PCB 4683; Fall, 2003

Course Outline

History, Philosophy, and Development of Evolutionary Theory

I will quickly go over the major ideas as we scan through the text book in lecture. You can highlight important parts and come back and read the chapters later. I will not lecture on this material. This is not "rocket science"; you can get it on your own from reading chapters 1 and 2 in Futuyma.

The Classical Tradition

· Plato (350 BC); eidos and the treatment of variation; Essentialism

· The Scala Naturae

· Aristotle (330 BC); applied Plato's theory of Forms to the living world; three kinds of psyche, the vegetative soul, the animate soul, and the rational soul

· Linnaeus; Systema Naturae , 1758; consistent binomial nomenclature; his idea of “relatedness” had nothing to do with common descent

Breakdown of Classical Tradition

· Buffon and Lamarck

· the Scala Naturae is not a fixed ladder of life but a moving scale (like an escalator) - a moving scale of progress; straight-line "evolution" up nature's scale

· Lamarck (1800); Philosophie Zoologique (1809); “organic progression” up a fixed scale of improvement; importance of environmental determinism - the "inheritance of acquired characters"

· The idea of explaining the origin of gaps in the scale nature and the origin of imperfections.

· Religious Philosophy - Natural Theology by Paley (1802 ); creative design, a plan, and a creator

· Environmental Philosophy - Voltaire (1750) - importance of environment in determining the characters of organisms; the general idea of "adaptation"

· Early writings on "evolution" - rejecting the fixity of the species. Lucretius - 55 BC; others, including Darwin's grandfather; Lamarckism as a kind of "evolution", but with a faulty underlying mechanism

Influences on Darwin

· Geology - catastrophism; age of earth and fossils

· Replacement of catastrophism by uniformitarianism; Ray, Hutton, and Lyell; Lyell's Principles of Geology (1832)

· Malthus - An essay on the principle of population, (1798); "standing room only"; economics and demography

Charles Darwin (1809-1882)

· He did not discover "evolution"

· His major contributions were (1) emphasizing common ancestry in evolutionary history and, (2) especially, proposing a novel mechanism for powering evolution - natural selection; "survival of the fittest"

· Voyage of the Beagle

· Importance of artificial selection and domestication

· Reaction to Darwinism

· "Origin of the Species ..." 1859

Perversions to Darwinism

· Marxism

· Hitler

Importance of Genetics

· Darwin's major works were written before the rediscovery of Mendel's work in 1900.

· Early Theories of Inheritance

· Blending Theory

· Darwin's Pangenesis

· Weismann's Germplasm Theory

· Mendel's Particulate Inheritance

· De Vries's Theory of Mutation

· Chromosomal Theory of Inheritance - began with Sutton and Morgan (early to mid-1900s)

The Modern Synthesis (1930s-1950s)

· Population Genetics - Fisher, Haldane, Wright

· Naturalistic Approach - Mayr, Simpson, Stebbins, Dobzhansky

Microevolutionary Processes and Population Genetics

Define Organic Evolution

· Anagenesis vs Cladogenesis

· Phenotype, genotype, environment, heritability

The Nature and Origin of Variation

· How does variation decompose

· Individual, deme, local population, metapopulation, race (subspecies), species, etc.

· Discrete (polymorphic) vs continuous (graded) variation

· What is a gene pool?

· What kind of variation are we interested in?

· Genetic variation, not environmentally induced.

· Variation at the single gene locus is a conceptual starting point

· Early thoughts on the nature and magnitude of variation

· Mostly "wild type", a few rare mutants

· What are some ways we can evaluate the level of variation in individuals within a deme or population

· Protein electrophoresis

· Amino acid sequencing of molecules

· DNA sequencing

· Protein Electrophoresis

· What is it, how does it work, what kind of data does it give you?

· What are the results of many years of study of many different organisms?

· Define genetic polymorphism

· Hardy-Weinberg Equilibrium

· Where does variation come from?

· Mutation is the original source of all genetic variation

· What is mutation, what are its important characteristics?

· Types of mutation and their consequences

· Point mutations

· Mobile genetic elements

· Chromosomal mutations

· Point Mutations; types and consequences

· Mutation rates

· Effect of mutation on changing allele frequencies

· Equilibrium allele frequencies

· Chromosomal Mutations (Aberrations)

· Recombination as a mechanism for increasing variation

· Gene flow as a means for moving alleles from one population to another

· What is a gene pool?

· How do genes move from one pool to another?

· Quantification of gene flow

Random Effects

· Genetic drift

· Inbreeding

What is genetic sampling error?

Genetic Drift

· Continuous

· Intermittent

· Founder effect

· What determines the magnitude of genetic drift?

Inbreeding

· What determines the magnitude of inbreeding?

· What are the effects of inbreeding and how do they differ from drift?

Natural Selection

· What is it, how does it work?

· Kinds of natural selection

· stabilizing

· directional

· disruptive

· frequency dependent

· Selection in relation to ecological factors

· r-selection vs K-selection

· Selection in relation to an adaptive landscape

· What is the concept of an adaptive landscape (topography)?

Quantification of selection

· How to calculate relative fitness

· Generalization of the selection model

· Complete selection against homozygous recessives

Balancing Selection

· Sickle-cell anemia

Mutation-selection equilibrium

· Hydraulic model

Natural selection in nature

· Pesticide resistance

· Industrial melanism

· pepper moth

Multilocus population genetics

· Supergenes

· Linkage disequilibrium

· Haplotype frequencies

· Epistasis

· Hitch-hiking effects

Quantitative Genetics

· Common-garden experiment approach

· Correlation approach

· Breeding (crossing) experiments

Response of continuous variables to long-term truncation experiments

Species Concepts and Speciation

What is "The Species Problem"?

· The species as a unit of classification and a unit of evolution

· The species from the viewpoint of taxonomy, systematics, and evolution

Species Concepts or Definitions

· Morphological (Typological)

· Non-dimensional

· Biological

· Other (Cladistic, Evolutionary, Ecological, etc.)

Why the Biological Species Concept has a good intuitive feel

Problems with the Biological Species Concept

· Asexuality

· Lack of information on breeding

· Evolutionary continuity through time

· Reproductive isolation based on habitat differences

· Different reproductive status in different populations

What are sibling species? Do they pose a problem for the Biological Species Concept?

Reproductive Isolating Mechanisms (RIMs) - what are they and how do they work?

· Premating vs Postmating Mechanisms - why the difference is important

· Premating

· Habitat isolation

· Seasonal isolation

· Ethological (Behavioral); detailed consideration of ethological because of importance in animals.

· Mechanical

· Postmating

· Gamete mortality or incompatibility

· Zygote mortality

· Hybrid breakdown

· hybrid inviability or weakness

· hybrid inferiority

· hybrid sterility (genic or chromosomal)

· Differences in plants and animals

· Pollination biology in plants and plant/pollinator coevolution

Speciation Mechanisms

· Define Allopatric, Sympatric, and Parapatric

· Allopatric (Geographic) Speciation Models

· Colonization or Budding

· Division

· Centrifugal

· Importance of small population size

· Geographic Speciation Models and Character Displacement

· Ecological character displacement

· Reproductive character displacement

· Sympatric Speciation Models

· What is sympatric speciation and how might it work

· Effects of disruptive selection

· Possible examples of sympatric speciation; Rhagoletis, Enchenopa, Drosophila pachea

· Parapatric Speciation Models

· What is parapatric speciation and how might it work

· Importance of small population size

· Correlation with ecological discontinuities

· Importance of chromosomal mechanisms (chromosomal or stasipatric speciation)

· Examples

· Polyploid Speciation

· Importance in plants

· Define autopolyploidy and allopolyploidy

· Creation of a "new species" in the laboratory

· Polyploid species complexes

· Evolutionary problems and potentials of polyploids

· Polyploidy in animals

· Hybridization as a speciation mechanism in plants

· Reticulate evolution

· "Recombinational Speciation"

· Mutation as a speciation mechanism in asexual organisms

· Unreasonable theories of speciation

· Rates of speciation

Variation Between Populations

How are organisms distributed in real populations

Relative degrees of genetic isolation among populations

Divergence vs convergence in deme gene pools

· Gene flow vs local selection

Patterns of variation

· Clinal variation; gradual clines and stepped clines

· Abrupt transitions

· Concordant and discordant patterns of variation

· Subspecies

· The "subspecies problem"

· Isolated vs contiguous subspecies

· Intergrades and intergrade zones

· Examples

Adaptation

Distinguish between adaptation and physiological or behavioral adjustment

Natural selection is the only known mechanism that can explain adaptation

What specific features of organisms represent adaptations?

· A historical perspective on the "purpose" an adaptation

Can one organism be "better adapted" than another?

Is every feature of an organism an adaptation?

· Biological significance

· Pleiotropic effects

· Hitch-hiking effects

Adaptation as a compromise

Generalized vs specialized adaptation

· Does the organism see the environment as "course-grained" or "fine-grained"

Why every feature of an organism might not be adaptive

· Difficulties with measuring the effects of improved adaptation

· Is the trait genetically controlled

· Is the trait due to random processes - genetic drift

· Are pleiotropic effects or linked genes involved; are we evaluating the right trait?

· Multiple adaptive peaks (crypsis)

· Adaptive constraints

· Time

· Phylogenetic

· Developmental

· Physical or Chemical

Usefulness of optimality models in studying adaptation

Adaptation in life history traits

· Relationship to population ecology

· Population growth models and parameters

· Adaptive expectations

· Semelparity vs iteroparity

· Reproductive effort

Sexual Selection

· Intrasexual vs Intersexual

· Kirkpatrick's model for sexual selection

· Run-away sexual selection

Levels of selection

· Vehicles vs replicators

· Gene, individual, group, species

Group selection

· The concept - Wynne-Edwards

· A model

· Altruism and related behaviors

The alternatives to group selection

· Kinship selection and inclusive fitness

· Eusocial insects

· Scrub jays

Complex adaptive systems

· Co-evolution

· Mimicry

· Mullerian

· Batesian

Taxonomy and Classification

What is a biological classification?

The general features of the hierarchical Linnean Classification used in biology.

What is the relationship of classification to phylogeny?

Major methods of biological classification

· Phenetic (Numerical)

· Evolutionary (Traditional)

· Cladistic (Phylogenetic)

Definitions of terms

· Monophyly, holophyly, paraphyly, polyphyly

Assumptions and rules of the cladistic method of character analysis

· Geneological descent

· Homologous characters

· Strict monophyly (holophyly)

· Simple dichotomy

· Symmetrical classification

Homoplasy

· Convergence, parallelism, reversal

Character Types

· plesiomorphic, synplesiomorphic, apomorphic, synapomorphic

How do you root a tree?

Example of a cladistic approach to the phylogeny of some birds.

Problems with the cladistic approach

· Converting cladogram into a classification

· Ancestral taxa

· Failure to recognize phyletic transformation

Inconsistency and difference of opinion in biological classifications.

Macroevolution

Review of terminology

· Lineage, phylogeny, phylogeneitcs, anagenesis, cladogenesis, stasigenesis

Differentiate between a Clade and a Grade

Differentiate between Phyletic Gradualism and Punctuated Equilibrium models

What is Species Selection?

How do Species Selection and patterns of Extinction influence our view of the phylogenetic history of a group?

· Differential speciation vs differential extinction

Evolutionary Trends

· Primitive (plesiomorphic) vs derived (apomorphic) characters

· Detailed consideration of character trends in horse evolution

· Phylogenetic and zoogeographic history of horses

· Relationship of macroevolutionary changes to adaptation to a new ecological zone

The concept of Adaptive Zones and relation to macroevolution

· Preadaptation and post-adaptation (expatation)

The viewpoint that the origin of new "higher" taxa (genera, families, etc.) is adaptive in nature and is explained by microevolutionary processes

· Hawaiian honeycreeper birds

· Mammal-like reptiles

The viewpoint that evolutionary novelties, defining new higher taxa, are not always adaptive, at least in the beginning

· Bird feathers

· Turtle shell

The importance of epigenetic factors that regulate the ontogenetic transformation of genotype to phenotype.

· Gene regulation

· A model of gene regulation (Brittan-Davidson)

The relationship between developmental biology and evolutionary biology

Review of Haeckel's Biogenetic Law (recapitulation) and von Bear's Law

Most important developmental principles

· Change by terminal addition

· Change by non-terminal addition

· Allometry

· Heterochrony

· Paedomorphosis - progenesis vs neoteny

· D'Arcy transformations

· Developmental integration

· Plasticity of development

Non-adaptive models of macroevolution (Gould)