Journal #3- Darwin described natural selection in his book, On the Origin of Species, in the following way: “I have called this principle by which each slight variation, if useful, is preserved, by the name Natural Selection.” -What did Darwin mean by the terms variation and preserved? *Illustrate: Adaptation, Survival of the Fittest, and Natural Selection

15-3 Darwin Presents His Case (Interactive 378-386)

Darwin's Findings The Galapagos “mockingbirds” were actually 3 different species found nowhere else The brown birds were all finches. (Darwin thought they were wrens, warblers, and blackbirds) The island animals found on the Galapagos looked a lot like the ones found on the South American Mainland, but were different species

Publication of On the Origin of Species Darwin waited over 20 years to publish his findings 1858 Alfred Russel Wallace wrote a short essay on Evolutionary change 1859 Darwin published On the Origin of Species Explained how evolution occurs through natural selection Very controversial at the time/ Now???

Inherited Variation & Artificial Selection Heritable or Genetic variation is used to improve crops or livestock Artificial Selection Nature provides the variation Humans select those that are useful to produce

Evolution by Natural Selection Struggle for Existence High Birth rates Competition for resources Survival of the Fittest The ability to survive and reproduce in the given environment Result of adaptations that increase survival Organisms with these adaptations live to produce more offspring while those that do not have them die or have few offspring

Natural Selection cont... Results in changes in the inherited characteristics of a population These changes increase a species' fitness in it's environment Descent with modification Over long periods Species change features as a result of occupying new habitats Each descended from other species

Common Descent The theory that all organisms descended from a common ancestor Tigers, panthers, cheetahs Farther back: a single tree of life that links all living things

Evidence of Evolution Fossils Showed life on earth has changed over time Distribution of Living Things around the world Animals in similar environments in different parts of the world had similar features Homologous (similar) body structures ex. the arms, wings, legs, fins of reptiles, birds, and mammals are all constructed from the same basic bones Similarities in Embryology Embryos of varying life forms look very similar during development

Fossil Evidence

Geographic Distribution

Homologous Body Structures

Similar Embryonic Development

Darwin's 5 Points Populations have variations (individual differences) Some variations are favorable (best suited to their environment) Organisms produce more offspring than can survive, and they must compete for resources Those that survive have favorable traits and produce more offspring to carry the trait or traits A population will change over time