This document provides key information about various classes of invertebrate phyla including Platyhelminthes, Annelida, Arthropoda, and Mollusca. It lists key defining characteristics such as body structure, habitat, life cycle stages, and example organisms for each class. The classes are further broken down with bullet points highlighting important morphological and physiological traits.

1. Department of Zoology
Syed Ammal Arts and Science College
Ramanathapuram
Zoology Study Materials –Key Words
19.11.2023

2. PLATYHELMINTHES
Turbellaria
Flatworms
Trematoda
Flukes- parasitic
Cestoda
Tapeworms-
parasitic

3. Class 1: Turbellaria
Body covering Ciliary
Free living and Parasitic
Body Unsegmented
Intestine Present
Suckers Present
Life Cycle Simple
Mouth is Ventral
Eg( Planaria),(Bipalium).

4. Class 2: Trematoda
Trematoda includes Flukes they have spiny skin
Parasites
Body covers Cuticle
Body Unsegmented
Mouth is Terminal
Intestine Bifid
Suckers present
Eg(Faciola hepatica), (Polystoum)

5. Class 3: Cestoda
Cestoda includes Tape worms
Parasites
Body covers Cuticle
Body is segmented – each segments Proglottid
Mouth and Alimentary canal absent
Sucker present
Life cycle – Larva and Intermediated hosts.
Eg( Taenia solium), ( Taenia saginata)

6. ANNELIDA
Polychaeta
Oligochaeta
Hirudinae
Archiannelida
Echiuroidea
Sipunculoidea
Priapulida
Myzostomaria

7. Class 1: Polychaeta
Bundles of Setae
Marine and Carnivorous
Body elongated and Segmented
Each segments has pair of Parapodia
Clitellum absent
Sexes separated
Fertilization external
Eg(Neres),(Serpula).

8. Class 2: Oligochaeta
Setae arranged individually
Mostly terrestrial and some species freshwater forms
Parapodia absent
Clitellum present
Hermaphrodites
Development is direct- Cocoons
Free larval stages is absent
Eg( Tubifex), (Megascolex)

9. Class 3: Hirudinae
Ecto parasite
Dorso ventral flattened body
Parapodia and Setae Absent
Body provide Posterior and Anterior Suckers
Hermaphrodite
Reproduction Sexual
Egg usually laid cocoons
Eg (Leech), (Glossiphonia)

10. Class 4: Archiannelida
 Exclusively marine forms
Body elongated and worm like
 Setae and Parapodia absent
Prostomium bears two or Three tentacles
Unisexual or Hermaphrodite
Larva is Trochophore
Eg (Polygordious), (Nerilla)

11. Class 5: Echiuroidea
Marine found Mud and Sand
More or less Cylindrical
Anus is terminal
Parapodia absent
Coelom is large and Undivided
Sex are separate
Larva is Trachophore
Eg (Echiurus), (Bonellia)

12. Class 6: Sipunculoidea
Marine found Mud and Sand, Coral in Boring sea shore
Body elongated Yellow or Greenish Colour
Parapodia and Setae Absent
Anus placed in Dorsal surface
Coelom is Spacious and Undivided
Sex are separate
Larva is Trachophore
Eg (Sipunculus), (Phascolosoma)

13. Class 7: Priapulida
Marine found Moderate depths, Burrowing in Sand
Body Cylindrical, worm like unsegmented
Mouth Anterior Anus Posterior
Short introvert without oral Tentacles
Sex are separate
Development in Unknown
Eg (Priapulus)

14. Class 8: Myzostomaria
Live as ecto and endo parasite specially Crinoids
Body unsegmented , flat and oval disc like shape
Five pairs of Parapodia with acicula and hooks present
Four pair suckers
Ten pair Cirri
Circulatory and Respiratory system absent
Single pair Nephridia
Larva is Trochophore
E.g (Myzostoma)

15. ARTHROPODA
Merostomata
Arachnida
Crustacea
Myriapoda
Insecta

16. Class 1: Merostomata
Aquatic and Marine
Abdominal appendages are modified into gills.
Abdomen ends in a Telson
Lateral compound eyes are present
Eg(Limulus)

17. Class 2: Arachnida
 Air breathing, Mostly terrestrial arthropods.
 Body two regions Cephalothorax and Abdomen.
 Antennae and true Jaw absent
 Respiratory organ varied – Terrestrial Tracheae and
Book lungs, Aquatic Gill and Book Gill
 Excretory organ – Malpighian tubles or Coxal gland
 Sex separated
 Eg( Scorpion)

18. Class 3: Crustacea
 Aquatic and Marine, Few live in moist
Body covered Chitinous cuticle
Triploblastic- Body divided into Head, Thorax,
Abdomen.
Respiration – Gill
Excretory organ- Green glands
Sex separated- Dimorphism
Development- Metamorphosis
E.g , Lobsters

19. Class 4: Myriapoda
 Air breathing arthropods
 Body elongated numerous segments
 Head distinct bearing many joined antennae, a pair of
eye
 Reparatory organ are tracheae
 Excretory organ one or two pair of Malpigion tubules
 Sex separated
 Eg(Millipedes and Centipedes)

20. Class 5: Insecta
 Air breathing mostly Terrestrial and Rarely aquatic
 Body divided into three- Head, Thorax, Abdomen
 Liver is absent but Salivary gland
 Respiration by branched trachea
 Excretion is malpighian tubules
 Sex separate
 Development metamorphosis
 E.g(Rhinoceros beetle)

21. MOLLUSCA
Aplacopora
Monoplacopora
Polyplacopora
Gastropoda
Scaphopoda
Pelecypoda
Cephalopoda

22. Class 1: Aplacopora
 Body is Worm like, Bilaterally symmetrical and
Cylindrical
 The head, mantle, foot, shell and nephridia are absent
 The Body covers spicule bearing cuticle
 Digestive track is straight with radula
 Eg( Neomenia), (Chaetoderma)

23. Class 2: Monoplacopora
 Body is bilaterally symmetrical and segmented
 Shell is formed of a single valve
 Head without eyes and tentacles
 Gill are external and serially arranged
 Nephridia are five pairs
 E.g(Neopilina galatheae)

24. Class 3: Polyplacopora
 Bilaterally symmetrical, dorsoventrally flattened
 Shell is composed 8 plates
 Foot is flat and ventral
 Radula well developed
 Eg(Chiton),(Cryptochiton)

25. Class 4: Gastropoda
 Gastro- Stomach, Poda- foot
 Unsegmented and Asymmentrical
 Shell is univalved and Spirally coiled
 Respiration Gills and Lungs
 Visceral mass is turned through 180 by Tarsion
 Circulatory system is open
 Hermaphrodite
 Eg( Natica), (Pila)

26. Class 5: Scaphopoda
 Foot is boat shaped
 Shell tubular opening at both ends
 No Head
 The eye, tentacles and Ctenidia absent
 Marine, bilateral
 Tusk shells
 Eg( Dentalium), (Pulsellum)

27. Class 5: Pelecypoda
 Bilateral symmetrical
 Bivalvia
 Head absent
 Mentle formed two lobes
 Radula absent
 Respiration – Gill
 Sexes are separated
 Eg( Mytilus),(Pecten)

28. Class 6:Cephalopoda
 Foot modified into funnel, tentacles present around
mouth
 Bilateral symmetry
 Visceral mass not coiled
 Respiration – Gill
 Two pair Kidney
 Sex are separate
 Development direct
 Eg( Loligo),(Sepia)