MacroevolutionExamplesHow Large Scale Changes OccurFossilsFossils in Sedimentary layersWhat does the Fossil Record Show?Plate TectonicsMore Plate TectonicsStill MoreBiogeographyContinents CollidingA More Recent CollisionComparative MorphologyMore DivergenceMorphological ConvergenceDevelopmental PatternsComparative BiochemistrySequence Analysis ExampleExampleCytochrome CProtein and DNA ComparisonsMolecular ClockTaxonomyHigher TaxaLarge Scale Classification SchemesThree Domain SchemeFive Kingdom SchemeMacroevolution•Macroevolution: major patterns and changes among living organisms over long periods of time.•The evidence comes from 2 main sources: fossils and comparisons between living organisms.ExamplesHow Large Scale Changes Occur•The classical Neo-Darwinists thought that the same forces that drive microeveolution also cause macroevolutionary changes, given enough time. That is, selection pressure gradually changes the form of a species, and speciation events cause two species to slowly diverge from each other. This theory can be called the “gradualist” model of macroevolution.•A more recent theory, “punctuated equilibrium”, says that the large scale changes occur rapidly in small, isolated groups, due to mutations that significantly alter the form of the organism. Gradual changes occur in between bouts of major changes. This theory’s modern version is due to Stephen Jay Gould and Niles Eldredge.Fossils•Fossils are the remains of living organisms, often converted into rock. Bones, teeth, shells, seeds, footprints, leaf prints, etc. •If an organism is buried so that large and small decay organisms don’t destroy it, water slowly dissolves away the organic material and replaces it with inorganic compounds: calcium carbonate is a common form. As sediments accumulate above, pressure squeezes fossils, so they are often distorted and flattened.•Some fossils are not turned to rock: insects in amber (fossilized tree sap) and sometimes ancient bones. Occasionally possible to extract DNA from them.•Fossils are exposed when erosion removes the overlaying rock, or when people dig them up n rock quarries and road cuts. •Becoming a fossil is very unusual: most organisms decay to nothing.Fossils in Sedimentary layers•Two main sources of rock layers: sediments piling up at the bottom of lakes and oceans, and volcanic ash.•Disruption of layers is caused by erosion, which can remove whole layers, and mountain-building, which folds the layers and sometimes even turns them over.•But, in most cases, older rocks are underneath newer ones.•Maps of rock strata show where different layers lie relative to each other, and where they are exposed on the surface. The maps can be used to detect loss of layers by erosion.What does the Fossil Record Show?•It is quite spotty. If you are looking for specific fossils, they are hard to find.•Estimated 250,000 fossil species known, mostly from the past 600 million years. Currently alive: estimated 4 million. So, lots are missing.•Bias in the fossil record: hard parts are easier to fossilize. Very few insect fossils, for instance, despite their prevalence in the world today.•General, obvious trend: living things get more complex over time. There were invertebrates before there were fish, fish before reptiles, reptiles before mammals, for example.•Clear intermediate forms are rare: the “missing link” between apes and humans, for example. However, there is a list of 139 examples of gradual species to species transitions that are very well documented in the fossil record. •The fossil record is like taking single frames from a movie—we miss much of the action and need to fill in the gaps ourselves. Lack of intermediate forms has stimulated the punctuated equilibrium idea. •“Explosions” of new species—adaptive radiation– is a common event in the fossil record.•Mass extinctions are also common. Note that mass extinctions can occur over thousands of years are still seem almost instantaneous in the fossil record—sediments are usually laid down slowly.Plate Tectonics•Plate tectonics = slow movement of continents over long periods of time. •From the earliest maps of the Atlantic Ocean and surrounding land it was obvious that the bulge of South America appears to fit into the side of Africa.•The idea that continents can move, that this isn’t just a coincidence, was proposed in the 1930’s by Albert Wegener. No good mechanism, and it didn’t fit current theories—his theory was ignored or attacked. •Mapping of the ocean floors in the 1960’s showed that new ocean floor was being created by volcanoes in the mid-ocean ridge, and then spreading out from there. Rocks get older as you move away from the ridge.•Conintental rock is ligher than ocean rock—continents float on top. The plates ocean rocks are pushed underneath continents at deep ocean trenches. Plates can also slide past each other (as in California) or crash into each other (as in India). •Volcanoes erupt near plate boundaries: the plates going underneath melt and buddle up to the surface again.•The theory is very widely accepted today, and it explains most of the world’s geology.More Plate TectonicsStill MoreBiogeography•How plate tectonics affects life. Biogeography is the study of how the spatial patterns of living things developed. •Continents have split apart, moved around, then rejoined, all very slowly. There are coal beds in Antarctica, for example, laid down when that part of the world was near the equator. •Identical rock layers with particular fossils in them are found in different continents—they were laid down as one bed, then the continents broke up and now they are widely separated.•Distribution of current species can also be explained by continental movements.Continents Colliding•The Great American Interchange. North and South America were not connected until about 3 million years ago. Separate groups of animals developed on each. South America had many marsupials (mammals with pouches, like kangaroos and opossums), armadillos, sloths. North America had rodents, canines, felines, bears.•When the continents were joined, it became possible for animals to pass between them•Many South American animals became extinct: giant ground sloths, marsupial carnivores—as their habitat was taken over by North American types.•Some South American animals have flourished in North