GENERAL HISTOLOGY

Detailed explanation-1: -The adult radial symmetry is pentamerous, with body parts occurring in fives or multiples of five. All echinoderms are marine and benthic. About 6000 extant species are known, but the fossil record includes about 13, 000 extinct species.

Detailed explanation-2: -Adaptations. Pentamerous Radial Symmetry. One characteristic of an echinoderm is that they all have pentamerous radial symmetry. This simply means they all have 5 equal body parts. You can divide these animals into five equal parts, and every part is the same.

Detailed explanation-3: -Today, Echinodermata is a diverse phylum, with numerous species in five classes: Asteroidea (star fish), Crinoidea (sea lilies and feather stars), Echinoidea (sea urchins and sand dollars), Holothuroidea (sea cucumbers), and Ophiuroidea (brittle stars).

Detailed explanation-4: -Although they may appear very different, echinoderms all have two major defining characteristics that set them apart from all other animals: a water vascular system and five-sided radial symmetry.

Detailed explanation-5: -Characteristics of Echinoderms Echinoderms are characterized by radial symmetry, several arms (5 or more, mostly grouped 2 left-1 middle-2 right) radiating from a central body (= pentamerous). The body actually consists of five equal segments, each containing a duplicate set of various internal organs.