The phylum Annelida includes segmented worms such as earthworms and leeches. Their bodies are bilaterally symmetrical and triploblastic, with a complete digestive tract that extends from the mouth to the anus. They possess a true coelom and metamerically segmented bodies. Locomotion is achieved through setae or hairs located in parapodia. The circulatory system is closed with one or more hearts, and respiration occurs through the skin. Excretion is through nephridia. Annelids play an important role in soil enrichment and some species have medical uses.

2. PHYLM
ANNELIDA
(SEGMENTED BODY)

3. • A phylum of coelomate and
usually elongated segmented
invertebrates ( e.g earthworm,
leeches , nereis )

4.  SEGMENTED BODY
They have elongated and segmented body
,their segments are complete i.e. externally and
inernally as well .The segments are known as
MATAMERS.
 SYMMETRY
They have bilaterally symmetrical body.

5.  TRIPLOBLASTIC
They ara triploblastic animals i.e. the
body develops from three –layers ,outer
ectoderm , middle mesoderm and inner
endoderm.

7.  ALIMENTRY CANAL
The alimentry canal is complete elongated
and tube like structure . It extends from the
mouth to the anus

8.  COELOM
These animals possess a true coelom (true body
cavity) , it lise between the layers of mesoderm due to
the presence of a true coelom they are called
COELOMATES . The entire coelom is divided into
compartments due to the presence of septa.

10.  LOCOMOTION
The locomotion of the body is by small hair
like structure ,called SETAE . They are found along the
segments in pair , the setae or cheetah are with or
without parapodia.

12.  CIRCULATORY SYSTEM
They have closed type
circulatory system i.e. the blood flows
in blood vessels . The blood is red due
to the presence of “haemoglobin” .
The major blood vessels are dorsal and
ventral blood vessels. The number of
heart is two or more.

14.  RESPIRATORY SYSTEM
There is no special respiratory organ
.The respiration takes place through ,the moist
skin through diffusion .

15.  EXCRETION
The excretion is by convoluted tube like organ ,
called nephredia.
,in each segment a pair or more nephredia are present.

16.  NERVOUS SYSTEM
Nervous system is consist of a brain and
double nerve cord , with a ganglion in each segment.

18. o CLASSES OF PHYLUM ANNELIDA :
CLASS-POLYCHAETA
CLASS-OLIGOCHAETA
CLASS-HIRUDINEA

19.  Their body is elongated and metamerically segmented .
 For each segment of body prominent organs are
developed , called Parapodia . Which bears setae ,setae
help in locomotion.

21.  Their head is distinct , called prostomium.It
possess eyes ,tentacles , antennae and bristle
or palps.

23.  THE sexes are separate . Fertilization is
external and development takes place by
thochophore larva

24. EXAMPLES :

25.  These animals possess few setae .
 The body is metamerically segmented consists of many
segments.
 The head is not prominent . Eyes and tentacles are also
absent .Mouth is present on first segment.

26.  Some segments of the body are covered by a structure
called CLITELLUM which is a reproductive device.

27.  Locomotion takes place by setae
.Parapodia are absent
EXAMPLE :
EARTHWORM

28.  The animals of this class are ectoparasites . They live
on the outer surface of their host body.

29.  Their body is elongated and flattened at both
sides.
 The body consists of definite number of
segments , 34 in number.
 They do not have chaetae like other annelids.

30.  They have suckers at both ends of their body. On the
anterior sucker mouth is present, by the help of which
they suck blood from the body of the host .The
suckers help in their attachment to the host body.

31.  Anus is present on the posterior sucker.
 Reproduction is sexual .Development of egg
takes place in cocoon.

33.  1. SEGMENTATION PROVIDES FLEXIBILITY
,THE BODY CAN EASILY BEND AND THE BODY
PARTS CAN WORK INDEPENDENTLY.
 2. THE INCREASED FLEXIBILITY ALSO
INCREASES POWER OF LOCOMOTION.
 3. THE COELOM HELP IN SWIMMING AND
BURROWING FUNCTION . COELOM SERVES AS
A HYDROSTATIC SKELETON.

34.  COELOM ALSO COOLECTS METABOLIC
WASTES DISCHARGED BY EXCRETORY
ORGANS .
 IT PROVIDES SPACE FOR MATURATION
OF EGGS AND SPERMS.

35.  Annelids, or segmented worms, are
important because some of them aerate
and enrich soil, which keeps it fertile.
Medicinal leeches are annelids that are
used in healing.
