BIO1011 Lecture Notes - Lecture 16: Trachea, Arthropod, Body Plan
10 Aug 2018
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Bio1011 lecture 16 animal diversity 2 - contiuned. Phylum annelida (segmented worms: bilateral symmetry, triploblastic, coelomates. Segmented body: series of rings, habitats, soil, marine, freshwater, moist forests. Annelids are coelomates: true coelom, mesoderm lines all sides of coelom. Annelid anatomy: cephalisation (cid:862)brain(cid:863, closed circulatory system, complex digestive system. Annelid locomotion: each segment is a compartment of coelomic fluid, two muscle groups act on hydrostatic skeleton, contraction of circular muscle lengthens segment, contraction of longitudinal muscle shortens segment. Ecdysozoa phylum nematoda (roundworms: bilateral symmetry, triploblastic, pseudocoelomates, habitats: soil freshwater. Nematodes are pseudocoelomates: triploblastic, ectoderm: secretes tough cuticle, mesoderm: various organs, endoderm: through gut, pseudocoelom, mesoderm lines only the outer wall of body cavity, digestive system, one-way: mouth to anus, muscular pharynx. Nematodes have a tough exoskeleton: cuticle, tough and flexible, requires moulting to grow, coelomic fluid under pressure, most nematodes are small, organ systems, no circulatory system, no excretory system, no respiratory system.
