BIOL 204 Lecture 5: lecture 5
Document Summary
Ancestral and derived characters: ancestral (plesiomorphic); inherited from a ancient ancestor, evolved a long time ago, derived (apomorphic); evolved recently, both relative and depend on the taxon being discussed. Synapomorphies: synapomorphy: a derived character shared by 2 or more taxa, ex; notochord evolved in the common ancestor of all chordates- therefore notochord is a synapomorphy for chordates. Monophyletic groups: consists of an ancestor and all descendants. Chordate characters: vertebrates belong to phylum chordata, all chordates share 5 characters, dorsal hallow nerve cord, notochord, pharyngeal slits, post-anal tail, endostyle (homologous to the thyroid gland in vertebrates) In many vertebrates, it is functionally replaced by the vertebral column during development: useful for locomotion. Endostyle it is a groove filled with glandular tissue that produces mucus and processes iodine: arises from the ventral side of the pharynx during development, homologous to the thyroid gland of vertebrates, synapomorphy for chordates. Chordate characters: these 5 are all present at some developmental stage in chordates.
