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Biology Notes 4-7-08

Biology Notes 4-7-08 - Biology Notes April 7 2008...

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Biology Notes April 7, 2008 Protostome Animals There are 2 major groups: -Lophotrochozoans -Ecdysozoans What is a protostome? -Bilateria: triploblastic (all have mesoderm) -Two clades: protostomes and deuterostomes -protostomes: far more divers (millions of species), embryology is variable -In most the blastopore becomes the mouth -In some, spiral cleavage, and are determinate -Acoelomate, pseudocoelomate and eucoelomate Protostomes are bilaterally symmetrical -anterior brain that surrounds the digestive tract -ventral nervous system with paired or fused longitudinal nerve cords Modified Coeloms: Arthropods: lost coelom, the body cavity become a hemocoel or blood chamber -Mollusks: vestiges of a coelom, have an open circulatory system -Annelids: coelom, closed circulatory system Protostome Evolution: - Diverse feeding structures : allow species to take advantage of many food sources - Exoskeletons : evolved independently in many groups. Important for locomotion - Better locomotion : allowed prey to escape more easily, but also predators to
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Biology Notes 4-7-08 - Biology Notes April 7 2008...

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