Brent Cornell

    
The kingdom Animalia can be sub-divided into two main groups – invertebrates (no backbone) and vertebrates (most chordata)

• Examples of invertebrate phyla include porifera, cnidaria, platyhelmintha, annelida, mollusca and arthropoda
• All vertebrates belong to the phylum chordata – however not all chordata are vertebrates (e.g. invertebrate sea squirts)
• These phyla can be differentiated according to a few key recognition features

Porifera

• No body symmetry (asymmetrical)
• No mouth or anus (have pores to facilitate the circulation of material)
• May have silica or calcium carbonate based spicules for structural support
• Examples include sea sponges

Cnidaria

• Have radial symmetry
• Have a mouth but no anus (single entrance body cavity)
• May have tentacles with stinging cells for capturing and disabling prey
• Examples include jellyfish, sea anemones and coral

Platyhelmintha

• Have bilateral symmetry
• Have a mouth but no anus (single entrance body cavity)
• Have a flattened body shape to increase SA:Vol ratio and may be parasitic
• Examples include tapeworms and planaria

Annelida

• Have bilateral symmetry
• Have a separate mouth and anus
• Body composed of ringed segments with specialisation of segments
• Examples include earthworms and leeches

Mollusca

• Have bilaterial symmetry
• Have a separate mouth and anus
• Body composed of a visceral mass, a muscular foot and a mantle (may produce shell)
• Examples include snails, slugs, octopi, squid and bivalves (e.g. clams)

Arthropoda

• Have bilateral symmetry
• Have a separate mouth and anus
• Have jointed body sections / appendages and have a hard exoskeleton (chitin)
• Examples include insects, crustaceans, spiders, scorpions and centipedes

Chordata

• Have bilateral symmetry
• Have a separate mouth and anus
• Have a notochord and a hollow, dorsal nerve tube for at least some period of their life cycle
• Examples include mammals, birds, reptiles, amphibians and fish (also invertebrate sea squirts)

Invertebrate Phyla Recognition Features:

Overview of Invertebrate Phyla