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Natural Selection Darwin’s Voyages Chapter 5 Section 1 A Darwin Voyage • Evolution – A change over a period of time • Charles Darwin; 22 – Voyage on the Beagle • 1831 – 5-year trip around the world – Started in England Living Diversity • Diversity – The variety of living things on earth • Scientists estimate… – Between 5-50 million living species on earth right now • Quite a guess!!! Fossil Diversity • Fossils give us a glimpse into the past • Extinction – 99.9% of all species that have ever lived are now extinct Adaptations • Physical and behavioral traits – Enable organisms to survive • Catch food • Withstand conditions • Reproduce Fitness • The ability of an individual to survive & reproduce • To successfully pass on its genes to its offspring The Galapagos Islands • 1000 kilometers west of S. America – 600 miles • Small & short islands – Dry & hot • Larger & taller islands – More lush Darwin’s Finches • 1 species of finch evolved into many different “specialized” species Giant Tortoise Shells • Tortoises from different islands had different shells • Ah, hah!!!! – Natural Selection • Survival of the fittest – Evolution!!! Vestigial Organs • Wings on flightless birds • Tailbones on primates Homologous Structures • Develop from similar tissues in the early development stages of the organism Arguments for an Ancient Earth • River Valleys – Carved by glaciers over 100,000’s years • Shells found in high elevation mountains – Plate tectonics!!! Problems with Reproduction • Extinction – Birth Rate < Death Rate • Over Population – Birth Rate > Death Rate • Disease • Famine • War Peppered Moths • Before the industrial revolution, England – Trees were light in color from lichen growing on them • After the pollution from Ind. Rev. – Lichen died, leaving just the dark bark Helpful Mutations • Increases fitness – more offspring than others in population • Becomes more common in the population Evolution • Any change to the relative frequencies of alleles in the gene pool of a species Species • A group of similar-looking organisms that can breed with one another and produce fertile offspring – Bobcat & Lynx Natural Selection • The struggle for existence selects only the fittest individuals to survive in nature – Generation after generation Struggle for Existence • Only the fastest rabbits will escape the lynx • Only the fastest lynx will catch the rabbits