Chapter 25 The History of Life on Earth

Chapter 25 The History of Life on Earth - Chapter 25: The...

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Chapter 25: The History of Life on Earth 25.5: Major changes in body form can result from changes in the sequences and regulation of developmental genes Evolutionary effects of developmental genes Changes in Rate and Timing - Many striking evolutionary transformations are the result of heterochrony, an evolutionary change in the rate or timing of developmental events o An organism’s shape in part depends on the relative growth rates of different body parts during development o It can also alter the timing of reproductive development relative to the development of nonreproductive organs Sexually mature individuals of a species may retain body features that were juvenile structures in an ancestral species – a condition called paedomorphosis Changes in Spatial Pattern - Substantial evolutionary changes can also result from alterations in genes that control the placement and spatial organization of body parts o Master regulatory genes called homeotic genes determine such basic features as where a pair of wings and a pair of legs will develop on a bird
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Chapter 25 The History of Life on Earth - Chapter 25: The...

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