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Tracing Evolutionary History Speciation in Real time
Chapter 15 Tracing Evolutionary History Speciation in Real time
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Are Birds Really Dinosaurs with Feathers?
Did birds evolve from dinosaurs? Or did they evolve from of earlier group of reptiles that are more closely related to today’s crocs and alligators? Evolutionary biologists Have been pondering this question for decades
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Recent fossil finds Support this notion: 1861 Archaeopteryx
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MACROEVOLUTION AND EARTH’S HISTORY
15.1 The fossil record chronicles macroevolution Macroevolution: activity The cumulative effects of many speciation events over vast tracts of time and encompasses the origin of evolutionary novelties, such as feathers. The fossil record Documents the main events in the history of life Glimpses of long term evolutionary changes Allows science to create geological records
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In the geologic record Major transitions in life-forms separate eras
Smaller changes divide eras into periods
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The geologic record The oldest known fossils:
Table 15.1 The oldest known fossils: Prokaryotes date back 3.5 billion years ago. Eukaryotes date back 2.2 billion years ago.
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Use Table 15.1 to estimate how long prokaryotes inhabited the Earth before Eukaryotes evolved.
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15.2 The actual ages of rocks and fossils mark geologic time
Radiometric dating Measures the decay of radioactive isotopes Can gauge the actual ages of fossils and the rocks in which they are found
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15.3 Continental drift has played a major role in macroevolution
Is the slow, incessant movement of Earth’s crustal plates on the hot mantle Edge of one plate being pushed over edge of neighboring plate (zones of violent geologic events) Antarctic Plate Australian Plate Split developing Indian Plate Eurasian Plate North American Plate South American Plate Nazca Plate Pacific Plate Arabian Plate African Plate Figure 15.3A
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The formation of Pangaea
Altered habitats and triggered extinctions Figure 15.3B 65 135 245 Millions of years ago Paleozoic Mesozoic Cenozoic North America Eurasia Africa South America India Antarctica Australia Laurasia Gondwana Pangaea
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The separation of the continents
Affected the distribution and diversification of organisms North America South Europe Asia Africa Australia = Living lungfishes = Fossilized lungfishes Figure 15.3C Figure 15.3D
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CONNECTION 15.4 Tectonic trauma imperils local life
Volcanoes and earthquakes result from plate tectonics The movements of Earth’s crustal plates San Andreas Fault North American Plate San Francisco Santa Cruz Los Angeles Pacific California Figure 15.4A, B
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15.5 Mass extinctions were followed by diversification of life-forms
Occurred at the end of the Permian and Cretaceous periods
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The Cretaceous extinction, which included the dinosaurs
May have been caused by an asteroid Figure 15.5 North America Chicxulub crater Yucatán Peninsula
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A rebound in diversity Follows mass extinctions
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PHYLOGENY AND SYSTEMATICS
15.6 Phylogenies are based on homologies in fossils and living organisms Phylogeny, the evolutionary history of a group Is based upon the fossils that are available to study Is based on identifying homologous (similarities due to a shared ancestor) and molecular sequences that provide evidence of common ancestry Generally, organisms that share very similar morphologies or similar DNA sequences are likely to be closely related.
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Analogous similarities
Result from convergent evolution in similar environments Species from different evolutionary branches may come to resemble another if they live in very similar environments Figure 15.6 Two plants look similar (analogous) even though they are not closely related. On the left is ocotillo, a plant that is grown in Baja California. On the right is allauidia, which grows in the dessert of Madagascar.
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Systematics Involves the analytical study of diversity and phylogeny
The evolutionary relationships between organisms
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15.7 Systematics connects classification with evolutionary history
Linnaeus’ system was not based upon genealogy or evolutionary relationships. Two concepts of classification are still used today: Binomial naming Two part Latinized name hierarchical Taxonomists assign a binomial Consisting of a genus (first part of the name) and a species name (second part of the name), to each species A genus May include a group of related species
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A genus May include a group of related species
Felis is the group in which a cat belong
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Genera are grouped into progressively larger categories
Family, order, class, phylum, kingdom, and domain Species Genus Family Order Class Phylum Kingdom Domain Felis catus Felidae Carnivora Mammalia Chordata Animalia Eukarya Figure 15.7A
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A phylogenetic tree Is a hypothesis of evolutionary relationships
These branching diagrams reflect the hierarchical classification of groups nested within more inclusive groups Species Felis catus (domestic cat) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) lupus (wolf) Genus Family Order Felidae Carnivora Mustelidae Canidae Figure 15.7B The highest, or most inclusive taxon is at the bottom. Each branch represents the divergence of two lineages from a common ancestor.
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Using figure 15.7A How much of the classification do we share with the domestic cat?
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15.8 Cladograms are diagrams based on shared characters among species
Cladistics uses shared derived characters To define monophyletic taxa Identifying ‘clades’ provides branching patterns of evolution Taxa Ingroup (Mammals) Outgroup (Reptiles) Eastern box turtle Duck-billed platypus Red kangaroo North American beaver Characters Long gestation Gestation Hair, mammary glands Vertebral column Figure 15.8A 3 2 1
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Shared derived characteristics
Groups that share a new, or derived, trait are more closely related to each other. Shared primitive characters Traits present in the ancestral groups Taxa Ingroup (Mammals) Outgroup (Reptiles) Eastern box turtle Duck-billed platypus Red kangaroo North American beaver Characters Long gestation Gestation Hair, mammary glands Vertebral column Figure 15.8A 3 2 1 Cladogram: illustrate patterns of shared characteristics
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The simplest (most parsimonious) hypothesis
Creates the most likely phylogenetic tree Figure 15.8B Lizards Snakes Crocodiles Birds Common reptilian ancestor
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15.9 Molecular biology is a powerful tool in systematics
Molecular systematics Develops phylogenetic hypotheses based on molecular comparisons Brown bear Polar bear Asiatic black American black bear Sun Sloth Spectacled Giant panda Raccoon Lesser Pleistocene Pliocene 10 15 20 25 30 35 40 Oligocene Miocene Millions of years ago Ursidae Procyonidae Common ancestral carnivorans Figure 15.9A
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Studies of ribosomal RNA sequences
Have shown that humans are more closely related to fungi than to green plants Student Mushroom Tulip Common ancestor Figure 15.9B
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DNA Comparisons Molecular comparisons of nucleic acids
Often pose technical challenges Can reveal the most fundamental similarities or differences between species
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Molecular Clocks Some regions of DNA
Change at a rate consistent enough to serve as molecular clocks to date evolutionary events
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Genome Evolution Homologous genes Are found in many species Human
Chimpanzee Gorilla Orangutan Common ancestor Figure 15.9C
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15.10 Arranging life into kingdoms is a work in progress . Activity
In the five-kingdom system Prokaryotes are in the kingdom Monera Eukaryotes (plants, animals, protists, and fungi) are grouped in separate kingdoms Monera Protista Plantae Fungi Animalia Earliest organisms Prokaryotes Eukoryotes Figure 15.10A
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Recognizes the prokaryotic domains Bacteria and Archaea Eukaryotes
The domain system Recognizes the prokaryotic domains Bacteria and Archaea Eukaryotes Are placed in the domain Eukarya Bacteria Archaea Eukarya Earliest organisms Prokaryotes Eukoryotes Figure 15.10B
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