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Macroevolution -Evolution of species- What is macroevolution? • Macroevolution: major biological changes evident in the fossil record – Includes origin of different species (speciation), extinction, and evolution of major new features in organisms – Species: members of pop’s that can interbreed to have fertile offspring Why aren’t horses and donkeys considered the same species? + Horse = Donkey Mule • Because their offspring (mules) are sterile (can’t have more offspring) Reproductive barriers • Reproductive barriers keep 2 closely related species that live in the same environment from interbreeding – Creates reproductive isolation Types of reproductive barriers • Timing – the 2 similar species have different breeding seasons • Behavior – the 2 similar species have different mating behaviors (courtships, mating songs/calls) • Habitats – the 2 similar species live in different habitats of the same location – Bottom feeder vs. Open water feeder Geographical isolation can create speciation • Geological processes constantly change and rearrange Earth’s features – Possibly creating geographical isolation (separation of pop’s as a result of geographical change or an arrival of a pop to a geographically isolated area) Example of Geographical Isolation Harris’ antelope squirrel White-tailed antelope squirrel North rim South rim GRAND CANYON Geographical Isolation • Isolating the pop. by a geographical barrier can lead to speciation – We can apply microevolution (genetic drift and Natural Selection) to the evolution of the new species – Ex. Darwin’s finches Continental drift & Macroevolution • Continental drift: the movement of the Earth’s continents as a result of plate tectonics Plate tectonic basics • The Earth’s surface is broken up into large plates, which float on molten lava – As the plates shift, they cause: • Earthquakes, volcanoes, and mountain building • The continents to move (relative to each other) Pangaea • 250 million years ago, the Earth’s continents are believed to have been 1 large landmass (Pangaea) • 180 million years ago, Pangaea drifted apart into 2 isolated continents – Species on each continent would’ve encountered their own evolution