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Lecture_3_4 - Homology Biogeography and the Fossil Record...

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Homology, Biogeography, and the Fossil Record Evolutionary theory Provides a cohesive explanation for many kinds of observations
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Homology Homology Is similarity resulting from common ancestry
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Anatomical Homologies Homologous structures between organisms Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor Figure 22.14 Human Cat Whale Bat
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Comparative embryology Reveals additional anatomical homologies not visible in adult organisms Figure 22.15 Pharyngeal pouches Post-anal tail Chick embryo Human embryo
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Vestigial organs Are some of the most intriguing homologous structures Are remnants of structures that served important functions in the organism’s ancestors
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Molecular Homologies Biologists also observe homologies among organisms at the molecular level Such as genes that are shared among organisms inherited from a common ancestor
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Homologies and the Tree of Life The Darwinian concept of an evolutionary tree of life Can explain the homologies that researchers have observed
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Anatomical resemblances among species Are generally reflected in their molecules, their genes, and their gene products Figure 22.16 Species Human Rhesus monkey Mouse Chicken Frog Lamprey 14% 54% 69% 87% 95% 100% Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide
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Biogeography Darwin’s observations of the geographic distribution of species, biogeography Formed an important part of his theory of evolution
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Sugar glider AUSTRALIA NORTH AMERICA Flying squirrel Figure 22.17 Some similar mammals that have adapted to similar environments Have evolved independently from different ancestors
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The Fossil Record The succession of forms observed in the fossil record Is consistent with other inferences about the major branches of descent in the tree of life
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The Darwinian view of life Predicts that evolutionary transitions should leave signs in the fossil record Paleontologists Have discovered fossils of many such transitional forms Figure 22.18
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What Is Theoretical about the Darwinian View of Life? In science, a theory Accounts for many observations and data and attempts to explain and integrate a great variety of phenomena
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Evolution of populations Overview: The Smallest Unit of Evolution One common misconception about evolution is that individual organisms evolve, in the Darwinian sense, during their lifetimes Natural selection acts on individuals, but populations evolve
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Genetic variations in populations Contribute to evolution Figure 23.1
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Population genetics provides a foundation for studying evolution Microevolution Is change in the genetic makeup of a population from generation to generation Figure 23.2
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The Modern Synthesis Population genetics Is the study of how populations change genetically over time Reconciled Darwin’s and Mendel’s ideas
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The modern synthesis
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