NEET BIOLOGY

Detailed explanation-1: -Parazoa includes only Phylum Porifera. They have a cellular level of organization in which cells are not organized into tissues. Parazoa are animals whose body consists of loosely aggregated cells.

Detailed explanation-2: -In sponges, cells are arranged as loose cell aggregates.

Detailed explanation-3: -Loose aggregates are the phenomenon, in which, cells are dissociated and tend to ungroup themselves with cells of their own type. Loose cells can migrate easily, in contrast to epithelial cells. Example: Tumour cells of loose aggregation can move to other parts and reaggregate themselves and spreads cancer.

Detailed explanation-4: -Animals included in phylum Porifera are Parazoans because they do not show the formation of true tissues (except in class Hexactinellida). These organisms show very simple organization, with a rudimentary endoskeleton. Sponges have multiple cell types that are geared toward executing various metabolic functions.

Detailed explanation-5: -Although sponge is a multicellular animal but the cells do not function in coordination with each other. Most of the cells work independently. Thus, there is no division of labour; as seen in the tissue-level organization.