SQ's + answers-L17-18-Arthropod

SQ's + answers-L17-18-Arthropod - BIS 1B (Winter 2008)...

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BIS 1B (Winter 2008) Study questions: Arthropoda (lectures 17-18) 1. What are some similarities between arthropods and annelids? Which of these are synapomorphies (shared derived similarities)? Arthropods and annelids share the basic features of eucoelomate protostomes. They are bilaterally symmetrical and triploblastic; exhibit spiral cleavage (at least some arthropods); have a mouth arising from the blastopore; possess a true coelom that arises by schizocoely; have a complete gut and ventral nerve cord; etc. In addition arthropods and annelids are both segmented animals, and muscle and nervous structures are repeated in each segment. Moreover, they show teloblastic growth (segments added at growth area at posterior end of animal). It is unclear whether the features associated with segmentation are actual synapomorphies, and hence indicative of a sister-group relationship between Arthropoda and Annelida, or whether, as supported by the most recent data from DNA sequencing, annelids are instead more closely related to Mollusca (as indicated by both annelids and molluscs having a trochophore larva, for example). In the latter case, we would have to presume that segmentation
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This note was uploaded on 04/15/2008 for the course BIS 1b taught by Professor Kimsey during the Spring '08 term at UC Davis.

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SQ's + answers-L17-18-Arthropod - BIS 1B (Winter 2008)...

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