NEET BIOLOGY

Detailed explanation-1: -Parazoa is the animal sub-kingdom that includes organisms of the phyla Porifera and Placozoa . Sponges are the most well-known parazoa. They are aquatic organisms classified under the phylum Porifera with about 15, 000 species worldwide.

Detailed explanation-2: -The simplest of all the invertebrates are the Parazoans, which include only the phylum Porifera: the sponges (Figure 4.3. 1). Parazoans (“beside animals”) do not display tissue-level organization, although they do have specialized cells that perform specific functions.

Detailed explanation-3: -Parazoa are animals whose body consists of loosely aggregated cells, e.g., Porifera.

Detailed explanation-4: -The phylum Porifera comprises the sponges. Sponges are simple invertebrate animals that live in aquatic habitats. Although the majority of sponges are marine, some species live in freshwater lakes and streams.

Detailed explanation-5: -The name is a reference to the porous nature of the sponge animal. The sponges are sessile, mostly upright filter-feeding animals (see Figures A and B). Although they are metazoans, they exist at the cellular grade of organization, and, as such, lack true tissues.