Phylm annelida characteristics.

1. PHYLM ANNELIDA (SEGMENTED BODY)

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

3. 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. CHARACTERISTICS

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

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

6. 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 .

7. 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 .

8. 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.

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

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

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

12. CLASSES OF PHYLUM ANNELIDA : CLASS-POLYCHAETA CLASS-OLIGOCHAETA CLASS-HIRUDINEA

13. 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. CLASS-POLYCHAETA :

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

15. T HE sexes are separate . Fertilization is external and development takes place by thochophore larva

16. EXAMPLES : NEREIS SABELLA

17. 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. CLASS-OLIGOCHAETA

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

19. Locomotion takes place by setae . Parapodia are absent EXAMPLE : EARTHWORM

20. The animals of this class are ectoparasites . They live on the outer surface of their host body. CLASS-HIRUDINEA

21. 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.

22. 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.

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

24. EXAMPLE :

25. 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. ADVANTAGES OF SEGMENTATION AND COELOM

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

27. 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.   IMPORTANCE ;