Question

Define the phyletic characteristics of the Echinodermata. How are these bizarre
diagnostic characteristics developmentally related to the bilateral larval form of the
phylum? (Address the evolutionary advantage of this radial morphological organization in
the Crinoidea and the basic difference of how oral surface podia of the water
vascular system are used in the primitive Crinoidea vs more recent starfish of the
Asteroidea.)

Answer 1

the echinodermata are marine animals. larval forms are of bilateral symmetry. when developed into adults they show radial symmetry. they are triploblastic animals. organ system grade of organizations are present . thee bodies are uniquely shaped. adult Echinodermatas have water vascular System with external tube feet. a mesh of collagen Fibres are connected to ossicles. the larval forms of echinoderms lose the symmetry during metamorphosis. usually it is bilateral symmetry. development of these larval forms is supported by lecithotrophy. these forms have no functional gut and simple pattern of ciliation. this. these affect the further development of the larval form. the radial symmetry of has many advantages. they help the organism to regenerate their body parts easily. the Organism with radial symmetry can put pressure on the predators. these features help to balance the number of individuals in a population and thereby good Reproduction. the treats from all sides can be seen and can grab food from any side. the water vascular system of starfish consists of numerous tube feets and Crinoidea consists limited tube feets. the asteroidea has mouth on the bottom side of the body and the Crinoidea has mouth is situated on the top of the body.