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Transcript
Species Change Over Time What is evolution? • Definition: • The gradual change in a species over time • Takes a Looooong time • Results from a change in the GENETIC material of an organism • Not acted on at the individual level • Passed on from one generation to the next Early Ideas of Evolution • Lamarck • When an individual organism acquires a new trait IN ITS LIFETIME it passes that trait to its offspring • Ex. A giraffe wanted to reach a higher tree so it stretched its neck. This longer neck was passed onto the next generation • No Evidence! What replaced Lamarcks idea? • Charles Darwin • Developed his idea aboard the Beagle • Studied rock formations and collected fossils • Compared animals • Galapagos Islands • Located off the South American coast • Came up with natural selection Galapagos Islands South America Darwin = populations on islands evolved from mainland species Darwin versus Lamarck What is natural selection? • The process through which members of a species are best suited to their environment survive and reproduce at a higher rate than other less suited members of the species • Species adapt to their environment • Adaptation • A characteristic, a behavior, or an inherited trait • Fitness • How well you are equipped to survive the environment you live in Simpler view of Natural Selection • Survival of the fittest • The most “fit” animals will be selected for and will survive. • Ex. Giraffes were all born with different heights. The ones with longer necks were more “fit” and they were able to get additional food, survive, and pass on those traits. Example • Depending on the food source and environment, different birds survived and changed to best fit each island Natural Selection • Often based on • Overproduction • Variation • Adaptation • Selection Overproduction • When a plant or an animal reproduces it usually creates more offspring than the environment can support • Ex. Salmon lay 100’s of eggs but only a few will survive Variation • Within a species there are natural differences in traits • Occur due to mutations • Change in genetic material/DNA • Genetic variations are passed from one generation to the next Adaptation • Mutation that makes an individual better able to survive • Gives organism an advantage Selection • Individual organisms with a particular adaptation will survive long enough to reproduce • Adaptation becomes more common in next generation New Species Evolve from Earlier Species • Speciation • Evolution of a new species from an existing species • May occur when the environment changes dramatically or gradually • Ex. Finch (mentioned previously); Cichlid (fish); Polar Bear What can contribute to speciation? • Isolation by geographical or other barriers • Species can also be isolated if they feed on different things or reproduce at different times of year Examples of Natural Selection: The Evolution of The Polar Bear Our story begins with the Polar Bear’s closest living relative – the Brown Bear The Evolution of The Polar Bear Around 300,000 years ago a small group of Brown Bears became reproductively isolated from the rest of the population The Evolution of The Polar Bear This small founding population of Brown Bears were able to survive and reproduce living in the Arctic Tundra. After MANY generations, a random genetic mutation occurred . . . The Evolution of The Polar Bear Because of the genetic mutation, a litter of Brown Bears exhibited WHITE coloration The Evolution of The Polar Bear How do you think the white fur color affected these bears chances of surviving long enough to have cubs of their own? REMEMBER: Natural Selection Rests on 4 Premises: Overproduction, Variation, Adaptation, Selection The organism “most fit” for the environment will survive to reproduce Not every organism will be able to reproduce. The ones most fit will X X X X Remember traits have a genetic basis, or are inherited from parents Advantageous traits, which allows organisms to have more offspring, will become more common in the population over time. X X X X X X X X X X X X X X X X X X X X X X X X X X X X X What Happened? Through Reproductive Isolation and Natural Selection . . . One Species Evolved Into Another New Species By Adapting To Its New Environment How long do you think this took?
