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Nematoda and Annelida

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Biology (Sci)
BIOL 111
Irene Gregory- Eaves

13/10/11 Development of digestive tract enables: 1. specialization of gut regions 2. sequential food processing 3. continuous operation (multiple tasks at once) Gastrulation occurs = development of gut cavity  Blastopore forms then second opening forms 1. Protostomes (1 is mouth) a. blastore  mouth b. new opening  anus 2. Deuterostomes (2 is mouth) a. Blastopore anus b. New opening  mouth Protostomes: 1. Lophotrocozoans: have one of the characteristics: - lophophore: ciliated feeding/gas exhange structure - trocophore: ciliated free living larval form - unsure about rise of these two forms, perhaps common ancestor had both and some lost one 2. Exdysozoans: - have external covering secreted by epidermis that must be shed in order for animal to grow Presence /type of body cavities (coelom) differentiate protostomes: 1. Pcoelomate: no coelom, solid digestive space (ex. Flat worms) a. mesenchyme: unspecialized cells derived from mesoderm 2. Pseudoceloemate: false coelom (ex nematodes) a. mesoderm lines the outside of coelom 3. Coelomate a. Mesoderm lines entire cavity (peritoneum) i. Lining derived from mesoderm 2 ways to make a coelom: 1. Schizocoely: a. Splitting within the mesoderm  form ceolom b. In protostomes 2. Enterocoely: a. Mesoderm forms pochets from guy b. In deuterostomes Phylum nematoda: Roundworms - Blunt anterior end/tapered posterior end - Ecdysozoans – diffusion of gas across thin flexible cuticle o Live in moist habitats to help with diffusion of gases across 13/10/11 - Pseudocelomates - Longitudinal muscles – move by thrashing - Bilaterally symmetrical - Triploblastic - Fluid filled body cavity = hydrostatic skeleton - No respiratory system - Completely digestive tract - No circulatory system – gas exchange happens within ceolom - Extremely abundant - Terrestrial or aquatic - Free living (scavengers, predatory) or parasitic Ex. C. Elegans: white rat of geneticists and developmental biologist because they have exactly 905 cells  able to track cells through development Part of soil food web: Root feeder on bacteria/fungi, predators, or predated upon Most are scavengers/predator, but some are parasitic: - Parasitize protists, plants and animals: ex. On soy plants, dealt with by not planting soy… - 50 parasitize humans: o hook worm in topic/subtropics:  in bad water (in rice patty for example), travelling through vascular system to lungs, up trachea in esophagus into gut where it eats red blood cells - largest nematode 9m on placenta of sperm whales Annelida: segmented worms ~ 16500 species - Terrestrial (in moi
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