Chapter 24 Natural Selection

Chapter 24 Natural Selection - Chapter 24: Evolution by...

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Unformatted text preview: Chapter 24: Evolution by natural selection 1 Evolution The theory of evolution has replaced the theory of special creation in science. The theory of special creation asserts that each species is a unique type, created by God. The theory of evolution asserts that species have changed through time ( evolved ). Does this mean that scientists dont believe in God? 1.1 Change through time * (pp. 484486) Fossils A fossil is a physical trace of an organism that lived in the past Fossils can be dated using (complicated) radiometric and geological techniques Fossils provide information about the history of life (see Chapter 27) The fossil record refers to the collection of all known fossils Extinction Many fossils have been left by organisms that are no longer around We say such organisms are extinct Extinction is one piece of evidence that species are changing 1 Transitional forms When a species disappears from the fossil record, a similar species often appears This often happens in the same geographic area Consistent with species evolving: changing through time Fig 24.4 Vestigial traits A vestigial trait is a structure that has no function, but is similar to functioning structures in related species Examples? Fig. 24.5 Directly observed evolution Although much evolution occurs very slowly, some kinds of evolution can be, and have been, observed on faster time scales Peppered moths Ground finches * (pp. 493495) 1.2 Relationships between species * (pp. 486489) If species evolved from a common ancestor, we expect to see evidence that they are related to each other Species fall naturally into groups Geographic patterns of relatedness Homology 2 Geographic relationships Species in the same geographic area (e.g., nearby islands) often seem to be closely related This is what we would expect if these species evolved independently, starting from a common ancestor in the region Support for the theory of evolution Fig. 24.6 Evolution and similarity In nature we observe many, often surprising, similarities between or- ganisms Almost identical developmental genes in fruit flies and people Similar limb bone structure in turtles and people...
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Chapter 24 Natural Selection - Chapter 24: Evolution by...

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