Chapter 7 _ Evolution and the Fossil Record

Chapter 7 _ Evolution and the Fossil Record - Chapter 7...

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Chapter 7 – Evolution and the Fossil Record Very little of what is known about life would make sense in any context other than that of organic evolution It is important to remember however that organic evolution doesn’t encompass every kind of biological change The term refers ONLY to changes in populations, which consists of groups and individuals that live together and belong to the same species Adaptations Each organism on our planet functions in its own particular circumstance o Ex) cats have evolved to have sharp fangs at the front of their mouths for killing prey and bladelike molars at the back to slice meat o Plants also differ in their ways of life depending on where they live These specialized features of animals and plants that perform one or more useful functions are known as ADAPTATIONS Each individual organism possessed many adaptations that function together to equip it for its particular way of life It is now widely acknowledged that the features now recognized as adaptations are not perfect and this comes mainly as a result of the species’ evolutionary heritage In other words, a species might develop a useful new feature with which to perform a function, but the evolution of the feature will sometimes be constrained by the structure of the ancestral organism The business of evolution is and always has been REMODELLING RATHER THAN NEW CONSTRUCTION Looking at teeth gives a good example of the fact that evolution is a remodeling process o The teeth of mammals serve difference functions in different species but the nonetheless have a common “ground plan” or fundamental biological architecture o Common ground plans suggest common origins, and they are one of the many pieces of evidence indicating that groups of species of the modern world have a common evolutionary heritage Charles Darwin’s Contribution Through his observations, Darwin became convinced of the workings of evolution Darwin was surprised to fins South America inhabited by animals that differed substantially from those in Europe, Asia, and Africa He found different species of birds as well as the sloth and armadillo species In south America Darwin began to dig up fossil remains of extinct giant relatives of the living forms and he wondered why all the south American birds and sloth
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and armadillo families were found nowhere but in the Americas He also found that different species lived on different sides of the Isthmus of Panama despite the fact that it is a rather narrow neck of land Darwin’s most striking observations concerned life forms on oceanic islands. He found that no small island situated more than 5000 kilometers from a continent or from a larder islands was inhabited by frogs, toads, or land mammals unless they had been introduced by humans o The only mammals native to such islands were bats which could originally have flown there o So this observation led Darwin to suspect that SPECIES COULD
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This note was uploaded on 12/05/2011 for the course BIO 211 taught by Professor Jessica during the Spring '11 term at University of Toronto.

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Chapter 7 _ Evolution and the Fossil Record - Chapter 7...

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