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Transcript
Evolution Change over time What is evolution? Evolution is change over time The theory of evolution states that evolution is the process by which modern organisms have descended from previous organisms What is a theory? A common misconception is that a theory is simply a statement of ones ideas. In a scientific sense this is not true A theory is a well supported testable explanation of phenomena that have occurred in the natural world Some common theories include Gravity, the big bang and evolution Who was this Darwin guy? Charles came from a family of doctors He dropped out of med school Eventually he signed on to the HMS Beagle as the ships biologist Charles Darwin, 1859 Most educated people in Europe and the Americas during the 19th century had their first full exposure to the concept of evolution through the writings of Charles Darwin . Clearly, he did not invent the idea. That happened long before he was born. However, he carried out the necessary research to conclusively document that evolution has occurred and then made the idea acceptable for scientists and the general public. This was not easy since the idea of evolution had been strongly associated with radical scientific and political views coming out of post-revolutionary France. These ideas were widely considered to be a threat to the established social and political Charles Darwin, 1859 http://anthro.palomar.edu/evolve/evolve_2.ht What does this have to do with anything? Darwin’s ship sailed to the Galapagos islands where Darwin made many observations and collections While the ship was at sea, and between bouts of sea sickness, Darwin studied these specimens. The voyage of the Beagle Great Britain Europe North America Pacific Ocean Atlantic Ocean Africa Galápagos Islands Equator South America Australia Cape of Good Hope Tasmania Cape Horn Tierra del Fuego http://www.rit.edu/~rhrsbi/GalapagosPages/D arwinFinch.html New Zealand Figure 13.1B Darwin’s Observations Darwin was intrigued by how well adapted plants and animals were to their environment Darwin also collected fossils during his voyage He noticed that some fossils very closely resembled modern organisms and some did not Why? organisms produce more offspring than the environment can support organisms vary in many characteristics these variations can be inherited Differences Among Organisms The differences that Darwin observed within organisms was identified as adaptations Adaptations- characteristics that helps and organism survive and reproduce in its environment Ex-color of moths, hummingbirds long beak or the red color of poisonous berries. The Galápagos Islands have species found in no other part of the world, though similar ones exist on the west coast of South America. Darwin was struck by the fact that the birds were slightly different from one island to another. He realized that the key to why this difference existed was connected with the fact that the various species live in different kinds of environments. http://anthro.palomar.edu/evolve/evolve_2.htm Darwin identified 13 species of finches in the Galápagos Islands. This was puzzling since he knew of only one species of this bird on the mainland of South America, nearly 600 miles to the east, where they had all presumably originated. He observed that the Galápagos species differed from each other in beak size and shape. He also noted that the beak varieties were associated with diets based on different foods. He concluded that when the original South American finches reached the islands, they dispersed to different environments where they had to adapt to different conditions. Over many generations, they changed anatomically in ways that allowed them to get enough food and survive to reproduce. The Origin of Species This was the title of Darwin’s book in which he outlined the theory of… Evolution by Natural Selection Darwin based much of this theory on work that had been done by English farmers What is a species? A group of similar organisms that can breed and produce fertile offspring Examples People Dogs Not all animals that breed are the same species A horse and a donkey may produce a hybrid offspring, a mule Mules are sterile Figure 14.2C Prove it to me The fossil record Fossils are the remains of once living organisms Aquatic fossils (shells, fish, etc.) are found in areas that are now deserts Many different species were present on this planet in the past This shows the earth is constantly changing So how old is this place? The oldest rocks on this planet are around 3.5 billion years old The oldest rocks on the moon are around 4.5 billion years old The oldest meteorites found on the planet are around 4.5 billion years old These ages are determined by gauging the decay of uranium which has a 1/2 life around 4.5 billion years B) Comparing Organisms- 1) Homologous Structuresstructures that have a common origin but not necessarily a common function. Ex. Arm, wing vs. fin. -This common bone combination was passed from one species to the next. 2) Vestigial structures- structures in the body that have no current function for the organism. (But in the past it did) Ex. Appendix in humans, pelvis in whales. -Left over structure not needed today to be 3) Embryo similarities- human embryos and embryos of other very different animals are very similar early on in development. Evidence of Evolution Vestigial organs Organs that serve no purpose Homologous structures Biochemical evidence The similarity of DNA structure and genes found in all life Experiments In a laboratory setting it is possible to cause a population of organisms to evolve Vestigial Organs Organs that are no longer useful to the organism Your appendix Eyes on the naked mole rat These organs were present and used in the past and have since become useless Natural selection has favored the eyeless moles 4. Biochemical Evidence By comparing the DNA and RNA of organisms scientists can quantify how alike or different two organisms are There is a high level of similarity among all organisms All life on this planet is over 90% the same when viewed at the DNA level Evolution in the lab It is possible to make a population of organisms evolve in a particular manner Take for example a population of insects If the population is sprayed with a certain pesticide and some survive, the surviving insect will go on to reproduce Over time if this resistance to pesticide is selected for then the gene will become part of the population Artificial Selection Farmers breed plants and livestock to gain desired characteristics. In artificial selection, nature provided the variation among the different organisms, and humans selected those variations that they found useful. A good example of this is the different breeds of dogs Natural Selection Over reproduction of offspring There’s a struggle for existence There is competeion for food, living space, & mates There is variation within the population Those members that are best suited (“fittest”) will survive, reproduce and pass their traits on to the next generation. Natural Selection cont. Survival of the Fittest What does it mean to be fit? Darwin described this as an animals ability to survive and reproduce in its environment. Fitness is the result of adaptations An adaptation is any inherited trait that increases an organisms chance of survival These adaptations can be physical or behavioral How do species form? Separation Reproductive barriers Genetic mutation Adaptive radiation Separation When two populations become separated by a geologic barrier The populations on either side can change independently When the two populations are brought back together they may now be different species Ground squirrels and the Grand Canyon Two different species of ground squirrels can be found on either side of the grand canyon The two species look similar but cannot interbreed Gene Flow (Thick Arrow – High) (Thin Arrow – Low) Gene Flow (Thick Arrow – High) (Thin Arrow – Low) Gene Flow (Thick Arrow – High) (Thin Arrow – Low) Gene Flow (Thick Arrow – High) (Thin Arrow – Low) Gene Flow (Thick Arrow – High) (Thin Arrow – Low) Would gene flow, across this Canyon, in hawks be influenced in the same manner as it is in squirrels? No. WHY? Reproductive Barriers Physical incompatibility EX. Dogs- Are a Chihuahua and a Great Dane the same species? Different mating habits Ex. Different mating grounds, times, rituals Mutation Common in plants Can result in new genes or polyploidy organisms Polyploidy can result from a mistake in cell reproduction Mitosis Error Prophase Cell Mitosis Error Prophase Cell Metaphase Mitosis Error Prophase Metaphase Anaphase Normal Mitosis Error Prophase Metaphase Anaphase Mitosis Error Mitosis Error Prophase Metaphase Anaphase Mitosis Error 2n= 8 chromosomes 2n= 8 chromosomes Original cell: 2n = 4 Adaptive Radiation The emergence of many new species when a common ancestor is introduced into new and diverse environments Example- Darwin's Finches Island Forms Mainland ancestor Adaptive radiation on an island chain 1 A Species A from mainland 2 B Species A Evolves into Species B B B 3 B C 4 C C C C D D D 5 Figure 14.4B How predation can lead to evolution Coevoloution- A series of reciprocal adaptations in two species A change in one species results in selection in another Example Cheetah and Gazelle Both can run over 60 mph Convergent Evolution When two organisms develop similar traits due to similar environments but are not closely related Bats and Birds Both have developed wings for flight