protostomes 2

Protostomes 2 - More eucoelomate protostomes(Annelids and Mollusks Porifera Cnidaria Platy Nematoda Arthropoda Annelida Mollusca helminthes Echino

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More eucoelomate protostomes ( Annelids and Mollusks ) Porifera Cnidaria Platy- Nematoda Arthropoda Annelida Mollusca Echino- Chordata helminthes dermata fundamental symmetry and number of germ layers development pattern the nature of the body cavity presence or absence of a body cavity Protostoma Deuterostoma Eucoelomates Pseudocoelomates other Bilateria Acoelomates Protistan ancestor Eumetazoa Parazoa Bilateria Radiata phylum Annelida (little rings; segmented worms) About 15,000 described species in most habitats (marine, freshwater, terrestrial; primarily free-living). Structurally diverse but all share several common features: Organ system level of organization, cephalization , bilateral symmetry; complete gut circulatory system (overcomes diffusion limitations) hydrostatic skeleton, circular and longitudinal muscles (good control of movement) -- nematodes have only longitudinal muscles and are restricted to a ‘thrashing’ motion. Segmentation , segments separated by septa (each segment has replicated functions such as nerve ganglia and excretory organs, but is coordinated with the rest of the animal). septum segments Coelom Gut, lined with mesoderm Functional attributes of annelid body plan: Segmentation, hydrostatic skeleton, nerve net, and bidirectional antagonistic muscles --> better movement control than in nematodes. • coelom permits internal storage of specialized organs. no cuticle , so vulnerable to water loss and restricted to aquatic and moist terrestrial habitats. phylum Annelida (little rings; segmented worms) Three major classes: Oligochaeta , mainly freshwater and moist terrestrial habitats (example: earthworms) • small setae (spines) in pairs in each segment • small and unspecialized head • Segments relatively undifferentiated Abundant, ecologically important, especially in soil. Generally hermaphroditic and egg-laying; hatchlings like miniature adults (no distinct larval stage). Gippsland giant earthworm (Australia) phylum Annelida (little rings; segmented worms)
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Polychaeta , mainly marine; very diverse structurally • well-developed head, often with elaborate feeding organs or tentacles. • parapodia (fleshy flaps or extensions) on each segment, as well as setae -- spines, often large (top view): Parapoida function in locomotion (swimming, crawling, burrowing) and gas exchange (large surface area) Feeding organs on head Parapodia with setae phylum Annelida (little rings; segmented worms) Polychaeta • Generally sexual • larval stage ( trochophore ) is charcteristic. Very different from adult; generally planktonic. Ecologically diverse: scavengers, predators, filter-feeders; some planktonic, others burrowing, others crawl around, some swim. mouth
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This note was uploaded on 04/17/2008 for the course BIO 005b taught by Professor Chappel during the Spring '07 term at UC Riverside.

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Protostomes 2 - More eucoelomate protostomes(Annelids and Mollusks Porifera Cnidaria Platy Nematoda Arthropoda Annelida Mollusca helminthes Echino

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