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Chapter 4

BCH447 lecture 8.docx

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University of Toronto St. George
Larry Moran

BCH447 lecture 8 We have parents and we have grandparents... And weve lost the memory of our great grand parents. If we go down far enough on our tree we have an exponential increase in the number of relatives... If we are caucasian one of our relatives is sharlaman. If asian blood... The they are related to atila the hun. At the year 700 we have a million ancestors. For africans its some other guy. Usually we dont draw backwards trees... We usually draw them forward from the past to now. So, atila the hun may be one of the ancestors... But so are a million other people. The history of life. We want to distinguish between genetics and taxonomy. Lineaus about 100 years ago started classifying things and he groupd similar organisms together, and he ended up with a classification system that looked a little like that of what we have today when we use genetics with some flaws. What linaeus was saying that because things look alike they are probably related. A problem with taxonomy is that cladism doesnt necessarily agree with this. Cladistics is the attempt to make taxonomy andthe genetic tree agree with each other. One of the problems we face is that for example we dont wanna be called apes even though we are in the ape category. They tried doingthis by seperating all of the organisms into three groups... Animals, plants, and protista for the small thingies... And they said that our three kingdoms have a common ancestor somewhere. This was huckel. As times arose different classification schemes arose. The five kingdoms is one of the most famous. We used to taxonomy and classify things into 5 major groups. That is, plants, animals, fungi, eukaryotes, protista and bacteria (monera). Cladists dont like this, because it makes it look as if everything arose from bacteria. The five kingdoms is the book for this.... Lin margulis... Animals were divided into 37 fila. Lin margulis ran the endosymbiotic theory. It is easy to classify protista and monera into fila.. But its difficult to show how those fila are related. Finally we reached our tree by looking at 16s ribosomal rna. They then came up with the three domain hypothesis. The assumption is that we have three domains from bacteria, bacteria, archaebacteria, and eukaryotes. We seperate everything into three monophyletic clades. The problem was that this tree greatly modified the five kingdom idea. All animals are just a twig of all the species today on the tree of life. So then they wanted to bring taxonomy into this new tree. Norman pace says there is a problem with the idea of a prokaryote. Prokaryotes does not refer to all the groups of organisms that share a common ancestor. Prokaryotes... Or bacteria are a paraphyletic clade, they are not a seperate taxonomic group. Therefore, they should not be treated as such. Procaryotes technically lump bacteria
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