Marb 435 1st Edition Lecture 7 Current Lecture Bilateria Review on symmetry Sponges are metazoans with no symmetry and they have no axis or plane of symmetry Jellyfish have radial symmetry and they have multiples planes of symmetry that intersect at the oral aboral axis Bilateral animals such as flat worms have Bilateral symmetry they have a single plane of symmetry known as a midsagittal plane that transects the animal from anterior to posterior and dorsal to ventral Terms to know 1 2 3 4 5 6 7 Biradial two planes of symmetry comb jellies Tetramerous radial body parts in multiples of 4 Hexamerous radial body parts in multiples of 6 Octamerous radial body parts in multiples of 8 Pentamerous radial body parts in multiples of 5 Superficial radial symmetry external radial symmetry but internal bilateral symmetry Secondary bilateral symmetry bilateral symmetry superimposed on radial symmetry sand dollar 8 Cephalization formation of a head where the central nervous system is located 9 Central nervous system brain and longitudinal nerve cords are located here 10 Cleavage rapid sequence of cell division without growth leading from zygote to blastula 11 Diploblastic 2 germ layers 12 Triploblastic 3 germ layers all bilaterians are triploblastic 13 Coelom fluid filled body cavity that is completely lined by mesodermal epithelium 14 Pseudocoelom fluid filled body cavity that is not completely lined by mesodermal tissue Coelomates have a true coelom examples are segmented worms Pseudocoelomates partially lined coelom but does not count as a true coelom nematoeds or round worms Acoelomates no extra body cavity only the digestive tract No coelom at all flat worms These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Coelom Functions Suspension of internal organs Hydrostatic skeleton Storage of gametes nutrients and waste products Filtration and storage of primary urine Excretion serves to maintain homeostasis by elimination excess substances such as water salt and metabolic nitrogenous waste that is produced from protein metabolism More on excretion will be continued on the next lecture after the test Know the difference between the different variations on the coelom
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