If you prefer to obtain the book from official sources, you can try:
: How certain traits become more or less common based on their impact on survival and reproduction. Genetic Drift
: The introduction of new genetic material into a population's gene pool. Stochastic Processes
Because the book is out of print. Because used hardcovers cost $300. Because the prose is austere (Crow writes with a dry Wisconsin wit, but Kimura’s sections are pure mathematical poetry). an introduction to population genetics theory pdf
The assumption of infinite population size is a useful idealization, but most real populations are finite. This chapter tackles the consequences of "random genetic drift"—the random fluctuations in gene frequencies due to the sampling of gametes each generation. This is where the concept of effective population size ( Ne ) is formally defined and explored in depth, showing how it determines the rate of inbreeding, the loss of genetic variation, and the variance in gene frequency among populations.
: Detailed analysis of Darwinian fitness and selection pressures. Populations in Approximate Equilibrium : Situations where mutation and selection balance. Properties of a Finite Population : Introduction of genetic drift. Stochastic Processes
Before delving into genetics, the book establishes a mathematical foundation for understanding how population size changes over time. It introduces four distinct models—ranging from discrete, nonoverlapping generations to continuous change with overlapping generations—and discusses Fisher's measure of reproductive value, which is crucial for predicting an individual's genetic contribution to future generations. If you prefer to obtain the book from
| Chapter | Title | Focus | | :--- | :--- | :--- | | 1 | Models of Population Growth | Introduces foundational mathematical models, comparing discrete, non-overlapping generations to overlapping ones to frame biological dynamics. | | 2 | Randomly Mating Populations | A key focus on the , a fundamental concept describing how allele frequencies remain constant in a large, random-mating population without external forces. | | 3 | Inbreeding | Explores the genetic consequences of non-random mating, including how it affects genotype frequencies through the inbreeding coefficient. | | 4 | Correlation Between Relatives and Assortative Mating | Extends the analysis of non-random mating by examining patterns of mate choice and their effects on genetic resemblance among relatives. | | 5 | Selection | Forms the book's core, analyzing how natural selection (with Darwinian fitness as a measure) changes gene frequencies and shapes population attributes. | | 6 | Populations in Approximate Equilibrium | Discusses the balance between evolutionary forces like selection, mutation, and migration under realistic conditions. | | 7 | Properties of a Finite Population | Addresses the crucial role of population size, introducing genetic drift —the random fluctuation of allele frequencies in finite populations. | | 8 | Stochastic Processes in the Change of Gene Frequencies | Introduces a more advanced, stochastic approach to modeling genetic change over time, which is a hallmark of the book. | | 9 | Distribution of Gene Frequencies in Populations | Further examines probabilistic models describing how gene frequencies are distributed across a theoretical metapopulation . | | Appendix | Some Statistical and Mathematical Methods | A valuable section providing direct reference to frequently used techniques, making it exceptionally useful. |
Crow and Kimura end their introduction with a line that still echoes:
Proposed by Motoo Kimura in the late 1960s, this theory argues that most evolutionary changes at the molecular level are caused by genetic drift of neutral mutant alleles, rather than by natural selection. It serves as the foundation for molecular clocks. Why Study Population Genetics Today? Because used hardcovers cost $300
By tracking how these frequencies shift, scientists can determine whether a population is stable or actively evolving, and identify which evolutionary mechanisms are at play. 2. The Baseline Model: The Hardy-Weinberg Principle
: The movement of alleles between different populations through the dispersal of individuals or gametes, which can introduce new variation or homogenize separate groups. Historical and Advanced Frameworks Introduction to Population Genetics - MaBS