Chapter 23

Chapter 23 - Please, Turn Your Cell Phones OFF Now. Thanks!...

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Unformatted text preview: Please, Turn Your Cell Phones OFF Now. Thanks! Cell Phone Policy Laptop Policy Name Signs Drop with a W deadline today Study Questions posted under Course Documents Handouts, Notes, Study Questions, etc. Chapter 43 Things to keep in mind. Which of the following statements about evolution is (are) CORRECT? A. Over time species get larger, more complex, or better in some sense. B. Individual organisms evolve when natural selection occurs. C. Individuals with high levels of fitness are stronger or bigger or more dominant. A. A. and C. B. None of the above. KEY CONCEPTS Natural selection occurs when individuals with certain alleles (and with the traits those alleles determine) produce the most offspring in a population. At the level of genes, Evolution = changes in allele frequencies in a population over time . Evolution by Natural Selection Jointly proposed by Charles Darwin and Alfred Russel Wallace in 1858 Pattern vs. Process The Pattern of Evolution: Have Species Changed through Time? Darwin described the pattern of evolution as descent with modification , Change over time produced modern species from ancestral species. Evidence for Change through Time Fossils are traces of organisms that lived in the past Those that have been found and described in the scientific literature make up the fossil record . Most fossils are found in sedimentary rocks (rocks that form in layers from sand, mud, or other materials deposited at locations such as beaches or river mouths) Researchers use radioactive isotopes to assign absolute ages to the geologic time scale ( see Chap 2 ). Geologic data show that Earth is about 4.6 billion years old, and fossil data show the earliest signs of life in rocks about 3.85 billion years old. Species have gone extinct __________ A. in a few catastrophic events. B. in one catastrophic event. C. throughout Earths history. Extinction Many fossils provide evidence for extinct species unlike any known living organisms. Traditional concept (special creation): All species were created independently, each had its appointed role; both species and their environment were static . Extinction was not envisioned. It was expected that living examples of fossils would eventually be found somewhere in the world. Cuvier (1812): Analysis of Irish elk fossil showed it was an enormous deer. Too large to have been missed by explorers. Too distinctive to be considered simply a larger version of a living species. Extinct species were impossible to reconcile with the view that the Earth was static and that life forms were immutable. Darwin interpreted extinction as evidence that species are dynamic and can change. Please, Turn Your Cell Phones OFF Now....
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This note was uploaded on 04/07/2008 for the course BIOL 100 taught by Professor Staff during the Fall '07 term at UMBC.

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Chapter 23 - Please, Turn Your Cell Phones OFF Now. Thanks!...

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