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Natural Selection and Evolution of mammals http://www.youtube.com/watch?v=FNz9aHUTAT8 6:40 Evolution are the changes in the gene pool of a population over time. Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully. Adaptation is an inherited characteristic that increases an organism’s chance of survival. 13:13 http://www.youtube.c om/watch?NR=1&v=s vHQ4BQY__o&feature =endscreen Darwin Wolf Pinta Marchena Genovesa Santiago Bartolomé Fernandia Råbida Pin zon Seymour Baltra Santa Cruz EQUATOR Santa Fe Tortuga Isabela San Cristobal Española Floreana Galåpagos Islands Marine Iguana Land Iguana KONA FINCH extinct KAUAI AKIALAOA AMAKIHI LAYSAN FINCH IIWI AKIAPOLAAU APAPANE MAUI PARROTBILL fruit and seed eaters insect and nectar eaters FOUNDER SPECIES Based on his observations, Darwin proposed that EVOLUTION occurs by NATURAL SELECTION. Darwin’s Postulates • 1. Individuals within populations vary. • 2. Some of these variations are passed on to offspring. • 3. In every generation some individuals are more successful in surviving or reproducing than others. • 4. Survival and reproduction are not random. Individuals with the most favorable variations are more likely to survive and reproduce. MONOTREMES Platypus Spiny anteater MARSUPIALS Koala Tasmanian Devil PLACENTAL MAMMALS Bat Arctic Fox Walruses Manatee RACCOON RED PANDA DIVERGENCE approximately 40 million years ago GIANT PANDA SPECTACLED BEAR SLOTH SUN BEAR BEAR BLACK BEAR POLAR BEAR BROWN BEAR DIVERGENCE 15-20 million years ago Fig. 20.10, p. 319