Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Charles Darwin and The Origin of Species Jean Baptiste Lamarck argued that fossils were relics of the ancestors of modern species. Lamarck believed that organisms acquired new traits over their lifetimes and then passed them on to their offspring. He called this the inheritance of acquired characteristics.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Charles Darwin and The Origin of Species Darwin argued that evolution—heritable changes in organisms over time— explained the origin of all organisms on Earth.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Darwin was inspired by: His travels on the Beagle. The work of geologist Charles Lyell The work of economist Thomas Malthus

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Darwin’s Galápagos Island finches were significant because they provided what appeared to be an example of how a single species could evolve into multiple species, each adapted to a different lifestyle. The 13 species of finches he found varied in beak size and shape, depending on their diet.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley How Natural Selection Works In any population, individuals have traits, many of which show variation. Traits that are determined by genes are heritable. Advantageous traits benefit an organism and allow it to leave more offspring—this is natural selection. Advantageous traits become more common in a population, resulting in adaptation.

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How Natural Selection Works Adaptations are traits that make an organism better suited to living in and reproducing in its environment. Many adaptations help organisms survive. Some adaptations help organisms attract mates— this is called sexual selection. Other adaptations relate to bearing and raising offspring.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Natural Selection How Natural Selection Works

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Animal Adaptations to Heat and Cold Animals thermoregulate: Surface-to-volume ratio is an important factor in heat balance. Bergmann’s Rule says that animals found in cold habitats are often larger than related forms in warm habitats. Allen’s Rule states that appendages will be longer/larger in hot-climate animals and shorter/smaller in cold-climate animals.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Animals also control body temperature with: Coloration Insulation

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Natural selection is classified into three modes: Directional selection Stabilizing selection Diversifying selection

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley The Modern Synthesis incorporates modern genetics into Darwin’s theory of evolution. It focuses on evolution as changes in the allele frequencies of genes over time.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Four different mechanisms produce evolution: Natural selection Mutation pressure Genetic drift Migration

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley How Species Form A species is a group of organisms whose members can interbreed with each other but not with members of other species. The key to speciation—the development of new species—is the evolution of reproductive barriers that prevent two groups of organisms from interbreeding.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley How Species Form There are two kinds of reproductive barriers: Prezygotic reproductive barriers prevent members of different species from mating in the first place or prevent fertilization from occurring. Postzygotic reproductive barriers prevent hybrids from surviving or from reproducing if they do survive.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Is a mule an example of a prezygotic reproductive barrier or a postzygotic reproductive barrier? Explain your answer to your neighbor. How Species Form CHECK YOUR NEIGHBOR

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley A mule provides an example of a postzygotic reproductive barrier. It is the hybrid offspring of two different species, a horse and a donkey. Mules are sterile and cannot reproduce. How Species Form CHECK YOUR ANSWER

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley How Species Form New species may develop as a result of: Allopatric speciation (geographic barriers dividing a population in two) Sympatric speciation (speciation without a geographic barrier). Examples: hybridization and chromosomal changes, such as polyploidy.

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Speciation Animation Animation II

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Evidence of Evolution Evidence for evolution includes: Natural selection in action Human-imposed artificial selection (e.g., domesticated animals and plants) Shared anatomy, patterns of development, and DNA among living creatures The fossil record Biogeography

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Artificial Selection

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Evidence of Evolution

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Evidence of Evolution

Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Does Evolution Occur Gradually or in Spurts? Gould and Eldredge proposed the theory of punctuated equilibrium—species maintain stability (“equilibrium”) for long periods and then evolve in rapid bouts (“punctuated”) that occur during speciation.

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