Marb 435 1st Edition Lecture 7Current Lecture: BilateriaReview 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. Biradial- two planes of symmetry (comb jellies)2. Tetramerous radial- body parts in multiples of 43. Hexamerous radial- body parts in multiples of 64. Octamerous radial- body parts in multiples of 85. Pentamerous radial- body parts in multiples of 56. Superficial radial symmetry- external radial symmetry but internal bilateral symmetry7. Secondary bilateral symmetry- bilateral symmetry superimposed on radial symmetry (sand dollar)8. Cephalization- formation of a head where the central nervous system is located9. Central nervous system- brain and longitudinal nerve cords are located here10. Cleavage- rapid sequence of cell division without growth leading from zygote to blastula11. Diploblastic- 2 germ layers12. Triploblastic- 3 germ layers (all bilaterians are triploblastic)13. Coelom- fluid filled body cavity that is completely lined by mesodermal epithelium14. 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 urineExcretion serves to maintain homeostasis by elimination excess substances such as water, salt and metabolic nitrogenous waste that is produced from protein metabolismMore on excretion will be continued on the next lecture after the test!Know the difference between the different variations on the
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