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Unformatted text preview: 6/13/11 1 millipedes centipedes insects crustaceans (the best…) trilobites (extinct) Phylum Arthropoda (“jointed-foot” animals) spiders ticks mites horseshoe “crabs” pycnogonids (“sea spiders”) scorpions “chelicerates” “myriapods” Most of animal diversity is made up of arthropods. Phylum Arthropoda • largest phylum of animals ( well over 1,000,000 species) • about 80% of all known animal species (see precious slide) • insects (subphylum Hexapoda) account for almost all arthropod species diversity • estimated to be 200 million insects alive for every human today • arthropod pests cause significant economic losses • found in all major environments: from the deep-sea to mountain tops • trilobites (extinct) represent the oldest known examples of arthropods coelomates bilaterial /triploblastic Characters shared with other phyla not unique to annelids and arthropods: annelid ancestor? • coelomate • triploblastic • protostomate • bilateral symmetry Evolutionary relationships between the arthropods and the other phyla uncertain and in flux… 6/13/11 2 Evolutionary relationships between the arthropods and the other phyla uncertain and in flux… 5 th ed.: Clade Panarthropoda = Arthropoda & 2 other phyla, Onychophora & Tardigrada (note: no Annelida here) Fig. 12.1 (5 th only) Among living non-arthropod forms, Phylum Onychophora (“velvet worms”) seem to be good candidates for the closest living relatives of arthropods (5 th ed. p. 231, 4 th ed. p. 268) - ~ 70 terrestrial, mostly tropical species (leaf litter); 500 MY-old fossils - numerous paired, UNJOINTED legs on each segment end in claws - soft outer cuticle is molted (i.e., ecdysozoan) - metameric nephridia, open circ. system with blood bathing organs within a HEMOCOEL (true coelom is reduced) ; anterior brain -respiratory TRACHAEL SYSTEM of tubes leading to surface pores for air (similar to insects); dioecious Phylum Tardigrada (“water bears”): 5 th ed. p. 231 4 th ed. p. 268 - sufficient developmental and phylogenetic info lacking - maybe possess a true coelom, but reduced & have primarily a HEMOCOEL? (need more developmental evidence) - if coelomate, enterocoelic (i.e., deuterostome?) - molecular evidence suggests affinity to arthropods (crustaceans, insects) (i.e., protostome?) Phylum Tardigrada “water bears” or “moss piglets” • > 900 species worldwide; all habitats, but mostly live in mosses & lichens- look like stumpy caterpillars • TEENY : 0.2-0.5 mm in length, about the size of a pencil dot; eutely • outer cuticle is molted (i.e., ecdysozoan) • dioecious, lay eggs • 4 pairs of UNJOINTED legs ending in claws ; • nervous system (brain, ventral nerve cord, metameric ganglia) • excretory system, complete digestive system • complex pharynx to pierce & suck small prey & plants • NO respiratory organs 6/13/11 3 Tardigrades are capable of cryptobiosis (“hidden life”) a tardigrade “tun” • they are capable of surviving:...
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This document was uploaded on 11/03/2011 for the course BSC2011L BSC2011L at FSU.

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arthropoda1Slides - 6/13/11 1 millipedes centipedes insects...

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