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1/15/13 Descent with Modification Darwin s voyage on the Beagle • The principle of Natural Selection GREAT BRITAIN EUROPE NORTH AMERICA 1. Variation 2. Differential survival or reproduction 3. Inheritance ATLANTIC OCEAN AFRICA Pinta Marchena Santiago Fernandina Isabela • Evidence for Evolution Santa Santa Cruz Fe PACIFIC OCEAN San Cristobal Española Equator SOUTH AMERICA Daphne Islands Pinzón Florenza – Direct observations – Homology – Fossils Genovesa AUSTRALIA Andes The Galápagos Islands Cape of Good Hope Tasmania Cape Horn Tierra del Fuego New Zealand Fig. 22-5 Jan 16, 2013 Species are unique, but can also be grouped. (a) Cactus-eater (c) Seed-eater (b) Insect-eater Fig. 22-6 (a) A flower mantid in Malaysia Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium Barytherium Deinotherium Mammut Platybelodon (b) A stick mantid in Africa Stegodon Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 34 24 Millions of years ago 5.5 2 104 0 Years ago Fig. 22-8 Fig. 22-12 1 1/15/13 The power of selective breeding Terminal bud Cabbage Lateral buds Brussels sprouts Flower clusters Leaves Kale Cauliflower Stem Wild mustard Flowers and stems Broccoli Observation #1: Members of a population often vary in their traits Kohlrabi Fig. 22-9 Observation #2: Traits are inherited from parents to offspring Kirk Douglas and Michael Douglas Fig. 22-10 Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support F1 Generation F2 Generation Maple tree seedlings Spore cloud Fig. 15-4 Fig. 22-11 2 1/15/13 Observation #4: Owing to lack of food or other resources, many of these offspring do not survive • Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations. Spore cloud Maple tree seedlings • Inference #1: Individuals whose inherited traits result in high survival and reproduction in a given environment tend to leave more offspring. Fig. 22-11 R S Evolutionary Response = Selection Difference * heritability Evidence supporting evolution Last paragraph of the Origin of Species It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. Percent of HIV resistant to 3TC We can use these principles to predict change 100 Patient No. 1 Patient No. 2 75 50 Patient No. 3 25 0 0 2 4 6 Weeks Evolution of Drug Resistant HIV 8 10 12 Fig. 22-14 3 1/15/13 Rapid evolution in response to an introduced food plant 10 On native species, southern Florida 8 Homologous structures reveal shared ancestry Number of individuals 6 4 2 0 Museum-specimen average 10 On introduced species, central Florida 8 6 4 Human 2 0 6 7 8 9 Beak length (mm) 10 Cat Whale Bat All are modifications of the forelimb of their common ancestor 11 Evolution by Natural Selection produces adaptation to a particular environment Sugar glider NORTH AMERICA AUSTRALIA Similarities can also be the result of Convergent Evolution Fig. 22-20 Flying squirrel Natural selection: important points 1. Natural selection is an editing mechanism, not a creative force. 2. Natural selection favors traits that increase fitness in the current, local environment. 4