Invertebrates are categorized into several phylogenetic groups based on their evolutionary relationships and body structures. The Lophotrochozoa, with nearly 139,000 species, include diverse organisms such as flatworms, molluscs, and segmented worms.
Example Organisms: Sea stars (Asterios forbesii) and Sea cucumbers (Parastichopus californicus)
Defined primarily by DNA similarities, not developmental similarities
Two main groups:Echinodermata and Chordata (three groups of chordata are invertebrates: they consist of lancelets, tunicates, and hagfishes), and includes hemichordata
About 59,085 species
Ecdysozoa
Example Organisms: Parasitic nematode (Trinchinella spiralis) and Fruit flies (Drosophila melanogaster)
They are the most species-rich animal group, proven by having more known species than all other protist, fungus, plant, and animal groups combined
Two main groups: Nematoda and Arthropoda, which includes loriciferans, priapulans, tardigrades, velvet worms, roundworms, insects, crustaceans, and arachnids
Nearly 1,030,000 species
Lophotrochozoa
They are a part of clades Eumetazoa and Bilateria
Example Organisms: Sea mat (Membranipora membranacea) and the Giant squid (Architeuthis dux)
Known and indentified by molecular data, that also has the most diverse animal clade in terms of body form
Six main groups: Platyhelminthes, Rotifera, Ectoprocta, Brachiopoda, Mollusca, and Annelida. These include flatworms, ectoprocts, rotifers, lamp shells, ribbon worms, molluscs, segmented worms, acanthocephalans, and cycliophoran
Nearly 139,00 species
Cnidaria
They are a part of clade Eumetazoa, but not Bilateria
Example Organism: Sea wasp (Chironex fleckeri)
They have radially symmtrical bodies
Includes corals, jellies, and hydras
10,000 species
Calcarea and Silicea
NOT a part of clade Eumetazoa or Bilateria because they do not have tissues
Example Organism: Azure vase sponge (Callyspongia plicifera)
They lack true tissues, but are still defined as animals
