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Tracing Evolutionary History

Tracing Evolutionary History. Chapter 15. Macroevolution and the fossil record. Macroevolution consists of the major changes in the history of life The fossil record chronicles these changes, which have helped to devise the geologic time scale

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Tracing Evolutionary History

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  1. Tracing Evolutionary History Chapter 15

  2. Macroevolution and the fossil record • Macroevolution consists of the major changes in the history of life • The fossil record chronicles these changes, which have helped to devise the geologic time scale • Studying fossils in rock strata in an area can show long-term evolutionary change in an area, measured in eras • Eras are time periods that are marked by mass extinctions • Replaced by species that diversified from the survivors

  3. The Age of Rocks and Fossils • The sequence of fossils in rock strata indicates the relative ages of different species • Radiometric dating can gauge the actual ages of fossils • Once an organism dies it stops accumulating carbon and the carbon starts to decay, carbon-14 decays at a specific rate called the half-life • Determine how much is left

  4. EurasianPlate NorthAmericanPlate AfricanPlate PacificPlate Splitdeveloping NazcaPlate SouthAmericanPlate Indo-AustralianPlate Antarctic Plate Edge of one plate being pushed over edge of neighboring plate (zones of violent geologic events) Continental Drift • Continental drift is the slow, incessant movement of Earth’s crustal plates on the hot mantle

  5. CENOZOIC Eurasia North America Africa India SouthAmerica Australia Antarctica Laurasia Millions of years ago MESOZOIC Gondwana Pangaea PALEOZOIC • This movement has influenced the distribution of organisms and greatly affected the history of life • Continental mergers triggered extinctions • Separation of continents caused the isolation and diversification of organisms

  6. San Andreas fault San Francisco Santa Cruz Los Angeles The Impact of Tectonic Plates • Plate tectonics, the movements of Earth’s crustal plates, are also associated with volcanoes and earthquakes • California’s San Andreas fault is a boundarybetween two crustal plates

  7. By forming new islands, volcanoes can create opportunities for organisms • Example: Galápagos • But volcanic activity can also destroy life • Example: Krakatau

  8. Mass Extinction and Diversification • At the end of the Cretaceous period, many life-forms disappeared, including the dinosaurs • These mass extinctions may have been a result of an asteroid impact or volcanic activity • Every mass extinction reduced the diversity of life • But each was followed by a rebound in diversity • Mammals filled the void left by the dinosaurs

  9. How did some survive? • Pure Luck- • Less affected area • Adaptation- • Already adapted to new environment • In a similar environment • Able to rapidly adapt to the new environment • Little adaptation needed • May have already had adaptations and used them to serve other purposes

  10. Evolutionary Trends • Evolution is a trend not a preordained destination • Depending on conditions, one species may prevail over another • It does not mean one species is better than another • Evolutionary trends may reflect unequal speciation or survival of species on a branching evolutionary tree

  11. Phylogeny • Phylogeny is the evolutionary history of a group of organisms • Represented in trees that trace the evolutionary relationships between species • Fossils can help fill in the history, but the tree is not certain • Represents the most likely hypothesis based on available evidence

  12. Cactusground finch Smalltree finch Mediumtree finch Woodpeckerfinch Mediumground finch Smallground finch Large cactusground finch Vegetarianfinch Largetree finch Mangrovefinch Greenwarbler finch Largeground finch Sharp-beakedground finch Budeaters Seedeaters Cactus flowereaters Insecteaters Ground finches Tree finches Warbler finches Common ancestor fromSouth America mainland

  13. Systematics • Systematics includes taxonomy, naming and classification of species and groups of species • Use binomial names • The first name, the genus, covers a group of related species • The second name refers to a species within a genus • Genus and species: Homo sapiens

  14. Systematics • Also group them into broader categories • Domain, kingdom, phylum, class, order, family, genus, species • Sometimes it is difficult and there is debate over placement

  15. Feliscatus(domesticcat) Mephitismephitis(stripedskunk) Lutralutra(Europeanotter) Canisfamiliaris(domesticdog) Canislupus(wolf) SPECIES GENUS Felis Mephitis Lutra Canis FAMILY Felidae Mustelidae Canidae ORDER Carnivora

  16. Homology vs. Analogy • Homologous structures are evidence that organisms have evolved from a common ancestor • In contrast, analogous similarities are evidence that organisms from different evolutionary lineages have undergone convergent evolution • Their resemblances have resulted from living in similar environments

  17. Molecular Biology and Systematics • Anatomical characteristics are still the mainstay of classification, but molecular biology is now being used to identify similar species • The evolutionary split of species correlates to the accumulation of differences in their DNA • The more recently two species split from each other the closer their DNA sequences are

  18. Polarbear Asiaticblack bear Americanblack bear Giantpanda Spectacledbear Brown bear Sunbear Slothbear Lesserpanda Raccoon Pleistocene Pliocene Miocene Ursidae Procyonidae Oligocene Common ancestralcarnivorans

  19. Molecular Biology and Systematics • Used in species that are very distantly related and have very few structural similarities

  20. Molecular Biology and Systematics • Used in species that are very distantly related and have very few structural similarities • DNA and protein analysis • Amino acid and nucleotide sequences in electronic databases are used for comparison • Regions of genomes that change at a constant rate can be used to show divergence when no fossils are found

  21. Scientists try to make classification match evolutionary history • Clades are evolutionary branches that consist of an ancestral species and all of its descendants • Cladistic analysis is often a search for the simplest hypotheses about a species evolutionary history • Cladistic analysis tends to be more objective than classical methods

  22. Lizards Snakes Crocodiles Birds Lizards Snakes Crocodiles Birds • Phylogenetic tree according to cladistic analysis • Phylogenetic tree according to classical systematics Class Reptilia

  23. MONERA PROTISTA PLANTAE FUNGI ANIMALIA Earliestorganisms Classification is a work in progress • For several decades, systematists have classified life into five kingdoms

  24. BACTERIA ARCHAEA EUKARYA Earliestorganisms • A newer system recognizes two basically distinctive groups of prokaryotes • The domain Bacteria • The domain Archaea • A third domain, the Eukarya, includes all kingdoms of eukaryotes

  25. Classification systems are not fixed and are changed as further information becomes available • These classifications are a system developed by man, not by nature and are therefore hypotheses

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