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Phylum Arthropoda

Phylum Arthropoda - 4 pairs of legs(5 in horseshoe crabs No...

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Phylum Arthropoda -extremely diverse: conservative estimate: 1.5 million species -segmented body plan (tagma), -locomotion: extrinsic limb muscles, muscle inside body, limb is external and light -exoskeleton made of chitin -Tracheal system – quick respiration -image forming eye – compound eye – dozens and dozens of smaller eyes -extensive use of metamorphosis – different forms and goals of life -trilobytes – sister to all other arthopods - extinct -3 major groups -Chelicerata: horseshoe crabs, spiders, ticks, mites, scorpions, seas spiders 6 pairs cephalothoracic appendages, including chelicerae (mouthparts) One pair have become pedipalps
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Unformatted text preview: 4 pairs of legs (5 in horseshoe crabs) No antennae Feed by sucking liquid on prey-pycnogonida – sea spiders 300 species-body is small, legs make up for most of size-merostomata – horseshoe crabs 5 species – use to be very diverse, many extinct-400+ million years old, fossil record shows body plan-book gills-arachnida – spiders, scorpions, mites – 100000 species -light limbs, muscle in thorax fast movement -complex nervous system, distinct brain-ticks and mites are parasitic Picture of phylogeny on lecture 17 page 5 Spiders have 8 eyes Chiton on body as “hairs” Synapomorphies not important...
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