BIOL 112 1st Edition Lecture 3 Outline of Last Lecture I. Categories of Scientific ModelsII. Levels of Scientific ModelsIII. ParadigmsIV.Value JudgmentsV. Bad TheoriesOutline of Current LectureVI.The Scientific MethodVII. EvolutionA. Observations Significant to EvolutionVIII. FossilsIX.Macroevolution of HorsesX. How Old are Fossils?A. Relative DatingB. Absolute DatingXI.Dating MathA. Calculating AgeXII. Carbon DatingXIII. Geological DatingXIV. Dating ObservationsCurrent LectureI. The Scientific MethodThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Two major aspects:•Observations -- Facts, what we see•Interpretations -- Theories, what it meansA "good" theory does two things:•Explains what happens, shows how things work•Predicts what will happen, if certain conditions are established. Not fortune-telling or predicting the future, but expected data from specified situations (experiments).II. EvolutionEvolution: a change in population of organisms over a long period of timeBasis of change -- change in genetic composition of population.Genetic changes produce:•Change in biochemistry•Change in morphology•Change in behavior•Any other aspects of organisms under genetic controlA. Observations Significant to Evolution•Fossil Record•Anatomical Homologies (current organisms)•Vestigial Organs (organs that deteriorate after lack of use)•Embryological Development•Molecular (Sequence) Homologies - genomeIII. Fossils•From the Greek: "dug up"•Preserved parts of plants or animals that were once alive•Hard parts have highest chance of being preserved: bones, teeth, wood, shells•Taphonomy -- the science of the decay of organisms over time, and how this relates to fossilization•Soft parts found less frequently: skin, feathers, leaves, flowers; rarely, even cell structures are found•Organic materials usually replaced by inorganic materials (stone)•You can determine the colors and physical characteristics based on the fossils.•Fossils can help us to determine animal behavior alsoIV.Macroevolution of HorsesShows general trends over the past 60 millionyears:•Increasing body size; change in proportions•Shift of toe structure from many digits to onedigit (toes to hoof)•Change in diet/dentition from soft leaves/brushto hard grassesExample of macroevolutionary sequenceRepeated branching speciation events (AdaptiveRadiations) followed by selective survival and ex-tinctionsV. How Old are Fossils?Two dating methodologies:A. Relative Dating: distinguishes older from younger using stratigraphyIndex fossils: used as markers to recreate a whole his-tory of strata from different locations in one sequenceAssembled strata sequence is called the geological time scaleWe need to apply dates to time scale using absolute dat-ing.B. Absolute Dating: gives an age estimate in years usually by using radioactive decay methodologyRadioactive isotopes of various elements will decay (inter-nal nuclear event/rearrangement in atom). Individual atoms decay as random events, but probability of decay is predictable for a mass sample of the radioactive form.Rates of decay can’t be influenced by ambient physical or chemical environments/treatments.VI.Dating MathWe can estimate how much Carbon is originally present in a sample, and we can measure the amount present now. We can also determine how old the same is from the time that the carbon has been present (which means when the living thing died and started releasing Car-bon).A. Calculating Age Half-life is unaffected by normal ambient conditions: tempera-ture, pressure, chemicals, etc.In one half life, half of the original sample of radioactive mate-rial will have decayed.In two half lives, 3/4 of the original sample will have decayed, etc.VII. Carbon DatingGood only for organic materials and for a few thousands of years; maximum practical date is about 60,000 years.New wood has 14Carbon content of 15.3 dam; older wood would be proportionally less.We assume that the rate of 14Carbon production is constant. (This as-sumption has been tested and is not completely accurate. The rate of 14Carbon production was lower in the past and has increased over the past 30,000 years.)14Carbon dates have now been calibrated against wood samples of known age by growth ring counts (for example, bristlecone pines, Pines longaeva); now corrected out to 30,000-40,000 years.VIII. Geological Dating•Useful for fossil strata and good for up to a few billion years•Usually done in crystals from igneous rocks (i.e. lava flows) layered among fossil-bearing strata; provides absolute data reference ages along the relative stratigraphy series•Fossils can be dated using a combination of relative and absolute systems.IX.Dating Observations•Age of the Universe: around 12 x 109 years•Oldest Rocks (age of Earth): 4.6 x 109 years•Earliest fossils (bacteria-like): 3.5 x 109 years•Evidence of aerobic photosynthesis: 2.2 x 109 years•Earliest eukaryotic fossils: 2.1 x 109 years•Multicellular organisms: 1.5 x 109 years•Animal fossils become common (“Cambrian Explosion”): 5.5 x