Zoology Lec. Module 7-8 PDF

**ZOOL 1 -- General Zoology** **Objectives:** After the completion of the chapter, students will be able to: 1\. Characterize the classes under phylum Echinodermata. 2\. Enumerate sample species under each class. Phylum Echinodermata - Echinoderm is the common of all marine animals under thi...

**ZOOL 1 -- General Zoology** **Objectives:** After the completion of the chapter, students will be able to: 1\. Characterize the classes under phylum Echinodermata. 2\. Enumerate sample species under each class. Phylum Echinodermata - Echinoderm is the common of all marine animals under this phylum. - Adults are distinct with their radial symmetry - These includes the starfish , sea urchins , sea cucumbers , sand dollars , brittle stars and sea- lily  - Exclusively marine - Multicellular organisms with well -- developed organ systems - They share same characteristic features. (marine organisms) - Colorful organisms with unique shapes - Ecologically and geologically very important - The water vascular system presents in echinoderms accounts for gaseous exchange, circulation of nutrients and waste elimination. - They have a star-like appearance and are spherical or elongated. - They are exclusively marine animals. - The organisms are spiny-skinned. - They exhibit organ system level of organization. Most members have a circulatory system as well as a digestive system. - They are triploblastic and have a coelomic cavity - The skeleton is made up of calcium carbonate. - They have an open circulatory system (no heart or blood vessels) - They respire through gills or cloacal respiratory tree. - They have a simple radial nervous system, and the excretory system are absent. - The body is unsegmented with no distinct head. - The mouth is present on the ventral side while the anus is on the dorsal side. - The tube feet aid in locomotion. - They reproduce sexually through gametic fusion and asexually through regeneration.   - Development is indirect - They possess the power of regeneration. - They have poorly developed sense organs. These include chemoreceptors, tactile organs, terminal tentacles etc. - The larval forms show bilateral symmetry and adult forms show radial [symmetry](https://www.toppr.com/guides/maths/symmetry/line-of-symmetry/) - They have a true coelom. - The body is uniquely shaped. It can star like, elongated or spherical. - The body is unsegmented without a head. - The body surface is covered with calcareous spicules. - Body cavity has the distinguishing water vascular system - The brain is absent, but a nervous system is present with a nerve ring and radial nerve cords. - Respiration occurs through tube feet and gills. - Sense organs are poorly developed and include tactile organs, chemoreceptors, terminal tentacles etc. - Sexes are separate. - They have a flattened, star-shaped body with five arms. - They have tube feet with suckers. - They respire through papulae. - The body comprises of calcareous plates and movable spines. - Pedicellaria is present. - Examples: Crown of Thorns Starfish , Aster (a star) Starfish  - The body is flat with pentamerous discs. - The tube feet are devoid of suckers. - They respire through Bursae. - The long arms are demarcated from the central disc. - Example: Brittle stars **Echinoidea** - The body is hemispherical. - The tube feet contain suckers. - The body does not have arms. - The body has a compact skeleton and movable spines. - Examples: Sand dollars, Sea urchins, Cake urchins & Heart urchins **Holothuroidea** - The body is long and cylindrical. - The arms, spines, and pedicellariae are absent. - They respire through the cloacal respiratory tree. - They possess tube feet with suckers. - Example: Sea cucumbers - The body is star shaped. - The tube feet have no suckers. - The arms are bifurcated. - Spines and pedicellariae are absent. - Example: Sea- lily