50 ^|

A Handbook of Biology

Unique

features

Unsegmented

(except

tapeworm),

dorso- ventrally

flattened

body (except

tape worms),

excretion by

flame cells

(protonephridia),

Hooks & suckers

in parasitic

forms, some

absorb nutrients

from the host

through their

body surface

Syncitial

epidermis,

thick cuticle,

an excretory

tube to remove

body waste

through excretory

pore, sexual

dimorphism

(females are

longer than

males)

True

segmentation,

longitudinal

and circular

muscles help

in locomotion,

locomotory

organs are

setae (in

earthworm)

or parapodia

(in Nereis),

excretion by

Nephridia,

paired ganglia

connected by

lateral nerves

to a double

ventral nerve

cord

Jointed

appendages,

body has

3 regions:

head, thorax

& abdomen,

body is covered

by chitinous

cuticle

(exoskeleton),

excretion by

malpighian

tubules, sensory

organs are

antennae,

compound &

simple eyes,

statocysts

(balance

organs)

Examples

Taenia solium

(Tape worm),

Fasciola (Liver

fluke), Planaria

(shows high

regeneration

capacity)

Ascaris

(Roundworm),

Ancylostoma

(Hookworm),

Wuchereria

(Filarial worm)

Pheretima

(earthworm),

Hirudinaria

(blood sucking

Leech), Nereis

Spider,

Scorpion,

Crab, Prawn,

Insects etc,

Economically

important

insects: Apis,

Bombyx,

Laccifer,

Vectors:

Mosquitoes

(Anopheles,

Culex & Aedes),

housefly etc,

Gregarious

pest: Locusta

Living fossil:

Limulus (King

crab).

Features

Mollusca (Soft-

bodied animals)

Echinodermata

(Spiny-skinned

animals)

Hemichordata

Levels of

organisation

Organ system

Organ system

Organ system

Symmetry

Bilateral

Radial (Bilateral

in larval stage)

(AIPMT 2004)

Bilateral

Germ layers

Triploblastic

Triploblastic

Triploblastic