Wiens-lecture 8-12April

Wiens-lecture 8-12April - Todays Lecture Phylogeny and...

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Today’s Lecture • Phylogeny and diversity of lophotrochozoans
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Phylogeny of animals Friday Today Wednesday Friday April 19–28
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How do protostomes and deuterostomes differ? • Protostomes: blastopore forms mouth, not anus • Some protostomes have spiral cleavage • Protostomes have coelom derived from mesoderm, not endoderm
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What other traits do protostomes share? • Anterior brain • Ventral nervous system (paired, longitudinal nerve cords)
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Phylogeny of Protostomes
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Lophotrochozans vs. ecdysozoans Many lophotrochozoans share: • Lophophore : organ for food collection and gas exchange; ridge around mouth with rows of tentacles
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Lophotrochozans vs. ecdysozoans Many lophotrochozoans share: • Trochozoan larvae : has bands of cilia for locomotion
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Lophotrochozans vs. ecdysozoans Many lophotrochozoans share: • Spiral cleavage : as opposed to radial cleavage • Occurs in flatworms, ribbon worms, annelids, mollusks, and others
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Phylogeny of Lophotrochozoans
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Ectoprocts (or Bryozoans) • Around 4,500 species • Colonial, marine (mostly) • Colony of small individuals (1-2 mm) up to around 2 million individuals per colony, connected by tissue; reproduce asexually
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Phylogeny of Lophotrochozoans
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Ribbon worms (Nemertea) • Around 1,000 species; mostly marine, some freshwater, terrestrial • Most < 20 cm, but some > 30 meters • Complete digestive tract (mouth to anus) • No respiratory system (oxygen diffuses through skin)
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Phylogeny of Lophotrochozoans
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Rotifers • Around 1,800 species; mostly freshwater • Microscopic size (50–500 micrometers long); complete gut (mouth to anus); move by beating cilia • Have head with “corona” crowned with cilia; moves food into “mastax” where it is ground up
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Rotifers • Some groups have sexual reproduction, but others are asexual • Bdelloid rotifers are ancient group with only females;
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Wiens-lecture 8-12April - Todays Lecture Phylogeny and...

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