<p>Name______Date______Per_____</p><p>Darwin: Natural Selection & Evolution Charles Darwin  1831 – set sail for __5__ years on HMS _Beagle as a Naturalist  22 year old English Medical student  Questioned the belief that organisms never Change</p><p>Natural Selection  In 1859, Darwin offered an explanation – evolution occurs by Natural Selection.  He published his idea in The Origin of Species.</p><p>Darwin’s Observations  Diversity – each area of the world has very different organisms.  Fossils - preserved remains of an organism that lived in the past. The fossils Darwin saw looked different than organisms living at that time.  Characteristics of Galapagos Islands organisms – organisms were different from organisms elsewhere and from organisms on other Galapagos Islands</p><p>Adaptations  Adaptation - trait that helps an organism survive & reproduce  Examples: the finches’ beaks; the iguanas’ claws; poison & bad taste; bright colors of flowers; animal coloring</p><p>Evolution  Darwin studied his observations for 20 years after returning to England.  Reasoned that organisms arriving on Galapagos faced conditions different from on the mainland of South America  He hypothesized the species gradually changed over many generations & became better adapted to the new conditions  This gradual change is called Evolution.  However Darwin could NOT explain how the changes happened Natural Selection  Natural selection – process by which individuals that are better adapted to their environment are more likely to survive & reproduce than other members of the same species  Factors that affect natural selection o Overproduction – produce more offspring than can survive o Variation – any variation between individuals of the same species o Competition – members of a species will compete for resources</p><p>Organisms with a helpful variation will survive & reproduce. Poor variations will die out. Over a long time, natural selection will lead to change. Reasons for Species Variation (speciation):</p><p>Climate: example is snowshoe rabbit Geographic Isolation: example is Kaibab squirrel and Abert squirrel Interaction Between Species:  Mutualism – relationship in which Both species Benefit  Commensalism – relationship in which one species benefits and the other is neither helped nor harmed  Parasitism – 1 organism lives in or on another organism and harms it</p><p>Genetic Mutation: - chromosomal changes</p><p> Darwin knew that changes happened, but couldn't explain how.  At the same time, Mendel was explaining how change happens through genetics.</p>