Chapter 22 23 Descent with Modification A Darwinian View of Life Evolution of Populations PowerPoint Lectures for Biology Eighth Edition Neil Campbell and Jane Reece The historical context of Darwin s life and ideas Linnaeus classification Hutton gradual geologic change Lamarck species can change Malthus population limits Cuvier fossils extinction Lyell modern geology Darwin evolution nutural selection Mendel inheritance American Revolution 1750 Wallace evolution natural selection French Revolution U S Civil War 1800 1850 1900 1795 Hutton proposes his theory of gradualism 1798 Malthus publishes Essay on the Principle of Population 1809 Lamarck publishes his theory of evolution 1830 Lyell publishes Principles of Geology 1831 1836 Darwin travels around the world on HMS Beagle 1837 Darwin begins his notebooks on the origin of species 1844 Darwin writes his essay on the origin of species 1858 Wallace sends his theory to Darwin 1859 The Origin of Species is published 1865 Mendel publishes inheritance papers Figure 22 2 Ideas About Change over Time Fossils Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 22 3 Layers of deposited sediment Younger stratum with more recent fossils Older stratum with older fossils Lamarck s Theory of Evolution The Voyage of the Beagle England NORTH AMERICA EUROPE ATLANTIC OCEAN PACIFIC OCEAN Gal pagos Islands HMS Beagle in port SOUTH AMERICA AUSTRALIA Andes Darwin in 1840 after his return AFRICA Cape of Good Hope Cape Horn Tierra del Fuego Tasmania New Zealand Gal pagos finches a Cactus eater The long sharp beak of the cactus ground finch Geospiza scandens helps it tear and eat cactus flowers and pulp Figure 22 6a c c b Insect eater The green warbler finch Certhidea olivacea uses its narrow pointed beak to grasp insects Seed eater The large ground finch Geospiza magnirostris has a large beak adapted for cracking seeds that fall from plants to the ground Evolutionary Trees Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 22 8 Hyracoidea Hyraxes Sirenia Manatees and relatives Moeritherium Barytherium Deinotherium Mammut Platybelodon 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 9 Terminal bud Cabbage Lateral buds Flower clusters Brussels sprouts Leaves Kale Cauliflower Stem Wild mustard Flowers and stems Broccoli Kohlrabi Darwin s 4 Observations of Nature Observation 1 Members of a population often vary greatly in their traits Observation 2 Traits are inherited from parents to offspring Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Darwin s 4 Observations of Nature Observation 3 All species are capable of producing more offspring than the environment can support Observation 4 Owing to lack of food or other resources many of these offspring do not survive Spore cloud Darwin s 2 Inferences from Observations Inference 1 Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference 2 This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings Fig 22 12 a A flower mantid in Malaysia b A stick mantid in Africa Anatomical Homologies Human Figure 22 14 Cat Whale Bat Vestigial organs Are some of the most intriguing homologous structures Are remnants of structures that served important functions in the organism s ancestors Comparative embryology Reveals additional anatomical homologies not visible in adult organisms Pharyngeal pouches Post anal tail Chick embryo Figure 22 15 Human embryo Molecular Homologies Anatomical resemblances among species Are generally reflected in their molecules their genes and their gene products Species Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide 100 Human Rhesus monkey 95 Mouse 87 Chicken 69 Frog Figure 22 16 Lamprey 54 14 Biogeography NORTH AMERICA Sugar glider AUSTRALIA Flying squirrel Missing Links Paleontologists have discovered fossils of many such transitional forms Figure 22 18 Dolphin found 10 28 06 in Japanese waters Ch 23 Evolution of Populations Natural selection acts on individuals but populations evolve MAP AREA CANADA ALASKA Gene Pools and Allele Frequencies Beaufort Sea Porcupine herd range N TE OR RR TH IT W E O S RI T ES Fortymile herd range ALASKA YUKON Fairbanks Whitehorse A population in Hardy Weinberg equilibrium Gametes for each generation are drawn at random from the gene pool of the previous generation 80 CR p 0 8 20 CW q 0 2 Sperm CR 80 CW 20 pq Eggs CR 80 p2 CW 20 p2 64 CRCR 16 CRCW 16 CRCW qp 4 CWCW q2 If the gametes come together at random the genotype frequencies of this generation are in Hardy Weinberg equilibrium 64 CRCR 32 CRCW and 4 CW CW Gametes of the next generation 16 CR from CRCW homozygotes 64 CR from CRCR homozygotes 4 CW from CW CW homozygotes 16 CW from CRCW heterozygotes 80 CR 0 8 p 20 CW 0 2 q With random mating these gametes will result in the same mix of plants in the next generation 64 CRCR 32 CRCW and 4 CWCW plants Genetic Drift Statistically the smaller a sample The greater the chance of deviation from a predicted result Describes how allele frequencies can fluctuate unpredictably from one generation to the next CWCW CRCR CRCR CRCW Only 5 of 10 plants leave offspring CRCR CRCR CRCW Only 2 of 10 plants leave offspring CRCR Tends to reduce genetic variation CW CW CRCR CWCW CRCR CRCW CRCW CRCR CWCW CRCW CRCR CRCW Generation 1 p frequency of CR 0 7 q frequency of CW 0 3 CRCR CRCR CRCR CRCR CRCR CRCR CRCR CRCW CRCW Generation 2 p 0 5 q 0 5 Figure 23 7 CRCR CRCR Generation 3 p 1 0 q 0 0 The Bottleneck Effect Original population Bottlenecking event a Shaking just a few marbles through the narrow neck of a bottle is analogous to a drastic reduction in the size of a population after some environmental disaster By chance blue marbles are over represented in the new population and gold marbles are absent Surviving population The Bottleneck Effect Can increase understanding of how human activity affects other species i e overhunting b Similarly bottlenecking a population of organisms tends to reduce genetic variation as in these northern elephant seals in California that were once
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