ST. MARY’S Sr. SEC SCHOOL BAHUAKBARPUR ROHTAK TEACHER’S NAME – REGIN BABU CLASS – XI SUBJECT - BIOLOGY ANIMAL KINGDOM

Phylum Annelida Characteristics They are mostly aquatic; marine or freshwater some terrestrial,

burrowing or tubicolous, sedentary or free-living, some commensal and

parasitic.

The body is elongated, triploblastic, bilaterally symmetrical, truly

coelomate and vermiform. The body is metamerically segmented; externally by transverse grooves

and internally by septa into a number of divisions; each division is

called a segment, metamere or somite.

Body organization is of organ grade system.

The epidermis is of a single layer of columnar epithelial cells, covered by thin cuticle not made of chitin.

The body wall is contractile or dermo-muscular consisting of outer

muscle fiber circular and inner longitudinal.

Appendages are jointed when present. Locomotory organs are segmentally repeated chitinous bristles called

setae or chaetae, embedded in the skin. It may be bored by lateral

fleshy appendages or parapodia.

The presence of true schizocoelous coelom usually divided into compartments by transverse septa. Mostly well-developed in leeches.

Coelomic fluid with cells or corpuscles.

The alimentary canal is straight tube-like, complete, extending from

mouth to anus. Digestion is entirely extracellular. Respiration occurs through moist skin or gills of parapodia and head.

The blood vascular system is a closed type. Blood is red due to the

presence of hemoglobin or erythromycin dissolved in plasma.

Excretion is by metamerically disposed coiled tubes; nephridia which

communicate the coelom to the exterior. The nervous system consists of a pair of cerebral ganglia; brain and

double ventral nerve cord having segmentally arranged ganglia and

lateral nerves in each segment.

Receptor organs include tactile organs, taste buds, statocysts, photoreceptor cells and sometimes eyes with lenses in some.

They are monoecious i.e. hermaphroditic or sexes separate cleavage

spiral and determinate; dioecious or unisexual form also present.

Their development is direct in monoecious form but indirect in dioecious form.

Larva, when present is a trochophore is characteristics in case of

indirect development, while in others this stage is passed through

development.

Regeneration is common. Asexual reproduction occurs in some.

Classification of Phylum Annelida About 8,700 known species of Annelida are divided into four main classes,

primarily on the basis of presence and absence of parapodia, setae,

metameres, and other morphological features.

Class 1- Polychaeta (Gr., poly=many,

chaeta=bristles/hair)

Chiefly marine, some freshwater.

Carnivorous

Body segmentation is internal and external.

Head consists of prostomium and peristomium and bears eyes, tentacles cirri, and palps.

Setae numerous on lateral parapodia.

The clitellum is absent.

Cirri or branchiae or both may be present for respiration. The coelom is spacious usually divided by intersegmental septa.

The alimentary canal provided with the eversible buccal region and

protrusible pharynx.

The excretory organ is segmentally paired nephridia.

Sexes separate. Gonads temporary and in many segments. Fertilization external.

Asexual reproduction by lateral budding.

Trochophore larva present.

Polychaeta divided into two subclasses, Errantia and sedentaria after Fauvel (1959). However, according to Dab (1963), this division is artificial and not a

natural one.

Subclass 1. Errantia Free-swimming, crawling, burrowing or tube-dwelling and predatory

polychaetes. Segmentation similar, except at anterior and posterior ends.

The prostomium is distinct with sensory organs.

Parapodia, provided with cirri, are equally developed throughout.

Pharynx protrusible, enlarged and usually with jaws and teeth. Examples: Nereis, Aphrodite, Polynoe, Phyllodoce, Tomopteris, Syllis, E

unice, Histriobdella.

Subclass 2. Sedentaraia Burrowing and tube-dwelling form.

Body made of 2 or more regions, with unlike segments and parapodia. Head is small or much modified without eyes and tentacles, prostomium

small.

No acicula and compound setae.

Pharynx non-protrusible without jaws and teeth.

Gills, when present, localized to the anterior segments. Feeding on plankton or organic detritus.

Examples: Chaetopterus, Arenicola, Owenia, Sabella, Terebella, Sabella

ria, Pomatocerous.

Class 2- Oligochaeta (Gr., oligos=few+

chaete=hair) Mostly terrestrial or some freshwater forms.

Body with conspicuous external and internal segmentation. Head indistinct, without sensory organs.

Setae few, embedded in the skin.

Parapodia absent.

Glandular clitellum present for cocoon formation. The pharynx is not eversible and without jaws.

Hermaphroditic i.e. sexes united.

Testes anterior to ovaries.

Development is direct. fertilization external (in cocoon); no larval stage.

Order 1. Archioligochaeta Mostly freshwater form.

The body consists of a few segments.

Setae are present in bundles.

The gizzard is poorly developed, non-muscular or absent.

The clitellum is simpler consists of a single layer of cells and situated far towards.

Eyespots are frequently present.

Male reproductive openings lie in front of female reproductive openings.

Reproduction asexual and sexual. Examples: Tubifex, Aelosoma.

Order 2. Neooligochaeta Usually terrestrial forms.

The body is large and many segmented.

Setae are managed in a lumbricine Manner.

The gizzard is well developed. The clitellum is composed of two or more layers of cells and never

begins before twelfth segments.

Female genital aperture is always on the 14th segment and the male

pore lies a few segments behind them. Vasa differentia are elongated extending over 3 or 4 segments.

Eyespots are never developed.

Reproduction sexual. Asexual reproduction is not known.

Examples: Pheretima, Eutypheus, Megascolex, Lumbricus.

Class 3- Hirudinea (L., hirudo= a leech) Mostly ectoparasitic, blood-sucking or carnivorous. Few are marine,

freshwater or terrestrial.

The body is elongated and usually flattened and dorso-ventrally or

cylindrical.

The body consists of a fixed number of segments (33). Each segment breaks up into 2 to 4 rings or annuli.

Segmentation external without internal septa.

Par podia and setae are absent.

Both anterior and posterior ends of the body with ventrally situated suckers.

The mouth opens on the ventral surface on anterior suckers, while anus

opens dorsal to the posterior suckers.

Coelom much reduced due to filling by botryoidal tissues, and form haemocoelomic sinuses.

Hermaphrodite with one male and one female gonopore.

Fertilization internal.

Asexual reproduction is not known. Eggs are always laid in cocoons.

Development is direct without a free-swimming larval stage.

Order 1. Acanthobdellida Mostly parasitic on the fins of salmon fishes.

The body comprises 30 segments only.

They are primitive, without anterior suckers, proboscis, and jaws. Double rows of setae are present in 5 anterior segments.

The body cavity is spacious and incompletely divided by septa.

The vascular system consists of the dorsal and ventral vessels.

Nephridial opening situated on the surface between the segments. Examples: a single genus and species (Acanthobdella) parasitic on

salmon.

Order 2. Rhynchobdellida

Parasites on snails, frogs and fishes, marine and freshwater form.

Each typical body segment consists of 3,6 or 12 rings.

The mouth is a small median aperture situated in the anterior suckers.

A protrusible proboscis with no jaws. Coelom without compartments.

Blood vascular system separated from coelomic sinuses.

Blood is colorless.

Examples: Placobdella, Helobdella, Piscicola, Branchellion.

Order 3. Gnathobdellia Freshwater and terrestrial form. Ectoparasitic blood-sucking leeches.

Each typical body segment consists of 5 rings or annuli.

Anterior suckers with 3 jaws, 1 median dorsal and 2 ventrolateral.

The proboscis is absent.

Blood is red-colored. Botryoidal tissues present.

Examples: Hirudo, Hirudinaria, Haemadipsa, Herpobdella.

Order 4. Pharyngobdellida Terrestrial and aquatic. Some predaceous.

Pharynx non- protrusible. No teeth but one ore two styles may be present.

Examples: Erpobdella, Dina.

Class 4- Archiannellida (Gr., arch=first) Exclusively marine form.

Body elongated and worm-like. Setae and parapodia are usually absent.

External segmentation is slightly marked by faint, while internal

segmentation is marked by coelomic septa.

Prostomium bears 2 or 3 tentacles. Sexes usually separate, hermaphrodite.

Usually trochophore larva.

Examples: Polygordius, Dinophilus, Protodrilus.

Phylum Arthropoda

General Characteristics and Classification of Arthropoda 4.06/5 (647)

General Characteristics and Classification of Arthropoda

Arthropoda (Arthon- Jointed; podos- legs)

Arthropoda, animals having jointed appendages or legs.

It is a phylum of triploblastic, haemocoelomic, segmented invertebrates having head,

thorax and abdomen, a chitinous exoskeleton and jointed legs and appendages.

Most successful phylum on the Earth that has ever existed.

Arthropods were first studied by Aristotle.

Von Siebold coined the term Arthropoda.

General characters

1. Cosmopolitan in distribution found in aquatic, terrestrial and aerial forms.

Some are ectoparasitic and vectors of disease.

2. Body have jointed appendages or legs (which are modified to different structures to

perform different functions like jaws, gills, walking legs, paddle). There may be 3 pairs,

4 pairs, 5 pairs, many pairs.

3. Body is triploblastic.

4. Bilaterally symmetrical.

5. Organ system level of organization.

6. Body is divisible into head, thorax and abdomen.

NOTE: In some (crustacean and arachnida) body is divisible into cephalothorax (head

and thorax is fused) and abdomen.

7. This is the first group to develop a true head, which contains sense organs and feeding

organs specialized for their particular habitats.

8. Body is covered with chitinous exoskeleton.

9. They are haemocoelomate. Coelom i.e. body cavity is filled with blood or fluid.

10. Head bears a pair of compound eyes and antenna.

11. Locomotion takes place by jointed appendages.

12. Digestive system is complete, straight and well developed.

The mouth bears mouth parts for ingestion of foods. Mouths are modified for chewing,

biting, sponging, piercing, siphoning.

13. Respiration takes place by general body surface or gills (in Crustaceans) or trachea ( in

insects, diplopoda and chilopoda) or booklungs (Arachnida) and book gills (in king

cobra).

14. Circulatory system is of open type i.e. do not have blood vessels and enters directly into

the body chambers. The blood is colorless.

15. Excretion takes place through Malphigian tubules (in terrestrial form) or green glands or

coxal glands (in aquatic forms).

NOTE: Aquatic forms are ammonotelic, terrestrial forms are uricotelic.

16. Nervous system is of annelidian type, which consists of brain and ventral nerve cord.

17. Unisexual i.e. sexes are separate.

18. Fertilization is internal or external.

19. They are either oviparous or ovoviviparous.

20. Development may be direct or indirect.

21. Sensory organ include antennae, sensory hairs for touch and chemoreceptor, simple and

compound eyes, auditory organs (in insects) and statocysts (in crustacean).

Examples

Zoological name Common name

Limulus Horse shoe crab or King crab

Daphnia Water flea

Cancer Crab

palaemon Prawn

Astacus Cray fish

Scolopendra Centipede

Julus Millipede

Aranea Spider

Periplaneta americana Cockroach

Bombyx Moth

Pieris Butterfly

Musca Housefly

Apis Honeybee

Melanopus Grasshopper

Palamnaeus Scorpion

Insects as disease carriers

Insects Disease

Housefly Typhoid, Cholera, Dysentry, Diarrhoea

Mosquitoes Malaria, Filariasis, Encephalitis, Dengue fever

Kissing bug Chaga’s disease

Rat flea Bubonic plaque.

Sand fly Kala-azar

Bed bug Typhus fever

Tsetse fly African sleeping sickness

Body louse Relapsing fever

Classification

On the basis of jointed appendages, arthropods are classified into following classes:

Character Crustacean Myriapoda Arachnida Insect

Habitat

Mainly aquatic,

few live in

moist place.Few

are parasitic

form

Terrestrial,

found under

logs of wood

stones etc.

Terrestrial.

Some are

parasitic.

Terrestrial and

rarely aquatic.

Some are

parasitic.

Appendages/

walking legs Five pairs Many pairs Four pairs Three pairs.

Division of

body

Cephalothorax

and abdomen.

Head, thorax

and abdomen.

Cephalothorax

(prosome) and

abdomen

(opisthosoma)

Head, thorax

and abdomen.

Antenna Two pairs One pair No antenna One pair

Respiration

takes place by Gills Trachea

Trachea and

book lungs Trachea

Eye Compound eye Compound eye Distinct eye Compound eye

Excretion

Coxal gland or

Green gland or

Antennary

Malpighian

tubules Green gland

Malpighian

tubules

Examples Prawn Millipede Spider,

Scorpion Butterfly, Moth

Things to Remember

1. Largest phylum in the animal kingdom.

2. Body is covered by chitinous exoskeleton which undergoes periodical ecdysis. The

process of casting off of skin or integument is called ecdysis or moulting.

3. Cuticle is secreted by epidermis of skin. It protects the internal organs and provides space

for the attachment of muscles.

4. Spider produces web by means of spinnerets.

5. Scorpion produces toxin by means of telson (tail).

6. In prawn, only oxygenated blood flows.

7. Prawn has 19 pairs of appendages.

8. Larva of cockroach is called Nymph.

9. In cockroach heart is thirteen chambered.

10. Female cockroach lack anal style. Whereas male cockroach are stylish.

11. Cockroach receives ultrasonic sound by means of anal circuit.

12. Mouth parts adapted for various modes of feeding in Arthropods are:

Biting and chewing type: Cockroach, grasshoppers

Chewing and lapping type: bees and wasps

Piercing and sucking type: Bugs, Aphids, Mosquitoes

Sponging type: Housefly

Siphoning type: Butterflies and moth

13.Haemoglobin absent in blood so called haemolymph.

14. Periplatus is a connecting link between Annelida and Arthropoda.

Phylum Mollusca

General Characteristics of Phylum Mollusca

Mollusca (Molluscus- soft bodies)

Study of Mollusca is called Malacology. The term Mollusca was first applied by Aristotle to cuttle fish. Lamarck coined the term Molluscus. Study of molluscan shell is called conchology.

The animals of this phylum are soft-bodied, non-metameric, triploblastic coelomates and fundamentally bilaterally symmetrical invertebrates with a thin fleshy envelope the mantle, around the visceral (internal organs of the body) which may secrete calcareous shell. They are sluggish animals.

General characters

1. Widely distributed over the world. Mostly aquatic (marine and few are fresh-water) and some are terrestrial living in damp soil.

2. Body is soft and unsegmented (except Neopilina). 3. Bilaterally symmetrical except gastropodas (asymmetrical) because the shell is

coiled. 4. Schizocoel or Haemocoel cavity found as coelom. 5. Triploblastic 6. Organ system level of body organization. 7. Body is divisible into head (absence in pelecypoda and scaphopoda), dorsal visceral

mass, ventral muscular foot and mantle. Mantle- is a dorsal glandular fold of the body wall. It is thick and muscular and encloses a mantle cavity. Head- anterior part of the body, which contains mouth, eyes and tentacles and other sense organs. Foot-is ventral in position usually thick and muscular and generally forms the main locomotory organs. Visceral mass- on dorsal side contains digestive, circulatory and reproductive organ of the body and it forms a hump or dome.

8. Body is covered by a hard calcareous structure, made up of calcium carbonate, called shell. In some molluscus, it is internal or reduced or even absent (oplacophora).

9. Locomotion takes place by ventral muscular foot. 10. Digestive system is well developed with a hard chitinous structure, called radula. 11. Respiration takes place through one or more gills or ctenidia, lungs (pulmonary sac)

or general body surface in the terrestrial forms. 12. Circulatory system is closed or open type. 13. Head consists tentacles and compound eyes.

Presence of one pair tentacles except octopus where tentacles are modified into arm.

14. Excretion takes place by paired metanephridia (kidney).

15. Nervous system consists of many paired ganglia, connectives and nerves. 16. Sense organs are eyes, tentacles, osphradium and statocyst. 17. Sexes are usually separate but some are monoecious.

Pila- sexual dimorphism. Limax- hermaphrodite Helix- hermaphrodite

18. Fertilization is external (in sessile group such as in oyster) or internal. 19. Development may be direct or indirect. Larva is trochopore or veliger or parasitic

stage called glochidium larva.

Examples

Zoological Name Common Name

Pila Apple snail

Helix Garden snail

Limax Slug

Turbinella Shankha

Unio Fresh water mussel

Dentallium Elephant’s tusk shell

Mytilus Sea water mussel

Teredo Ship worm

Pinctada vulgaris Pearl oyster

Sepia Cuttle fish

Octopus Devil fish

Loligo Squid

Things to remember

1. Neopilina is considered as connecting link between Annelida and Mollusca. It is primitive with segmented body.

2. 2nd largest animal phylum after Arthropoda. 3. Unio contains a digestive gland called Green gland, which is comparable to liver of

vertebrates. 4. Statocysts- for maintaining equilibrium of the body. 5. Osphradia- chemoreceptor to test chemical nature of the water. 6. Excretion by a pair of kidneys or organs of Bojanus and pericardial gland or Keber’s

organ. 7. Octopus is known as devil fish. It is a cephalopod having 8 arms and without a shell. 8. Heart is myogenic. 9. Ink glands are present in cephalopoda that are concerned with protection. 10. Blood consists of copper containing pigment called haemocyanin. So blood color is

blue or green.

Phylum Echinodermata

General Characteristics of Phylum Echinodermata:

1. Habitat:

All existing echinoderms are marine. They generally live at sea bottom borne are pelagic (free swimming in open water) and a few are sessile (attached to the substratum).

2. Body Form:

It varies considerably. The body is star-shaped, spherical or cylindrical. It is un-segmented. The body lacks head.

3. Spines and Pedicellariae:

Many echinoderms bear spines and pincer-like pedicellariae. The spines are protective in function. The pedicellariae keep the body surface clear of debris and minute organisms.

4. Symmetry:

The symmetry is bilateral in larvae but pentamerous radial in adults i. e., body parts are arranged in fives or multiples of five.

5. Body Wall:

Epidermis is single layered and ciliated. In many echinoderms there is endoskeleton of calcareous plates in the dermis which are mesodermal in origin.

6. Body Cavity:

There is a true enterocoelic coelom.

7. Ambulacral System (= Water Vascular System):

Presence of ambulacral system is the characteristic feature of phylum echinodermata. A perforated plate called madreporite is present in this system. The pores of the madreporite allow water into the system Tube teet of this system help in locomotion, capture of food and respiration. Water vascular system is of coelomic origin.

8. Digestive Tract:

It is usually complete. Brittle stars have incomplete digestive tract.

9. Haemal and Perihaemal Systems:

Instead of blood vascular system, there are present haemal and perihaemal systems which are of coelome ongin.Thus the so called circulatory system is open type and includes haemal and perihaemal systems. The so blood is often without a respiratory pigment. There is no heart.

10. Respiratory Organs:

Gaseous exchange occurs by dermal branchae or papulae in star fishes peristominal gills in sea urchins, genital bursae in brittle stars, and cloac respiratory ‘trees in holothnrians. Exchange of gases also takes place through tnbe feet.

11. Excretory Organs:

Specialized excretory organs are absent. Nitrogenous wastes are diffused out via gills. Ammonia is chief excretory matter.

12. Nervous System:

It consists of a nerve ring and radial nerve cords. Brain as such is absent.

13. Sense Organs:

They are poorly developed.

14. Sexes and Fertilization:

Except a few individuals, the sexes are separate. There is no sexual dimorphism. Fertilization is usually external.

15. Asexual Reproduction:

Some forms reproduce asexually by self-division.

16. Autotomy and Regeneration:

Phenomena of autotomy and regeneration are often well marked in echinoderms.

17. Development:

The development is indirect and includes a ciliated, bilaterally sym-metrical larva that undergoes metamorphosis to change into the

radially symmetrical adult. Different larval forms are found which are mentioned in the classes of Echinodermata.

Unique Features:

(i) Presence of spines and pedicellariae.

(ii) Ambulacral system (water vascular system),

(iii) Haemal system,

(iv) Mesodermal endoskeleton of calcareous plates,

(v) Bilateral symmetry in the larva and radial symmetry in the adult.

Degenerate Characters:

(i) Lack of head,

(ii) Simple sense organs,

(iii) Incomplete digestive tract in some forms,

(iv) Reduced circulatory system,

(v) Absence of excretory system.

Resemblance with Chordates:

(i) Radial and indeterminate cleavage,

(ii) Gastrulation by invagination,

(iii) Mouth derived as an ectodermal invagination,

(iv) Adult anus derived from embryonic blastopore,

(v) Mesodermal endoskeleton.

(vi) Enterocoelous coelom.

(vii) Both are deuterostomes.

From these resemblances, it is clearly proved that the Echinoderms are nearer to the Chordates than any other group. It also indicates that the chordates have been evolved from Echinoderm-like ancestors.

Classification of Phylum Echinodermata:

Phylum Echinodermata is divided into five classes.

Class 1. Asteroidea (Gk. aster- star, eidos- form):

Body is star-like. Five arms are usually present which are not sharply marked off from the central disc. Larval forms are Bipinnaria and Brachiolaria. Examples: Asterias (Star fish), Pentacews (Star fish), Astrvpecten (Star fish).

Class 2. Ophiuroidea (Gk. Ophis- snake, Oura- tail, eidos- form):

Body is star-like. Arms are sharply marked off from the central disc. Ambulacral grooves”Sre absent. Pedicellariae are absent. Larval form is Ophiopluteus.

Examples:

Ophiothrix (brittle star), Ophioderma (brittle star), Ophiocoma (brittle star), Ophiura (brittle star).

Class 3. Echinoidea (Gk. echinos- hedgehog, eidos- form):

Body is globular or dislike. Biting and chewing apparatus with teeth called Aristotle’s Lantern is present. Ambulacral grooves are absent. Larval forms are Platens and Echinopluteus.

Examples:

Echinus (sea-urchin), Clypeaster (cake urchin), Echinarachinus (sand dollar), Echinocardium (heart urchin).

Class 4. Holothuroidea (Gk. Holothurion- sea cucumber, eidos- form):

Body is elongated and cylindrical. Oral end has mouth surrounded by tentacles. Ambulacral grooves are absent. Spines and pedicellaria are absent. Larval forms are Auricularia and Doliolaria.

Examples:

Holothuria (sea cucumber), Cucumaria (sea cucumber).

Class 5. Crinoidea (Gk. Crinon- lily, eidos- form):

Body has a central disc which is attached to the substratum. Arms are branched. Spines and pedicellariae and madreporite are absent. Larval form is Doliolaria. They are commonly called feather stars or sea lilies.

Example:

Antedon (feather star). Sea lilies.

Asterias (Star Fish):

It possesses great power of regeneration and shows autotomy. At the terminal end of each ambulacral groove lies a bright red eye. The aboral surface bears many stout spines distributed irregularly. In between the spines, there are present soft dermal branchiae.

They act as respiratory and excretory organs. In between two arms near the anus, there is present a perforated circular plate, the madreporite. There are present microscopic pincer-like structures known as pedicellariae. They also act as organs of offence.

Ophiura (Brittle star):

Brittle stars also swim like snake with their arms. Anus is absent.

Echinus (Sea urchin):

It moves with the help of spines. The sea urchin has a masticatory apparatus, called Aristotle’s Lantern because of its resemblance to ancient Greek ship lantern. It is formed by five strong and sharp teeth.

Cucumaria (Sea cucumber):

The sea cucumbers respire by respiratory trees in the cloaca. For this, water is drawn in and expelled through the anus alternately. The mouth is anterior and is surrounded by tentacles.

Antedon (Feather star):

It has great power of autotomy and regeneration. The body comprises a cup shaped central disc and five slender arms. Each arm is bifurcated, bearing a row of pinnules on each side. It is attached to the substratum.