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Embryological development: embryonic growth depends directly on mitosis. through this type of cell division, the zygote divides, producing a series of cells that also compose differentiated tissues and organs via mitosis until the formation of a complete individual. four initial stages are the morula, blastula, gastrula, and neurula stages
characteristics: notochord - flexible rod-like structure that forms the main support of the body in the lowest chordates (primitive spine); nerve cord - dorsal tubular cord of nervous tissues above the notochord of a chordate; pharyngeal slit - filter-feeding organs found in non-vertebrate chordates and hemichordates living in aquatic environments
major groups within phyla: reptilia, amphibia, chondrichthyes, agnatha, mammalia
distinction of how groups are different: different locations of life; some are scaly, amphibians "two lives", different skeleton (some are made up of cartilage), some are warm blooded, and some are jawless
anatomical characteristics: have four key characteristics - notochord, pharyngeal slit, nerve cord, and the post anal tail
Important life cycles: begins with fertilization. in its primitive form, fertilization occurs externally in the water. asexual reproduction takes place in tunicates and in some vertebrates (female of some fish and lizards can reproduce without fertilization)

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embryological development: have a development that is quite different from other animals. asexual reproduction usually involves the divsion of the body into two or parts and the regeneration of missing body parts. fragmentation is a common method of reproduction
characteristics: rich fossil history and are well represented by many bizarre groups, most of which are now extinct
major groups within phyla: crinoidea, echinoidea, holothuroidea, asteroidea, ophiuroidea, and concentricycloidea
distinction of how groups are different: different build such as sea lilies, feather stars, sea stars
anatomical characteristics: are bilaterally symmetrical as larvae but metamorphose to radially symmetrical adults. hard, spiny covering or skin, internal skeleton, water vascular system derived from coelom
Important life cycles: in most species sexes are separate. although reproduction is usually sexual, involving fertilization of eggs by spermatozoa, several species of sea cucumbers, starfishes, and brittle stars can also reproduce asexually

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Echinodermata means spiny skinned animals. This name was first proposed by Jacob Kelin (1734) for echi-noids. It was Leuckert (1847) who first established Echinodermata as a distinct group of the animal kingdom.

1) They are exclusively marine.

2) They are free living. Some are pelagic. Some are creeping on the sea bottom.

3) These are all triploblastic and co-elomate animals.

4) Adults show pentaradial symmetry and larval form show bilateral symmetry.

5) The size varies from moderate to considerable size.

6) Shape of the body is spherical or globular or elongated. It shows oral aboral and sides.

7) Exo and endo skeletons will be present.

8) Endo-skeletoh is mesodermal. It is made by hard polygonal plants.

9) Body walls include only Epidermis, dermis and peritonium.

10) Body cavity or coelome is large. It is an entero-coelome. It is lined by
ciliated peritonium.

11) Respiration is carried on by

a) Papullae-Star fish.

b) Peristomial gills - Sea urchin.

c) Genital bursae - Brittle star.

d) Respiratory trees - Holothurians.

12) Excretory organs are absent.

13) Nervous system is primitive. Brain is absent.

14) Special sense organs are poorly developed. Eye spots and statocysts are present.

15) Reproduction is sexual. Sexes are separate. Sexual dimorphism is absent. Gonads are iarge.

16) Gametes are iiberated into the water. Fertilisation is external.

17) Eggs are homolethial. Cleavage is radial and indeterminate type.

18) Life history includes larval stage.

19) They can show autotomy and regeneration.

Classification of Echinodermata:

The classification followed here is based on Hyman's Classification.

SUB PHYLUM I : PELMATOZOA : Mostly extinct echinoderms. Mouth and anal.aperture present on the oral surface. Tube feet are primarily food catching. They do not show suckers, pelmatozoa has only one living class.

Class : Crinoidia: Extinct and living forms. Living members are with stalk. Oral surface is directed upwards. Mouth is usually central. Anus is usually excentric. They are present on the oral surface. Arms movable, simple mostly branched, usually five or ten in number. Madreporite, spines and pedicellariae are present. Larva is doliolaria.

Order : Articulata : Mouth and ambulacra! grooves remain exposed.

Ex : Antedon, Metacrinus.

SUB PHYLUM D : ELEUTHEROZOA : Mostly living echinoderms. Stem or stalk is absent. They are living forms. Body structure is usually pentamerous. Oral surface has mouth. It is downwards. Anus usually on the aboral surface.

Class 1 : Holothuroidea : Body bilaterally symmetrical, usually elongated in the oral aboral axis having mouth at or near one end and anus or near the other end.

Order 1: Aspidochirota : A pair of well developed respiratory trees is present.

Ex: Holothuria.

Order 2 : Elaslpoda : Many tube feet. Mouth is usually ventral and surrounded by 10-20 branched tentacles: Ex: Elphidia.

Order 3 : Dendrochlrota : Tube feet are numerous. Oral tentacles are dendritic or branched like tree branches. Respiratory trees are present. Ex : Thyone, Cucumaria.

Order 4: Molpadonia : Tube feet are absent. Oral tentacles are digitate or finger shaped.

Ex : Molpadia.

Order 5: Apoda: Body vermiform having smooth or watry surface. Tube feet are absent. Oral tentacles are 10-20, simple, digitate or pinnate. Ex : Synapta.

Class 2 : Echinodea : Body is spherical, disc like, oval or heart shaped. Body is enclosed in an endoskeletal shell or test of closely fitted calcareous plates covered with movable spines. Ambulacral grooves are absent. Pedicellariae are stalked and three jawed. Sexes are separate. Larval form is echinopluteus larva.

Subclass 1: Regularla : Body is gbbular, mostly circular and sometimes oval in shape. Symmetry is pentamerous. Aristotle's lantern is well developed.

Order 1: Lepidocentroida :

Ex : Poormosoma.

Order 2 : Cidaroidea :

Ex : Cidaris, Notocidaris.

Ex.: Diodema, Astropyga.

Order 4 : Camarodonta ;

Ex : Echinus, Strongylocentrotus.

Subclass 2 : Irregularia : Test is mostly flattened oval to circular. Symmetry is bilateral. Mouth centrally placed on the oral surface. '

Order 1 : Clypeatrolda : Aristotle's lantern is present. Gills are absent. Ex : Clypeaster.'

Order 2 : Spatangoida : Test is oval or heart shaped, Gills absent. Ex : Lovenia, Echinocardium.

Class 3: Asteroidea : Body is flat, pentagonal or star shaped. Oral and aboral surfaces are distinct. Sexes separate, gonads radially arranged. Development includes bipinnaria or brachiolaria larva..

Order 1; Phanerozonia: Arms are provided with two rows of conspicuous marginal plates. Pedicellariae are alveolar or sessile type. Tube feet are arranged in two rows.

Ex : Astropecten.

Order 2: Spinulosa : Arms are generally without conspicuous marginal plates. Pedicellariae are rarely present. Ex : Astorina, Echinaster.

Order 3: Forcipulata : Podia or tube feet are arranged in four rows and provided with suckers. Papulae are on both surfaces. Mouth frame is of ambulacral type.

Ex: Asterias.

Clsss 4 : Ophiuroidea : Body is flattened with a pentamerous or rounded central disc. Oral and aboral surfaces are distinct. Arms usually five, rarely six or seven, are long and slender. Ambulacral grooves are absent. Madreporite is on the oral surface. Sexes are separate.

Order 1 : Ophiurae : Arms are simple, mostly five in number.

Ex : Ophioderma, Ophiothrix.

Order 2 : Euryalae ; Arms are simple or branched. Disc and arms are without or poorly developed. One madreporite in each inter radius. Ex : Astrophyton, Astroporpa.

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Echinodermata means spiny skinned animals. This name was first proposed by Jacob Kelin (1734) for echi-noids. It was Leuckert (1847) who first established Echinodermata as a distinct group of the animal kingdom. 1) They are exclusively marine. 2) They are free living. Some are pelagic. Some are creeping on the sea bottom.

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embryological development: in the embryonic development of some arthropods the fusion of metameres takes place, forming structures such as the cephalothorax of arachnids
characteristics: triploblastic- have three germ layers and are coelomate organisms. they are evolutionarily closer to annelids, as they have segmented bodies.
major groups within phyla: insects, crustaceans, arachnids, onychophorans, diplopods, chiopods
distinction of how groups are different: some are marine and some are on land
anatomical characteristics: exoskeleton, segmented bodies, jointed appendages, bilateral symmetry, open circulatory system
important life cycles: proceed from an egg, through larval and/or nymphal stages, to the adult. larval applies to stages in which major morphological changes occur, and these stages are often fixed in number. "nymph" applies to stages which change in little other than size between molts and are usually indeterminate in number

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Photos Crabs - Animals Arthropoda Animals

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Download wallpaper with tags: Crabs - Animals Arthropoda Animals. Free picture, image and photo. Desktop wallpapers for PC, Tablet

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Embryological Development: fertilization is internal, sperms penetrate the body wall into the pseudocoel to fuse with ova. few rotifers have copulatory apparatus and so copulate. if not fertilized they develop parthenogenetically into males, if fertilized they become thick walled and diploid dormant resting or winter eggs
Characteristics: divided into four sections - head, neck, body, and foot. the jaws are called trophi, found inside the throat behind mouth entrance - break down edible material in the water as it funnels through the body
Major Groups within Phyla: seisonidea, bdelloidea, monogonota
Distinction of how groups are different: largest group is monogonota with about 350 species
Anatomical characteristics: bilaterally symmetrical; extremely variable, slender, broad, flattened, or spherical, usually microscopic
Important life cycles: inability to reproduce is one of its most interesting characteristics - the cells of most animals divide at regular intervals to make up for dying cells. this process is essential for long term health of humans and most animals. cells of rotifera grow larger as the organism ages, but they don't increase in number. females are larger than males and are able to reproduce asexually without the help of a mate

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Phylum Rotifera. - ppt video online download

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Phylum Rotifera 3 general regions: head, trunk, foot Corona Phylum Rotifera Head Mastax Trophi 3 general regions: head, trunk, foot pedal gland in toes glue rotifer to substrate ciliary corona for feeding, locomotion complete digestive tract mastax = muscular pharynx trophus = grind food Trunk Foot

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Embryological Development:
- Are protostomes, mouths first. The small opening into the embryonic ball of cells that appears early in animal development is called blastopore. This becomes the mouth, and the anus appears later on the opposite side. They develop by spiral cleavage, and their embryonic cells are determinate, the fate of the embryonic cells is fixed early on in development.
Characteristics:
- Mostly marine but many occur in fresh water and some even in damp soil. The sexes are generally separate but some are hermaphrodite.
Major Groups within Phyla:
- Monoplacophora: shell is spoon or cup shaped (neopilina)
- Amphineura: present non-ganglionated nerve ring around mouth with two pairs of interconnected nerve cord (chaetopleura)
- Scaphopoda: shell is tubular and open at both ends (dentalium)
- Gastropoda: shell is made up of one piece (Umax, Pila, Helix)
- Pelecypoda/Bivalvia: mude of of two halves (Unio, Mytilus, Solen)
- Cephalopoda: head and foot region combined (Sepia, Loligo, octopus)
Distinction of how Groups are different:
- groups are different due to anatomical features. Some groups have shells that are one shell and other groups have two halve shells.
Anatomical Characteristics:
- unsegmented with a distinct head, muscular foot and visceral hump. Bilateral symmetry however in Pila, due to torsion, the adults become asymmetrical. They have complete digestive tracts.
Important Life Cycles within groups: varies among species, that of most squid follows a similar pattern. female squid spawn, leaving fertilized eggs in water. depending upon environmental conditions, the eggs hatch within about two weeks

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Introduction : Mollusca includes soft bodied animals . It was first applied by Ariistotle to the cuttle-fish of the Aegean Se. The Moiluscans are soft bodied, triploblastic coelomate & bilaterally symmetrical animals. There are about 10,000 living species. It is the second biggest phylum of the animal kingdom.

General Characters :

1. They are mostly aquatic ani mals, mostly marine and a few are fresh water. Some are terrestrial.

2. The body is soft and unsegmented.

3. The body shows 4 parts. 1) visceral ma.s 2) the head 3) the foot and 4) mantle. Head is absent in Pelecypoda.

4. They are bilaterally symmetrical, but some gastropod are assymmetrical.

5. Head bears a terminal mouth, eyes, tentacles and other sensory organs. It is absent in the Pelecypoda and the Scaphopoda.

6. The foot is ventral, muscular and locomotory organ. It is absent in the oysters.

7. The visceral mass, includes the vital organs of the body.

8. The mantle or pallium is muscular fold of the body wall which covers the visceral mass dorsally and laterally.

9. The space present between the mantle and the visceral mass is called pallial cavity.

10. In the pallial cavity gills and the openings of the digestive, and reproductive systems are present.

11. The mantle secretes a hard shell, which covers the body. It may be absent in some molluscs Ex: Doris.

12. The body cavity is haemecoel.

13. The true coelomic cavities are restricted.

1,4. Open type of circulatory system is seen except cephalopoda. The ciorsai hear t Having one to fcuf auricles and one ventricle, is enclosed within the pen ardial cavity.

15 Tht olood is colourless. Respiratory pigment, if present is haemocyanin.

16. The alimentary canal is straight, or 'U-shapedor coiled.

17 The buccal cavity contains a raduia, except in bivalve.

18. A large digestive gland or hepatopancreas and salivary glands are present.

19. The espiratory organs are ctenidia. Pulmonary chamber is developed for

aer' I respiration in the terrestrial forms.

20 The excretory system contains one to six pairs of kidney.

21. The nervous system shows paired cerebral, pleural pedal and viscera!

ganglia.

22. The sexes are usuaUy separate. Few are hermaphrodite.

23. Cleavage is spiral, and holoblastic. The development is either direct or indirect. Glochidium larva is seen in Unio.Veliger larva is seen in Gastropods.

Classification : The classification followed here is based on Morton and Yonge (1964)

The Phylum is divided into six classes.

Class 1 : MONOPLACOPHORA: Body is bilaterally symmetncal. with internal segmentation. Shell shows single piece. Foot is ventral and flat. Heart contains 2 ventricles. Most of the species were extinct.

Ex: Neopilina galathea is recently described species.

Class 2 : AMPHINEURA : Body is cylindrical. They show bilateral symmetry. Body is covered by a shell consisting oi a row of eight transverse plates cn the dorsal side. In some animals shell is absent. Mouth and anus are terminal. Heart contains one ventricle. One pair of nephridia will be present.

It is divided into 2 orders.

Order 1: Aplacophora ( Solenogastrea): These are worm like amphineurans. Shell is absent. Foot is absent or vestigeai. Mantle is thick, and show calcareous spicules. Sexes are separate or bisexual.

Ex-. Neomania, Chaetoderma.

Order 2: Pclyplacophora : Shell is made of eight plates present on the dorsal side. Foot is large, muscular and ventral. In between the mantle and body many gills are present. Sexes are separate. They are marine animais. Ex: Chiton.

Class 3: SCAPHOPODA: These are burrowing molluscs called tusk shells. Body is bilaterally symmetrical. Distinct head is absent. Eyes and gills are absent. They are marine. Shell has single valve and open at both ends. Foot is conical and used for burrowing, Sexes are separate.

Ex: Dentalium.

Class 4: GASTROPODA: These are asymmetrical molluscans. Head is distinct with one or two pairs of tentacles and eyes. Buccal cavity has radula. Shell has single valve. Foot is large and ventral. One or two nephridia are present. Sexes are separate. Some are bisexual.

Sub Class I : Prosobranchia : Mantle cavity opens anteriorly and contains gills. Head shows a single pair of tentacles. It undergoes 180" torison. Nervous system becomes "8" shaped. Sexes are separate.

Order 1 Archacogastro poda : Primitive forms show bilateral

symmetry They contain 2 ctenidia

Ex : Patella, Haliotes.

Order 2 : Mesogastropoda i They show single monopectinate

ctenidium. The nervous system is more concentrated. Ex : Pila, Strombus.

Order 3 : Neogastropoda . Single monopectinate ctenidium is seen Ex: Murex, Buccinum.

Sub Class II: Opisthobranchia : Mantle cavity opens posteriorly and contains one ctenidium and one nephridium . Shell is reduced or absent. Bisexual animals.

Order 1: Tectibranchia: The shell is thin and has a large head Ex : Aplysia.

Order 2: Nudibranchia : Shell, mantle cavity and ctenidia are absent. Anal gills are present.

Ex : Doris, Eolis.

Sub- Class III : Pulmonata : Anterior part of mantle becomes pulmonary cavity. Gills are absent. Shell is spiral or absent. Head has 1 or 2 pairs of tentacles, and one pair of eyes. Hermaphrodite animals are included

Order 1 : Stylommatophora : They live in moist places. They show 2 pairs of tentacles.

Ex: Helix, Umax.

Order 2 : Basommatophora : They are fresh Water forms. Head bears one pair of tentacles.

Ex: Lymnaea, Planorbis.

Class 5 PELECYPODA :Body is bilaterally symmetrical. Radula and tentacles are absent. Shell is bivalved & wedge shaped. Gills are 1 or 2 pairs in number. They are marine and fresh water arms. '

Order 1 . Protobranchia : Primitive members. Gills are-posteriorly placed. Foot is flat. 2 adductor muscles are seen. Ex: Nucula.

Order 2 : Filibranchia : Gill filaments are long, folded with ciliary connections between lamellae. Adductor muscles are two. Anterior muscles may be reduced.

Ex: Mytilus, Ostraea, Pecten.

Order 3 s Eulamellibranchla * Gill filaments folded and lamellae are united by tissue junctions, 2 equal size adductor muscles are present.

Ex: Unio, Anodonta. Order 4 : Septibranchia : Gills become horizontal muscular partitions in between inhalent chamber and suprabranchial cavity.

Ex: Poromya.

Class 6: CEPHALOPODA : Body is elongated. Bilaterally symmetrical animals. Distinct head bears large eyes, radula and jaws. Shell is external, or internal or absent. Foot is modified into arm around the head and into siphon. All are marine and free-swimming.

Sub-Class I: Nautioidea (Tetrabranchia): External shell is present. Tentacles are many suckerless Nephridia are two pairs. Two pairs of gills will be seen.

Ex : Nautilus.

Sub-class II- Coleoidea (Dibranchia): Shell is internal or absent. 8 to 10 arms are present with suckers. Nephridia are one pair of gills will be seen. Order 1: Decapoda Body shows 2 long tentacles and 8 short arms. Ex: Sepia, Loligo

Order 2 : Octopoda : Body shows 8 equaj arms. Ex: Octopus. Argonauta, Loligo.

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Introduction : Mollusca includes soft bodied ani­mals . It was first applied by Ariistotle to the cuttle-fish of the Aegean Se. The Moiluscans are soft bodied, triploblastic coelomate & bilaterally symmetrical animals. There are about 10,000 living species. It is the second biggest phylum of the ani­mal kingdom. General Characters : 1.

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embryological development: loose arrangement of primary circular and longitudinal muscles encloses the whole embryo. circular muscles differentiate in an anterior-posterior progression creating a segmental pattern. the development begins with one pair of prominent longitudinal muscles differentiating ventrally along the right and left germ band. these muscles provide a guiding structure for the parallel organization of the afterwards differentiating longitudinal musculature
characteristics: coelom - often used as a storage area for gametes and acts as a hydrostatic skeleton for locomotion. generally organized as a series of compartments divided by intersegmnetal septa
major groups within phyla: polychaeta, oligochaeta, and hirudinea
distinction of how groups are different: different anatomical features - marine or land
anatomical characteristics: bilaterally symmetrical, coelom - fluid filled cavities between the outer body wall and gut, parapodia, nervous system, sensory organs, circulation and respiratory structures, and segmental organs
important life cycles: some produce asexually and others produce sexually - some do both. when reproducing asexually they do it by dividing themselves into two or more pieces, otherwise they have sex with a member of the opposite sex even though they all have both reproductive systems. many annelids have both the female reproductive system and male reproductive system, or they change throughout their life

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General Characteristics of Phylum Annelida:

Some of the general characters of Phylum Annelida are listed below:
1. Habitat:
Annelids occur in fresh water, sea water or moist soil. Some are free living, some are burrowing and a few are parasitic.
2. Metameric Segmentation:
The annelids are characterised by metameric segmentation, viz., the body is divided externally by ring like grooves the annuli (Latin, annulus: little ring) and internally by transverse septa. The segments are called metameres. The first segment is called peristomium. An outgrowth, known as prostomium, arises from the peristomium.
3. Setae and Parapodia:
Except leeches, un-jointed chitinous setae are often present. Some annelids such as Nereis have un-jointed, locomotory structures, the Para podia (Para parallel, podia- feet).
4. Body wall.
The body wall consists of thin, and moist non-cellular cuticle, single layered epidermis and circular and longitudinal muscles. The muscles are smooth which are highly contractile and help in locomotion.
5. Coelom (Body Cavity):
A true coelom is present. From evolution point of view, annelids are, perhaps, the first animals to have a true schizocoelic coelom. In most annelids coelom is divided by septa into compartments. The coelom is filled with coelomic fluid which contains cells.
6. Hydro skeleton:
The coelomic fluid serves as a hydro skeleton.
7. Digestive Tract:
It is complete.
8. Respiratory Organs:
Exchange of gases usually occurs through the skin (cutaneous respiration). In some annelids gaseous exchange also occurs through gills (branchial respiration), e.g., Terebella.
9. Blood Vascular System:
It is usually closed type. Blood is red due to the presence of respiratory pigment haemoglobin or erythrocruorin, found dissolved in the blood plasma. Free amoeboid blood corpuscles are present, but there are no red blood corpuscles.

In leech, there is no true blood vascular system, the coelomic space and fluid have been modified to form the circulatory system. It is called haemocoelomic system and red coelomic fluid is called haemocoelomic fluid.
10. Excretory System:
It consists of coiled tubular structures, called nephridia which help in osmoregulation and excretion. Ammonia is chief excretory waste.
11. Nervous system:
The nervous system consists of a nerve ring and a solid, double, mid ventral nerve cord with ganglia. A ganglion is an aggregation of nerve cells.
12 Receptors:
Tactile receptors (sensitive to touch), gustatoreceptors (receptors of taste) and photoreceptors (sensitive to light) are usually found. Some forms have statocysts (balancing organs).
13. Sexes:
Both unisexual (e.g., Nereis) and bisexual (e.g., Earthworm, Leech) forms are found.
14. Development:
It is mostly direct. If there is indirect development (e.g.. Nereis), it includes a trochophore larva.
Unique Features.
(i) Metameric segmentation,

(ii) Haemoglobin in the plasma,

(iii) Nephridia for excretion and osmoregulation,

(iv) Setae.

Advancement over Roundworms:

(i) Metameric segmentation,

(ii) Circular and longitudinal muscles are present in both body wall and the wall of the alimentary canal,

(iii) True coelom,

(iv) Blood vascular system contains red blood.

Classification of Phylum Annelida:

On the basis of number and presence or absence of setae phylum Annelida is divided into five classes.
Class 1. Polychaeta (Gk. polys-many + chaete = hair):
They have well developed Para podia with numerous setae. The development is indirect, undergoing metamorphosis with a free swimming trochophore larva.

Examples: Nereis, Aphrodite (Sea mouse) Polynoe (Scale worm), Chaetopterus (Paddle worm), Sabella (Peacock worm), Arenicola (Lug worm), Amphitrite, Terebella and Serpula (Fan worm). Both Polynoe and Chaetopterus are bioluminescents. Arenicola, Amphitrite, Terebella and Serpula have gills.

Class 2. Oligochaeta (Gk. Olivos- few + chaete - hair):
The body has few sectae. There is no metamorphosis, e.g., Pheretima, (Indian 'Earthworm), Lumbricus, (European Earthworm) Tubifex, Magascolex (common earthworm of South India).
Class 3. Hirudinea (L. hirudo- leech):
They are ectoparasitic leeches. There are no Para podia or setae. Beneath the muscular layer of the body wall and surrounding the alimentary canal is found botryoidal tissue (peculiar connective tissue). Leeches have haemocoelomic system.

Examples: Hirudinaria (Blood sucking leech), Pontobdella, Hirudo, Acanthobdella.
Class 4. Archiannelida:
External segmentation is faint but internal segmentation is by septa and is complete. Examples Polygordius, Dinophilus.
Class 5. Echiurida:
These annelids are without external and internal segmentation. Setae are rare. Examples Bonellia, Echiurus.

Neanthes (= Nereis):

It is commonly called clam worm or sand worm or rag worm which is found on the sea shore in the tubular burrows. Nereis is unisexual and its reproductive phase is called Heteronereis.

Fertilization occurs in sea-water. During development, a trochophore larva is present. Except the peristomium (first segment) and last anal segment, each segment bears laterally one pair of fleshy projections, the parapodia, used in swimming.
Hirudinaria granulosa- The cattle leech:
It is an ectoparasite on cattle. Hirudinaria feeds on blood and hence called sanguivorous. The saliva of the leech contains an anticoagulant, called hirudin which prevents clotting of blood during blood meal. It is hermaphrodite, but cross-fertilization occurs. It is important to note that the segments 9, 10, 11 develop a temporary clitellum during breeding season.

The leech bears two suckers: anterior and posterior. There are present five pairs of eyes on the dorsal surface. Some leeches are used as fish bait. Some leeches are used as surgical agents specially for curing diseases such as piles, baldness, etc., which is not correct.
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Phylum Annelida: Characters and Classification | Animal Kingdom

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ADVERTISEMENTS: In this article we will discuss about the General Characters and Classification of Phylum Annelida. General Characteristics of Phylum Annelida: Some of the general characters of Phylum Annelida are listed below: 1. Habitat: ADVERTISEMENTS: Annelids occur in fresh water, sea water or moist soil.

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embryological development: show presence of two membrane layers in the body that are derived from the endoderm and ectoderm of the embryo. They are diploblastic meaning they have two embryonic germ layers (the endo and ectoderm).
characteristics: contain specialized cells known as cnidocytes (stinging cells) which contain organelles called nematocysts (stingers). these cells are present around the mouth and tentacles, serving to immobilize prey with toxins contained within the cells.
major groups within phyla: anthozoa, cubozoa, hydrozoa, scyphozoa
distinction of how groups are different: some include corals, anemones, sea pens, box jellies with complex eyes, diverse groups with siphonophores, hydroids, fire corals, and true jellyfish
anatomical characteristics: radial symmetry, have tentacles, body contains a gastrovascular cavity and the body wall is diploblastic
important life cycles: different groups have different reproduction details. as a whole they have two body forms, the polyp medusa. Polyp form is usually anchored to the substrate with the mouth facing upwards. Medusa individuals are free-swimming with the mouth facing downwards

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The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle. Casually touching many cnidarians will make it clear how they got their name when their nematocysts eject barbed threads tipped with poison.

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embryological development: developed mechanisms to engulf the external yolk cells into the developing embryo, usually by forming one or more temporary epidermises, or hull membranes. juveniles develop from an embryonic blastema with the ventral side facing outwards, as observed in macrostomids.
characteristics: acoelomate - no body cavity; triploblastic - has three tissue layers; bilaterally symmetric - symmetric right and left sides usually definite head, and have organ systems
major groups within phyla: turbellaria, tramatoda, monogenea, and cestoda
distinction of how groups are different: some are human paraistes, endoparasites found in bile ducts of sheep, goats, and cattle, or parasites that infect various animals including man a
anatomical characteristics:
important life cycles: life cycles may be direct or have 1-3 intermediate hosts. auto-infection is possible for some species. adults are usually parasites of vertebrate animals, while larval forms may be free-living or infect vertebrates or invertebrates. some parasitic larval forms are capable of asexual proliferation

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The fact that one end of the flatworm is designated as the head is known as cephalization. The ganglia on the head act as a brain and specified regions are capable of detecting light, chemicals, and pressure. The platyhelminthes' nervous system is known as a simple bilateral nervous system; these organisms were the first to exhibit such a system.

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embryological development: Porifera do not produce zygotes that go through embryonic development to produce tissues, they only have a limited set of thee types of specialized cells with a few patterns of association. Their body plan consists of a middle layer of non-living skeletal tissue sandwiched between two layers of cells arranged with interior canal for water flow through the tube. They do not produce germ layers that develop into tissues and tissue systems in an organized body plan around a body axis. The most complex sponges have branching internal canals to increase the surface area in a nonsymmetric pattern.
characteristics: commonly called sponges, multi-cellular organisms which are sessile/sedentary in nature, most of them are marine while a few are fresh water forms
major groups within phyla: calcarea, hexactinellida, demospongiae
distinction of how groups are different: various shapes, based on their main axis and number of rays such as monaxons: single axis growing in one or more directions, skeleton make up
anatomical characteristics:  radial symmetry, body wall is diploblastic which consists of an outer layer called pinacoderm and an inner layer called choanoderm, the middle layer is called mesenchyme which has various kinds of wandering amoebocytes
important life cycles: reproduction cycle is important. are hermaphroditic, function as female or male for reproduction. can produce eggs and sperm at different points in life time. an adult sponge has two choices on how offspring can be produced, asexually or sexually.