BIOLOGY 280 Lecture : Phylogeny Continued 1030.docx
Document Summary
Review session monday the 4th 8pm in here. Changes in the number of repeated parts - meristic variation. Series of reiterated parts: what/how it happened. Hox genes: increase in complexity in body plan, from sponges to more complicated organisms the what . Increased number of hox = increased complexity in body plan! Increased # of hox genes does not = species diversity. Bony fishes most diverse, lots of hox genes, but athropods have a fraction of those hox genes and there are 10"s of millions of arthropods. Evolutionary diversification within phyla occurred within the context of shared genetic machinery. Changes in when and where genes are turned on: i. e. , variation in gene expression. Not differences in # of genes, but when and where the genes are turned on over development, which hox genes are expressed in which segments, segment identity ~ increase diversity.
