❖ Turgidity of the fluid in the parenchymal maintains the form of the body

(hydroskeleton).

❖ Dorsoventrally flattened body, bilateral symmetrical animals, free living

(terrestrial, fresh water or marine) or parasite.

❖ Triploblastic

❖ Bilaterally symmetry.

❖ Adhesive organs are present like suckers, hook.

❖ Nervous system is ladder like.

❖ Incomplete digestive system <if present> (have a common opening of

ingestion and excretion).

Platyhelminthes:

❖ Reproduce sexual as well as asexual (Transverse Binary fission), good power of

regeneration.(PLANARIA)

❖ Respiration – 1. Aerobic 2. Anaerobic

❖ Excretory organs are protonephridia or flame - cells (Solenocytes).

❖ They also help in osmoregulation.

❖ Animals are Bisexual.

❖ Fertilization may be self or cross and internal.

❖ beginning of cephalization(formation of

head).

❖ Found in fresh water, Nocturnal, Cannibalism, slow creeping omnivorous

❖Schistosoma- (Blood fluke):UNISEXUAL❖Taenia solium (Pork tapeworm)

❖Taenia saginata (Beef tapeworm)

❖Fasciola hepatica - (Liver fluke) causes

Liver-rot or Cirrhosis.

EXAMPLES:

❖ Nervous system comprises of circum pharyngeal ring (Brain).

❖ Sense organs like Papillae (Tangoreceptors), Amphids (Chemoreceptor)

❖ Phasmids (chemoreceptor) are found near hind end of body.

❖ Animal of this phylum are Cylindrical, tapering at both end without segmentation.

❖ Bilateral, Triploblastic, Organ-system level organization and having tube within

tube plan.

❖ Pseudocoelomates, Hydro skeleton.

❖ Digestive tract is complete

❖ Respiration is through body surface by diffusion.

❖ Excretory system is consists of excretory canal or excretory tube (Renette cell).

ASCHEHILMINTHES (NEMATODA)

❖ Reproduction system is (dioecious). Sexual dimorphism is present.

❖ Development is mostly direct.

❖ Numbers of cells are fixed from larva to adult development known as

Eutely.

Male Female

Body smaller, 15-30 cms long

and 3-5 mms. wide

Body larger, 20-40 cms long

and 6-8 mms. wide

Tail end curved ventral wards. Tail end straight

Anus and genital pore

common i.e ., a cloacal

aperture is present

Anus and genital pore-

separate. Genital pore

midventral at about 1/3rd.

Body length behind anterior

end.

Preanal and postanal papillae

present to help in copulation

No such papillae.

A pair of needle-like penial

setae in cloaca.

No penial setae.

External Features Of Sexual Dimorphism

in ASCARIS-

❖ Lamarck Coined The Term Annelida.

❖ Free Living Found In Moist Soil, Fresh Water,

Sea Or Few Are Parasite.

Body Wall

Cuticle Muscle LayerEpidermis

❖ Body Is Soft, Elongated, Cylindrical Or

Flattened, Metamerically Segmented By Ring

Like, Groves Called Annuli.

❖ Symmetry - Bilateral, Triploblastic, Organ-

system Level Of Organization Having Tube

Within Tube Plan.

❖ Have Chitinous Para Podia With Setae (Help

In Swimming) For Locomotion.

Circular Layer And Longitudinal Layer, Help In Locomotion.

ANNELIDA:

❖ True coelom, (schizocoelous), Hydrostatic skeleton.

❖ Prostomium (acron) is the first body segment

❖ The clitellum is a thickened glandular and non-

segmented section of the body wall near the head in

earthworms and leeches that secretes a viscid orange

white sac in which the eggs are deposited.

❖ Excretory organs are nephridia

❖ Excretory matter

(1) ammonia in aquatic form

(2) urea in land form.

❖ Nervous system consists of paired ganglia with a ventral solid and double nerve cord joined by lateral nerve in each segment.

❖ Circulatory system is close type.

❖ Respiration is cutaneous and by gills (brachial respiration).

Monoceous (eg earthworm, leech) or Dioceous (eg neries)

Development may be DIRECT (earthworm , leech) or INDIRECT(neries).

❖ They have Jointed appendages hence called ARTHROPODA, chitinous exoskeleton.

❖ Body cavity around viscera contains blood and is called the haemocoel. Digestive

Tract is complete.

❖ Body is Bilateral, Triploblastic with organ system level of body organization.

❖ Head is distinct, consists of well-developed sense organ such as have simple eyes,

compound eyes, antennae, statocysts or balance organ.

❖ Compound eye consists of many similar units ommatidia.

❖ Body is mostly divided into three region Head, thorax & abdomen

Biting and chewing type - Grasshopper, Cockroach, Termites,

Caterpillars.

Piercing- Sucking type - Mosquitoes, Bugs, and Fleas.

Chewing- Lapping type – Bees.

Sponging type - Housefly, fruit fly.

Siphoning type - Butterflies, moths

Mouth parts

adapted for

Arthropoda:

❖ Parthenogenesis phenomenon also found i.e. Development of an unfertilized

egg into an offspring.

❖ Male honey bees (drones) are formed by parthenogenesis.

Gregarious pest - Locusta (Locust)

Economically important insect - Apis (Honey bee), Bombyx (Silk worm),

Laccifer (Lac insect)

Vectors - Anopheles,

Culex Aedes (mosquitoes)

Living Fossil - Limulus (King crab)

Others - Butterfly, Scorpion, Prawn, Spider, Cyclops, Centipede,

Millipede, Peripatus (WALKING WORM)etc.

Examples

Arthropoda:

Circulatory system is Open.

•Blood with white corpuscle, colourless - Haemolymph. (E.g. Insects)

•Copper containing pigment haemocyanin (e.g. Prawn)

Antennary or green glands or

maxillary gland (e.g.

Crustaceans) opening directly

to the exterior.

Excretory organs

Coxal gland (e.g. Arachnids) Malpighian tubules

(e.g. Insects) opening into the gut.

Respiration is through body surface or special structure such as gills , Trachea (e.g.

Insects), Book-lungs (e.g. Scorpion), Book-gills (e.g. King crabs), etc.

Study of this phylum is known as Malacology & study

of molluscan shells is known as Conchology.

They are usually bilateral symmetrical.

These are triploblastic with Organ system level.

Body is unsegmented with a distinct head, muscular

foot and visceral hump.

Head with sense organ like Eyes, Tentacles

soft and spongy layer of skin more or less covering the

body is called mantle or pallium.

Shell may also be internal (Cuttle fish), reduced and

even absent (Octopus).

Cuttle fish

Octopus

MOLLUSCA:

❖ Coelom is greatly reduced. It is represented by cavities in the pericardium, kidneys and

gonads.

❖ Digestive tract is complete. Buccal cavity contains a file-like rasping organ called

Radula, with transverse row of teeth.

❖ Respiration is usually by feather like gills i.e. Ctenidia are in the mantle cavity which

also assists in excretion but respiration may takes place by body surface also. .

❖ Circulatory system is open.

❖ Blood has a copper containing, blue respiratory pigment Haemocyanin

❖ Excretory organs of molluscans is Metanephridia known as Kaber's organs or Organ of

Bojanus.

Mollusca – Example

❖ Senses organ includes Eye, Statocyst / Lithocyst and Osphradia

❖ Sexes usually separate or Dioecious.

❖ Body shape is star like. Body unsegmented with bilateral symmetry in larva and radial

pentamerous (arranged in five or multiple) in adult.

❖ They are triploblastic without head.

❖ Skin of echinoderms consists of spines, pedicellariae and endoskeletor of calcareous

plate (Ossicle). Echinoderms have true Coelom

❖ They have ambulacral system for locomotion

❖ Respiration takes place by body surface called dermal branchiae or papulae in most of

Echinoderms like Starfish. Genital bursae in Brittle star, cloacal respiratory trees Sea-

Cucumber, By Peristominal gills - Sea urchin.

❖ Circulation system is reduced and open type. Instead of blood vascular system, there

are present haemal and perihaemal system which are of coelomic origin. The blood is

often without a respiratory pigment.

ECHINODERMATA:

Excretory organ system absent

Nervous system is simple and less developed includes a nerve ring and radial nerves

with simple sense organ. (No brain)

Echinoderms have separate sexes and fertilization is external.

Echinoderms in angry or frightened state vomits out viscera (internal organ). This

phenomenon is known as evisceration.

STAR FISH SEA URCHINSTAR FISH SEA URCHIN

❖ Animals of this phylum are all fossorial.

Body

Proboscis Collar Trunk

❖ Body cavity is enterocoelus.

❖ Respiratory pigment : vanadium.

❖ Respire by gill or body surface, circulatory system

is open type.

❖ True notochord is absent..

❖ “Stomochordata” (outgrowth structure of gut)

❖ Excretion is done by Proboscis gland.

❖ Brain is present in the form of nerve - ring

Balanoglossus

HEMICHORDATA:

❖ Fertilization is external. Cleavage holoblastic.

❖ Development is direct or indirect because some

animals have tornaria larva just like bipinnaria larva of

Echinodermata.

Body

Enteropneusta Pterobranchia

E.g.:

a) Balanoglossus :- Tongue

worm or Acorn worm

b) Saccoglossus

c) Protoglossus

E.g.:

a) Rhabdopleura

b) cephalodiscus