in the embryo. In lower chordates, the visceral-clefts are used as a feeding mechanism throughout life, but in higher chordates, the gill-clefts often form some endocrine glands. The gill-slits serve primarily for the passage of the water from the pharynx to outside, thus, bathing the gills for respiration. The water current secondarily helps in filter feeding by retaining food particles in the pharynx. The above three common characters appear during early embryonic life of all the chordates. But all the above three characters rarely persist in the adult (e.g., Branchiostoma). Only one of these three primary characters of chordates is found in the adults of most of them, this is the dorsal tubular nerve cord, even this has its hollow lumen greatly reduced in some, and in Urochordata the central nervous system degenerates in the adult. The other two characters completely disappear in the adults of most chordates. However, the three primary characters are possessed only by chordates. The three common chordate characters were probably characteristics of the ancestral chordates. These characters distinguish chordates from all other animals and appear to reveal their common ancestry.

21 Chordate Zoology 30% OFF Publisher : SChand Publishing ISBN : Author : E L Jordan & Dr. P.S. Verma Type the URL : Get this ebook