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TOPIC: Evolution AIM: What evidence supports the theory of evolution? How does Charles Darwin explain evolution? Evolution: __________________________________________________ Geologic Time Scale: History of life • Earth= 4.5 billion years old • Organisms have evolved from _____________________________________ Evidence for Evolution 1. FOSSILS: _______________________________________________ • Bones • Imprint = impression in mud that hardens into rock • Mold = shape preserved in rock in hollow form • Cast = mold filled with minerals that hardens • Petrifaction = remains turn into stone 2. ANATOMICAL EVIDENCE: similarities in structure • HOMOLOGOUS STRUCTURES • __________________________________________________________ 3. EMBRYOLOGICAL EVIDENCE 4. BIOCHEMICAL SIMILARITIES similar DNA, proteins (hormones & enzymes) What does this evidence suggest? _________________________________________________________ Where are fossils found? • Layers of sedimentary rock • LAW OF SUPERPOSITION: ____________________________________ _____________________________________________________________ Fossil Record • Record of organisms that lived in past • Incomplete (gaps), bc not all turn into fossils ADAPTATION: Inherited trait • Favorable: _________________________________________________________________________ • Ex: Camouflage Charles Darwin: Galapagos Islands (1830’s) Darwin’s Model of Evolution • • • • • • • He was amazed by the variety of life on the islands. Darwin observed 13 species of finches on the Galápagos Islands that were similar except for differences in body size, beak shape, and eating habits. Hypothesis: All organisms migrated from Central and South America. • Species become adapted to their environments. • Evolved over time into different species. He noticed that all finches were similar to 1 finch he saw on the South American coast. Darwin reasoned that the Galápagos finches must have had to compete for food. Finches with beak shapes that let them eat food survived longer & reproduced more than finches without those beak shapes After many generations, these groups of finches became separate species Main Points of Natural Selection 1. Overproduction • More offspring than can survive • Better adapted à survive & reproduce 2. Competition • Limited resources à compete à more adapted will survive & reproduce 3. Variation • __________________________________ • Better adapted à survive & reproduce • Ex: Polar bears with thicker fur (Darwin wasn’t able to explain where variations came from) 4. Survival of the Fittest • Most “fit” (favorable adaptations) will survive & reproduce 5. Speciation • Over generations, favorable adaptations stay & unfavorable adaptations disappear à NEW SPECIES RATE OF EVOLUTION 1. GRADUALISM • Evolution slow & continuous through time 2. PUNCTUATED EQUILIBRIUM • Evolution fast & sudden changes after long period of no change *BOTH THEORIES SEEMED TO HAVE OCCURRED DURING EARTH’S HISTORY* What organisms evolve quickly? • Reproduce at very fast rate • (bacteria, insects) What organisms evolve quickly? • • • _______________________________________ (bacteria, insects) Ex: Many bacteria have evolved resistant to certain antibiotic Sources of Genetic Variation in a Species 1. ______________________________ 3. _________________________ 2. ______________________________ 4. __________________________ What can cause EXTINCTION? • ______________________________________________________________ • Major environmental change à adaptation no longer favorable à all organisms die à extinction