BIOLOGY 152 Lecture Notes - Lecture 9: Hox Gene, Reproductive Isolation, Synapomorphy
1 Mar 2017
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Document Summary
Post zygotic isolating mechanisms when horses and donkeys make a mule it increases reproductive isolation barrier between the two species. Phylogeny- hypothesis about the evolutionary relationships among taxa. Branch length may not scale to time but it usually means time. Derived characters shared by a group of species (a taxon) = synapomorphies. The origin of tetrapods from finned precursors seems an almost insurmountable transition between life in water and life on land. What darwin never knew- fish was the ancestor of all limbed creatures. Depending on how genetic shifts are changes on and off. Homology- (morphological changes = structural homology) similarity between species due to shared ancestry. Species are similar because they inherited a trait from a shared ancestor hox genes- encode transcription factors that regulate other genes during early development. Confer segment identity along the anterior-posterior axis of an animal.
