Paper1, Unit1
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Ms. Amruta Daulat Pharande
Assistant Professor, Sathaye College.
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Course Information
T. Y. B. Sc. Zoology: Semester VI (Theory)
Course Code: USZO601
Topic: Taxonomy - Chordates and Type Study
Instructor: Ms. Amruta Daulat Pharande (MSc, SET, NET)
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Unit I: Phylum Chordata
Group Protochordata and Group Euchordata I
1.1 General Characters
Difference between non-chordates and chordates
1.2 Protochordata
General characters of Group Protochordata
Distinguishing characters of Subphylum Urochordata and Cephalochordata
Description of Urochordata and Cephalochordata
1.3 Group Euchordata I
General characters and Subphylum Vertebrata
Distinguishing characters of Division Agnatha and Gnathostomata
Examples:
Class Ostracodermii (e.g. Cephalaspis)
Class Cyclostomata (e.g. Petromyzon - Lamprey)
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General Characters of Chordates
Notochord
Present between nerve cord and alimentary canal
Vacuolated cells
Dorsal, tubular central nervous system
Brain and spinal cord
Pharyngeal gill clefts
Present in fishes, respiratory function
Post anal tail
Present in all chordate embryos.
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Additional Characterization of Chordates
Bilateral symmetry
Metamerism
Not visible externally
Triploblastic body wall
Ectoderm, mesoderm, endoderm
True coelom
Cephalization
Head with nervous tissue and sense organ
Efficient circulation
Closed type; heart located on the ventral side
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More General Characters
Hepatic portal system
Collect blood from digestive tract and liver
Complete digestive tract
Skeleton
Exoskeleton: Scales, feathers, nails, and hair
Endoskeleton: Notochord, axial, and appendicular skeleton
Paired appendages
Fins and limbs, with exceptions in protochordates
Cranium presence
Thyroid gland and endostyle presence
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Reproductive Features
Deuterostome classification
Reproduction via sexual methods or parthenogenesis.
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Comparison of Non-Chordates and Chordates
Symmetry:
Non-Chordates: Asymmetrical, bilaterally symmetrical, or radial
Chordates: Bilaterally symmetrical
Metamerism:
Non-Chordates: True or pseudometamerism, absent
Chordates: True metamerism
Post Anal Tail:
Non-Chordates: Absent
Chordates: Muscular post anal tail present
Grade of Organization:
Non-Chordates: Protoplasmic to organ system grade
Chordates: Organ system
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Continuation of Comparison
Germ Layers:
Non-Chordates: Absent, or Diploblastic, or Triploblastic
Chordates: Triploblastic
Coelom:
Non-Chordates: Acoelomate, pseudo, true
Chordates: True coelomate.
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Further Characteristics
Notochord:
Non-Chordates: Absent
Chordates: Present
Pharyngeal Gill Slits:
Non-Chordates: Absent
Chordates: Present
Alimentary Canal:
Non-Chordates: Absent or present
Chordates: Present.
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Theories on Ancestry of Chordates
Annelids as ancestors
Arachnids as ancestors
Affinities with Echinodermata.
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Similarities with Annelids
Bilateral symmetry
Metamerism
Cephalization
Locomotory appendages
Coelom
Complete digestive tract
Closed circulatory system.
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Differences with Annelids
Cleavage patterns
Annelids: Spiral cleavage
Chordates: Radial cleavage
Mesoderm and Coelom types
Annelids: Schizocoely
Chordates: Enterocoely.
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Cleavage Types
Radial Cleavage:
Zygote Development
Spiral Cleavage:
First quartet of cells arrangement and further division.
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Mouth and Anus Development
Annelids: Protostome
Chordates: Deuterostome.
Larval Stages:
Annelids: Trochophore larva
Chordates: Tornaria larva.
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Arachnid As Ancestor
Paleozoic arachnids: Eurypterids
Similarities between eurypterids and jawless vertebrates (ostracoderms).
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Affinities with Echinodermata
Similarities: Deuterostomes
Serological tests to study blood serum show relatedness between echinoderms, hemichordates, and chordates.
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Phylum - Chordata
Groups: Protochordata (Acrania), Euchordata/Vertebrata
Subphyla: Urochordata, Cephalochordata.
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Habitat of Protochordates
Exclusively marine, small, primitive chordates
Characteristics: absence of head, cranium, vertebral column, jaw, brain, paired appendages.
Sedentary or free swimming, solitary or colonial.
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Physiology of Protochordates
Respiratory system: Gill slits/general body surface
Digestive system: Complete, ciliary feeders
Nervous system: Dorsal tubular nerve cord
Reproduction: Monoecious/dioecious, retrogressive metamorphosis, indirect development, external fertilization.
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Metamorphosis Types
Complete Metamorphosis: Egg to larva, adult
Incomplete Metamorphosis: Egg to nymph/adult, including tadpole larva and adult ascidian.
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General Characters of Urochordata
Features of an incurrent and excurrent siphon.
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Characteristics of Urochordata
Body shows variation in size and form; unsegmented and lacks tail.
Covered by a test formed by tunicin; one-layered epidermis; coelom absent.
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Further Details on Urochordata
Atrial cavity surrounds the pharynx with openings for gill slits, anus, and genital ducts.
Larva has notochord in the tail, which disappears during metamorphosis.
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Circulatory and Nervous Systems of Urochordata
Open type circulatory system
Heart located ventrally
Nervous system represented by a single dorsal ganglion in adult form
Reproduction: Budding and cross-fertilization favored.
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Urochordata Development
External fertilization with free-swimming tadpole larva featuring a tail, dorsal nerve cord, and notochord that disappears in life history.
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Classes of Urochordata
ASCIDIACEA: E.g. Herdmania
Features include branchial aperture and siphons.
THALIACEA: E.g. Salpa
LARVACEA: E.g. Oikopleura with larval characteristics.
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Features of Class Ascidiacea
Brightly colored marine animals, solitary or colonial, adult sessile, larvae planktonic.
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Metamorphosis in Ascidiacea
Most chordate characteristics present during larval stage disappear during metamorphosis into adult.
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General Characters of Herdmania
Sea squirts, sedentary, sac-like, oval body, transparent test, filter feeders, complete digestive system.
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Physiology of Herdmania
Respiratory system utilizing inner body wall of branchial aperture; circulatory system has a tubular heart located ventrally; nervous system features solid elongated ganglion.
Reproductive characteristics include hermaphroditism.
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Characteristics of Class Thaliacea
Pelagic urochoridates, solitary or colonial; thin transparent tunic; presence of incurrent and excurrent siphons.
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Class Salpa Characteristics
Free swimming, pelagic, exhibit alternation of generations with asexual phase (oozooid) and sexual phase (blastozooid).
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Detailed Anatomy of Salpa
Digestive system is complete; heart located posteriorly on ventral side of endostyle; reproduction can be sexual or asexual.
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Class Larvacea Characteristics
Tiny, marine planktonic uro-chordates; retain larval characteristics throughout life; features two gillslits.
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Characteristics of Oikopleura
Solitary, free swimming, body covered by loose test called 'house'; complete digestive system with heart situated below stomach.
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Phylum Chordata Structure
Groups: Protochordata (Acrania), Euchordata/Vertebrata; include Subphyla and classes.
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Physical Characteristics of Protochordates
Features include head and tail, absence of appendages, fins present; notochord extends fully.
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Circulatory and Excretory Features in Protochordates
Closed circulatory system; paired protonephridia; sexual reproduction is external.
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General Characteristics of Lancelet (Cephalochordata)
Night-active, elongated, semi-transparent, fishlike structure, dorsoventrally compressed.
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Lancelet Features
Oral cirri or tentacles for filtering; has trunk and tail, with three unpaired fins (dorsal, ventral, caudal).
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Basic Physiology of Lancelets
Respiration occurs through gills or body surface; circulatory system is simple and closed type.
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Phylum - Chordata Structure
Groups and subclassifications including agnatha and gnathostomata.
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Characteristics of Higher Chordates
Prominent head, cranial features, both aquatic and terrestrial habitats; notochord present in embryonic stages.
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Detailed Features of Higher Chordates
Closed circulatory system; reproductive systems separation; various digestive structures.
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Reproductive Characteristics
Sexual reproduction, direct and indirect developmental processes.
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Introduction of the Term Vertebrata
Coined by Ernst Haeckel in 1866, involving features such as notochord and structure classifications.
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Skeletal Structure
Axial skeleton includes skull and vertebral column; appendicular skeleton includes limbs and girdles.
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Digestive and Respiratory Systems
Alimentary canal and glands' presence; respiratory differences in aquatic versus terrestrial chordates.
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Kidney Types and Reproductive Characteristics
Metanephric kidneys, various pairs of cranial nerves, and hormonal functions.
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Phylum Structure Continuation
Classification breakdown involving Agnatha and Gnathostomata subdivisions.
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Unique Features of Class Osteichthyes
Present features include notochord presence, absence of paired appendages, and simple nasal structures.
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Details on Class Ostracodermii
Extinct class, characterized by dermal bony plates and features such as slits for respiration.
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Characteristics of Jawless Fish
Mouth and gill structures, paired cranial nerves, and example species descriptions.
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Cephalaspis Description
Features of skin, body structure including fins and openings; approximate timeline of existence.
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Characteristics of Class Cyclostomata
Eel-like body structure with differences in anatomy related to gill pouches and skeleton types.
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Details on Example Species
Physiological features of lamprey including body structure and anatomical characteristics.
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Petromyzon (Lamprey) Characteristics
Detailed body structure, feeding mechanisms, and lifestyle adaptations.