Bio-Zoology Higher Secondary First Year Volume 1 PDF

GOVERNMENT OF TAMIL NADU BIO-ZOOLOGY HIGHER SECONDARY FIRST YEAR VOLUME - I Untouchability is Inhuman and a Crime A publication under Free Textbook Programme of Government of Tamil Nadu Department Of Scho...

GOVERNMENT OF TAMIL NADU BIO-ZOOLOGY HIGHER SECONDARY FIRST YEAR VOLUME - I Untouchability is Inhuman and a Crime A publication under Free Textbook Programme of Government of Tamil Nadu Department Of School Education Government of Tamil Nadu First Edition - 2018 NOT FOR SALE Content Creation The wise possess all State Council of Educational Research and Training © SCERT 2018 Printing & Publishing Tamil NaduTextbook and Educational Services Corporation www.textbookso nline.tn.nic.in II  CONTENTS BIO-ZOOLOGY UNIT I Chapter 1 The Living World 01 Chapter 2 Kingdom Animalia 18 UNIT II Chapter 3 Tissue Level of Organisation 49 Chapter 4 Organ and Organ Systems in Animals 64 UNIT III Chapter 5 Digestion and Absorption 98 Chapter 6 Respiration 120 Chapter 7 Body Fluids and Circulation 142 E-book DIGI links Lets use the QR code in the text books ! How ? Download the QR code scanner from the Google PlayStore/ Apple App Store into your smartphone Open the QR code scanner application Once the scanner button in the application is clicked, camera opens and then bring it closer to the QR code in the text book. Once the camera detects the QR code, a url appears in the screen.Click the url and goto the content page. III  Conceptual picture with caption relating to every chapter is given in this text book. STROKE VOLUME IS DEPENDENT ON VENOUS RETURN Chapter Outline Presents a complete overview of the chapter Goals to transform the classroom processes into Learning Objectives: learner centric with a list of bench marks Amazing facts, Rhetorical questions to lead students to biological inquiry Note: Additional inputs to content is provided Directions are provided to students to conduct activities Activity in order to explore, enrich the concept. Infographics Visual representation of the lesson to enrich learning. HOW TO USE THE BOOK Superfluous information about a personality or day to day life experience relating to the content To motivate the students to further explore the content digitally and take them to virtual world ICT To enhance digital Science skills among students Concept Map Conceptual diagram that depicts relationships between concepts to enable students to learn the content schematically Glossary Explanation of scientific terms Evaluation Assess students to pause, think and check their understanding Career corner List of professions particular to that chapter References List of related books for further details of the topic Web links List of digital resources *V  Career options in Zoology Courses Institutions Professions and Scope for Future Studies Medical course ▶ AIIMS, New Delhi Civil surgeon / Civil assistant surgeon in central and state govt hospitals and in private ◉ MBBS – Allopathy ▶ JIPMER sector. Specialist in various medical fields like Cardiologist, Endocrinologist, Neurologist, ◉ MD ◉ MS ▶ Government & Private Medical Colleges Orthopedician, Paediatrician, Haematologist, Pathologist and Anaesthetist. ◉ BUMS – Unani ◉ BNYS _ Naturopathy ▶ AFMC, AMU ◉ BHMS – Homeopathy ◉ BDS _ Dental ◉ Cardiology ◉ Pulmonology ◉ Nephrology ◉ Diabetology ◉ Dermatology, ◉ BAMS – Ayurveda ◉ BSMS _ Siddha ◉ Anaesthesiology ◉ Ophthalmology ◉ Obstetrics and Gynaecology Veterinary Course ▶ State Veterinary Universities & Colleges (Veterinary Surgeon/ Veterinary Assiatant Surgeon in central and state govt ◉ B. V. Sc. (Bachelor of Veterinary Sciences) hospitals and in private sector). ◉ Animal Biochemistry ◉ Dairy Science ◉ Animal Biotechnology ◉ Dairy Technologisty ◉ Animal Genetics and Breeding ◉ Livestock Production Management ◉ Animal Nutrition ◉ Animal Physiology ◉ Bio-Statisticis ◉ Food Quality and ◉ Poultry Science Safety Assurance ◉ Veterinary Bacteriology ◉ Indian Traditional Foods ◉ Veterinary Immunology Preservation & Packaging State level institutes Agri Courses ▶ IARI, Delhi (Agriculture Officer in state and central government service and other ◉ B. Sc. (Agriculture) ▶ Agriculture Universities & Colleges private employment oppurtunites ) V ◉ B. Tech (Agriculture) ◉ Agricultural Engineer ◉ Environmental Sciences ◉ B. Sc. (Horticulture) ◉ Agronomist ◉ Fruit Sciences and ◉ B. Sc. (Forestry) ◉ Bioinformatics Horticultural Technology ◉ B. Sc. (Sericulture) ◉ Entomologist ◉ Plant Pathology Post graduation and Doctorate courses in National and ◉ B. F. Sc. (Bachelor of Fisheries Sciences) ◉ Soil science & Agro Chemistry Para Medical courses ▶ All India Institutes of Medical Sci- ◉ Nursing ◉ Nuclear Medicine Technician ◉ B. Sc. (Nursing) ences (AIIMS), New Delhi, Bhopal, ◉ Pharmacy Occupational therapist ◉ B. Sc. (Trauma Care Management) Bhubaneswar, Jodhpur, Patna, Raipur, ◉ Anaesthesia Technician ◉ Operation Theatre Technician ◉ B. Pharm, D. Pharm Rishikesh. ◉ Cardiac Technician ◉ Ophthalmic Assistant ◉ BPT (Bachelor of Physiotherapy) ▶ JIPMER, Puducherry ◉ Dental Mechanic ◉ Physiotherapst ◉ BOT (Bachelor of Occupational Therapy) ▶ All Government & Private Medical ◉ Health Inspector ◉ Radiographic Assistant ◉ B. Optom. (Bachelor of Optometry) Colleges ◉ Medical Imaging & Technician ◉ Radiotherapy Technician ◉ Medical Lab Techician ◉ Rehabilitation Technician ◉ Medical X-ray Technican ◉ Respiratory Therapy Technician ◉ Blood Transfusion Technician General Courses Government Arts and Zoo keepers, Creators, Bird watchers in Airports and Lab Technician. ◉ B.Sc. Zoology ◉ B.Sc. Food Technology Science Colleges in TamilNadu ◉ B.Sc. Dietician & Nutritionist ◉ B.Sc. Dairy Technology ◉ B.Sc. Sericulture ◉ B.Sc. Mass Communication ◉ B.Sc. Oceanography ◉ B.Sc. Multimedia ◉ B.Sc. Forensic Sciences ◉ B.Sc. 3D Animation Bachelor of Science and Education (BSc, B.Ed) Regional Institute of Education BT.Assistant (Science teacher for secondary level) M.phil in Education IDGC Ph.D (Mysore, Ajmeer, Bhopal,Bhuvaneswar), Shillong *Civil Service Exams for all india services (IAS, IPS, IFoS) and other central services &*Other service exams conducted by TNPSC, IBPS, NDA, CDS, SSC and RRB.  Career options in Zoology Master of science and Education (MSc, B.Ed) Regional Institute of Education PG.Assistant (Mysore, Ajmeer, Bhopal,Bhuvaneswar) (Zoology, teachers, professors in collegeslectures and universities higher secondary level) Master of science in Zoology Government arts and science colleges in Researchers in variegated subjects in zoology and life science, Scientist, Environmetolo- TamilNadu - Madras University gyist, Dietician and Nutritionist Master of science in Marine Zoology National institute of Oceanography Career opportunities in National Marine park and Marine Engineers ▶ Andhra University(Visakhapatnam) ▶ Anna University (Chennai) ▶ Dr. Babasaheb Ambedkar Marathwada University Marine Research Laboratory (Maharashtra) ▶ Bharathidasan University (Tiruchirappalli) Master of science in zoology with ▶ Co-operative institute of health science ◉ Lab Technician ◉ Nuclear Medicine specialization in Medical Microbiology (Kerala) ◉ Medical Imaging and techni- ◉ Health Inspector ▶ Dolphin institute of Bio-Medical and cian ◉ Blood transfusion technician Natural Science (Dehradun) ◉ Respiratory therapy technician ▶ Himalayan University (Arunachal Pradesh) Master of philosophy and Ph.D in Zoology ▶ 4UBUF
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Professor, Research scholar Scientist in University , Documentarist in National Geographic Channel, Animal clinics, National parks, Museum Fisheries and aquaculture PharmaceuticBl companies, animal trainers. VI Medicine Related Entrance Exams Exam Selection Process & Test Pattern No. of Questions Tentative Schedule NEET Physics 45 Form out: Last week of Jan. www.aipmt.nic.in Chemistry 45 Last Date: 1st week of March Time: 3 Hours Biology 90 Test Date: 1st week of May Timing: NA Total Questions 180 Negative Marking: +4/-1 Mode: Pen and Paper Marks: 720 Forms Available: Online AIIMS Physics 60 Form out: Mid Jan All India Institute of Medical Sciences Chemistry 60 Last Date: Mid Feb www.aiimsexams.org Biology 60 Test Date: Mid May Time: 3.5 Hours GK 20 Negative Marking: +1/- 1/3 rd Timing : NA Total questions 200 Marks: 200 Mode: Computer based Forms Available: Online JIPMER Physics 60 Form out: Last week of March Jawaharlal Institute of Postgraduate Chemistry 60 Last Date: 1st week of May Medical Education & Research Biology 60 Test Date: 1st week of June www.jipmer.edu.in Logic & Quantitative 10 Negative Marking: Nil Time: 2.5 Hours Reasoning 10 Marks: 800 Timing: NA English Comprehension 200 Forms Available: Online Mode: Computer based Total Questions The Details given above are tentative and have been prepared as per trends of previous years. Please visit individual exam/institute website for exact details.  Famous National Institutes for Biologists AIIMS JIPMER NDRI SIDDHA IVRI Undergraduate Courses (UG) Undergraduate Courses (UG) Undergraduate Courses (UG) x MVSc PG programme in Siddha x BVSc & AH x MBBS x M B B S x B.Tech. (Dairy Technology) x Maruthuvam x Animal Biochemistry x B.Sc Nursing (post Certificate) x B Sc Nursing Postgraduate Courses (PG) x Gunapadam x Animal Biotechnology x B.Sc. (Hons.) Nursing x B Sc Allied medical Sciences Microbiology x Pura Maruthuvam x Animal Genetics and Breeding x Paramedical Courses (PM) x B.Sc. Medical Laboratory Technology x Dairy Microbiology x Varma Maruthuvam x Animal Nutrition x B.Sc. (Hons.) Opthalmic Techniques x B.Sc. Cardiac Laboratory Technology x Dairy Chemistry x Siddhar Yoga Maruthuvam x Bio-Statistics x B.Sc. (Hons.) Medical Technology x B.Sc. Dialysis Technology x Dairy Technology x Kuzhandhai Maruthuvam x Epidemiology x B.Sc. 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RCI approved) x Dairy Extension Education x Noi Nadal x Veterinary Medicine x Agricultural chemicals x Animal Biotechnology x Veterinary Parasitology x Nanju Maruthuvam x Agronomy Postgraduate Courses (PG) x Agronomy (Forage production) x Veterinary Pathology x Bioinformatics x General Surgery x Animal Reproduction, Gynecology x Veterinary Pharmacology x Entomology and Obstetrics x Obstetrics & Gynaecology x Veterinary Physiology x Horticulture x Food Quality and Safety x Ophthalmology x Veterinary Public Health x Molecular biology and biotechnology Assurance x Orthopedic Surgery x Veterinary Surgery & Radiology x Environmental sciences x Oto-Rhino Laryngology (E.N.T.) x Veterinary Virology x Plant pathology NIN ( Hyderabad) x Plant genetic resources IIT (Chennai) National Diploma x Nematology x MSc (APPLIED NUTRITION) x National Diploma in Animal Husband- x Microbiology x Biological Sciences - x POST-GRADUATE ry (NDAH) Division of Animal Nutrition Dual Degree (BS & MS) CERTIFICATE x National Diploma in Animal Reproduc- COURSE IN NUTRITION tion (NDAR) Division of Animal Reproduction x National Diploma in Veterinary Biological Products (NDBP) Division of Biological Products x National Diploma in Equine Husband- PhD ry, Medicine and Surgery (NDEHMS) x National Diploma in Fodder and Feed x Animal BiochemistryB.V.Sc.& AH x Animal NutritionB.V.Sc.& AH with x Veterinary BacteriologyBVSc & AH with x Veterinary Gynaecology and ObstetricsB.V.Sc. & Technology(NDFFT) Division of with Master's degree in concerned Master's degree in concerned discipline. Master’s degree in Vet. Bacteriology/Vet. AH with Master's degree in concerned discipline Animal Nutrition discipline. x Livestock Production and Manage- Virology/ Vet. Microbiology/ Vet. Public x National Diploma in Meet and Meat x Veterinary ImmunologyBVSc & AH with Master’s x Animal BiotechnologyBVSc & AH mentB.V.Sc.& AH with Master's degree Health/ Avian Diseases/ Vet. Immunolo- degree in Vet. Immunology or MVSc in Vet. Microbi- Products Technology (NDMPT) with Master’s degree in Biotechnolo- in concerned discipline. gy/Epidemiology/ Biotechnology ology/Virology/ Bacteriology/ Pathology/Biotechnol- Division of Livestock Products gy/ Animal Biotechnology/Animal x Livestock Products TechnologyB.V.Sc.& x Veterinary Extension EducationBVSc & ogy/Avian Diseases/Parasitology/ Animal Biochem- Technology Biochemistry/ Microbiology/ Immu- AH with Master's degree in concerned AH with Master’s degree in concerned istry with minor in Vet. Immunology x National Diploma in Poultry Husband- nology/ Virology discipline. discipline/ Vet. Medicine/ Vet. Gynaecol- ry (NDPH) CARI x Veterinary MedicineB.V.Sc.& AH with Master's x Animal Genetics and BreedingBVSc x Poultry ScienceB.V.Sc.& AH with ogy & Obstetrics/ Vet. Surgery/ Animal degree in concerned discipline x National Diploma in Preventive & AH with Master’s degree in Master's degree in concerned discipline. Nutrition Veterinary Medicines (NDPVM) Div. of concerned discipline B&M UNIT UNITI I C hCahpatpetre 1r 1 The TheLiving LivingWorld World Chapter Outline Chapter Outline 1.1. Diversity in the Living world 1.2.1.1. Diversity Need in the Living world for Classification 1.3.1.2. Need forand Taxonomy Classification Systematics 1.4.1.3. Taxonomy Three Domainsandof Systematics life 1.5.1.4. Three Domains Taxonomic of life Hierarchy 1.6.1.5. Taxonomic Hierarchy Nomenclature “Our task“Our musttaskbe to…embrace all living must be to…embrace 1.7.1.6. Nomenclature Concept of Species creatures and theall whole livingofcreatures nature and anditsthe beauty. whole” 1.8.1.7. Concept Tools of Species for study of Taxonomy of nature and itsEinstein — Albert beauty.” 1.8. Tools for study of taxonomy — Albert Einstein Learning Objectives: have to depend on plants and animals for food. Animals are also used as source Learns the importance of labour, in farming, as pets, and for of the living world and other economic benefits. Understanding its diversity animals and their unique characteristics, Understands the need habitats, behaviour and evolutionary for classification relationships is very important. This Creates an interest in systematics chapter deals with, diversity in the living and understands the importance world, need for classification, types of of taxonomy for classification of classification, taxonomical hierarchy, animals nomenclature and tools for studying Knows the key rules of nomenclatures taxonomy. and their uses 1.1 Diversity in the Living All living forms co-exist with each other. There are about 8.7 million species of World animals which have been identified, Earth has numerous habitats with a wide named, described and classified. A study range of living organisms inhabiting reports that 86% of all species on the land them. Plants and animals are present in and 91% of those in the seas are yet to be almost all of the places, from polar ice discovered, described and catalogued. caps to volcanic hot springs, from shallow Though humans are placed in the top lagoons to the deepest oceans, from most position on the hierarchy, they tropical rain forests to dry and parched 1  A new estimate of biodiversity on Earth (2017) 0.4% 1% 0.1% 4.1% 2.8% 7.3% 5.6% 7.4% 78% 17.6% 0.02% 90.5% 7.3% 4.9% 73.1 Wilson (1992) Mora et al (2011) Brenden Wilson (1992) Mora et al (2011) Brenden etetalal (2017) (2017) A traditional estimate of the An estimate based on An estimate based on the relative richness of different groups of projected richness of different projected richness of organisms based on numbers of groups of organisms. different groups of organisms. described species. Animals Fungi Plants Protists Bacteria Newly Discovered Species Threatened Species in India (2016) in India Platyhelminthes Crustaceas Reptiles 13% Amphibians 1% 2% Fishes Invertebrates 13% 31% Insects 40% Vertebrates Mammal Birds Reptiles Amphibian Fishes Invertebrates New Species Discovered in India (2016) Of the new animal species discovered in India, 258 are invertebrates and 55 vertebrates. As many as 97 species According to IUCN, 172 species of animals are considered of insects, 27 of fishes, 12 species of amphibians, 10 of globally threatened in India or 2.9% of the world’s total Platyhelminthes, 9 of Crustacea and 6 of reptiles have been number of threatened species. discovered and described by scientists. There are 61 species These include 53 species of mammals, 69 birds, 23 reptiles of moths and butterflies (order Lepidoptera) and 38 of beetles and 3 amphibians, 2 fishes and 22 invertebrates. (Coleoptera). 2 deserts. There are a variety of species waste lot of time in finding an item. In that have been adapted successfully to the same way, libraries also organize the live in diverse ecosystems. Ecosystem is books alphabetically or genres-wise into a community of living organisms (plants autobiographies, novels, kids stories, and animals), non-living environment science fictions, etc. Likewise it is nearly (including minerals, climate, soil, water, impossible to study all the living organism sunlight) and their interrelationships hence it becomes necessary to device some (A.G. Tansley, 1935). The presence of a means and methods to make this possible large number of species in a particular and this process is called classification. ecosystem is called ‘biological diversity’ Classification is a process by which things or in short ‘biodiversity’. The term are grouped in convenient categories, biodiversity was first introduced by based on easily observable characters. The Walter Rosen (1985), and defined by E.D. scientific term used for these categories Wilson. is taxa (taxon–singular). Taxa indicates categories at different levels, for example Difference between the Living and Kingdom Animalia, includes multicellular Non-living animals such as reptiles, mammals, etc. Living organisms show a variety Based on their characteristics, all living of unique characters different organisms can be classified into different from non-living matter. The key taxa. This science of classification is characters of living organisms are, called taxonomy. External and internal cellular organization, nutrition, structures along with developmental respiration, metabolism, growth, response processes and ecological information to stimuli, movement, reproduction, of organisms are essential, as they excretion, adaptation and homeostasis. form basis of the taxonomical studies. Numerous scientists and taxonomists Hence, characterisation, identification, have made tremendous contribution and nomenclature and classification are the documentation in the observation and scientific stages that are basic to taxonomy. study of even minute characters in living The basic need for classifications are: organisms. Their keen observations have To identify and differentiate closely led to the classification of living organisms related species and the study of their interrelationships. To know the variation among the species 1.2. Need for classification To understand the evolution of the We come across many places where species things are arranged in specific categories. To create a phylogenetic tree In super markets, the shelves can have rows and columns of groceries, cosmetics, among the different groups toys, stationeries, snacks and utensils. To conveniently study living If it is not arranged in a well organized organisms manner, customers and sales persons will 3 1.3 Taxonomy and the organisms. Apart from the above Systematics said features, evolutionary history of the species and the environmental adaptations Taxonomy (G. taxis- arrangement ; nomos- and interrelationship between species are law) is the science of arrangement of also being investigated in systematics. living organisms along with classification, description, identification, and naming History of Classification of organisms which includes all flora and Early classification of organisms were fauna including microorganisms of the based on only two criteria, beneficial or world. The word taxonomy was coined by harmful animals. An ancient classification Augustin Pyramus de Candole (1813). system recognized 5 animal groups - Taxonomy is a theoretical study of domestic, wild, creeping, flying and classification with well defined principles, sea animals. Initially the classification rules and procedures. Aristotle is called was based on organism’s fundamental the father of taxonomy (classical) and characteristics such as the habitat and Carolus Linnaeus is the father of modern morphology only. taxonomy. Aristotle (384 to 322 BC), was the first to classify all animals in his History of Systematics (G. System/sequence) Animals (Historia Animalium in Latin). The objectives of taxonomy and He attempted a basic classification of all systematics are very similar; their goal living organisms into Plants and Animals. is to classify organisms with stipulated Animals were classified based on rules. The main criteria of systematics locomotion; walking (terrestrial), flying is identifying, describing, naming, (aerial) and swimming (aquatic). Based arranging, preserving and documenting on the presence or absence of red blood he classified the animals into two as Enaima with blood and those without blood as Carolus Linnaeus is Anaima. the father of modern Aristotle’s classification system had taxonomy, which is limitations and many organisms were not the system of classifying and fitting into his classification. For example, naming organisms. One of the tadpoles of frogs are born in water and his contributions was the have gills but when they metamorphosed development of a hierarchical into adult frogs they have lungs and can live system of classification of nature. both in water and on land. How to classify Today, this system includes frogs and where to place them? Aristotle eight taxa: domain, classified organisms based on locomotion, kingdom, phylum, hence, birds, bats, and flying insects were class, order, family, grouped together just by observing one genus, and species. single characteristic feature, the flying ability. On the contrary to the above said 4 example, the ostrich, emu and penguin organisms. A modification of this system are all birds but cannot fly. So Aristotle is the numerical taxonomy, which evolved would not have classified them as birds. in the 1950s. This system evaluates the In spite of these limitations Aristotle’s resemblances and differences through classification system was followed for statistical methods followed by computer more than 2000 years upto 1700. analyses to establish the numerical degree After Aristotle, his student of relationship among individuals. Later Theophrastus (372-287 BC) continued on biologists initiated studies on the his research on the classification of evolutionary and genetic relationships plants, and he was known as the “Father among organisms, which led to the emerge of of Botany.” There was a huge gap till phylogenetic classification or cladistics. 16th century, then the English naturalist It is an evolutionary classification based John Ray (1627–1705) wrote several on how a common ancestry was shared. important works through his life. His Cladistic classification summarizes the most important contribution was the genetic differences between all species establishment of species as the ultimate in the ‘phylogenetic tree’. Ernst Haeckal unit of taxonomy. In 1682 he published introduced the method of representing the Methodus Plantarum Nova, which evolutionary relationships with the help contained about 18,000 plant species, of a tree diagram known as cladogram. a result of a relatively narrow species This system of classification takes concept. His complicated classification into account ancestral characters (traits was based on many combined characters, of basic body design which would be in as opposed to earlier taxonomists. John the entire group) and derived characters Ray also aimed at publishing a complete (traits whose structure and functions system of nature, which included works differs from those of ancestral characters). on mammals, reptiles, birds, fishes and One or more derived characters which insects. The Swedish biologist Carolus appeared during evolution resulted Linnaeus (1707 - 1788) father of modern in the formation of new subspecies. taxonomy and founder of modern In a cladogram each evolutionary systematics developed a scientific system step produces a branching and all the of taxonomy and binomial nomenclature, which is still (with modifications) in use. Figure 1.1. Example of a Cladogram Aristotle to Linnaeus employed easily observable single to few traits for classification of organisms. With 6KDUNV 5D\)LQQHG 5D\  )LQQHG ILVK $PSKLELDQV &URFRGLOHV %LUGV 5RGHQWV UDEELWV 3ULPDWHV increased knowledge of the several biological domains, many characters were +DLU (JJVZLWKVKHOOV considered for classifying organisms. $PQLRWLFHJJ This represented the phase of classical )RXUOLPEV taxonomy which was based on overall %RQ\VNHOHWRQ similarities or affinities derived from 9HUWHEUDH morphology, anatomy and embryology of 5 members of the branch would possess the 1.4. Three Domains of life derived character which will not be seen Three domain classification was proposed in organisms below the particular branch by Carl Woese (1977) and his co-workers. point. Arranging organisms on the basis They classified organisms based on the of their similar or derived characters difference in 16S rRNA genes. The three which differ from the ancestral characters domain system adds the taxon ‘domain’ produced a phylogenetic tree or cladogram higher than the kingdom. This system (Figure 1.1). emphasizes the separation of Prokaryotes Depending on the system of into two domains, Bacteria and Arachaea, classification, organisms were classified and all the eukaryotes are placed into the into two or three kingdoms. Later into four, domain Eukarya. Archaea appears to have five, six and now into seven kingdoms. more in common with the Eukarya than R.H.Whittaker (1969) proposed the Five the Bacteria. Archaea differ from bacteria kingdom Classification, the Kingdoms in cell wall composition and differs from defined by him were Monera, Protista, bacteria and eukaryotes in membrane Fungi, Plantae, and Animalia based on composition and rRNA types. the cell structure, mode of nutrition, mode of reproduction and phylogenetic relationships. Table 1. gives a comparative account of different characteristics of the Thermus aquatics is a five kingdoms. bacterium which can Classification has come a long way and tolerate high temperatures. now takes into an account even molecular The first DNA polymerase enzyme was level DNA and RNA identification. The isolated from T. aquaticus it is advancement in molecular techniques used in PCR (Polymerase Chain and biochemical assays has led to a new Reaction ) for DNA amplification. classification - The “Three Domain” classification. THREE DOMAINS (Carl Woese, 1977) ARCHAEA BACTERIA EUKARYA (Extremophiles) Cyanobacteria & (Eukaryotes) Methanogens, Halophiles, Eubacteria, beneficial& Protista, Fungi, Plants Thermoacidophiles pathogenic and Animals 6 1. Domain Archaea are photosynthetic blue green algae which This domain includes single celled produce oxygen. These had played a key role organisms, the prokaryotes which have the in the changes of atmospheric oxygen levels ability to grow in extreme conditions like from anaerobic to aerobic during the early volcano vents, hot springs and polar ice geologic periods. caps, hence are also called extremophiles. They are capable of synthesizing their food Curd is one of the best sources without sunlight and oxygen by utilizing of probiotics, which are friendly hydrogen sulphide and other chemicals bacteria that can improve our health. from the volcanic vents. Some of the them e.g. Lactobacillus sp. produced methane (methanogens), few live in salty environments (Halophiles) and are 3. Domain Eukarya (Eukaryotes) thermoacidophiles which thrive in acidic Eukaryotes are animals which have true environments and at high temperatures. nucleus and membrane bound organelles. 2. Domain Bacteria DNA in the nucleus is arranged as a linear chromosome with histone proteins, Bacteria are prokaryotic, their cells have no ribsosomes of 80S type in the cytosol and 70S definite nucleus and DNA exists as a circular type in the chloroplast and mitochondria. chromosomes and do not have histones Animals in this domain are classified under associated with it. They do not possess kingdoms, namely, Protista, Fungi, Plantae membrane bound organelles except for and Animalia. ribosome (70S type). Their cell wall contains peptidoglycans. Many are decomposers, In 1987, Cavalier-Smith revised the some are photo-synthesizers and few cause six kingdom system to Seven Kingdom diseases. There are beneficial probiotic system. The concept of super kingdom was bacteria and harmful pathogenic bacteria introduced and revised to seven kingdom which are diversely populated. Cyanobacteria classification. The classification is divided FIVE KINGDOM CLASSIFICATION KINDS OF KINGDOM Salient features Monera Protista Fungi Plantae Animalia Cell type Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic Cell wall Non-cellular Present in Present Present Absent some Body Cellular Cellular Multicelluar Tissue Tissue organisation Tissue Organ Organ Organ system Mode of Autotrophic Autotrophic Heterotrophic Autotrophic Heterotrophic nutrition Heterotrophic Heterotrophic Table 1. Five Kingdom Classification 7 into two Super Kingdoms (Prokaryota and Archaebacteria) and five Eukaryotic and Eukaryota) and seven kingdoms, Kingdoms (Protozoa, Chromista, Fungi, two Prokaryotic Kingdoms (Eubacteria Plantae and Animalia). The Three-Domain System Bacteria Archaea Eukarya The traditional Five – Kingdom system Monera Protista Fungi Plantae Animalia The Six –Kingdom system Bacteria Archaea Protista Fungi Plantae Animalia The Seven – Kingdom system Archae- Eubacteria Protozoa Chromista Fungi Plantae Animalia bacteria 1.5. Taxonomic hierarchy In biological classification, the taxonomical intermediate categories such as subkingdom, hierarchy includes seven major categories grade, division, subdivision, subphylum, namely kingdom, phylum, class, order, superclass, subclass, superorder, suborder, family, genus and species and other superfamily, subfamily and subspecies. Hinny Mule Liger Tigon Figure 1.2 Sterile offsprings 8  Family: It is a taxonomic category Biological nomenclature which includes a group of related genera derives from the binomial (or with less similarity as compared to genus binominal) nomenclature and species. For example, the family that was originally codified in the Felidae includes the genus Felis (cats) works of Linnaeus, Species Plantarum and the genus Panthera (lions, tigers, (1753) and Systema Naturae, 10th leopards). Edition (1758). These publications Order: This category includes an are the starting points for the modern assemblage of one or more related families biological nomenclature in most groups which show few common features. One of plants and animals. or more similar families are grouped together to form an order. For example, family Canidae and Felidae are placed in Phylum: The group of classes with the order Carnivora. similar distinctive characteristics Class: This category includes one or constitute a phylum. The classes Pisces, more related orders with some common Amphibia, Reptilia, Aves and Mammalia characters. For example order Primata constitute the next higher category, comprising monkeys, apes and man is phylum Chordata. These classes share placed in the Class Mammalia, along with some common features like presence of the order Carnivora which includes dogs a notochord and a dorsal tubular nerve and cats. cord hence included in the phylum Recently Discovered Chordata. species in South India Kingdom: All living Scientists have discovered a animals belonging to new and unusual species of frog in the various phyla are included Western Ghats in India in August 2017. in the Kingdom Animalia The frog has shiny, purple skin, a light and it is the top most of blue ring around its eyes, and a pointy the taxonomic hierarchy. pig-nose. It is named as Bhupathy’s purple frog (Nasikabatrachus bhupathi) to honour Dr.Subramaniam Bhupathy, In July, 2017, a 9 years herpetologist who lost his life in the old boy discovered a new Western Ghats in 2014. Freshwater species of Jellyfish in the Kodaikanal lake, Tamilnadu. 1.6. Nomenclature Giza, Inimene, Emberi, Manna, Doanna, Umano ……. In all probability these words must be new to you…but they all mean “Human” 10 in different foreign languages! There are of the International Code of Zoological presently more than 6000 languages in Nomenclature (ICZN). The scientific the world and an animal can be named name ensures that each organism has only in more than 6000 ways! Unfortunately one name. it is impossible for anyone to have a good functioning knowledge of most languages Binomial Nomenclature and hence there arises a need for a (L. Bi-two; Nomen-Name) universally accepted scientific naming Biologists follow universally accepted system for all organisms. The process of principles to provide scientific names assigning scientific names to animals or to known organisms. Each name has taxonomic group is called nomenclature. two components, a generic name and a For example, worldwide, the scientific specific epithet. This system of naming name Homo sapiens denotes human. the organism is called Binomial Classification and grouping were done to Nomenclature which was popularised facilitate a deeper understanding of the by Carolus Linnaeus and practised by unique characteristics of each organism biologists all over the world. Example, and its interrelationship among closely the National Bird (Indian Peafowl) – related species. It plays a vital role in Pavo cristatus, the National Animal tiger the arrangement of known species based as Panthera tigris, and the Tamil Nadu on their similarities and dissimilarities. State bird is the common Emerald dove Numerous characters such as morphology, Chalcophaps indica. genetic information, habitat, feeding pattern, adaptations, evolution, etc., are Trinominal Nomenclature examined before an organism is named. (Tri – three) One of the primary responsibilities of systematic biology is the development This naming system was proposed by of biological nomenclature and Huxley and Stricklandt, Trinomen means, classification. Nomenclature is not an three names: generic name, species name end to systematics and taxonomy but it is and sub-species name. When members of necessary in organizing information about any species which have large variations biodiversity. Nomenclature, functions then trinomial system is used. On the to provide names for all taxa at all levels basis of dissimilarities, this species in the hierarchy of life. Naming of the gets classified into subspecies. It is the organisms is done based on the guidelines If you find an animal with four legs, with two eyes, paired ear pinna, A newly discovered Himalayan covered with fur, possessing forest thrush bird was named mammary gland , which class will after the birdman of India, you position it? How will you give Ornithologist Dr. Salim Ali. a binomial name, if you are the first The name of the bird is “ Zoothera salimalii”. A fruit bat is also named after him “Latidens person to discover and report that salimalii” animal. 11 extension of binominal nomenclature discovered and named after Scientist system which has an addition of Varad Giri, Cyrtodactylus varadgirii. subspecies. All the three names are set in italics and only the generic name is 1.7. Concept of species capitalized, if handwritten then it should Species is the basic unit be underlined separately E.g.Corvus of classification. The splendens splendens (Indian house crow) term species was coined Tautonymy: The practice of naming the by John Ray, and in his animals in which the generic name and book “Historia Generalis species name are the same, is called Plantarum” (3 volumes) Tautonymy. e.g. Naja naja (The Indian in 1693 described species as a group of Cobra). morphologically similar organisms arising from a common ancestor. Carolus Linnaeus What may be the reasons for the in his book “Systema naturae” considered extinction of Dinosaurs? If you know species as the basic unit of classification. the reasons for their extinction, why Species can be defined as a group of Sparrows are listed as endangered organisms that have similar morphology and species? physiology and can interbreed to produce fertile offsprings. In 1859 Charles Darwin Rules of Nomenclature in his book Origin of species explains the The scientific name should be italicized evolutionary connection of species by the in printed form and if handwritten, it process of natural selection. should be underlined separately. The generic name’s (Genus) first 1.8 Tools for study of alphabet should be in uppercase. taxonomy The specific name (species) should be Tools and taxonomical aids may be different in lowercase. for the study of plants and animals. The scientific names of any two Herbarium and Botanical garden may be organisms are not similar. used as tools for the study of plant taxonomy. In the case of animal studies, the classical The name or abbreviated name of tools are Museum, Taxonomical Keys and the scientist who first publishes the Zoological and Marine parks. scientific name may be written after the species name along with the year of publication. For example Lion-Felis leo Arignar Anna Zoological Park, also known Linn., 1758 or Felis leo L., 1758. as the Vandalur Zoo is in the south western If the species name is framed after any part of Chennai, Tamil Nadu, spreads over person’s name the name of the species an area of 1500 acres, is one of the largest shall end with i, ii or ae. zoological parks in India. The zoo houses For example, a new species of a ground- 2,553 species of both flora and fauna. dwelling lizard (Cyrtodactylus) has been 12  The important components of the of DNA sequences), DNA fingerprinting taxonomical tools are field visits, survey, (to identify an individual from a sample identification, classification, preservation and of DNA by looking at unique patterns in documentation. Many tools are being used for their DNA), Restriction Fragment Length taxonomical studies, amongst them some of Polymorphisms (RFLP) analysis (difference the important tools are discussed below: in homologous DNA sequences that can be detected by the presence of fragments The classical taxonomical tools of different lengths after digestion of the Taxonomical Keys: Keys are based on DNA samples), and Polymerase Chain comparative analysis of the similarities Reaction (PCR) sequencing ( to amplify a and dissimilarities of organisms. There specific gene, or portion of gene,) are used are separate keys for different taxonomic as taxonomical tools. categories. Museum: Biological museums have Automated species identification tools collection of preserved plants and animals It consists of Cyber tools. For example: for study and ready reference. Specimens DAISY, ALIS, ABIS, SPIDA, Draw wing, etc. of both extinct and living organisms can be ALIS o Automated Leafhopper studied. Identification System. Zoological parks: These are places DAISY o Digital Automated where wild animals are kept in protected Identification System. environments under human care. It enables ABIS o Automatic Bee Identification us to study their food habits and behaviour. System. Marine parks: Marine organisms are SPIDA oSpecies Identified Automatically maintained in protected enviroments. (spiders, wasp and bee wing characters). Printed taxonomical tools consist of Draw wing o Honey bee wing identification cards, description, field guides identification. and manuals. Neo taxonomical tools – This is based on Electron Microscopy images to study the Molecular taxonomical tools molecular structures of cell organelles. Technological advancement has helped Ethology of taxonomical tools – Based to evolve molecular taxonomical tools on the behaviour of the organisms it can from classical tools to molecular tools. The be classified. For example sound of birds, accuracy and authenticity is more significant bioluminescence, etc. in the molecular tools. The following e-Taxonomic resources – INOTAXA methods are being used for taxonomical is an electronic resource for digital images classification. and description about the species which Molecular techniques and approaches was developed by Natural History Museum, such as DNA barcoding (short genetic London. INOTAXA means Integrated marker in an organism’s DNA to identify Open TAXonomic Access. it as belonging to a particular species), DNA hybridization (measures the degree of genetic similarity between pools 13 Activity ___________________________________________ The main objective of this activity is to check the students understanding about animals and its characteristics before learning the lesson. Observe the picture given below, identify the animals and classify them according to you own understanding; write one character about each class of animals. Take the students to the school ground and ask them to observe and identify few invertebrates (insects, earthworm, spiders etc). Ask the students to write few characteristics of each animal which they have observed. Sl.No Name of the Animal Known Character Class Habitat 1 2 3 4 14  ICT Corner Deep Tree Let’s do this activity to know the position of a particular species in the Evolution path. Step – 1 Type the URL in the browser. Click ‘Play Game’ button then use your personal or school id to login. Otherwise use Guest Pass to enter. Then click the DEEP TREE icon that is given below The Evolution Lab to start the activity. Step – 2 Input the common name of any animal in the SEARCH tab given at the bottom of the activity window, select the appropriate Zoological name from the list appeared. Step – 3 7KH&ODVVL¿FDWLRQDQGWKHSODFHRIWKHVSHFLHVLQWKHDQLPDO.LQJGRPFDQEHYLHZHGE\ clicking the Icon placed next to the search tab. Step – 4 7ZR GL൵HUHQW VSHFLHV FDQ EH FRPSDUHG E\ FOLFNLQJ RQ WKH 5(/$7( EXWWRQ JLYHQ DW the bottom of the activity window. The relation between those species can be learnt by clicking the DNA icon appeared. ^ƚĞƉϭ ^ƚĞƉϮ ^ƚĞƉϯ ^ƚĞƉϰ DEEP TREE url ŚƩƉ͗ͬͬǁǁǁ͘ƉďƐ͘ŽƌŐͬǁŐďŚͬŶŽǀĂͬůĂďƐͬůĂďͬĞǀŽůƵƟŽŶͬ ΎWŝĐƚƵƌĞƐĂƌĞŝŶĚŝĐĂƟǀĞŽŶůLJ 15 Summary Earth has numerous habitats with a wide The taxonomical hierarchy includes seven range of living organisms inhabiting it. categories namely kingdom, phylum, class, Living organisms show a variety of unique order, family, genus and species. The process characters different from non-living matter. of assigning scientific names to animal or Classification is the process by which taxonomic group is called nomenclature. Each anything is grouped in a convenient category scientific name has two components, generic based on some easily observable characters. name and a specific epithet. The important Taxonomy is the science of arrangement of component of the taxonomical tools are field living organisms. R. H. Whittaker proposed visits, survey, identification, classification, the five kingdom classification. Three preservation and documentation. Molecular domain classification was proposed by Carl taxonomical tools are more accurate, authentic Woese and his co-workers. and significant for taxonimical classification. Glossary Shared character – A shared character is one that two lineages have in common Cladogram – A branching diagram show- ing the relationship between a number of Derived character – Derived character is species. one that evolved in the lineage leading up to a clade. Phylogeny – Relationships among vari- ous biological species based upon simi- Threatened species – Species which are larities and differences in their physical vulnerable to endangerment in the near or genetic characteristics. future. Phylogenetic tree – A phylogenetic tree or evolutionary tree is a branching dia- gram or "tree" showing the inferred evo- lutionary relationships upon similarities and differences in their physical or genet- ic characteristics. Evaluation 1. A living organism is differentiated from 2. A group of organisms having similar non-living structure based on traits of a rank is a. Reproduction a. Species b. Growth b. Taxon c. Metabolism c. Genus d. Movement d. Family 16  3. Every unit of classification regardless of 8. Molecular taxonomic tool consists of its rank is a. DNA and RNA a. Taxon b. Mitochondria and Endocplamic b. Variety reticulum c. Species c. Cell wall and Membrane proteins d. Strain d. All the above 4. Which of the following is not present in 9. Differentiate between probiotics and same rank? pathogenic bacteria a. Primata 10. Why mule is sterile in nature? b. Orthoptera 11. List any five salient features of the c. Diptera family Felidae d. Insecta 12. What is the role of Charles Darwin in 5. What taxonomic aid gives comprehensive relation to concept of species? information about a taxon? 13. Why elephants and other wild animals a. Taxonomic Key are entering into human living area? b. Herbarium 14. What is the difference between a Zoo c. Flora and wild life sanctuary? d. Monograph 15. Can we use recent molecular tools to 6. Who coined the term biodiversity? identify and classify organisms? a. Walter Rosen 16. Explain the role of Latin and Greek b. AG Tansley names in Biology. c. Aristotle d. AP de Candole 7. Cladogram considers the following characters a. Physiological and Biochemical b. Evolutionary and Phylogenetic c. Taxonimic and systematic d. None of the above References 1. Peter H. Raven, George B. Johnson, Holt Rinehart & Winston Harcourt Susan R. Singer, Jonathan B. Losos Education Company. (2004) Biology 7th Edition Published 3. Peter H. Raven, George B. Johnson, by McGraw-Hill Science. Kenneth A. Mason, Jonathan B. Losos, 2. Janet L. Hopson and John Postlethwait Susan R. Singer (2013) Biology 9th Edition. (2006) Modern Biology Published by Published by McGraw-Hill Science. 17 UNIT I Chapter 2 Kingdom Animalia Chapter Outline 2.1 Basis of Classification 2.2 Classification of Kingdom Animalia 2.3 Non Chordates (Invertebrata) upto Phyla level 2.4 Chordata upto Class level March 20th is celebrated as World Sparrow day to conserve this endangered species, House sparrow (Passer domesticus) Learning Objectives: are invertebrates or animals without backbone. The remaining represents Justifies the need for vertebrates or animals with backbone. classification. On the basis of the presence or absence Understands the salient of notochord (vertebral column), animals features of the animal are also categorised into two major groups phyla. and they are non chordates and chordates. Kingdom Animalia comprises millions 2.1 Basis of classification of animal species and studying them without a basic classification may lead Multicellular organisms are structurally to confusion. In addition to this, there and functionally different but yet they are several new species of animals being possess certain common fundamental constantly discovered. Classification is features such as the arrangement of cell very essential for identification, naming layers, the levels of organisation, nature and assigning a systematic position to of coelom, the presence or absence the newly discovered species. Animal of segmentation, notochord and the Kingdom is classified mainly based on the organisation of the organ system. closely resembling characteristic features. Kingdom Animalia is characterised of 2.1.1. Levels of organisation eukaryotic, multicellular, heterotrophic All members of Kingdom Animalia organisms. They include about 35 phyla are metazoans (multicellular animals) of which 11 are considered as major and exhibit different patterns of cellular phyla. Almost 99 percent of animals organisation. The cells of the metazoans 18 are not capable of independent existence Organ level of organisation is a further and exhibit division of labour. Among advancement over the tissue level of the metazoans, cells may be functionally organisation and appears for the first isolated or similar kinds of cells may be time in the Phylum Platyhelminthes and grouped together to form tissues, organ and seen in other higher phyla. organ systems. Organ system level of organisation Cellular level of organisation The most efficient and highest level This basic level of organisation is seen of organisation among the animals is in sponges. The cells in the sponges are exhibited by flatworms, nematodes, arranged as loose aggregates and do not annelids, arthropods, molluscs, form tissues, i.e. they exhibit cellular level echinoderms and chordates. The evolution of organisation. There is division of labour of mesoderm in these animals has led to among the cells and different types of cells their structural complexity. The tissues are functionally isolated. In sponges, the are organised to form organs and organ outer layer is formed of pinacocytes (plate- systems. Each system is associated with a like cells that maintain the size and structure specific function and show organ system of the sponge) and the inner layer is formed level of organisation. Highly specialized of choanocytes. These are flagellated nerve and sensory cells coordinate and collar cells that create and maintain water integrate the functions of the organ flow through the sponge thus facilitating systems, which can be very primitive respiratory and digestive functions. and simple or complex depending on the individual animal. For example, the Animals such as sponges lack nervous digestive system of Platyhelminthes has tissue and muscle tissue, what does this only a single opening to the exterior which tell you about sponges? serves as both mouth and anus, and hence called an incomplete digestive system. Tissue level of organisation From Aschelminthes to Chordates, all animals have a complete digestive system In some animals, cells that perform similar with two openings, the mouth and the functions are aggregated to form tissues. anus. The cells of a tissue integrate in a highly coordinated fashion to perform a common Similarly, the circulatory system is function, due to the presence of nerve of two types, the open type: in which cells and sensory cells. This tissue level of the blood remains filled in tissue spaces organisation is exhibited in diploblastic due to the absence of blood capillaries. animals like cnidarians. The formation of (arthropods, molluscs, echinoderms, tissues is the first step towards evolution of and urochordates) and the closed type: body plan in animals. (Hydra - Coelenterata). in which the blood is circulated through blood vessels of varying diameters Organ level of organisation (arteries, veins, and capillaries) as Different kinds of tissues aggregate to form in annelids, cephalochordates and an organ to perform a specific function. vertebrates. 19 2.1.2. Diploblastic and Triploblastic an axis are identical. An animal’s body organisation plan results from the animal’s pattern of development. The simplest body plan is During embryonic development, the seen in sponges (Figure 2.2). They do not tissues and organs of animals originate display symmetry and are asymmetryical. from two or three embryonic germ layers. Such animals lack a definite body plan On the basis of the origin and development, or are irregular shaped and any plane animals are classified into two categories: passing through the centre of the body Diploblastic and Triploblastic. does not divide them into two equal halves Animals in which the cells are arranged (Sponges). An asymmetrical body plan is in two embryonic layers (Figure 2.1), the also seen in adult gastropods (snails). external ectoderm, and internal endoderm are called diploblastic animals. In these animals the ectoderm gives rise to the epidermis (the outer layer of the body wall) and endoderm gives rise to gastrodermis (tissue lining the gut cavity). An undifferentiated layer present between the ectoderm and endoderm is the mesoglea. (Corals, Jellyfish, Sea anemone) Animals in which the developing embryo has three germinal layers are called triploblastic animals and consists of outer Figure 2.2. Asymmetry in sponges ectoderm (skin, hair, neuron, nail, teeth, etc), inner endoderm (gut, lung, liver) and Symmetrical animals have paired body middle mesoderm (muscle, bone, heart). parts that are arranged on either side of Most of the triploblastic animals show a plane passing through the central axis. organ system level of organisation (Flat When any plane passing through the worms to Chordates). central axis of the body divides an organism into two identical parts, it is called radial symmetry. Such radially symmetrical animals have a top and bottom side but no dorsal (back) and ventral (abdomen) side, no right and left side. They have a body plan in which the body parts are organised in a circle around an axis. It is the principal symmetry in diploblastic animals. Cnidarians such as sea anemone Figure 2.1 Germinal layers and corals (Figure 2.3) are radially symmetrical. However, triploblastic 2.1.3. Patterns of symmetry animals like echinoderms (e.g., starfish) Symmetry is the body arrangement in have five planes of symmetry and show which parts that lie on opposite side of Pentamerous radial symmetry. 20  Animals which possess two pairs show bilateral symmetry (Figure 2.5). of symmetrical sides are said to be It is an advantageous type of symmetry biradially symmetrical (Figure 2.4). in triploblastic animals, which helps in Biradial symmetry is a combination of seeking food, locating mates and escaping radial and bilateral symmetry as seen in from predators more efficiently. Animals ctenophores. There are only two planes of that have dorsal and ventral sides, anterior symmetry, one through the longitudinal and posterior ends, right and left sides and sagittal axis and the other through are bilaterally symmetrical and exhibit the longitudinal and transverse axis. (e.g., cephalisation, in which the sensory and Comb jellyfish – Pleurobrachia) brain structures are concentrated at the Animals which have two similar anterior end of the animal (Figure 2.6). halves on either side of the central plane 2.1.4. Coelom The presence of body cavity or coelom is important in classifying animals. Most animals possess a body cavity between the body wall and the alimentary canal, and is Radial symmetry in Pentamerous radial lined with mesoderm. sea anemone symmetry in starfish Animals which do not possess a body Figure. 2. 3 Radial and Pentamerous cavity are called acoelomates. Since there radial symmetry is no body cavity in these animals their body is solid without a perivisceral cavity, this restricts the free movement of internal organs. (e.g., Flatworms) In some animals, the body cavity is not fully lined by the mesodermal epithelium, but the mesoderm is formed as scattered pouches between the ectoderm and endoderm. Such a body cavity is called a pseudocoel and Figure 2.4 Biradial symmetry is filled with pseudocoelomic fluid. in comb jelly Animals that possess a pseudocoel are called pseudocoelomates e.g., Round worms. The pseudocoelomic fluid in the pseudocoelom acts as a hydrostatic skeleton and allows free movement of the visceral organs and for circulation of nutrients. Eucoelom or true coelom is a fluid- filled cavity that develops within the Figure 2.5 Bilateral symmetry in Insects mesoderm and is lined by mesodermal 21