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Why Evolution is True Jerry Coyne Summary

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James Thomson

Chapter 1 – What is Evolution?  Paley argued that the existence of well adapted organisms was similar to the existence of a watch – there is a designer just as there is a watchmaker The theory of evolution: life in earth evolved gradually beginning with one primitive species that lived more than 3.5 billion years ago - it branched over time, resulting in new and diverse species; the mechanism for most of evolutionary change is natural selection - Evolution - Gradualism - Speciation - Common ancestry - Natural selection - Other mechanisms of evolutionary change Evolution  Species undergoes genetic change over time due to changes in the DNA, which originate as mutations  Theory does not predict that species will be constantly evolving or how fast they evolve Gradualism  Takes many generations to produce a substantial evolutionary change  Strong natural selection leads to fast evolutionary change – paces are dependent on evolutionary pressures Speciation  Speciation is the evolution of one species into two different groups that can‟t interbreed - Group was split, and over time, developed differences  The common ancestor “X” between species is called the missing link  Vast majority of species go extinct, others can live millions of years without speciation (gingko trees) Common Ancestry  Flip of speciation: all species trace back to a common ancestor. Those that are modernly more closely related have more recent common ancestors  Such nested arrangement only arrives with objects that have arisen from evolutionary processes  Nowadays, by comparing DNA, we see that species with similar DNA are more closely related (i.e. they have common ancestors that lived more recently Natural Selection  When there are differences in one species, „good genes‟ will lead to higher reproduction rates - Creates species that are best adapted for their habitats  Natural selection cannot produce from scratch – it can only alter what‟s already existent - Creates „fitter‟ not the „fittest‟  Because natural selection must work with organism as a whole, there are tradeoffs  New species are created by mutations of old species  Mutationism: new groups should arise instantly from old one, withou
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