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slatkin9Answers - Bio 1B, Spring, 2007, Evolution section 1...

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Bio 1B, Spring, 2007, Evolution section 1 of 3 Updated 3/15/07 1:20 PM Lecture 9 9 Macroevolution. Reading; 7 th edition 482-488; 6 th edition 476-481. Microevolution to macroevolution A basic idea of Darwinism and neo-Darwinism is that macroevolution is the result of the accumulated effects of microevolution. Darwin’s discussion of the evolution of the vertebrate eye is still regarded as correct and representative of how complex characters evolve. Evolutionary novelties Most evolutionary novelties are greatly modified version of existing structures A few characteristics had to be true novelties. Early chordates, such as the lancelet, had no limbs. In an early lineage leading to fishes, the first proto-limbs appeared. Limbs in vertebrates are greatly modified versions of the first limb-like structures. The bones of the inner ear in mammals provide an example of a new structure that is derived from an existing structure in an ancestor. They are derived from parts of the jaw of species ancestral to mammals. Evolutionary novelties are often derived from repeated structures that become differentiated. Alismatales is a group of monocots thought to be ancestral to orchids. Alismatales flowers are radially symmetric. In contrast, petals of orchid flowers are extremely differentiated. Multigene families have evolved from a single ancestral gene. For example, α - and β -globin, which together form the hemoglobin molecule in mammals, are derived from an ancestral globin gene. So are other members of the globin gene family. Origin vs. maintenance One question about evolutionary novelties is whether the conditions that favor their maintenance are the same as the conditions that favored their origin. For the vertebrate eye, they probably did.
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This note was uploaded on 09/07/2008 for the course BIO 1B taught by Professor Carlson,mischel,power during the Spring '07 term at Berkeley.

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slatkin9Answers - Bio 1B, Spring, 2007, Evolution section 1...

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