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)
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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.
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.
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.
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.
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.