Animal Kingdom

Phylum Mollusca is the second largest animal phylum (Figure). Molluscs are terrestrial or aquatic (marine or fresh water) having an organ-system level of organization. They…

Phylum Arthropoda is the largest phylum of Animalia which includes insects. Over two-thirds of all named species on earth are arthropods (Figure). They have organ-system…

Phylum Annelida may be aquatic (marine and fresh water) or terrestrial: free-living, and sometimes parasitic. They exhibit the organ-system level of body organization and bilateral…

The body of the Aschelminthes is circular in cross-section, hence, the name roundworms (Figure). It can be free-living or parasitic. They may be free-living, aquatic…

Phylum Platyhelminthes have dorso-ventrally flattened body, hence are called flatworms (Figure). These are mostly endoparasites found in animals including human beings. Flatworms are bilaterally symmetrical.…

Phylum Ctenophora or Ctenophores commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organization. The…

Phylum Coelenterata are aquatic, mostly marine, sessile or free-swimming, radially symmetrical animals (Figure). The name cnidaria is derived from the cnidoblasts or cnidocytes (which contain the…

Members of phylum porifera are commonly known as sponges. They are generally marine and mostly asymmetrical animals (Figure). These are primitive multicellular animals and have cellular level…

Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals. Animals with notochord are called chordates and…

Diploblastic: Animals in which the cells are arranged in two embryonic layers, external ectoderm, and internal endoderm, are called diploblastic animals, for example, coelenterates. An…