The first volume of Evolutionary Bio/ogy was published eleven years ago. Since that time eleven volumes and one supplement have appeared. As stated in earlier prefaces, we are continuing the focus of this series on critical reviews, commentaries, original papers, and controversies in evolu- tionary biology. lt is our aim to publish papers primarily of greater length than normally published by society journals and quarterlies. We therefore invite colleagues to submit chapters that fall within the focus and standards of Evolutionary Bio/ogy. The Editors vii Contents 1. Precambrian Evolution of Photosynthetic and Respiratory Organisms lohn M. 0/son Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Basic Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Photosynthetic Energy Conversion and Electron Transport . . . . . . . 6 Oxygen-Evolving Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Photosynthetic Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Photoassimilation and Cyclic Electron Flow . . . . . . . . . . . . . . 13 . . . . . Acetate Assimilation . . . . . . . . . . . . . . . . . . . . . . . . . . 15 . . . . . . . . . . . The Common Ancestor . . . . . . . . . . . . . . . . . . . . . . . . . . 17 . . . . . . . . . . . Chlorophyll. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 . . . . . . . . . . . . . Quinone................................................ 19 Linear Electron Transport . . . . . . . . . . . . . . . . . . . . . . . 22 . . . . . . . . . Light-Harvesting Systems. . . . . . .. . . . . . . . . . . . . . . . . 22 . . . . . . . . . Evolution of Photosynthetic Bacteria . . . . . . . . . . . . . . . . . . 22 . . . . . . . Purpie and Green Bacteria . . . . . . . . . . . . . . . . . . . . . . . 23 . . . . . . . . . Evolution of Blue-Green Algae . . . . . . . . . . . . . . . . . . . . . . 24 . . . . . . . . Weak Electron Donors for the Protoalgae . . . . . . . . . . . . . . 25 . . . . . Evolution of Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . 29 . . . . . . . . . . General Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 . . . . . . . . . . . . . . 2. Molecular Structure and Protein Variation within and among Populations Richard K. Koehn and Waller F. Eanes Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 . . . . . . . . . . . . . . Molecular Properlies and Structural Variation . . . . . . . . . . . . . 45 . . . . Amino Acid Composition and Quaternary Structure . . . . . . . . 46 . . Protomer Size and Quaternary Structure . . . . . . . . . . . . . . . 47 . . . . . ix X Contents Enzyme Polymorphism and Quaternary Structure . . . . . . . . . . . 50 . . . Enzyme Polymorphism and Subunit Size . . . . . . . . . . . . . . . . 53 . . . . . . Data and Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 . . . . . . . . . . . Drosophila Enzyme Polymorphism . . . . . . . . . . . . . . . . . . 60 . . . . . . . Human Enzyme Polymorphism . . . . . . . . . . . . . . . . . . . . 63 . . . . . . . . Enzyme Polymorphism: Structure and Size . . . . . . . . . . . . . . . 67 . . . . . 
