BIOL 202 Lecture Notes - Lecture 14: Placodermi, Cloaca, Sperm Competition
4 Mar 2016
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Old name for bony fish: osteichthyes polyphyletic. Cyclids: subclasses have been raised to full classes. Why are bony fishes more successful than chondryicthyes: operculum is bony and strong, lung or swim bladder or both. Being used for buoyancy mainly rather than gas exchange: sarcopterygians have extremely muscular fins. Climate drier, land masses, fresh water basins, first seed plants: up until this time, everything was marine, now, we"re starting to get freshwater environment. Operculum: osteon in compact bone: osteocytes in lacunae arranged around osteonic canal, originated in primitive jawed fish too (acanthoidians, extinct) but not all ancestors retain it (e. g. ratfish) Have well-defined vertebral column, except jawless vertebrates (lampreys, hagfish have notochord instead) Jawed fish may have cartilaginous or bony vertebrae. All bony fish have operculum (ratfishes don"t) Ribs are important for sites of muscle attachment and projecting organs. Sacs changed location and became reduced to a single sac swim bladder.
