Bio153_lecture13_Protostomes_sv - Protostome Animals...

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Protostome Animals Protostomes • Biologists estimate that there are > 10 million arthropod species • A hectare of pasture in England may contain 45 million beetles • In tropical rainforests, 40% of total mass of organisms are beetles and other insects • Ants: estimates are 1 million billion individuals • Mollusks: > 93,000 species Protostomes include some of the most familiar and abundant animals on Earth Protostomes: consumers, predators, and scavengers in many marine ecosystems The Relative Abundance of Animal Lineages Major protostome phyla Major non-protostome phyla Insects Other phyla Porifera Cnidaria Chordata Echinodermata Nematoda Ectoprocta Annelida Platyhelminthes Mollusca C h e l i c r a t s Arthropoda M y ia p o d u n Using the Fossil Record all of the protostome phyla appear very early in the history of animal evolution two major events occurred in the fossil record of protostomes: • extinction of the trilobites (250 mya) • appearance of insects
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Overview of Protostome Evolution 1. undergo spiral cleavage after fertilization - during gastrulation, the initial pore becomes the mouth - coelom arises when openings form within blocks of mesodermal tissue An Overview of Protostome Evolution 2. are bilaterally symmetrical - have 3 embryonic tissues - have a coelom: exceptions - 3. some exhibit segmentation; Annelids, Arthropods 4. monophyletic group Protostomes: A Monophyletic Group Comprising Two Major Lineages Protostomes A c o e lo m rp h a Lophotrochozoa Ecdysozoa Protostome development C te n p ra id ria P rife N to d R tife M l u s lid la ty lm in th O y r T ig ro E ta rd Bilateral symmetry Triploblasty Coelom Once the protosome pat ern of development had evolved, protostomes split into the lophotrochozoans and ecdysozoans There are 22 phyla of protostomes, but the eight major phyla shown account for about 99.5% of the known species 2 major subgroups exist within the protostomes 1. Lophotrochozoans grow by adding to body elements flatworms, rotifers, annelids, molluscs 2. Ecdysozoans grow by molting Protostomes: 2 main lineages:
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Bio153_lecture13_Protostomes_sv - Protostome Animals...

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