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How did the giraffe get its long neck? Observation #1 More offspring are produced that can possibly survive. BUT populations tend to remain stable AND there are limited resources SO the inference is: There is a struggle for survival between individuals of a population and not all will survive Aphaenogaster tipuna ants fighting over food OBSERVATION #2 Organisms display a lot of variety in their characteristics Much of this variety is inherited Inference #2: Those individuals whose inherited traits best fit them to their particular environment will leave more offspring Inference #3: This unequal ability of individuals to survive and reproduce will cause a gradual change in the population Favorable characteristics will accumulate in the population over time Individuals DO NOT EVOLVE. Populations evolve Evolution is not caused by a NEED of an individual. Surviving does not contribute to evolution alone. There also has to be reproduction Acquired characteristics are not passed down to the next generation. Adaptations depend on the environment Fossils provide evidence of the change of life throughout time Comparative Anatomy Anatomical Homologous structures: indicators of a common ancestor Show divergent evolution vestigial structures Homologous structures with no or little function in organism Embryological homologies Compare DNA sequences or proteins (amino acid sequences) The more differences the longer ago the two species diverged from a common ancestor Generation to generation change in the frequencies of alleles in the gene pool Causes: natural selection Genetic Drift: changes in allele frequencies due to chance Gene flow immigration or emigration of individuals (and their genes) Mutation introduces new alleles Examples of Genetic Drift Bottleneck effect Natural disaster wipes out a portion of a population Fig. 13-11a-1 Original population Fig. 13-11a-2 Original population Bottlenecking event Fig. 13-11a-3 Original population Bottlenecking event Surviving population Example #2 Relatively few individuals start a new population in isolation founder effect A population that is not evolving is in equilibrium Hardy-Weinberg Equilibrium p=frequency of the dominant allele q=frequency of the recessive allele p+q=1 p2 +2pq +q2=1 p2 = frequency of homozygous dominants 2pq= frequency of heterozygotes q2= frequency of homozygous recessives Conditions required for a population to maintain Hardy-Weinberg equilibrium 1. 2. 3. 4. 5. Large population Random mating No natural selection No mutation No gene flow Analogous structures Evolved independently and don’t indicate close relationships A) Divergent evolution results in homologous structures B) Convergent evolution results in analogous structures Population or group of populations that have the potential to interbreed with each other in nature and produce viable offspring Key idea: reproductive isolation Fig. 14-3 Fig. 14-3a Habitat isolation Fig. 14-3b Behavioral Isolation Behavioral Isolation Fig. 14-3c Mechanical Isolation Fig. 14-3d Gametic Isolation Fig. 14-3e Postzygotic Barriers Hybrids do not develop into fertile adults National Geographic http://www.youtube.com/watch? v=1zOWYj59BXI Speciation is the formation of a new species Often it comes about because of some kind of geographic barrier Adaptive radiation is a type of speciation One population evolves into several different species, each with different adaptive characteristics Phylogenetic trees Cactus ground finch Medium ground finch Large ground finch Small Large cactus ground finch ground finch Sharp-beaked ground finch Seed eaters Cactus flower eaters Ground finches Is the medium ground finch more closely related to the small ground finch or to the large ground finch? Small tree finch Vegetarian finch Medium tree finch Large tree finch Bud eaters Woodpecker finch Mangrove finch Green warbler finch Insect eaters Tree finches Warbler finches Which finch is most closely related t the Green warbler finch? Loss of tail 3 toes Big eyes • Beastie Activity Duck-billed platypus Kangaroo Beaver TAXA Iguana CHARACTERS Fig. 15-16aa Long gestation 0 0 0 1 Gestation 0 0 1 1 Hair, mammary glands 0 1 1 1 Character Table Fig. 15-16ab Iguana Duck-billed platypus Hair, mammary glands Kangaroo Gestation Beaver Long gestation Phylogenetic Tree Loss of tail 3 toes Big eyes Brown bear Polar bear Asiatic black bear American black bear Sun bear Sloth bear Spectacled Giant panda bear Lesser Raccoon panda Miocene Pleistocene Pliocene Oligocene Ursidae Procyonidae Common ancestral carnivorans Figure 15.12A Classification • For several decades, scientists have classified life into five kingdoms MONERA PROTISTA PLANTAE Earliest organisms FUNGI ANIMALIA Figure 15.14A A newer system is the 3 Domain system • This system recognizes two basically distinctive groups of prokaryotes – The domain Bacteria – The domain Archaea • A third domain, the Eukarya, includes all kingdoms of eukaryotes BACTERIA ARCHAEA EUKARYA Earliest organisms Figure 15.14B • Organisms are grouped into progressively larger categories (taxons) Table 15.10 CLASSIFICATION (TAXONOMY) DOMAIN KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES (SMALLEST GROUP) NAMING OF ORGANISMS BINOMIAL NOMENCLATURE EX: Homo sapiens Pan troglodytes (chimpanzee) FIRST NAME IS GENUS NAME SECOND NAME IS SPECIES NAME 5 KINGDOMS 1) MONERA 2) PROTISTA 3) FUNGI 4) PLANTAE 5) ANIMALIA eyCDA/CliffsReviewTopic/Classification-Plants-Other-Organisms.topicArtic