EvolutionGeologySlide 3FossilsSlide 5Radioactive DatingSlide 7Slide 8Slide 9LamarckSlide 11Darwin and WallaceEvolution through Natural SelectionArtificial SelectionNatural SelectionSummary of Natural SelectionGene Pool and Allele FrequenciesSlide 18Selection Changes Allele FrequenciesPopulations in EquilibriumSlide 21Slide 22Conditions Necessary for EquilibriumEffects of Hardy-Weinberg ConditionsNon-random MatingSlide 26Directional SelectionExamples of Directional SelectionStabilizing SelectionDisruptive SelectionSexual SelectionMore Sexual SelectionHeterozygote AdvantageNeutral MutationsMy Boyfriend is Type BGenetic DriftBottlenecksSlide 38Founder EffectEvolution•Basic tenet of science: everything in the natural world has a natural cause and explanation.•How did life originate?•There are many forms of life, displaying many similarities and differences. How did they get that way?•Aristotle and his medieval European followers believed that all living things could be arranged on a scale, from lowest to highest: the Great Chain of Being. In this view, the work of biologists was to find the place of each organism in the Chain.Geology•The theory of evolution grew out of geology. Specifically, the realization that the Earth is very old.•Current estimate of the age of the Earth is 4.6 billion years.Geology•James Hutton (late 1700’s) and Charles Lyell in the 1820’s and 1830’s developed the theory of Uniformitarianism: that the geological processes we see today are the same ones that operated in that past. For example, we can see rivers slowly eroding rocks. Carried on for a long enough time, a river can erode its way through a mile of rock to form the Grand Canyon. •Another example: high mountains are raised gradually through a series of earthquakes and volcanic eruptions. Oceans lay down sediments that are washed off the land, and eventually they build up to miles deep deposits. •If the geology we see is due to the same slow forces in operation today, the Earth must have been here for a very long time•The contrasting theory in Lyell’s time was Catastrophism: specifically, the great Flood of Noah caused the visible geology of the Earth in a very short period of time.Fossils•Fossils are the remains of ancient life, turned to stone by chemical processes.•They have been known since ancient times, but their significance wasn’t clear until the 1800’s. Fossils can be created by burying the remains of living things in sediments that slowly compress into layers of rock.↑ The first good geological maps of the layers of rocks in England showed that each layer had its own distinct set of fossils. And, the older the rocks—the deeper the layer was—the simpler the fossils were.Fossils•Long before rocks could be dated, the geological ages were defined based on their characteristic fossils. •Most fossils come from the hard parts: bones, teeth, shells. These structures first appeared about 600 million years ago. Fossils before this time are much more difficult to detect: mostly microscopic. And, very old rocks are hard to find and often very distorted. But, the earliest fossils come from about 3.8 billion years ago, in almost the oldest rocks known, close to the beginning of the Earth,3.5 billion year old Apex Chert microfossilsRadioactive Dating•Ancient rocks are dated by looking at radioactive isotopes. There are numerous methods, and ages are often estimated by several different methods.•We will discuss the potassium-argon dating method. This method is used to find the age of volcanic deposits, and it has been heavily used to date the remains of ancient human ancestors in east Africa.Radioactive Dating•Potassium is a element that is common in volcanic rock. The isotope potassium-40 (atomic weight of 40 protons + neutrons) is radioactive: it decays into argon-40. The rate of decay is steady and not affected by external conditions at all. It takes 1.25 billion years for ½ of the potassium-40 to convert into argon-40.•Argon is a “noble” gas: it has 8 electrons in its outer shell and doesn’t combine with other atoms to form compounds. Under all earthly conditions, argon is a gas.•When a volcano erupts, the lava is molten, and all of the argon gas is released into the atmosphere. When the rock freezes, it contains potassium-40 but no argon-40. Over time, argon-40 builds up from the decay of the potssium-40. By measuring the ratio of potassium-40 to argon-40, the amount of time since the rock was molten can be determined.Radioactive Dating•Other dating methods use uranium and lead, or carbon-14, or a variety of other radioactive isotopes.Radioactive Dating•The time scale used in evolutionary studies is calibrated by counts of tree rings. In some places this scale goes back 9000 years.Lamarck•By the end of the 1700’s, it was clear from the diversity of life and the fossil record that organisms had changed over time. The force driving the change remained mysterious.•One common idea was the “inheritance of acquired characteristics”, a theory associated with Jean Lamarck. This theory states that during the course of an individual’s life, various needs and desires bring about changes in the body’s internal state, and that these changes are then passed along to the offspring. For example, if you exercise heavily, your children will be born with heavier muscles than you were. Or, giraffes stretch their necks to reach leaves on tall tress, so their offspring have longer necks. •This theory is known to be wrong. Inherited changes do occur, but they are random in nature, not influenced by the needs of the individual. The cells that generate the sperm and eggs are separate from the rest of the body’s cells.Lamarck•Many demonstrations disproving inheritance of acquired characteristics: in the late 1800’s one researcher cut the tails off a groups of mice at birth for 200 generations. Even after that time their tails were as long as in the original generation.•Another: take blood from black rabbits and transfuse it into white rabbits. The offspring of the white rabbits are still white, even though the blood was supposed to carry the germs of the acquired characteristics. •The real problem for Lamarck is that no one was able to do an experiment that demonstrated inheritance of acquired characteristics under controlled conditions. If a theory is repeatedly tested and never successful, people