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The phylum Porifera is further divided into classes mainly according to the composition of their skeletons: [17] [29] Hexactinellida (glass sponges) have silicate spicules, the largest of which have six rays and may be individual or fused. [17] The main components of their bodies are syncytia in which large numbers of cell share a single ...
Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include greater than 90% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). [5] They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite [citation ...
Parazoa (Parazoa, gr. Παρα-, para, "next to", and ζωα, zoa, "animals") are a taxon with sub-kingdom category that is located at the base of the phylogenetic tree of the animal kingdom in opposition to the sub-kingdom Eumetazoa; they group together the most primitive forms, characterized by not having proper tissues or that, in any case, these tissues are only partially differentiated.
The calcareous sponges [2] [3] (class Calcarea) are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate, in the form of high-magnesium calcite or aragonite. While the spicules in most species are triradiate (with three points in a single plane), some species may possess two ...
Bolosoma stalked glass sponge. Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges.They are usually classified along with other sponges in the phylum Porifera, but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma.
The definition was posited because extinct organisms are hardest to classify: they can be offshoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired. By Budd and Jensen's definition, a phylum is defined by a set of characters shared by all its living representatives.
They are sessile organisms, attaching themselves to hard substrate like rocks, logs and sometimes to ground. [3] Using their ostia and osculum these sponges filter the water for various small aquatic organisms such as protozoans , bacteria , and other free-floating pond life . [ 4 ]
As members of the oldest phylum of metazoans, Suberites serve as model organisms to elucidate features of the earliest animals. [2] [3] [4] Suberites and their relatives are used to determine the structure of the first metazoans [2] and have been studied to determine how totipotency has replaced by pluripotency in most higher animals. [5]