BLG 144 Chapter Notes - Chapter 33: Polysaccharide, External Fertilization, Body Plan
27 Dec 2017
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Molecular phylogenies support the hypothesis that protostomes are a monophyletic group divided into two major subgroups: the lophotrochozoa and the ecdysozoa. Key events triggered the diversification of protostomes, including several lineages making the water-to-land transition, a diversification in appendages and mouthparts, and the evolution of metamorphosis in both marine and terrestrial forms. In numbers of individuals and species richness, protostomes are the most abundant and diverse of all animals and the arthropods are by far the most abundant and diverse of the protostomes. Arthropoda insects, chelicerates (spiders and mites), crustaceans (shrimp, lobster, crabs) and myriapods (centipedes), Mollusca (snails, clams, chitons), and cephalopods (octopuses and squid). Most animals are protostomes (about 70% of earth are insects, most of them beetles. Humans and other vertebrates are deuterostomes in the phylum chordata. Two major groups of bilaterally symmetric, triploblastic, coelomate animals: the protostomes and deuterostomes.
