Phylum Echinodermata - General Characters and Classification скачать в хорошем качестве

Phylum Echinodermata - General Characters and Classification

Echinoderms are exclusively marine animals and cosmopolitan in distribution. They are spiny skinned animals and named by Jacob Klein. Echinodermata was first recognized as a distinct group by Leuckart and Frey in 1854. Typically bottom dwellers and sluggish in nature and few are stalked and sedentary. All are free living and none of them are parasitic. Possess a special organ system all 'Water vascular system or Ambulacral system' meant for locomotion, food capturing, transportation of food and respiration. This system is a modified coelomic portion. They show a special type of symmetry - Bilateral symmetry during larval stage and Radial symmetry (Pentamerous) during adult stage. They are non-chordate deuterostomes and enterocoelomates unlike other non-chordates. Reduced circulatory system and primitive nervous system. Hypothetical 'Dipleurula larva' is regarded as ancestor of all echinoderms. Regeneration is well marked and some show autotomy or self amputation of body parts for protecting themselves from predators and later regenerate lost parts. A five jawed masticatory apparatus called 'Aristotle's Lantern' is present in the mouth of some species (Echinoids).