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Transcript
Darwin’s Theory of Evolution by Natural Selection “The single most important scientific idea that anyone has ever had.” “Evolution is just a theory” Like… GERM CELLS ATOMS RELATIVITY GRAVITY Evolution: Isn't Evolution Just a Theory? What is a scientific theory? theory: A well-substantiated explanation of some aspect of the natural world that typically incorporates many confirmed observations, laws and successfully verified hypothesis. How is a scientific theory different from a plain old talk-at-the-dinner-table theory???? TAKE A MINUTE AND WRITE A PARAGRAPH EXPLAINING THE DIFFERENCE SCIENCE is… “an organized way of using evidence to learn about the NATURAL world.” Point, blank, period. Charles Darwin • Born in England Feb. 12, 1809 • Held a degree in theology from Cambridge University and had considered becoming a preacher • After college he joined the crew of the HMS Beagle and set sail in 1831 for a trip around the world • During this voyage he made observations, collected data, and developed his hypothesis on the origin of species • Published “On the Origin of the Species” in 1859 and rocked the world! What questions did Darwin ask? As he observed patterns of diversity, “Why aren’t animals the same everywhere?” Considering fossils and modern animals, “Why are some fossils the same as modern species while many have disappeared?” On the living things seen on the Galapagos Islands, “Why are they similar to things living on the mainland but not exactly alike?” Ideas that shaped Darwin’s thinking European concepts of the day included 1. Earth and all of its life forms had been created only a few thousand years ago. 2. Since their creation, neither the Earth or its species had changed. Discoveries that changed these perceptions A rich fossil record which showed previous extinctions and led some scientists to suggest there had been several “creations” The Earth was very old- how do we know??? 1. James Hutton- concluded that geologic forces had changed the Earth over millions of years 2. Charles Lyell- proposed that scientists must explain past events in terms of processes that can be observed today-principle of The Uniformity in the Order of Nature How do we know who had the right idea??? How did the Grand Canyon form? We know: • The Grand Canyon was formed by the Colorado River • The river is currently eroding rock layers at a rate of 0.3 m/millenium • The canyon is 1800 meters deep in some places. Using this rate of erosion, how long did it take for the canyon to form? Soooooo… Can the Earth be only a few thousand years old????? How “long is evolution”? If one whole lifetime (100 years) is like walking a mile, then the amount of time that evolution had is not just like walking all the way from California to Africa- it is like walking to the moon, and back, a hundred times over! I repeat, if a hundred years is like walking a mile, then evolution walked all the way to the moon and back a hundred times over!!! 238, 857 miles • Time Zero: 13-14 billion years ago all galaxies, all matter, all of space compressed into a hot, dense volume about the size of the sun and then… a stupendous nearly instantaneous expansion and distribution of all matter and energy in the universe…the BIG BANG!!! And then??? • Next billion years saw the formation of stars as gaseous particles collide and condense under gravities force • 4.6 billion years ago clumps of debris formed our solar system including Earth (which by the way, was a very nasty place with a very different atmosphere, sky was probably pink, not blue, due to its chemical make-up) • 3.8 billion years ago rain began eroding mineral salts from rocks which ran off and collected to form oceans The scene had been set for some very interesting developments…. WHAT DO WE KNOW? • The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates: • 3.8 billion years of simple cells (prokaryotes), 3 billion years of photosynthesis, 2 billion years of complex cells (eukaryotes), 1 billion years of multicellular life, 600 million years of simple animals, 570 million years of arthropods (ancestors of insects, arachnids and crustaceans), 550 million years of complex animals, 500 million years of fish and protoamphibians, 475 million years of land plants, • • • • • • • • • • • • • • • • • • • • 400 million years of insects and seeds, 360 million years of amphibians, 300 million years of reptiles, 200 million years of mammals, 150 million years of birds, 130 million years of flowers, 65 million years since the non-avian dinosaurs died out, 2.5 million years since the appearance of the genus Homo, 200,000 years since humans started looking like they do today, 25,000 years since the disappearance of Neanderthal traits from the fossil record. 13,000 years since the disappearance of Homo floresiensis from the fossil record. HOW??? Evolution is… •Change over time •Change in a species •Change in the frequency of an allele in a population What are the components of Darwin’s Theory of Evolution? Variation exists within a species All organisms compete for limited natural resources. Organisms produce more offspring than can survive. The environment selects organisms with beneficial traits. NATURAL SELECTION Traits are passed on to offspring. Darwin’s Theory of Evolution by Natural Selection 1.Variation exists within a species 2.All organisms compete for limited natural resources 3.Organisms produce more offspring than can survive. 4.The environment selects organisms with beneficial traits. 5.Traits are passed on to offspring. So exactly where in his theory did Charles Darwin say humans came from monkeys? NO WHERE!!!