Lecture_3_4

Lecture_3_4 - Homology, Biogeography, and the Fossil Record...

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Unformatted text preview: Homology, Biogeography, and the Fossil Record Evolutionary theory Provides a cohesive explanation for many kinds of observations Homology Homology Is similarity resulting from common ancestry 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 Comparative embryology Reveals additional anatomical homologies not visible in adult organisms Figure 22.15 Pharyngeal pouches Post-anal tail Chick embryo Human embryo Vestigial organs Are some of the most intriguing homologous structures Are remnants of structures that served important functions in the organisms ancestors 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 Homologies and the Tree of Life The Darwinian concept of an evolutionary tree of life Can explain the homologies that researchers have observed 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 Biogeography Darwins observations of the geographic distribution of species, biogeography Formed an important part of his theory of evolution 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 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 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 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 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 Genetic variations in populations Contribute to evolution Figure 23.1 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 The Modern Synthesis Population genetics Is the study of how populations change genetically over time Reconciled Darwins and Mendels ideas...
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This note was uploaded on 04/17/2008 for the course BIO 051 taught by Professor Land during the Fall '07 term at Pacific.

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Lecture_3_4 - Homology, Biogeography, and the Fossil Record...

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