Phylum Annelida PDF

10.7 GRADE: BILATERIA TRIPLOBLASTIC ANIMALS COELOMATES PHYLUM ANNELIDA The Segmented Worms  10.7.1 (a)General Characteristics of Annelids (b)Segmentation and its advantages (c) Coelom and its advantages Habit & habitat: Annelids some are aquatic found in marine,...

10.7 GRADE: BILATERIA TRIPLOBLASTIC ANIMALS COELOMATES PHYLUM ANNELIDA The Segmented Worms  10.7.1 (a)General Characteristics of Annelids (b)Segmentation and its advantages (c) Coelom and its advantages Habit & habitat: Annelids some are aquatic found in marine, freshwater, Some terrestrial habitats Free living, some are ectoparasites. General characteristics: Tissue level organization : Eumetazoa Symmetry : bilaterally symmetrical Germ layer :Triploblastic Coelom: coelomate  General characteristics: Fate of blastopore: develop mouth ( protostome) The body is vermiform, meta meric segmented Each segment is separated from contiguous ones by a transverse septum The body is covered with a flexible non- chitinous cuticle.  Body system Skeleton : Hydrostatic skeleton Locomotion :by circular and longitudinal muscles and chitinous setaea or chaetae with or without parapodia Digestive system: is complete , tube like with mouth and anus opening Circulatory system :is present closed type. Blood red having hemoglobin.  Body system Excretory system: present typically consists of a pair of metanephridia per segment Nervous system :A well developed central nervous system (CNS) is present in annelids. It comprises of simple brain and a ventral nerve cord. The Respiratory system : Absent , exchange of gases is by diffusion through the skin into blood capillaries.  (B) SEGMENTATION AND ITS ADVANTAGES  Linear series of body segments is called segmentation Annelides show metameric segmentation Has internal and external many segments which have same repetition of organs and tissues after regular interval which are structurally , morphologically and functionally similar like metanepridia , circulatory muscles , longitudinal muscles , blood vessles , nerves  Each segment in annelids is called metamere / somite Advantages: give flexibility to body , help in better movement  (c) COELOM AND ITS ADVANTAGES Coelom is true body cavity develop by splitting of mesoderm Advantages 1. Give definite shape. 2. Prevent from mechanical shocks. 3. It also gives cushioning effects to the internal organs from damage on minor bends. 4. The coelomic fluid is a hydrostatic skeleton that helps in locomotion for soft-bodied animals.  10.7.2 CLASSIFICATION OF ANNELIDS  Phylum ANNELIDA Class Class Class POLYCHAETA OLIGOCHETA HIRUDINA Sabella Hirudinaria (Peacock PHERITEMA (Common worm) and EARTHWORM Indian NERIES Leech)  Class - POLYCHAETA General Characteristics: Mostly marine and free-living Many setae, on fleshy lateral outgrowths of the body wall known as parapodia Well developed head bearing appendages Sexes separate, with a free-swimming trochophore larva SABELLLA (PEACOCK WORM Nereis  2- CLASS OLIGOCHAETA They are usually terrestrial, free living and burrowing forms. Organs of locomotion are setae without parapodia. All are hermaphrodite (bisexual). Head region not prominent or distinct. No larva formed during development. E.g. Lumbricus terrestris, Pheritima posthuma (common earthworms)  CLASS OLIGOCHAETA (Few setae) General Characteristics Are terrestrial with a few freshwater species Have few setae. No parapodia. No distinct head appendages. Clitellum present. Hermaphrodites. Eggs are deposited in a cocoon and development is direct. Example: Pheretima(earthworm) Pheretima (Earthworm) Bisexuality favours self fertilization but earthworms are cross fertilizing organisms. This is because the male reproductive organs mature earlier than the female parts, i.e., they are PROTANDROUS, which in turn makes them cross fertilizing  CLASS HIRUDINEA General Characteristics: Ectoparasites, some free living predators. Usually dorso-ventrally flattened. No setae or parapodia Clitellum present only during reproduction Two suckers – anterior and posterior. Example: Hirudinaria,leech.  They have an anticoagulant secretion which is passed into the wound to allow smooth flow of blood into its digestive system where it can be stored for a long time. E.g. Hirudo medicinalis (medicinal leech) Hirudinaria (common Indian leech) AMERICAN MEDICINAL LEECH  10.7.3 IMPORTANCE OF ANNELIDS Soil Health and Agriculture Soil Aeration: Earthworms burrow through the soil, improving aeration and water infiltration, which enhances root growth and agricultural productivity. Nutrient Recycling: They break down organic matter, facilitating nutrient cycling and increasing soil fertility. Their castings are rich in nutrients, making them valuable for organic farming Fisheries Bait: Annelids like polychaetes and oligochaetes are used as bait for fishing. Medicinal Uses Leeches in Medicine: Medicinal leeches (Hirudo medicinalis) are used in medical treatments, particularly in plastic and reconstructive surgery, for their ability to promote blood circulation and LEECHES produce anticoagulant chemicals prevent blood clots