lecture 2

14 human cat whale bat molecular homologies biologists

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Unformatted text preview: s among organisms •  Morphological •  Genetic –  Biogeography –  The fossil record 8 9/30/12 Homology •  Homology –  Is similarity resulting from common ancestry Anatomical Homologies •  Homologous structures between organisms –  Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor Figure 22.14 Human Cat Whale Bat Molecular Homologies •  Biologists also observe homologies among organisms at the molecular level –  Such as genes that are shared among organisms inherited from a common ancestor 9 9/30/12 •  Anatomical resemblances among species –  Are generally reflected in their molecules, their genes, and their gene products Species Percent of Amino Acids That Are Iden8cal to the Amino Acids in a Human Hemoglobin Polypep8de 100% Human Rhesus monkey 95% Mouse 87% Chicken 69% Frog Figure 22.16 Lamprey 54% 14% The uniformity of the genetic code •  Is another example of homology •  One of the most convincing pieces of evidence that all life on earth has a common ancestor Homologies and the Tree of Life •  The Darwinian concept of an evolutionary tree of life –  Can explain the homologies that researchers have observed 10 9/30/12 Biogeography •  Is the study of the geographic distribution of species –  Formed an important part of his theory of evolution –  Explains why related species may today be found in disconnected places (with plate tectonics) •  For example marsupials in S. America and Australia •  Some similar mammals that have adapted to similar environments –  Have evolved independently from different ancestors –  This is called convergent evolution the opposite...
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This note was uploaded on 02/06/2014 for the course BILD 3 taught by Professor Wills during the Fall '07 term at UCSD.

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