S.Y.B.Sc. ZOOLOGY Paper I- Animal Systematics and Diversity- Classification

 S.Y.B.Sc.

ZOOLOGY Paper I- Animal Systematics and Diversity

According to Revised New Syllabus 2014

University of Pune

Salient features and classification of Arthropoda, Mollusca and    Echinodermata.

1. Salient features and classification up to classes of the following: (any two

Examples from each class):                                                                                                                                                                                                                                                                     

1.1       Arthropoda: - Crustacea, Arachnida, Insecta, Myriapoda, Onychophora.

1.2       Mollusca: - Aplacophora, Gastropoda, Pelecypoda, Scaphopoda, Cephalopoda.

1.3       Echinodermata: - Asteroidea, Ophuroidea, Holothuria, Echinoidea, Crinoidea.

1.1     PHYLUM ARTHROPODA:

 (Gr., arthros, joint + podos, foot) is the largest phylum of Animal Kingdom including about 1, 13, 40,000 species in all habitats which constitute about 83% of all the known species of animals. It is the most diversified group inhabiting the land, water and air.

General Characteristics:

1. Arthropods are triploblastic, bilaterally symmetrical, metamerically segmented animals.

2. Body is covered with a thick chitinous cuticle forming an exoskeleton.

3.  Appendages jointed, usually one pair to a somite, and with varied functions as jaws, gills, legs, etc.

4. Exoskeleton of dead chitinous cuticle that is shed at intervals, called ecdysis or moulting, for growth and development.

5. Body divisible into head, thorax and abdomen. Head and thorax often fused to form cephalothorax.

6. Body cavity is haemocoel. The true coelom is reduced to the spaces of the genital and excretory organs.

7. Musculature is not continuous, muscles mostly striated, usually capable of rapid contraction.

8. Digestive tract is complete; mouth and anus lie at opposite ends of the body.Mouth parts adapted for various modes of feeding.

9. Circulatory system is open with dorsal many-chambered heart, arteries and blood sinuses but without capillaries.

10. Respiration through general body surface, by gills in aquatic forms, tracheae or book lungs in terrestrial forms.

11. Excretory organs are green glands or Malpighian tubules true nephridia are absent.

12. Nervous system typically annelidan, with a dorsal brain connected with a nerve ring to a double ventral nerve chord.

13. Sensory organs comprises of eyes (simple and compound), chemo- and tactile receptors, and balancing and auditory organs.

14. Sexes usually separate (dioecious). Reproductive organs and ducts paired.

15. Fertilization usually internal, Oviparous or ovoviparous, Development direct or indirect with one to many larval stages, Parthenogenesis in some.

16. Cilia and flagella absent except in Onychophora.

17. Parental care often well-marked.

Classification:

Phylum Arthropoda and its various groups have been classified differently by different workers. But the classification of Arthropoda followed in the present text is generally based on vandal (1949), Snodgrass (1960) and Storer (1979). Onychophora, however, was considered to be arthropod for a long time but the modern trend is to consider it as an independent group of segmented animals.

Phylum arthropoda is divided into five classes: Crustacea, Arachnida, Insecta, Myriapoda, and Onychophora.

Class 1: Crustacea

(L., crusta=a hard shell)

1. Mainly aquatic, generally marine but few freshwater and few live in moist places.

2. Generally free living but few are parasitic forms.

3. Head often fused with thorax to form cephalothorax covered dorsally by carapace.

4. Head 5-segmented, bearing 2 pairs of antennae, 1 pair of mandibles and 2 pairs of maxillae, appendages typically biramous.

5. Exoskeleton chitinous, hard, limy (calcareous).

6. Thorax and abdomen often with a pair of biramous appendages modified for various purpose.

7. Respiration either by gills or general body surface.

8. Coelom greatly reduced, it is in the form of haemocoel.

9. Blood vascular system comprises a dorsal contractile heart communicating by valvular ostia with an enclosing pericardial sinus.

10. Excretory organs are modified coelomoducts which may be either maxillary glands or antennary (green) glands.

11. Sexes usually separate; sexual dimorphism is common.

12. Development includes metamorphosis with free larval stages.

Examples: Apus, Daphnia, Cypris, Argulus, Lepas, Sacculina, Squilla, Limulus, Palaemon, Hippa, Cancer etc.

Class 2: Arachnida

(Gr., arachne= spider +oid=like)

1. Mostly terrestrial, few aquatic.

2. Prosoma bears six pairs of appendages; one pair chelicerae one pair pedipalpi and four pairs of walking legs.

3. Eyes are simple.

4. Abdomen usually without appendages.

5. Respiratory organs tracheae, book-lungs or book-gills.

6. Excretory organs are Malpighian tubules or coxal glands or both.

7. Mostly oviparous, courtship before mating.

8. Sexes are separate, sexual dimorphism not conspicuous and development mostly direct.

Examples: Palamnaeus (Scorpion), Buthus, Galeodes, Charinus, Aranea (House spider), Sarcoptes, Idodex (Tick) etc.

Class 3: Insecta

(L., insectus=cut or divided)

1. Insects are air breathing mostly terrestrial and rarely aquatic arthropods.

2. Body is divided into three distinct regions head, thorax and abdomen.

3. Head consists of six fused segments and bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking, siphoning or sponging type.

4. Thorax comprises three free segments, each bearing a pair of legs and two pairs of wings borne on the second and third segments.

5. Abdomen comprises 7-11 segments and devoid of appendages.

6. Liver is absent but salivary glands are usually present.

7. Heart is elongated, tubular and is divided into eight chambers situated in the abdomen.

8. Respiration by branched tracheae. Spiracles lateral

9. Excretion by Malphigian tubules.

10. Sexes are separate.

11. Fertilization is internal, development is sometimes are direct, more usually complicated by metamorphosis.

Examples: Lepisma (silver fish), Mantis, Periplaneta, Grasshopper, Termite, Pediculus, Cimex (Bedbug), Aphids, Beetles, Musca (House fly), Culex (Mosquito), Drosophila (Fruit fly), Xenopsylla (Fleas), Butterflies etc.

Class 4: Myriapoda

(G., myrios, ten thousand + podos, foot)

1. Exclusively terrestrial, air-breathing mandibulate arthropods.

2. Body worm-like made of head and elongated trunk with many similar leg-bearing segments.

3. Antennae 1 pair jaws 3 pairs, legs more than 11 pairs.

4. Respiration by tracheae. Spiracles arranged segmentally.

5. Excretion by 1 or 2 pairs of Malpighian tubules.

6. Sexes separate, Gonad single. Gonoducts paired.

Examples: Spirobolus, Julus, Scutigera, Scolopendra, Pauropus etc.

Class 5: Onychophora

(G., onychos = claw + phoros, bearing)

1. Terrestrial, primitive, worm- like, unsegmented.

2. Single pairs of antennae, eyes and jaws.

3. Numerous stumpy, unjointed clawed legs.

    Example: Peripatus.

1.2     PHYLUM MOLLUSCA:

The word "mollusc" or "mollusk" (both are correct) is derived from the Latin word mollis meaning "soft". The study of molluscs, "malacology", comes from the Greek word for soft, malacos. The term "conchology" is also used for the study of molluscs; however, it is usually applied to those that study the shell only.

The word Mollusca was first applied by Aristotle to the cuttle-fish of the Aegean Sea. Mollusca is one of the most diverse groups of animals on the planet,  Mollusca which include clams, slugs, squids, octopods and nautili are triploblastic, bilaterally symmetrical animals with anus and coelom and without segmentation. They usually have shell and a characteristic ventral muscular foot. It is not possible to assess accurately the total of the known species. Estimates of accepted described living species of molluscs vary from 50,000 to a maximum of 120,000 species. 

General Characters

1. Molluscs are essentially aquatic mostly marine, few freshwater and some terrestrial forms.

 2. The body is soft, Triploblastic, coelomate, unsegmented (except in Monoplacophora) and bilaterally symmetrical.

3. Body divisible into head, mantle, foot and visceral mass.

4. Body is commonly protected by an exoskeletal calcareous shell secreted by the mantle. Shell, when present, usually univalve or bivalve, constituting an exoskeleton, internal in some

5. Head is distinct, bearing the mouth and provided eyes, tentacles and other sense organs except in Pelecypoda and Scaphopoda.

6. Body cavity is haemocoel. The true coelom is generally limited to the pericardial cavity and the lumen of the gonads and nephridia.

7. Digestive system is simple, complete with a digestive gland or liver (hepatopancreas); a rasping organ, the radula, usually present.

 8. Circulatory system open or mainly of closed type, but some emptying into sinuses; heart with one or two auricles and one verticle; blood with amoebocytes and haemocyanin.

9. Respiratory organs consist of numerous gill or ctenidia usually provided with osphradium at the base. Lung is developed in terrestrial forms. Respiratory pigment is usually haemocyanin.

10. Excretory system consists of a pair of metanephridia which are true coelomoducts and longitudinal and transverse connectives and nerves.

11. Nervous system consists of paired cerebral, pleural, pedal and visceral ganglia joined by longitudinal and transverse connectives and nerves.

12. Sense organs include eyes, statocysts and receptors for touch, smell and taste.

13. Dioecious or monoecious; but some are hermaphroditic, one or two gonads with gonoducts, opening into renal ducts or to exterior.

14. Fertilization internal or external.

15. Development is either direct or with metamorphosis through the trochophore stage called veliger larva.

Classification

Molluscs are classified into six classes according to their symmetry and the characters of food, shell, mantle, gills, nervous system, muscles and radula.

CLASS 1: APLACOPHORA OR SOLENOGASTERS

(Gr., a=not + plax=plate + pherein = bearing)

1. Body worm-like, bilaterally symmetrical and cylindrical.

2. Head, mantle, foot, shell and nephridia are absent.

3. Body covered with cuticle beset with numerous calcareous spicules.

4. Mouth and anus are terminal or subterminal at opposite end.

5. Digestive tract straight generally provided with a radula.

 6. A pair of coelomoducts in the form of gonoducts opening into the terminal part of intestine or independently.

7. A mid-dorsal longitudinal keel or crest is often present.

8. Sexes united (hermaphroditic) or separate (dioecious).

Examples: Neomenia, Proneomenia, Lepidomenia, Chaetoderma, Prochaetoderma etc.

CLASS 2: GASTROPODA

(Gr., gaster = belly + podos =foot)

1. Gastropods are marine, freshwater, terrestrial and few parasitic on echinoderms.

2. Body unsegmented, asymmetrical typically with a univalve, spirally coiled shell.

3. Head distinct bearing tentacles, eyes and mouth.

4. Foot is ventral, broad, flat and muscular forming the creeping sole and often bearing dorsally a hard piece, the operculum on its posterior end.

5. Visceral mass spirally coiled exhibiting torsion.

6. Mantle is a collar-like fold of body wall, lining the body whorl leaving a space, the mantle cavity, between itself and the body.

7. Buccal cavity contains an odontophore with a radula bearing rows of chitinous teeth.

8. Digestive system comprises a muscular pharynx, long oesophagus, stomach, long coiled intestine and anteriorly placed anus.

9. Respiration by gills (ctenidea) in most forms, through the wall of the mantle cavity in some forms and in many by lungs.

10. Circulatory system is open and the heart is enclosed in a pericardium.

11. Excretory organs comprise metanephridia which are paired in primitive forms and reduced to single nephridia in most forms.

12. Nervous system comprises distinct cerebral and pleural besides buccal, pedal, parietal and visceral ganglia.

13. Sexes are separate (dioecious) in most forms, while in some forms united (hermaphroditic).

14. Development includes trochophore and veliger larval stages.

Examples: Pila, Cypraea, Aplysia, Doris, Rhodope, Odostomia, Lymnaea etc.

CLASS 3: PELECYPODA

(Gr., pelekys = hatchet + podos = foot)

1. Aquatic, mostly marine, some freshwater forms.

2. Body is bilaterally symmetrical and laterally compressed.

3. Shell consists of two lateral valves, hinged together mid-dorsally.

4. Head is not distinct; pharynx, jaws, radula and tentacles are absent.

5. Foot is ventral, muscular which is plough-share.

6. Mantle is boiled, consisting of paired, right and left lobes.

7. Gills or ctenidia are paired, one on each side.

8. Coelom is reduced to a dorsally placed pericardium.

9. Alimentary canal is coiled with large paired digestive glands.

10. Heart is contained within pericardium and comprises median ventricle and two auricles.

11. Excretory organs are paired nephridia or kidneys open at one end into pericardium at the other end to the exterior.

12. Nervous system consists typically of four pairs of ganglia, viz., cerebral, pleural, pedal and visceral.

13. Cerebral and pleural of each side usually fused into a single cerebro-pleural ganglion.

14. Sense organs are statocyst and osphradia.

15. Sexes are separate or united.

16. Development is accompanied by metamorphosis which usually includes a trochophore larva.

Examples: Solenomya, Mytilus, Pecten, Unio, Teredo, Poromya etc.

CLASS 4: SCAPHOPODA

(Gr., scapha = boat + podos =foot)

1. Exclusively marine.

2. Body is bilaterally symmetrical, elongated and enclosed in a tusk-like shell open at both ends.

3. Eyes, tentacles and gills are absent.

4. Mantle tubular completely enclosing the body.

5. Mouth surrounded by lobular processes or outgrowths.

6. Foot is reduced, used for digging.

7. Heart rudimentary.

8. Sexes separate (dioecious), larva trochophore.

Example: Dentalium, Cadulus, Pulsellum etc.

CLASS 5: CEPHALOPODA (Siphonopoda)

(Gr., kephale = head + podos =foot)

1. Exclusively marine.

2. Body bilaterally symmetrical with head and trunk.

3. Shell spiral, chambered or usually with or without reduced shell embedded in the mantle.

4. Head bears large eyes and mouth.

5. Trunk consists of symmetrical and uncoiled visceral mass.

6. Mantle encloses posteriorly and ventrally a large mantle cavity.

7. Foot altered into a series of sucker bearing arms or tentacles encircling the mouth.

 8. Mouth bears jaws and radula.

9. Two or four pairs of bipectinate gills.

10. Circulatory system closed heart with two or four arteries.

11. Excretory system comprises two or four pairs of nephridia.

12. Nervous system is highly developed and the principal ganglia are concentrated around the oesophagus.

13. Sexes are separate.

14. Development meroblastic without metamorphosis.

Examples: Sepia, Loligo, Octopus, Nautilus, Ammonites etc.

CLASS 6 -POLYPLACOPHORA:

 (poly-plac-o-phor-a (lor-i-cat-a) Latin meaning:  poly = many    plac = plate    phor = carry, i.e.: bearer of many plates.

1. The POLYPLACOPHORA contain about 900 living species and are commonly known as chitons. 
2. They have a shell consisting of eight, usually overlapping plates, held together by a leathery "girdle". 
3. Respiration by mentle.
4. Chitons are with an ovoid, flattened body.
5. They range in length from 3 to 400+ millimeters. (1/8" to 1ft 4"+).
6. The animal is bilaterally symmetrical. With a well-developed foot surrounded by a groove in which there are 6 to 88 pairs of gills. 
7. The head lacks eyes and tentacles, but usually has light-sensitive areas and chemical receptors, for finding food and heading in the proper direction!
8. All chitons are marine inhabitants and most make a living by grazing algae from rocks and other hard substrates.
9. The great majority of them dwell in shallow and intertidal waters, but a few occur in depths down to 5,000+ meters.
10. All chitons are dioecious (i.e., they have two sexes). 

Class 7-MONOPLACOPHORA –(mono-plac-o-phora)

Latin:  mono=one    plac=plate    phor=carry : bearing a single single plate (shell)

1. They are mostly are known by their fossil records; however, there are about a dozen living species today. 
2. They have several foot retractor muscles, gills, and hearts similar to those of the annelid worms; however, their bodies are not segmented. 
3. All Monoplacophorans are marine inhabitants grazing on algae and microorganisms on the hard ocean bottom. 
4. They live at depths of 200 to 6,000 meters and they range in size from 2 to 35 millimeters.
5. Monoplacophorans possess a single, large, bilateral shell.  The shell is a simple depressed limpet or disk -shaped valve, less than 25 millimeters across usually and is often thin and fragile.         
6. Monoplacophorans possess a foot, round in outline and not very muscular, which is responsible for locomotion. 
7. The head of Monoplacophorans is much reduced in size lacks true eyes and tentacles.
8. Monoplacophorans possess a single ventricle and two auricles for circulating the blood per body segment. 
9. Connecting link between annelida & mollusca.

Examples –  Neopelina  (living fossil)

1.3     PHYLUM ECHINODERMATA:

Echinoderms are one of the most beautiful and most familiar sea creatures. (Gr., echinos, hedgehog; derma, skin) Echinodermata literally means "spiny or prickly skinned".  Echinoderms are exclusively marine, largely bottom dwelling, and triploblastic animals. Echinoderms are known since very ancient times. The name of this phylum was introduced by Klein in 1734 for sea urchins. For many years echinoderms and coelenterates were introduced as a class among Radiata, largely because of the radial symmetry of the adults. Echinodermata were first recognized as a group distinct from the Radiata by Leukart in 1847. There are 7,000 species known in Echinodermata.

1 Echinoderms have a pentamerous radial symmetry derived from an original bilateral symmetry. They possess an endoskeleton of calcareous plates or spicules embedded in the skin; a peculiar water-vascular system of coelomic origin; numerous podia or tube feet; an ectodermal nervous system; no definite head or brain; no nephridia; gonads open directly to the exterior by special ducts.

General Characters:

1. Echinoderms are exclusively marine and among the most common and widely distributed of marine animals.

2. They occur in all seas from the intertidal zone to the great depths.

3. Symmetry usually radial, nearly always pentamerous.

4. Body is triploblastic, coelomate with distinct oral and aboral surfaces and without definite head and segmentation.

5. They are of moderate to considerable size but none are microscopic.

6.  The body shape rounded to cylindrical or star-like with simple arms radiating from a central disc or branched feathery arms arise from a central body.

7. The body surface is rarely smooth; typically it is covered by five symmetrically spaced radiating grooves called ambulacra with five alternating inter-radii or inter-ambulacra.

8. The body wall consists of an outer epidermis, a middle dermis and an inner lining of peritoneum.

9. Endoskeleton consists of closely fitted plates forming a shell usually called theca or test or may be composed of separate small ossicles.

10. Coelom is spacious lined by petroleum occupied mainly by digestive and reproductive systems and develops from embryonic archenteron, i.e., intercool.

11. The presence of water vascular or ambulacral system is the most characteristic feature. It consists of tubes filled with a watery fluid.

12. Alimentary tract is usually coiled tube extending from the mouth located on the oral surface to the anus on the aboral or oral surface.

13. Circulatory or heal or blood lacunars system is typically present.

14. Respiration occurs through a variety of structures, i.e., papulae in starfishes, peristomial gills in sea urchins, genital bursae in brittle stars and cloacal respiratory trees in holothurians.

15. Excretory system is wanting.

16. Nervous system is primitive, consisting of networks concentrated into the radial ganglionated nerve cords.

17. Sense organs are poorly developed.

18. Sexes are usually separated (dioecious) with few exceptions. Gonads are simple with or without simple ducts.

19. Reproduction is usually sexual; few reproduce asexually or by regeneration.

20. Fertilization is external, while few echinoderms are viviparous.

21. Development is indeterminate including characteristics larvae which undergo metamorphosis into the radially symmetrical adults.

Classification:

The phylum Echinodermata is divided into five classes, namely Asteroidea, Ophuroidea, Holothuria, Echinoidea and Crinoidea.

Class 1: Asteroidea:

 (Gr., aster=star+ eidos=form)

1. Commonly called starfishes or sea-stars. Body is flattened, pentagonal or star-shaped.

2. The oral and aboral surfaces are distinct, the oral surface directed downwards and aboral surface upwards.

3. There are five to fifty long or short rays or arms radiating symmetrically from a central disc.

4. Mouth is centrally placed at the oral surface surrounded by a membranous peristome.

5. Anus is small and inconspicuous located more or less eccentrically on the aboral surface.

6. Tube feet in orally placed ambulacral grooves; with suckers.

7. Ambulacra are restricted to oral surface extending from the peristome to the tips of the arms, madreporite located on aboral surface.

8. Endoskeleton is flexible, made of separate ossicles.

9. Pedicellariae is small, movable spine-like always present.

10. Respiration by papulae.

11. Sexes separate, gonads radially arranged.

12. Development includes bipinnaria or brachiolaria larva.

13. Free-living, slow-creeping, predaceous and scavengerous.

Examples: Astropecten, Goniaster, Solaster, Asterina, Asterias, Heliaster etc.

Class 2: Ophiuroidea:

 (Gr., ophis=serpent/snake +oura=tail+eidos=form)

1. Commonly called brittle stars. Body is flattened with a pentamerous or rounded central disc.

2. Oral and aboral surfaces are distinct.

3. Arms usually five rarely six or seven are long, slender, smooth or spiny.

4. Ambulacral grooves absent or covered by ossicles; tube feet without suckers.

5. Anus and intestine are present, stomach sac-like; no anus.

6. Madreporite is on the oral surface.

7. Sexes are separate, gonads pentamerous.

8. Pedicellariae absent.

9. Development includes a free swimming pluteus larva.

Examples: Ophiura, Ophiothrix, Ophioderma, Ophiopholis, Gorgonocephalus (basket star), Asteronyx etc. 

Class 3: Holothuroidea:

 (Gr., holothurion= sea cucumbers /water polyp + eidos =form)

1. Commonly called sea cucumbers.

2. Body bilaterally symmetrical, usually elongated in the oral-aboral axis having mouth at or near one end and anus at or near the other end.

2. No arms, no spines.

3. Endoskeleton reduced to microscopic spicules or plates embedded in the body wall.

4. Mouth surrounded by a set of tentacles attached to water vascular system.

5. Podia or tube feet are usually present and locomotory.

6. Alimentary canal is long and coiled and cloaca usually with respiratory trees.

7. Sexes are usually separate and gonad single or paired tufts of tubules.

Examples: Cucumaria, Thyone, Holothuria, Actinopyga, Caudina, Synapta etc.  

Class 4: Echinoidea:

 (Gr., echinos =hedgehog +eidos=form)

1. Commonly called sea urchins and sand dollars.

2. Body is spherical, disc-like, oval or heart-shaped and without arms.

3. Body is enclosed in an endoskeletal shell or test of closely fitted calcareous plates covered with movable spines.

4. Outer calcareous plates are distinguished into five alternating ambulacral and five inter-ambulacral areas.

5. Podia or tube feet come out from the pores of ambulacral plates and are locomotory in function.

6. Mouth is centrally placed on the oral surface and surrounded by a membranous peristome. Anus is located at the aboral pole and surrounded by membranous periproct.

7. Ambulacral grooves covered by ossicles; tube feet with suckers.

8. Pedicellariae is stalked and three jawed.

9. Sexes are separate. Gonads are pentamerous.

10. Development includes a free swimming echinopluteus larva.

Examples: Bothriocidaris (extinct), Palaeodiscus, Melonechinus, Diadema, Arbacia, Echinus, Echinocardium etc.

Class 5: Crinoidea:

 (Gr., crinon=lily+ eidos=form)

1. Commonly called sea lilies or feather stars.

2. Both extinct and living forms. Living members are without stalk and free moving but extinct forms attached by a stalk.

3. Body consists of an aboral cup, the calyx and oral cover or roof, the tegmen and strongly pentamerous in structure.

4. Oral surface is directed upwards.

5. Mouth usually central, anus usually eccentric is present on the oral surface.

6. Arms movable, simple, mostly branched usually five or ten in number with or without pinnules.

7. Ambulacral grooves are open and extend along arms and pinnules to their tips.

8. Tube feet without suckers; no madreporite, spines and pedicellariae.

9. Sexes are separate.

10. Larva doliolaria.

Examples: Antedon (sea lily), Neometra (feather star), Rhizocrinus etc. 

REVIEW QUESTIONS

Long Answer Questions:

1. Give an outline classification of phylum Arthropoda up to classes and mention at least two examples of each class.
2. Describe in detail characteristic features of phylum Arthropoda and its classes.
3. Classify phylum Mollusca up to classes and give characters of all classes and two examples of each class.
4. Classify Phylum Mollusca up to class level with examples.
5. Describe in detail characteristic features of phylum Mollusca and its classes.
6. Give an account of general characters and classification of phylum Echinodermata up to classes and mention at least two examples of each class.
7. Classify Phylum Echindermata up to classes with examples.
8. Describe in detail characteristic features of phylum Echinodermata and its classes.
9. Give distinctive features of all classes of phylum Arthropoda with two examples from each class.
10. Give distinctive features of all classes of phylum Mollusca with two examples from each class.
11. Give distinctive features of all classes of phylum Echinodermata with two examples from each class.

Short answer Questions:

1. Write short note on:

1) Crustacea                 2) Arachnida

3) Insecta                     4) Myriapoda

5) Onychophora          6) Aplacophora

7) Gastropoda              8) Pelecypoda

9) Scaphopoda             10) Cephalopoda

11) Asteroidea             12) Ophuroidea

13) Holothuria             14)   Echinoidea

15) Crinoidea

2. Answer the following Questions:

1. What is the significance of the term Arthropoda?
2. Give four characters of Crustacea.
3. Give four characters of insecta.
4. Give four characters of acarina.
5. Give four characters of Mollusca.
6. What the term Mollusca signifies?
7. What the term Echinodermata signifies?