(EEB 122) This course presents the principles of evolution, ecology, and behavior for students beginning their study of biology and of the environment. It discusses major ideas and results in a manner accessible to all Yale College undergraduates. Recent advances have energized these fields with results that have implications well beyond their boundaries: ideas, mechanisms, and processes that should form part of the toolkit of all biologists and educated citizens.
This course was recorded in Spring 2009.
01 - The Nature of Evolution: Selection, Inheritance, and History
The lecture presents an overview of evolutionary biology and its two major components, microevolution and macroevolution. The idea of evolution goes back before Darwin, although Darwin thought of natural selection. Evolution is driven by natural selection, the correlation between organism traits and reproductive success, as well as random drift. The history of life goes back approximately 3.7 billion years to a common ancestor, and is marked with key events that affect all life.
02 - Basic Transmission Genetics
Genetic transmission is the mechanism that drives evolution. DNA encodes all the information necessary to make an organism. Every organism's DNA is made of the same basic parts, arranged in different orders. DNA is divided into chromosomes, or groups of genes, which code for proteins. Asexually reproducing organisms reproduce using mitosis, while sexually reproducing organisms reproduce using meiosis. Both these mechanisms involve duplication of DNA, which then gets passed to offspring. RNA is a key component in the duplication of DNA.
03 - Adaptive Evolution: Natural Selection
Adaptive Evolution is driven by natural selection. Natural selection is not "survival of the fittest," but rather "reproduction of the fittest." Evolution can occur at many different speeds based on the strength of the selection driving it. These types of selection can result in directional, stabilizing, and disruptive outcomes. They can be driven by frequency-dependent selection and sexual selection, in addition to more standard types of selection.
04 - Neutral Evolution: Genetic Drift
Neutral evolution occurs when genes do not experience natural selection because they have no effect on reproductive success. Neutrality arises when mutations in an organism's genotype cause no change in its phenotype, or when changes in the genotype bring about changes in the phenotype that do not affect reproductive success. Because neutral genes do not change in any particular direction over time and simply "drift" thanks in part to the randomness of meiosis, they can be used as a sort of molecular clock to determine common ancestors or places in the phylogenetic tree of life.
05 - How Selection Changes the Genetic Composition of Population
Genetics controls evolution. There are four major genetic systems, which are combinations of sexual/asexual and haploid/diploid. In all genetic systems, adaptive genetic change tends to start out slow, accelerate in the middle, and occur slowly at the end. Asexual haploids can change the fastest, while sexual diploids usually change the slowest. Gene frequencies in large populations only change if the population undergoes selection.
06 - The Origin and Maintenance of Genetic Variation
Mutations are the origin of genetic diversity. Mutations introduce new traits, while selection eliminates most of the reproductively unsuccessful traits. Sexual recombination of alleles can also account for much of the genetic diversity in sexual species. In some instances, population size can affect diversity and rates of evolution and fixation, but in other cases population size does not matter.
Very engaging and interesting, covers a wide swath of information in a unified and enlightening manner. In particular, this course offers excellent perspective on further understanding evolution and its mechanisms.