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DNA Take out Timeline & pink sheet if it is complete Take out or get a pencil Clear your desk SMILE! Theories of Evolution The Historical Perspective What is a theory? A well-supported testable explanation of phenomena that have occurred in the natural world. Views of Life on Earth Prior to 1800 Aristotle’s ideas prevailed Throughout the history of life on Earth, species were unchanging Theory of Acquired Traits Proposed by Jean Lamarck (1744-1829) Species change from generation to generation through the use and disuse of organs and appendages Theory of Acquired Traits Short necked giraffes stretched their necks to feed higher in the trees This made their necks longer When they reproduced, their offspring would also have longer necks Suggestions of Theory Women that dyed their hair blonde would have blonde children A person with an amputated leg would have children without that same leg Could traits be inherited in this manner? The answer is obviously NO. Today we know that Lamarck’s theory was a misconception. The Theory of Natural Selection (1859) Proposed by Charles Darwin (1809-1882) Organisms with favorable variations survive, reproduce, and pass the traits on to the gene pool How did Darwin formulate his theory? At the age of 22, Darwin was offered an opportunity to join the crew of a ship, the H. M. S. Beagle The ship’s mission was to chart the coasts of South America Darwin was the ship’s naturalist The Beagle Sets Sail The Beagle leaves England in 1831 The Fantastic Voyage of the HMS Beagle Entries from Darwin’s Journal Entries from Darwin’s Journal Returning to England, 1836 Darwin spent the next 22 years studying his collections and conducting experiments Darwin Published his Theory in 1859 Using the data he gathered from his voyage, Darwin formed his well known idea and published his theory on natural selection Darwin’s Major Findings Smaller tortoises with long necks were found where there was higher growing plants The Dryer Regions Larger tortoises with short necks primarily fed on grasses and low vegetation The more lush Regions Large Ground Finch Warbler Finch Small Tree Finch Finches Like the tortoises the birds also “fit” their habitats Their beaks ranged in size and shape and these shapes and sizes were perfect for their diets. 13 different species that fit into their own niche Mechanisms of Natural Selection 1. 2. 3. 4. Overproduction Competition Variation Survival of the Fittest Mechanisms of Natural Selection 1. 2. 3. Overproduction—many offspring are produced Competition—struggle for limited resources Variation—variety exists in organisms within a species (size, color, behavior) Mechanisms of Natural Selection 4. Survival of the fittest—organisms best adapted to the environment will survive. They will pass on genes for this trait to their offspring. The species will become more “fit.”