Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum Echinodermata, characterized by a hard, spiny covering or skin. Which of the following statements best describes symmetry in echinoderms? They have free-swimming, bilateral larvae that metamorphose (change as they mature) into adults with radial symmetry. MULTIPLE CHOICE. Echinoderms have a mouth surrounded by a central disc leading outward to the grooves having rows of podia. Sea urchins and sand dollars belong to which of the following classes? D) LARVAE have radial symmetry. Although echinoderm adults have radial symmetry, they evolved from ancestors that were bilaterally symmetrical. Members of the phylum This … Echinoderms have a unique water vascular system with tube feet. They can be found in the ocean from the equator to the poles. CIRCLE ALL THAT ARE TRUE. Echinoderms are marine invertebrates. They have radial symmetry as adults but bilateral symmetry as larvae. They include sea stars, sand dollars, and feather stars. During embryonic development of starfish and sea urchins, the position and the … Free-swimming larvae have bilateral symmetry, while the adult form is pentaradially symmetrical. Echinoderms are marine organisms that make up the phylum Echinodermata. The larva in echinoderms is bilaterally symmetrical, which later converts to radial symmetry in adult form. Pentameral symmetry is the major form and the other forms are derived from it. Echinoidea. This type of symmetry is what makes scientists believe that echinoderms posses a bilateral developmental mechanism. Echinoderms take many forms of symmetry. (Ji, 2012) Living species include sea lilies, sea urchins, sea cucumbers, starfishes, basket stars, and sea daisies. Echinoderm Definition. 2) Echinoderms are the only _____ A) invertebrate protostomes A) ADULTS have bilateral symmetry. They have a spiny endoskeleton. However, the ancestors of echinoderms, which originated from Cambrian period, were believed to be bilaterians. Echinoderm larvae are bilateral during their early development. The fact that the larvae are bilateral strongly suggests that radial symmetry in adult echinoderms is secondary (i.e. symmetry is secondary; echinoderms begin as bilateral free-swimming larvae and become radial at the time of metamorphosis. The echinoderm ancestry later developed radial symmetry as it was thought to be more advantageous to the species. that echinoderms evolved from a bilaterally symmetrical ancestor). The adult body usually has five-part organization. Learn more about echinoderms. Generalized dipleurula larva of echinoderm (upper left) There may be MORE THAN ONE correct answer. The first picture below shows an echinoderm larvae and the bilateral symmetry is clearly shown. They are among the most distinctive organisms within the animal kingdom.Members of the phylum include sea stars (starfish), sand dollars, and feather stars, shown in … As the animal develops and the hox gene cluster begins to be expressed, the asteroid begins to take change from bilateral, to radial symmetry. Also, in one echinoderm group, the sea cucumbers, partial bilateral symmetry is retained in the adult stages -- sea cucumbers are somewhat worm–like. There are 6,000 species of echinoderms; they are all marine. B) LARVAE have bilateral symmetry C) ADULTS have radial symmetry. 1) Which of the following is true about symmetry in ECHINODERMS? In the early stages of development, echinoderm larvae are bilateral. The bilateral symmetry can still be seen in the larvae of echinoderms but once they reach adulthood, they develop radial symmetry. Echinoderms. There are roughly 6000 living species of echinoderms. 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