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Theories of Evolution The Origin of Species or How we came to be Jean Baptiste de Lamarck (1749-1829) • French Scientist • Theory of Acquired Traits-Traits arise during an organism’s lifetime as a result of experiences or behaviors which are passed to offspring Example: Giraffes Thomas Malthus • In 1798, Malthus reasoned that if the human population grew unchecked, there wouldn’t be enough living space and food for everyone. Charles Darwin • At age 22, he was a naturalist on the H.M.S. Beagle (1831-1836) • He collected fossils, specimens and recorded his observations Darwin’s Journals He observed that fossils resembled living species from the same region, and living species resembled other species from nearby regions Galapagos Islands His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands west of South America He hypothesized that species from South America had colonized the Galápagos and speciated (become a new species) on the origin of new species ~ adaptation to the islands environment (a) Cactus-eater (c) Insect-eater (b) Seed-eater Alfred Wallace Charles Darwin (1823-1913) (1809-1882) developed a theory of natural selection similar to Darwin’s • In 1859 Darwin published On the Origin of Species • Two Theories: 1. Descent with Modification 2. Modification by Natural Selection Ideas from The Origin of Species Darwin explained three observations about life: The unity of life The diversity of life The match between organisms and their environment Descent with Modification O.V.I.S.T. • Overproduction • Variation • Inheritance • Selection • Time Evolution by Natural Selection Overproduction 1. In nature, there is a tendency toward overproduction. Examples: mice, ants, fish, pine cone Observation 2. The sizes of these populations and the resources they need remain constant over time. Conclusion • There is competition for survival and reproduction. • Not all offspring survive Variation • All life forms vary genetically within a population. It is this genetic variation upon which selection works. VARIATION Inheritance • Some of these variations are due to genetic differences which are inherited. • Adaptations! Selection • Natural Selection- Individuals with favorable variations for their environment will live longer and leave more offspring than individuals with unfavorable variations. Time • The genetic makeup of the resulting population will change as it becomes better adapted for its environment over time. Time • REMEMBER: The Population (the group of the same species) will evolve, change over time • CHANGE does not happen in an individual's life time, SO it is NOT the individual that evolves, but the species Survival of the fittest! Example of Natural Selection—Peppered Moths After The Industrial Revolution