pentaradial symmetry

Examples of pentaradial symmetry in the following topics:

• Phylum Echinodermata

  • Echinoderms are invertebrates that have pentaradial symmetry, a spiny skin, a water vascular system, and a simple nervous system.
  • Adult echinoderms exhibit pentaradial symmetry and have a calcareous endoskeleton made of ossicles, although the early larval stages of all echinoderms have bilateral symmetry .
  • The ring canal connects the radial canals (there are five in a pentaradial animal), and the radial canals move water into the ampullae, which have tube feet through which the water moves.

• Classes of Echinoderms

  • Of all echinoderms, the Ophiuroidea may have the strongest tendency toward 5-segment radial (pentaradial) symmetry.
  • Their early larvae have bilateral symmetry, but they develop fivefold symmetry as they mature.
  • Several sea urchins, however, including the sand dollars, are oval in shape, with distinct front and rear ends, giving them a degree of bilateral symmetry.
  • Although the basic echinoderm pattern of fivefold symmetry can be recognized, most crinoids have many more than five arms.
  • Sea cucumbers are the only echinoderms that demonstrate "functional" bilateral symmetry as adults, as they lie horizontally as opposed to the vertical axis of other echinoderms.

• Characteristics of Vertebrates

  • Animals that possess bilateral symmetry can be divided into two groups, protostomes and deuterostomes, based on their patterns of embryonic development.
  • Echinoderms are invertebrate marine animals that have pentaradial symmetry and a spiny body covering; the phylum includes sea stars, sea urchins, and sea cucumbers.

• Animal Characterization Based on Body Symmetry

  • Animals can be classified by three types of body plan symmetry: radial symmetry, bilateral symmetry, and asymmetry.
  • In contrast to radial symmetry, which is best suited for stationary or limited-motion lifestyles, bilateral symmetry allows for streamlined and directional motion.
  • Animals in the phylum Echinodermata (such as sea stars, sand dollars, and sea urchins) display radial symmetry as adults, but their larval stages exhibit bilateral symmetry .
  • This is termed secondary radial symmetry.
  • The larvae of echinoderms (sea stars, sand dollars, and sea urchins) have bilateral symmetry as larvae, but develop radial symmetry as full adults.

• Body Plans

  • Animal body plans follow set patterns related to symmetry.
  • Asymmetrical animals are those with no pattern or symmetry, such as a sponge.
  • Bilateral symmetry is illustrated in a goat.
  • Animals exhibit different types of body symmetry.
  • The sponge is asymmetrical, the sea anemone has radial symmetry, and the goat has bilateral symmetry.

• Vertebrate Axis Formation

  • Mutations in these genes leads to the loss of symmetry required for organism development.
  • Animal bodies have three axes for symmetry: anterior/posterior (front/behind), dorsal/ventral (back/belly), and lateral/medial (side/middle).

• Establishing Body Axes during Development

  • Animal bodies have three axes for symmetry (lateral-medial, dorsal-ventral and anterior-posterior) which are established in development.
  • Mutations in these genes leads to the loss of symmetry required for organism development.
  • Animal bodies have externally visible symmetry.

• Phylum Porifera

  • Sponges lack true tissues, have no body symmetry, and are sessile; types are classified based on presence and composition of spicules.
  • Therefore, sponges lack true tissues and organs; in addition, they have no body symmetry.

• Superphylum Lophotrochozoa

  • Species in this group have bilateral symmetry.

• Rhizaria

  • A second subtype of Rhizaria, the radiolarians, exhibit intricate exteriors of glassy silica with radial or bilateral symmetry .