In arthropods, protostomatic type of body plan is present.

Phylum Platyhelminth (flatworm) has multicellular body. 

Pila has bilateral symmetry in which body can be divided into two halves by midsagittal plane.

Leucosolenia has ascon type of canal system. 

They are large cells which are specialised to secrete adhesive material for attachment.

It is the smallest nematoblast which has a smooth thread tube that helps in glutination.

Obelia shows alternation of sexual and asexual phases. The asexual phase is represented by colony, while the sexual phase is medusa. These phases alternate in the life cycle of Obelia. This alternation between sexual and asexual phases is called metagenesis.

Petrospongia is the connecting link between phylum Protozoa and phylum Porifera.

Taenia solium is a digenetic endoparasitic platyhelminth whose primary host is man and secondary host is pig.

It is the non-feeding larval stage of Fascicola hepatica or liver fluke.

It is a free-living, leaf-like flatworm with a very ligh power of regeneration. It belongs to class Turbulleria.

Choanocytes or collar cells are the characteristic cells of sponges.

Obelia is a polymorphic colonial marine coelentrate which occurs in shallow coastal waters and is also known as sea fur.

It is a pigment present in the body of earthworm which gives brown colour to its body.

It is a simple, gradual and direct metamorphosis in which immature forms resemble the adult, except in size, and are referred to as nymphs. Grasshoppers have paurometabolic type of metamorphosis.

Also known as Indian earthworm, it belongs to class Oligochaeta.

It is the class of fossil arthropods which lived during Cambrian to Permian periods in marine habitats.

Epitoky is a form of reproduction observed in polychaete marine worms.

It is a phylum of triploblastic haemocoelomic, segmented invertebrates having head, thorax and abdomen, a chitinous exoskeleton and jointed legs and appendages. This phylum is the largest phylum in animal kingdom with 11 lakh species.

Polynoe, also known as scale worm, is an example of bioluminescent annelids.