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Charles Darwin From his observations he started writing: On the Origin of Species by Means of Natural Selection. Two main points: Species were not created in their present form, but evolved with modifications from ancestral species. Proposed a mechanism for evolution: NATURAL SELECTION Jean-Baptiste Lamarck (1 7 4 4 -1 8 2 9 ) First to hypothesize a mechanism for changes in organisms because they were adapted to their environments. But, his Theory of Inheritance of Acquired Characteristics, incorrectly stated that animals can pass on traits that they developed during their lifetime. Thomas Malthus (1766- 1834) Social Economist, author of Essay on the Principles of Population (1798). Argued that food supply increased in a linear fashion, while population increased “geometrically” (exponentially). Example of limited resources causing competition. Species variation….. Variation….. Adaptations Characteristics that make an individual suited to its environment and way of life. P u t t i n g i t a l l t o g e t h e r …… Struggle for survival…. Survival = more babies!! Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring. Heritable traits Individuals that reproduce pass on characteristics to their offspring. Summing up Natural Selection Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species. Adaptable……. Natural selection in action Insecticides Apply insecticide. Non resistant insects die. Resistant survivors live to reproduce. Resistance is inherited. Insecticide becomes less & less effective. New population allele frequency emerges. Antibiotic resistance in bacteria While on the Galapagos Islands Darwin noticed…. The Galapagos Finches Adaptive Radiation Genetic studies have shown that Darwin’s hypothesis was correct. We call this adaptive radiation. Emergence of numerous species from a common ancestor introduced to new and diverse environments.